GMT SYSTEM LEVEL PRELIMINARY DESIGN REVIEW December 13, 2013

Enclosure and Facilities Section 7

GMT SYSTEM LEVEL PRELIMINARY DESIGN REVIEW December 13, 2013

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ENCLOSURE AND FACILITIES 7–2 GMT SYSTEM LEVEL PRELIMINARY DESIGN REVIEW December 13, 2013

Table of Contents 7 ENCLOSURE AND FACILITIES ...... 7 7.1 Overview of the Enclosure and Facilities ...... 7 7.1.1 Introduction ...... 7 7.1.2 Description of the Enclosure Building ...... 8 7.1.3 Description of the Summit Support Building ...... 9 7.1.4 Description of the Support Site Buildings ...... 9 7.1.5 Sea Level Facilities ...... 11 7.1.6 Preliminary Design Drawings and Supporting Documents ...... 11 7.1.7 Value Engineering ...... 11 7.2 Enclosure and Facilities Design Requirements ...... 11 7.2.1 Key Design Requirements ...... 12 7.2.1.1 Enclosure Thermal Performance ...... 12 7.2.1.2 Vibration at the Pier to Rock Interface ...... 13 7.2.2 Environmental Requirements ...... 14 7.2.2.1 Wind ...... 14 7.2.2.2 Seismic Events ...... 15 7.2.2.3 Precipitation ...... 15 7.2.2.4 Temperature ...... 16 7.2.3 Reliability and Maintenance...... 16 7.2.4 Health and Safety ...... 17 7.3 Master Plan ...... 18 7.3.1 General Site Plan ...... 18 7.3.2 Interaction with LCO ...... 19 7.3.3 Access to the Site ...... 19 7.3.4 GMT Facilities ...... 21 7.3.4.1 Summit Site ...... 21 7.3.4.2 Support Site ...... 25 7.3.5 Utilities and Services Infrastructure ...... 28 7.3.5.1 Electrical Power Feed ...... 29 7.3.5.2 Electrical Distribution ...... 30 7.3.5.3 Water ...... 30 7.3.5.4 Domestic Sanitary Waste ...... 30 7.3.5.5 Communications ...... 30 7.3.5.6 Fuel ...... 30 7.3.5.7 LN2 ...... 30 7.3.5.8 Subsurface Utilities ...... 30 7.3.5.9 Guardrails ...... 31 7.3.5.10 Signage ...... 31 7.4 Enclosure Building ...... 31 7.4.1 Architectural Design ...... 33 7.4.1.1 Enclosure Geometry ...... 33 7.4.1.2 Enclosure Design ...... 35 7.4.1.3 Enclosure Base Design ...... 42 7.4.1.4 Telescope Pier ...... 47 7.4.1.5 Maintenance/Personnel Access ...... 49 7.4.1.6 Lifts and Cranes ...... 57 7.4.1.7 Materials Overview ...... 63 7.4.1.8 Architectural Seals ...... 63 7.4.2 Structural Design ...... 64

ENCLOSURE AND FACILITIES 7–3 GMT SYSTEM LEVEL PRELIMINARY DESIGN REVIEW December 13, 2013

7.4.2.1 Building Code and Reference Standards ...... 65 7.4.2.2 Design Wind Speeds ...... 65 7.4.2.3 Seismic Requirements ...... 66 7.4.2.4 Enclosure ...... 66 7.4.2.5 Uplift Restraints ...... 75 7.4.2.6 Enclosure Base ...... 76 7.4.2.7 Telescope Pier ...... 78 7.4.3 Enclosure Mechanisms ...... 80 7.4.3.1 Enclosure Azimuth Rotation Mechanisms ...... 80 7.4.3.2 Shutter Design Requirements ...... 89 7.4.3.3 Vertical Shutter Mechanisms ...... 89 7.4.3.4 Horizontal Shutter Mechanisms ...... 95 7.5 Summit Support Building ...... 99 7.5.1 Introduction ...... 99 7.5.2 Architectural Design...... 101 7.5.2.1 Facility Building ...... 101 7.5.2.2 Auxiliary Building ...... 104 7.5.2.3 Equipment Building ...... 110 7.5.2.4 Vibration Isolation ...... 113 7.5.2.5 Materials Overview...... 113 7.5.3 Structural Design ...... 114 7.5.3.1 Foundations ...... 115 7.5.3.2 Framing Overview ...... 116 7.6 Support Site Buildings ...... 119 7.6.1 Architectural Design...... 119 7.6.1.1 Utilities Building...... 119 7.6.1.2 Warehouse ...... 121 7.6.1.3 Mid-Level Water Storage Facility ...... 122 7.6.2 Structural Design ...... 122 7.6.2.1 Foundations ...... 123 7.6.2.2 Framing Overview ...... 123 7.7 Utilities ...... 125 7.7.1 Heating, Ventilation and Air Conditioning (HVAC) ...... 125 7.7.1.1 Weather Data Summary ...... 125 7.7.1.2 Enclosure and Pier Cooling & Ventilation ...... 126 7.7.1.3 Building HVAC ...... 131 7.7.2 Plumbing ...... 132 7.7.2.1 Chilled Water System Driving Requirements ...... 132 7.7.2.2 Chilled Water Systems ...... 132 7.7.2.3 Water & Waste...... 133 7.7.2.4 Fire Protection...... 135 7.7.3 Compressed Air ...... 135 7.7.4 Fueling Station and Tank Yard ...... 136 7.7.5 Liquid Nitrogen Bulk Storage ...... 136 7.7.6 Electrical ...... 137 7.7.6.1 Electrical Power Distribution System Overview ...... 137 7.7.6.2 Preliminary Load Summary ...... 138 7.7.6.3 One-Line Diagrams...... 139 7.7.6.4 Normal, UPS, and Emergency Power Distribution ...... 140 7.7.6.5 Lightning Protection Systems ...... 141 7.7.6.6 Grounding Electrode System ...... 141

ENCLOSURE AND FACILITIES 7–4 GMT SYSTEM LEVEL PRELIMINARY DESIGN REVIEW December 13, 2013

7.7.6.7 Interior Lighting and Control ...... 142 7.7.6.8 Life Safety Systems ...... 142 7.7.7 Controls ...... 143 7.8 Performance Analysis ...... 147 7.8.1 Enclosure and Facilities Thermal Performance Requirements ...... 147 7.8.2 Wind Tunnel Testing ...... 149 7.8.2.1 Terrain Study ...... 149 7.8.2.2 Flow Visualization ...... 150 7.8.2.3 Cladding Study ...... 150 7.8.2.4 Structural Load Study ...... 151 7.8.3 Enclosure Thermal Design ...... 154 7.8.3.1 Natural Ventilation ...... 154 7.8.3.2 Enclosure Outer Surfaces ...... 156 7.8.3.3 Forced Ventilation ...... 156 7.8.4 CFD Analysis ...... 156 7.8.4.1 Overview of the CFD Analyses ...... 156 7.8.4.2 Preliminary CFD Analyses ...... 157 7.8.4.3 CFD Thermal Analysis ...... 161 7.8.4.4 Methodology ...... 161 7.8.4.5 Results ...... 165 7.8.4.6 Conclusions ...... 165 7.9 Construction Planning ...... 177 7.9.1 Site Leveling ...... 178 7.9.2 Geotechnical Engineering ...... 179 7.9.3 Utilities and Infrastructure ...... 181 7.9.3.1 Electrical Power and Communications ...... 181 7.9.3.2 Water ...... 181 7.9.3.3 Construction camp ...... 181 7.9.4 Procurement Overview ...... 181 7.9.5 Site Work and Foundations ...... 182 7.9.5.1 Roads and Grading ...... 182 7.9.5.2 Underground Utilities ...... 182 7.9.5.3 Foundations ...... 182 7.9.6 Steel Fabrication ...... 183 7.9.6.1 Enclosure and Facilities Steel Fabrication ...... 183 7.9.6.2 Enclosure Mechanisms Fabrication ...... 183 7.9.7 Erection of the Structural Steel, Roof and Wall Panels ...... 183 7.9.8 Completion Work ...... 184 7.9.9 Construction Phase Infrastructure ...... 184 7.9.9.1 Construction Utilities ...... 185 7.9.9.2 Concrete Batch Plant ...... 185 7.9.9.3 Enclosure Building Laydown and Material Storage Areas ...... 185 7.9.9.4 Crane Pad Locations ...... 187 7.9.9.5 Construction Power ...... 188 7.10 Enclosure and Facilities Risks ...... 188 7.10.1 Summary of Current Enclosure and Facilities Risks ...... 188 7.10.2 Risk Mitigation Strategies ...... 192 7.10.3 Risk Mitigation since the Enclosure and Facilities PDR ...... 192 7.10.3.1 Enclosure Bogie and track Design (Risk0009) ...... 192 7.10.3.2 Enclosure and Facilities Costs (Risk0092) ...... 192 7.10.3.3 Reliability of the Shutters (Risk0006) ...... 192

ENCLOSURE AND FACILITIES 7–5 GMT SYSTEM LEVEL PRELIMINARY DESIGN REVIEW December 13, 2013

7.10.3.4 Enclosure Seals (Risk0007) ...... 192 7.11 Recent Design Activities ...... 193 7.11.1 Preliminary Design Review ...... 193 7.11.1.1 Enclosure and Facilities Preliminary Design Review ...... 193 7.11.2 Enclosure and Facilities Cost Reduction Studies ...... 193 7.11.2.1 Enclosure and Facilities Value Engineering ...... 193 7.11.2.2 Enclosure Height Reduction ...... 194 7.11.2.3 Telescope Pier Height Reduction...... 195 7.11.2.4 Enclosure Base Height Reduction and Optimization ...... 195 7.11.2.5 Control Building and M2 Lab Relocation ...... 195 7.11.2.6 Enclosure Mezzanine Elimination ...... 196 7.11.2.7 Site Utility Tunnel Elimination ...... 196 7.11.2.8 Enclosure Ventilation Building Redesign ...... 198 7.11.2.9 Summit Support Building - Building Area and Height Reduction ...... 198 7.11.2.10 Summit Support Building - Fire Protection Elimination ...... 200 7.11.2.11 Summit Support Building - Reduced Crane Size ...... 200 7.11.2.12 Utilities Building...... 201 7.11.2.13 Warehouse Building ...... 201 7.11.2.14 Summary of Cost Savings Achieved ...... 202 7.11.3 Alternate Enclosure Shutter Study ...... 203 References ...... 205

ENCLOSURE AND FACILITIES 7–6 GMT SYSTEM LEVEL PRELIMINARY DESIGN REVIEW December 13, 2013

7 ENCLOSURE AND FACILITIES 7.1 Overview of the Enclosure and Facilities 7.1.1 Introduction This chapter provides a detailed description of the telescope enclosure and facilities buildings, utilities and site infrastructure. The sections are generally structured to provide a short introduction, lists of the key functional and performance requirements and a description of design features implemented to satisfy the requirements. Section 7.2 summarizes the general requirements that apply to all aspects of the design. Specific design requirements for the major components of the enclosure and facilities are included later, in their appropriate sections. The Master Plan is described in Section 7.3. It covers the general site plan describing the locations and layout of the enclosure and facilities buildings at the summit site and support site as well as roads, utilities and utility paths as defined by particular design requirements. It describes the basic functions of the enclosure and summit support buildings at the summit site and the utilities building, warehouse and lodge at the support site. The design of the enclosure, summit support and support site buildings are presented in Sections 7.4 through 7.6. The mechanical design, sizing and specification of chillers, circulation pumps, air compressors and heating, ventilation and air conditioning (HVAC) equipment are covered in Section 7.7. Also included in this section is a description of the electrical power design and the enclosure control system. Enclosure thermal performance is described in Section 7.8. An overview of planned construction activities is given in Section 7.9. Enclosure and facilities risks and risk management strategies are described in Section 7.10. Recent design activities are described in Section 7.11. These include a summary of the January, 2013 Enclosure and facilities PDR and a successful value engineering phase that occurred after the PDR. An overall view of the GMT site is shown in Figure 7-1.

Figure 7-1. Overall site view

ENCLOSURE AND FACILITIES 7–7 GMT SYSTEM LEVEL PRELIMINARY DESIGN REVIEW December 13, 2013

7.1.2 Description of the Enclosure Building The Enclosure Building must protect the telescope from the environment when sealed, and have a minimal impact on telescope image quality when open during benign conditions. During high wind conditions otherwise suitable for observing, the enclosure building must be able to shield the telescope to reduce wind shake. During moonlit nights the enclosure building should protect the telescope from scattered moonlight where possible. Several considerations factor into the choice of the design. The structure will be large and yet rotate at a rate equal to that of the telescope. Similarly, the shutter will have a large clear span and relatively fast motion requirements. There are functional aspects associated with servicing the telescope and instruments that lead to requirements for personnel access and custom handling equipment. The enclosure and associated facilities will have to fit the local topography of the site such that the turbulent boundary layer does not adversely impact telescope performance.

The shape of the structure is a faceted cylinder. It incorporates a two piece horizontal shutter at the roof level and a three piece vertical shutter. The shutters provide a clear aperture for all viewing angles of the telescope and the shutter doors can be brought close to the incoming beam for maximum protection of the telescope from wind or moon light. Wind vents are built into alternating facets of the vertical enclosure walls. The quantity of vents is chosen to provide a well- ventilated telescope chamber during science operations and the opening size of the vent doors is adjustable to allow tuning of the flow through the enclosure to maintain control of the air velocity around the telescope structure. Several areas of the enclosure building are actively ventilated to remove residual waste heat. Air is drawn from the enclosure through a ventilation duct and exhausted at the west edge of the summit site, away from telescope viewing.

The enclosure rotates on a fixed enclosure base. The fixed base is an open structure allowing air to flow below the observing floor, minimizing the disruption of the air flow across the summit and encouraging the boundary layer to remain below the height of the shutter opening and wind vents. The telescope pier is located in the middle of the enclosure base, mechanically isolated from the surrounding structure.

The enclosure walls are tight to the swept volume of the telescope resulting in a compact design. This volume is defined by a fixed margin beyond the structural dimensions of the telescope, swept through its entire range of motion. The fixed base places the observing floor at approximately 12 meters above grade and the telescope elevation axis at over 22 meters above grade. A bridge crane is located at the top of the enclosure. This crane has 2 hooks, one with a 65 metric ton capacity and the other with a 10 metric ton capacity. The primary function of the bridge crane is to handle the primary mirror assemblies during mirror coating operations. The crane is also used for daily operation and maintenance activities, installation and removal of instruments and other telescope components and the assembly & integration of the telescope during construction.

A non-co-rotating enclosure and telescope was chosen for its simplicity and for ease of handling the primary mirror segments when they are removed from the telescope for recoating. The enclosure crane is used to lift the mirror assemblies from the telescope, through a hatch in the observing floor to a transport cart. The cart moves the primary mirror assembly to the coating facility on fixed steel rails. The rails extend from a lift platform at the center of the telescope pier to the far end of the auxiliary building to accommodate instrument handling as well.

ENCLOSURE AND FACILITIES 7–8 GMT SYSTEM LEVEL PRELIMINARY DESIGN REVIEW December 13, 2013

A view of the enclosure and summit support buildings is shown in Figure 7-2. In this view, the shutters and wind vents are completely open and the enclosure crane (yellow) can be seen in its parked position at the top of the enclosure. Note the open structural framing of the fixed enclosure base and the ventilation duct leading to the west side of the site.

Figure 7-2. Enclosure and summit support buildings

7.1.3 Description of the Summit Support Building The second major facility at the summit is the summit support building. It is a single structure that consists of the equipment building, auxiliary building and facility building. Functions provided within these buildings are necessary to support nighttime science operations, daytime operation and maintenance activities.

The equipment building houses the mechanical and electrical equipment used to provide the utilities and services for the telescope, enclosure and facilities. These include chilled water, compressed air, high-pressure hydraulic oil, treated and deionized water and the distribution of commercial, UPS and emergency electrical power. Space is also provided for pumps and electronics for the coating facility.

The auxiliary building provides high bay space for the primary mirror coating facility including the coating plant and mirror washing and stripping equipment, instrument storage and maintenance bays and an area for secondary mirror maintenance and calibration. It also includes an instrument machine shop and a large entry vestibule.

The facility building includes the telescope control and computer rooms, electronics and detector laboratories, a clean room and personnel space for offices, kitchen and conferencing.

7.1.4 Description of the Support Site Buildings Other non-essential facilities are located off of the summit at the support site. These include a utilities building, warehouse, fuel storage area, dormitories, recreation area and dining hall.

ENCLOSURE AND FACILITIES 7–9 GMT SYSTEM LEVEL PRELIMINARY DESIGN REVIEW December 13, 2013

The utilities building houses a machine shop, welding & heavy mechanical maintenance shop, a vehicle maintenance area and maintenance management office space. The main transformer and emergency generators are located in the electrical yard, adjacent to the utilities building. Fuel storage and a fuel dispensing area are also located nearby. An image of the utilities building is shown in Figure 7-3. Also seen in this view are the backup generators, main transformer and switchgear.

Figure 7-3. Utilities building and electrical yard

The warehouse is sized to store up to 5 primary mirror segments in their transportation containers during the initial construction phase. During operations, the warehouse will be used to store handling fixtures, equipment and spare parts. An image of the warehouse is given in Figure 7-4.

Figure 7-4. Warehouse

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A water storage facility will be located uphill of the support site to provide potable water for the support site buildings and fire protection water for the dormitories.

The dormitories, recreation area and dining hall are sized for the anticipated numbers of staff and visitors. Dormitories are located in quiet areas of the site. Work on the design and development of these structures has not yet begun. This is a Stage 2A activity.

7.1.5 Sea Level Facilities Sea level office space will also be provided, likely at the LCO El Pino site in La Serena. Requirements for these facilities have not yet been defined. The design and development of these facilities is a Stage 3 activity.

7.1.6 Preliminary Design Drawings and Supporting Documents The majority of the design and development work for the enclosure and facilities is being performed by M3 Engineering of Tucson, Arizona under contract with GMTO. The work includes the design of the enclosure building, summit support building, utilities building and warehouse, as well as all site grading and civil aspects of the observatory. Other work, not part of this contract includes the design of infrastructure to bring electrical power lines and fiber optic cables to the site, and the design and development of a summit lodge and sea level facilities. A preliminary design of the electrical power upgrade and infrastructure was completed by ASEGIM, Ltd. of Coquimbo, Chile. An overview of this design is presented in Section 7.3.5.

Preliminary design drawings, cut sheets of proposed material and equipment and engineering calculations have been completed. Drawing packages include the following:  Site Grading, Utilities & Improvements1  Enclosure, Enclosure Base & Telescope Pier2  Summit Support Building3  Utilities Building, Warehouse & Water Storage Facility4

Other reference material includes the following:  Material & Equipment Literature - Preliminary Design5  Calculations - Preliminary Design6

7.1.7 Value Engineering Value engineering work performed after the enclosure and facilities January 2013 PDR is described in Section 7.11.2. This work resulted in several changes to the design of the enclosure and facilities buildings and infrastructure. The current baseline design as presented herein includes all of these changes. In addition, conceptual work on an alternate vertical shutter concept as described in Section 7.11.3 has recently begun. This concept has the potential for significant structural, mechanical and thermal improvements as well as additional cost savings. The work however is only at the conceptual level and is not included in our baseline design. 7.2 Enclosure and Facilities Design Requirements The level 3 general requirements for the design of the enclosure and facilities buildings are summarized in this section. These include key requirements related to thermal performance and vibration as well as design requirements relating to environmental conditions, reliability, maintainability, health and safety. Detailed design requirements for the various buildings are contained in later sections which are focused on those particular design details. The design

ENCLOSURE AND FACILITIES 7–11 GMT SYSTEM LEVEL PRELIMINARY DESIGN REVIEW December 13, 2013 requirements are derived from the Level 1 Science7 requirements and the Operational Concepts Document8 and the level 2 System Level9 requirements. The complete set of functional and performance requirements for the enclosure and facilities are specified in the design requirements documents for the enclosure10 and the facilities11. Detailed structural requirements for the enclosure and facilities are defined in the International Building Code (IBC)12. Architectural features of the enclosure and facilities buildings are defined by the occupancy requirements specified in the IBC. The flow-down of requirements and documents that lead to the Level 3 design requirements documents is shown in Figure 7-5.

Figure 7-5. Requirements flow-down

7.2.1 Key Design Requirements 7.2.1.1 Enclosure Thermal Performance At level 2, the fundamental design requirement for the enclosure thermal performance is defined by an image quality error budget for dome seeing of 0.050 arcsec at 80% encircled energy. At level 3, this image quality requirement flows to a differential temperature requirement of less than or equal to 0.4 C between the air within the telescope optical path and that of the outside ambient. The 0.4 C temperature difference is equivalent to the 0.050 arcsec image quality degradation in accordance with the results presented by Racine13. Computational Fluid Dynamics (CFD) analyses described in Section 7.8.4.3 demonstrate that we are in compliance with this requirement.

Enclosure and Facilities design features implemented to enhance thermal performance start with the site layout. The Enclosure building is placed at the west end of the site and the summit support building is located approximately 50 meters away from the enclosure to the southeast, in the direction approximately perpendicular to the primary wind direction (the wind direction is from the northeast 80% of the time and from the south approximately 20% of the time). This layout

ENCLOSURE AND FACILITIES 7–12 GMT SYSTEM LEVEL PRELIMINARY DESIGN REVIEW December 13, 2013 minimizes the likelihood that the disruption of the air flow around the summit support building will migrate to the enclosure. Heat sources are located at the southeast side of the building so that waste heat flows directly off the summit to the south, away from the telescope. A ventilation duct that exhausts waste heat from the enclosure building is also oriented to direct that waste heat away from the telescope. The observing level is placed at approximately 12 meters above the ground level and wind tunnel testing has demonstrated that this is high enough to keep the turbulent ground layer flowing across the summit from entering the telescope chamber. All buildings, structures and mechanical equipment not essential for supporting nighttime operations and efficient daytime maintenance activities are located at a support site, a few kilometers away from the summit site.

The enclosure is well ventilated with large shutters and many wind vents. CFD analysis has demonstrated that the shutter and wind vent design is adequate to meet requirements for natural ventilation of the enclosure (see Section 7.8.3.1). The structure is designed for rapid thermalization using beams and columns with open cross-sections and thin flange and web plates. Closed sections and areas with mechanical equipment are actively ventilated. The exterior wall surfaces have low emissivity coatings to minimize sub-cooling at night.

7.2.1.2 Vibration at the Pier to Rock Interface At level 2, image quality requirements specify that vibration at the telescope pier to rock interface degrade image quality by no more than 0.050 arcsec at 80% encircled energy. This requirement is flows directly to the enclosure and facilities design requirements at level 3.

To minimize the effects of vibration at the telescope pier, several design aspects are included in the enclosure and summit support buildings. The telescope pier is a completely isolated structure from the enclosure base and the enclosure base foundations are designed to be as far away from the pier as is practical. All mechanical services passing to the pier include flexible connections at the interface to the pier.

Vibration sources include enclosure dynamic forces reacted by the enclosure base foundations due to wind excitation, mechanical vibration or enclosure motion dynamics. These forces are primarily reacted by the outer circumferential ring of enclosure base columns, over 15 meters distant from the telescope pier wall. The inner ring of enclosure base columns, closest to the pier react only static load from the observing floor. The enclosure bogies use variable frequency drives designed for smooth starting and stopping and include compliant elements in their attachment to the enclosure structure to reduce high frequency vibration transfer through the bogies to the enclosure base.

Mechanical equipment within the summit support building is also a source of vibration. This equipment includes compressors, chillers, water pumps and oil pumping systems. To mitigate the effects of vibration, all equipment are mounted on isolated reinforced concrete pads through secondary isolation systems to these foundations (see Section 7.5.2.4). In addition, the equipment is located at a distance of more than 60 meters from the telescope pier.

We are currently in-process with regards to demonstrating compliance with this requirement yet we are confident that through vibration isolation and keeping sufficient distance between vibration sources and the pier, we will meet the requirement. We will use finite element modeling of the rock/structure interaction as well as on-site testing to verify compliance with this requirement during the detailed design phase.

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7.2.2 Environmental Requirements The design limits for these operational and survival events are specified in the GMT Environmental Conditions Document14. The driving design requirements for the enclosure and facilities with regards to environmental conditions are listed in Table 7-1.

The flow down of these to specific design requirements for the enclosure and facilities is described in the following section along with a description of the design aspects implemented to meet these requirements. Details of the structural design of the enclosure and summit support buildings are given in Sections 7.4.2 and 7.5.3. The structural design of the utilities building and warehouse is described in Section 7.6.2.

Table 7-1. Enclosure and facilities key environmental design requirements (Level 3 requirements from Environmental Conditions Document GMT-SE-REF-00144) Requirement ID & Title Requirement Notes The enclosure and facilities shall be Critical aspects of the enclosure ENC-7831: Enclosure designed to support science observations design during operational Operating Conditions over the range of environmental conditions include ventilation and FAC-6386: Facility conditions specified in section 4.1.1 of thermal performance as described Operating Conditions GMT-SE-REF-00144 in Section 7.8 Wind, snow, ice and rain The facility shall be designed to survive ENC-7832: Enclosure environments are completely with inconsequential damage the extreme Survival Conditions specified in the design criteria for weather conditions specified in section FAC-6387: Facility the enclosure and facilities 4.1.2 of GMT-SE-REF-00144, with the Survival Conditions buildings. See Sections 7.4 enclosure closed and secured through 7.6. The facility shall be designed to survive FAC-7833: Enclosure with minimum consequential damage and Operational Level System level requirement to return to operations within 7 days for Earthquake assure that normal operations can earthquakes no more severe than the FAC-6389: Facility resume with minimal interruption maximum operational level earthquake as Operational Level after a moderate earthquake defined in Section 4.3 in GMT-SE-REF- Earthquake 00144 System level requirement to The facility shall be designed to survive ENC-7835: Enclosure assure that there will be no without major structural failure a Survival Level Earthquake collapse for personnel safety and maximum survival level earthquake as FAC-6390: Facility to ensure that it is possible to defined in Section 4.3 in GMT-SE-REF- Survival Level Earthquake resume normal operations after a 00144 severe earthquake

7.2.2.1 Wind Section 4.1.1 of the GMT Environmental Conditions Document defines the environmental conditions within which the telescope must meet its performance requirements. Specifically, the telescope must be within specification between the 25th and 75th percentile conditions. For the wind environment, this corresponds to wind speeds between 3.5 and 9.8 meters per second measured at 10 meters above grade.

In low wind conditions, the shutters and wind vents are opened to maximize natural ventilation by ambient air. As the wind speed rises, wind buffeting of the telescope increases resulting in performance degradation due to telescope wind shake. To maximize the delivered image quality in higher ambient wind conditions, the shutters and wind vents close as appropriate to balance the need to ventilate the enclosure and minimize wind buffeting of the telescope. Under the high

ENCLOSURE AND FACILITIES 7–14 GMT SYSTEM LEVEL PRELIMINARY DESIGN REVIEW December 13, 2013 operational wind conditions, the wind vents can be completely closed and the shutters closed as necessary to provide a minimum viewing aperture.

Computational Fluid Dynamics (CFD) analyses of the enclosure as described in Section 7.8 were completed to calculate the wind environment within the enclosure under these conditions and enclosure configurations. The wind velocity and pressure results were then used in the performance evaluation of the telescope in the wind environment (see Section 6.12).

The maximum design wind speed15 is 65 m/s. This speed was extrapolated from over 7 years of wind velocity measurements at Las Campanas peak using extreme event statistical methods as adopted by the IBC for establishing the design wind speed for structures such as the enclosure. Wind tunnel testing of a scaled model of the enclosure and site was performed in order to define the overall wind loading of the structure as well as surface pressures for the design of the exterior wall and roof panels. See 7.8.2 for a description of the wind tunnel test program.

7.2.2.2 Seismic Events Two seismic events were specified for the design of the enclosure and facilities structures: an Operational Level Event (OLE) and a Survival Level Event (SLE). The OLE was defined as the 100 year return period earthquake and the SLE was defined as 2/3 of the Maximum Considered Earthquake as defined by the IBC seismic design requirements12.

For the OLE, the structural design criteria states that the GMT will be designed to incur no significant damage to structural components. Structures will retain nearly all their pre-earthquake strength and stiffness. In addition, most non-structural components will be secure and will function, if utilities are available, following the event. The structures may be used for their intended purpose, although in an impaired mode.

For the SLE, significant damage to the structure may occur resulting in a substantial reduction in overall stiffness; however, the structure will retain a positive margin against collapse. Nonstructural elements are secured but may not function. Occupancy may be prevented until repairs can be made. The seismic structural design of the enclosure and facilities buildings follows these design criteria and requirements. Please see Sections 7.4.2, 7.5.3 and 7.6.2 for a detailed discussion about the seismic design of the enclosure and facilities buildings.

7.2.2.3 Precipitation The enclosure must protect the telescope from the severe environmental conditions associated with snow, ice and rain. These requirements are listed in Table 7-2.

Table 7-2. Design requirements for precipitation (Level 3 requirements from Environmental Conditions Document GMT-SE-REF-00144) Criterion Requirement Notes Maximum Rain Rate 50 mm/hour Based upon historical data Maximum Snow Accumulation 0.9 m Based upon historical data Maximum Ice Accumulation 0.1 m Based upon historical data

For the rain environment, provisions are made in the design for sealing the shutters and wind vents against the intrusion of water and for passive draining. The removal of accumulated snow and ice will occur naturally by exposure to the sun and with slow rotation of the enclosure during the day. Provisions are made to allow for personnel access to all roof areas for manual removal of the snow and ice if necessary.

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7.2.2.4 Temperature The air temperature environments are defined in Table 7-3.

Table 7-3. Air temperature operating and survival environments (Level 3 requirements from Environmental Conditions Document GMT-SE-REF-00144) Criterion Requirement Notes Systems must operate to specification Operating Temperature -10 C to +25 C within this range of temperatures Systems must operate to specification Survival Temperature -20 C to +45 C after being subjected to air temperatures within this range

All structural and mechanical components of the enclosure and facilities buildings are designed in accordance with these temperature limits.

The rate of change of temperature is an important factor in designing the structure of the enclosure to remain close to the ambient air temperature as it changes during the night. The site testing data indicates that the temperature falls at a rate of 0.45 C per hour approximately 25% of the time and 1 C per hour approximately 5% of the time. The shapes of structural steel elements within the enclosure have been designed using open cross-sectional shapes with a relatively thin flange plate thickness to provide rapid thermalization of the enclosure structure. See Section 7.8 for more detailed information on the thermal design aspects of the enclosure.

The mean daytime temperature is approximately 17.3 C. The 10th percentile daytime temperature is 9.3 C and the 90th percentile temperature is 24.2 C. The walls and roof of the enclosure building are heavily insulated and surfaces are treated with low emissivity coatings to minimize the temperature rise within the telescope chamber during the day. The low emissivity coatings are also used to minimize the risk of sub-cooling of the enclosure roof and wall surfaces due to radiation heat transfer to the nighttime sky.

7.2.3 Reliability and Maintenance The driving requirements for reliability and maintenance are listed in Table 7-4.

The budgets for down time and maintenance time specified in these requirements define the need for highly reliability in the mechanical design and selection of enclosure and facilities equipment. The preliminary design and specification of equipment has taken into consideration this need for high reliability. Per the GMTO Quality Assurance Plan, reliability, availability, and maintainability methods, such as a Failure Mode, Effect and Criticality Analysis (FMECA), will be performed on the subsystems and equipment in the detailed design phase to confirm that the enclosure and facilities equipment meets the specified down time and maintenance time budgets.

Design compliance with these requirements is summarized in Section 5.3.5, demonstrated in the enclosure and facilities compliance matrix (add reference), and design details are provided in Sections 7.4 through 7.6.

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Table 7-4. Key reliability and maintenance requirements (Level 3 requirement from GMT Maintenance Time Budget Document GMT-SE-REF-00420) Requirement ID & Title Requirement Notes The facility shall be designed for an operational lifetime no less than 50 years, FAC-1141: Facility Flow down from the science assuming routine maintenance of the Lifetime requirements facilities and periodic upgrades of field replaceable components and subsystems There are many competing The enclosure shall be designed to require operations that must be completed ENC-7838: Enclosure no more than 70 hours per year of daytime during the day and this amount of Daytime Maintenance of maintenance that precludes operation of time is based on the maintenance Telescope Systems the telescope time budget GMT-SE-DOC- 0042016. This is the total amount of time ENC-7839: Enclosure The enclosure shall require no more than available for shutdown based on Scheduled Maintenance 12 days per year for scheduled telescope the maintenance time budget Time shutdown maintenance GMT-SE-DOC-00420. The enclosure shall be designed to This is the time allocated in the ENC-7840: Enclosure contribute no more than 8 hours per year maintenance time budget GMT- Down Time toward telescope down time SE-DOC-00420. There are many competing The facility shall be designed to require no operations that must be completed FAC-5141: Facility more than 40 hours per year of daytime during the day and this amount of Daytime Maintenance of maintenance that precludes operation of time is based on the maintenance Telescope Systems the telescope time budget GMT-SE-DOC- 00420. This is the total amount of time FAC-6405: Facility The facility shall require no more than 12 available for shutdown based on Scheduled Maintenance days per year for scheduled telescope the maintenance time budget Time shutdown maintenance GMT-SE-DOC-00420. The facility shall be designed to contribute This is the time allocated in the FAC-6404: Facility Down no more than 5 hours per year toward maintenance time budget GMT- Time telescope down time SE-DOC-00420.

7.2.4 Health and Safety A detailed description of the observatory health and safety requirements, policies and procedures is given in Section 5.11. Driving requirements that flow to the design of the enclosure and facilities are listed in Table 7-5.

Table 7-5. Key Health and Safety Requirements (Level 3 requirement) Requirement ID & Title Requirement Notes The facility shall comply with all Flow down from the System Level FAC-1142: Facility applicable building and safety codes as Requirements and the Operational Compliance to Codes defined in GMT-SE-REF-00229 Concepts Document The facility shall comply with the laser FAC-6554: Facility Laser Laser safety standards per industry safety standards as defined in GMT-SE- Safety Standards and government codes REF-00229 Design safety practices will The facility shall conduct a hazard identify potential safety hazards FAC-7860: Facility analysis to identify and mitigate safety during the design phase to allow Hazard Analysis risks per the GMT Safety Plan GMT-SE- mitigation measures to be DOC-00347 included in the design.

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Requirement ID & Title Requirement Notes Interfaces to the Interlock and FAC-7859: Facility The facility shall provide safeguards and Safety System will be identified Interface to the Interlock interface to the ISS per GMT-2.1_7.0- through the enclosure and and Safety System ICD-00482 facilities hazard analyses The facility shall provide safety Observatories involve unique FAC-1143: Facility enhancements for the unique working circumstances that may not be Personnel Safety environment of an observatory addressed by industry codes.

7.3 Master Plan 7.3.1 General Site Plan The Giant Magellan Telescope will be located on Las Campanas Peak, in the northern region of Chile, approximately 160 km northeast of the city of La Serena. The site is within the Las Campanas Observatory (LCO) boundaries, and owned by the Carnegie Institution of Washington (CIW). The overall site plan of the Giant Magellan Telescope Facilities is shown in Figure 7-6.

The Master Plan describes the site layout, buildings at the summit including the telescope and enclosure building and the summit support building, buildings at the support site including the utilities building, warehouse, water storage facility and lodge, utilities, infrastructure and interactions with LCO.

Figure 7-6. GMT overall site plan Other, non-essential functions are supported by a utilities building, warehouse and lodge located at the support site, near the summit, a few hundred meters lower in elevation. These facilities are far enough away from the summit such that they do not adversely affect the performance of the telescope, but are close enough to support efficient operations work.

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The form and function of the individual buildings and layout of the site were driven by high level requirements related to observatory performance and the infrastructure necessary to adequately support operations and maintenance activities as listed in Tables 5-10 and 5-15 of Section 5.3.2. In particular, the facilities must be designed to minimize heat sources in the vicinity of the enclosure that could migrate into the line-of-sight of the telescope. As such, the structures located at the summit sight are only those necessary to support nighttime science operations and essential daytime operations and maintenance activities. These buildings are oriented on the site to take best advantage of the prevailing wind direction, as shown in Figure 7-6, to direct heat away from the telescope enclosure.

7.3.2 Interaction with LCO An agreement, the “Las Campanas Agreement” between GMTO and CIW was drafted in accordance with the GMTO Founders Agreement. It sets forth the conditions under which GMTO, as a Tenant, may build and operate the Giant Magellan Telescope and associated facilities at LCO and at the LCO headquarters (El Pino) in La Serena. The agreement also describes the services to be provided to GMTO by CIW at cost.

Consideration was given to expanding the current LCO common areas including the hotel, lodge and dining facilities to accommodate the future needs of the GMT staff, during construction and operations. It was quickly determined that space for such an expansion was not available and that the 7 km distance between Las Campanas peak and these facilities would impact operational efficiency. As such, it was decided that all such facilities for GMTO would be constructed at the GMT support site, on the approach road to Las Campanas peak.

The agreement sets forth the conditions on the use of common services including the improvements and maintenance of roads and utilities such as power, water and communications. LCO will be responsible for maintenance of the common infrastructure as well as snow removal from all roadways from the Pan American highway to all summit facilities.

7.3.3 Access to the Site The GMT site is accessible from the Pan-American Highway at km 589, 127 km North of La Serena, Chile. From the highway, an unpaved road connects to Las Campanas Peak as well as LCO. Both the highway and the unpaved road are able to accommodate large vehicles and wide loads.

The existing access road to Las Campanas Peak will be improved and widened in order to accommodate increased traffic and heavy loads. In addition to this renovation work, a new road will also be graded to allow for access to the support site buildings. Providing a separate access road to the support site will reduce vehicular noise that would otherwise have a negative impact on daytime sleeping astronomers at the lodge. Requirements for the access road are listed in Table 7-6.

The minimum width of the main access road and support site loop is 8 meters and its minimum radius is 25 meters. Road grades are kept at 10% maximum for the main access road and 15% for the support site loop. The intersections of the support site loop to the main access road are perpendicular to provide safe turning to and from the main access road. The steep support site loop grade transitions to a relatively flat platform prior to its intersection with the main access road to allow for safe stopping and starting of traffic at these intersections. Both of these grades are manageable by tractor-trailer traffic, large equipment and personal vehicles. The roads will be graded and finished with compact fill to handle heavy loads during construction. At the end of the

ENCLOSURE AND FACILITIES 7–19 GMT SYSTEM LEVEL PRELIMINARY DESIGN REVIEW December 13, 2013 construction period, the main access road will be paved from the support site to summit to minimize dust. An overall site plan showing details of the main access road and support site loop is shown in Figure 7-7.

Table 7-6. Access road design requirements (Level 3 requirement) Requirement ID & Title Requirement Notes The access road shall be designed FAC-1370: Access Road Load to support a load of 50,000 kg Capacity based upon the heaviest Capacity being transported on a tractor delivered part trailer The access road shall have guard FAC-1371: Access Road Guard rails for down-slope banks that are Required for safety Rails demountable to provide clearance for wide loads FAC-1372: Access Road The access road shall have a Required for safety and Maximum Grade maximum grade of 10% maneuvering of large vehicles The access road shall have a Required for maneuvering FAC-1373: Access Road Radius minimum radius of 25 meters oversized vehicles The access road bed shall be rough graded to a width of 8 FAC-1374: Access Road Grading Adequate for two traffic lanes meters from the turnoff of the main road to the support site The access road shall be paved FAC-1375: Access Road Paving between the support site and the To reduce dust during operations summit site

40m R. (Centerline)

55m R. (centerline)

25m R. (centerline) 12m R. & 14mR. (Centerline) 31m R. (Centerline)

8.0m wide Road, typ.

Main Access Road 14m R. (Centerline) LCO Access 14m R. (Centerline) Road Support Site Loop Figure 7-7. Site plan showing summit access road and support site loop

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The roads will be graded such that water will drain to the up-slope side where a ditch will collect the water and allow it to flow downhill. At low spots culverts will collect the runoff and pass it under and away from the road on the down-slope side. A typical road cross-section is shown in Figure 7-8.

Figure 7-8. Typical road cross-section

For the delivery of materials and equipment to Chile during the construction phase, studies currently underway are investigating the available ports for receiving this material by ocean transport. Ports from Valparaiso to Antofagasta are being considered. These studies include investigations of the capacity and resources necessary to offload and temporarily store the material prior to shipment to the site. For the large loads, roadway routes are being analyzed for capacity and clearance to the Pan-American Highway. Also under consideration are the planned roadway construction projects that may take place during the time that materials will be transported.

7.3.4 GMT Facilities The GMTO facilities are divided into two general areas:

 Summit Site Buildings: Buildings located on the summit proper (Las Campanas Peak).  Support Site Buildings: Buildings located near, but off the summit.

7.3.4.1 Summit Site Level 3 requirements for the summit site are listed in Table 7-7.

Table 7-7. Summit site design requirements (Level 3 requirement) Requirement ID & Title Requirement Notes The summit site shall be laid out to FAC-5805: Summit Future Requirement derived from a GMT permit the construction of a second Expansion Board action telescope at some future date FAC-6005: Summit The summit site shall maximize the use To minimize the ground thermal Ground Cover Thermal of fast thermalizing materials for ground effects on image quality Control cover FAC-6006: Summit The summit site shall provide dust- To minimize dust buildup on Ground Cover Dust minimizing ground cover surfaces for equipment and optics Control heavy traffic areas

Two large structures are located at the summit site; the enclosure building and the summit support building.

After completion of construction of the summit buildings, the site will be covered with a gravel ground cover to provide fast thermalization of the site and minimize the migration of dust. The

ENCLOSURE AND FACILITIES 7–21 GMT SYSTEM LEVEL PRELIMINARY DESIGN REVIEW December 13, 2013 southeast side of the site is set aside for the development of a future telescope. A summit site plan is given in Figure 7-9.

7.3.4.1.1 Enclosure Building The enclosure building is sited as far northwest on the summit site as possible, but with enough clearance to allow vehicular movement around the building both during construction and operations. The enclosure houses the telescope and consists of the rotating enclosure, fixed enclosure base and telescope pier. Vehicular access to the site is near the southwest of the summit site, preventing vehicles from arriving at the site near the enclosure building, minimizing traffic and related dust. A detailed description of the design of the enclosure building is provided in Section 7.4.

7.3.4.1.2 Summit Support Building The summit support building is located at the center of the summit site, between the enclosure building and the location of the possible future telescope as shown in Figure 7-9. The building consists of the facility building, auxiliary building, and equipment building. It houses functions critical to the day-to-day operations of the GMT. A detailed description of the design of the summit support building is provided in Section 7.5.

Figure 7-9. Summit site plan

The summit support building is located a distance of over 40 meters from the enclosure. Much of the equipment generating waste heat in this building has been placed in the predominantly downwind (south) side of the building and as such, approximately 80% of the time, wind carries this waste heat directly off the summit. The orientation of the buildings on site was chosen to take

ENCLOSURE AND FACILITIES 7–22 GMT SYSTEM LEVEL PRELIMINARY DESIGN REVIEW December 13, 2013 advantage of the predominant wind direction (NNE). The summit support building is offset from the enclosure in a direction perpendicular to the direction of the predominant winds, thus the likelihood that waste heat will flow toward the enclosure and adversely affect telescope performance is very small. A detailed discussion of analyses performed to demonstrate that the thermal performance of the summit site meets its requirements is presented in Section 7.8.

7.3.4.1.3 Facility Building The Facility Building provides space for observatory administrative & technical staff as well as visiting scientists. The control room and electronics rooms are located on the west side of the building, facing the enclosure. Lab and clean room space are provided for assembling and maintaining optics and instrumentation and these rooms are located in close proximity to M2 and instrument areas of the auxiliary building. The building also includes offices, a conference room, medical room and a common area. Architectural features provide occupants with protection from the wind and precipitation at its entrances. Space is provided to the north of the building for vehicular circulation during telescope operations.

7.3.4.1.4 Auxiliary Building The Auxiliary Building provides several high bays that will initially be used for the assembly, integration and testing of the primary mirror assemblies, secondary mirror assemblies and instruments during construction. It houses the coating facility including the coating plant and mirror washing and stripping area.

Figure 7-10. Auxiliary building location relative to the enclosure and future telescope

Separate bays are also provided for the M2 calibration system and instrument maintenance. The auxiliary building is sited directly between the center of the enclosure and the location of the future telescope. The site includes fixed rails that connect the auxiliary building to the enclosure base, ENCLOSURE AND FACILITIES 7–23 GMT SYSTEM LEVEL PRELIMINARY DESIGN REVIEW December 13, 2013 allowing the primary mirror cells and instruments to be easily transported between the buildings on wheeled carts. Expansion to accommodate a future telescope was taken into consideration when siting this building. A sketch showing the location of the auxiliary building relative to the enclosure building and future telescope is given in Figure 7-10.

7.3.4.1.5 Equipment Building The Equipment Building houses the major mechanical and electrical equipment required to support the GMT. It provides space for the hydrostatic bearings pumps and oil tank, vacuum pumps and helium compressors for the mirror coating chamber, air compressors and chillers for the primary mirror support and temperature control systems and building HVAC equipment. The main electrical distribution equipment for the summit site is also located within this building. Space is provided to the south of the equipment building for vehicular circulation during telescope operations. Underground utilities (electrical power, fiber optic cables, chilled water, compressed air, etc.) are routed to the equipment building from the support site and between the equipment building and the enclosure. The location of the equipment building is shown in Figure 7-9.

7.3.4.1.6 Weather Tower and DIMM System Level requirements listed in Table 5-43 state that the summit site shall include a weather tower and an atmospheric seeing and turbulence monitor (MASS/DIMM). The preliminary location of these sensors is shown in Figure 7-11. They are located on the windward side of the site in an area between the enclosure and summit support buildings. The weather tower is 100 feet tall, well outside of the boundary layer over the summit site. At its current location, the MASS/DIMM has an unvignetted view of the sky at any azimuth angle within a zenith angle of approximately 35 degrees. A detailed description of the environmental monitoring system is provided in Section 5.4.2.3.

Figure 7-11. Summit site plan showing the location of the weather tower and MASS/DIMM

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7.3.4.1.7 Enclosure Ventilation System The enclosure ventilation system consists of ventilation fans and exhaust ducts that are used to remove waste heat from multiple sources within with the enclosure building. Exhaust air from the enclosure building is pulled through an above grade ventilation duct and exhausted off the summit site to the west. The ventilation equipment location and exhaust direction has been determined through computational fluid dynamics analysis as described in Section 7.8. Figure 7-12 shows the location of the exhaust fans and ventilation duct.

Figure 7-12. Enclosure ventilation system

7.3.4.2 Support Site The support site is located below the summit and will house several structures and facilities including the following:  Utilities building  Electrical yard  Fuel station and tank yard  Warehouse

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 Water storage facility  Lodge o Dormitory o Dining hall o Recreation facility

The support site buildings take advantage of a natural depression on the southwestern face of Las Campanas Peak. The site layout separates industrious functions from private functions. The industrious functions are associated with operations and maintenance activities and are housed in the utilities building, warehouse, and water storage facility. The private functions are housed at the lodge, which includes dining, recreation, and a dormitory. As a result, the support site is configured in multiple tiers, allowing a physical separation between the different functions. The location of the support site is shown in the overall site plan in Figure 7-6.

7.3.4.2.1 Utilities Building and Warehouse The Utilities Building and Warehouse are sited on a common building pad located just above the lodge. The general layout of these buildings is shown in Figure 7-13. A single access road, with adjacent parking, is provided between the buildings. Open space at the end of the site pad has been reserved for the fuel station, fuel tank yard, and future building expansion/laydown. Adequate space is provided for large vehicle turnaround and maneuvering. The warehouse will initially store the primary mirror segments in their shipping containers until they are ready for integration into their cells. During operation, the warehouse will serve as a general storage area for spare parts, carts, handling fixtures and other equipment.

The utilities building includes a mechanical fabrication shop and a vehicle maintenance area. Office space for maintenance management and desk/countertop areas for maintenance technicians is also provided. The main electrical service from the commercial provider terminates at the electrical yard outside of the utility building and electrical power is distributed to the site from an electrical room within the building.

A detailed description of the design of the utilities building and warehouse is given in Section 7.6.

Figure 7-13. Utilities building and warehouse

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7.3.4.2.2 Lodge A lodge, consisting of a dormitory, dining hall and recreation facility will be provided to support the operations staff. The design for the lodge facilities has not yet begun (Stage 2A activity). A location for these structures has been defined in the Master Plan and infrastructure necessary to support the space, electrical power, water and septic system has been provided.

7.3.4.2.2.1 Dormitory Requirements The staffing plan17 was used to determine the capacity requirements for the dormitory. Driving requirements for the dormitory are listed in Table 7-8.

Table 7-8. Key design requirements for the lodge (Level 3 requirement) Requirement ID & Title Requirement Notes The support site shall include a dormitory FAC-1360: Dormitory that is detached from other support Location optimized for daytime Location buildings and away from noise sleepers generating areas The dormitory shall have 22 rooms that FAC-1362: Dormitory share a bathroom between 2 rooms (22 The staffing plan includes 75 Capacity m2) and 60 rooms with private bathrooms overnight staff and visitors (26 m2). FAC-1366: Dormitory The dormitory shall provide rooms that Room Construction have construction standards similar to the Standard existing LCO dorms

The GMTO staff will operate on shifts and the dormitory will have to support both day and night sleepers. As such, the dormitory buildings are located away from the access roads and active maintenance areas such as the utilities building. The architectural style of the buildings will be similar to that of the existing LCO dormitory buildings consisting of detached structures with a small number (4-6) of individual units per building.

7.3.4.2.2.2 Dining hall & Recreation Facility Requirements Level 2 requirements for staff support include the specification of requirements for a dining hall and recreation facility to support the on-site operations staff and visitors. Driving requirements for the dining hall and recreation facility are listed in Table 7-9.

Table 7-9. Dining hall and recreation facility requirements (Level 3 requirement) Requirement ID & Title Requirement Notes The support site shall include a dining FAC-6205: Dining Hall hall with all facilities for food storage Location and preparation FAC-1357: Dining Hall The dining hall shall serve up to 80 The staffing plan includes 80 Capacity persons daytime staff and visitors FAC-1358: Dining Hall The dining hall shall include office space Administrative support Offices for the kitchen staff The dining hall shall include a seating FAC-1356: Dining Hall area with space and furnishings to seat 64 Maximum mealtime capacity Seating persons FAC-1359: Dining Hall The dining hall shall include a recreation

Recreation Room room with furnishings

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7.3.4.2.3 Water Storage Facility The requirements for the water storage facility are driven by building code requirements associated with the design of the support site buildings.

The water storage facility (Figure 7-14) is located at the mid-level point between the summit site and support site as shown in Figure 7-6. The facility houses two exterior water tanks and a mechanical room. The equipment in the mechanical room receives water from the summit site and prepares it for transfer to the support site. The location of the water storage facility has been established using the natural terrain elevation difference to achieve the required water pressures of the domestic and fire water supply lines.

Figure 7-14. Water storage facility

7.3.5 Utilities and Services Infrastructure Requirements for the permanent utilities and services infrastructure are largely derived from the designs of telescope, buildings and functions of the observatory. Existing utilities infrastructure at LCO will be used to the extent possible including:

 The main electrical power feed to the observatory will use the existing LCO power line path and structures to the extent possible. Any upgrades necessary to supply GMT with permanent electrical power needs will be based on modifications to the existing LCO infrastructure if practical.  Domestic and fire protection water will be obtained from the existing LCO well.  Fiber trunk lines for communications will tap into existing LCO infrastructure.

An overall site plan showing the elements of the infrastructure is given in Figure 7-15.

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Figure 7-15. Permanent site infrastructure

7.3.5.1 Electrical Power Feed The permanent electrical power feed to the observatory will originate at the interface between the LCO power and the Chilean electrical power infrastructure adjacent to the Pan-American Highway. The electrical demands of GMT will require an increase in the conductor size and density of utility poles between the Highway and LCO. A new power line will be constructed between LCO and the GMT support site at the electrical yard adjacent to the utilities building. The new line will follow the LCO access road to the west slope of Las Campanas peak, then south and around the GMT access road to the support site.

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7.3.5.2 Electrical Distribution The point of connection for the electrical power feed will occur at the utilities building. Electrical power lines will enter overhead to a pad-mounted switch and transformer. From this equipment it will be fed to medium voltage rated switchgear and then to the remainder of the summit site and support site buildings via underground lines. A detailed description of electrical distribution is provided in Section 7.7.6.

7.3.5.3 Water Water for domestic and fire water use will originate from the existing underground concrete water storage tank located at the summit. This water will be pumped to holding tanks at the summit support building and water storage facility locations. A detailed description of water distribution is provided in Section 0.

7.3.5.4 Domestic Sanitary Waste No existing sanitary waste infrastructure exists on site so this infrastructure will be added as part of GMT construction. Domestic sanitary waste will pass through aerobic waste treatment tanks and then the effluent will be discharged into leach fields

7.3.5.5 Communications The point of connection for the communications feed will occur at the utilities building. Fiber optic lines will enter overhead to a communications room within the utilities building. From there fiber optics lines will be distributed to the remainder of the summit site and support site buildings via underground conduit. A description of network and communications infrastructure is provided in Section 7.7.7.

7.3.5.6 Fuel Fuel for the backup generators and vehicles is stored and dispensed at the fueling station and tank yard located adjacent to the utilities building as shown in Figure 7-9. A description of the fuel storage infrastructure is provided in Section 7.7.4.

7.3.5.7 LN2

A concrete pad will be provided adjacent to the auxiliary building to allow a Liquid Nitrogen (LN2) storage tank to be installed by a contractor after construction is complete. A description of the LN2 infrastructure is provided in Section 7.7.5.

7.3.5.8 Subsurface Utilities Subsurface utilities are routed from the support site to the summit site through the use of a common underground utilities trench. These utilities include domestic water, fire suppression water, fiber optic cables (in conduit), spare fiber optic conduit, electrical power cables (in conduit), and spare power conduits. All utilities are direct bury and are concrete encased at all road crossings. Figure 7-16 shows a typical section through a subsurface utilities trench.

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Figure 7-16. Utility trench section

7.3.5.9 Guardrails Vehicular guardrails are provided at all fill boundaries and at cut conditions where the embankment is less than 0.9 meters in height. Guardrails will be installed after all construction has been completed. This will allow wider construction vehicles to have unhindered access to the summit site and eliminate potential damage during the construction phase. See Figure 7-8 for a cross section of the access road, including guardrails.

7.3.5.10 Signage Signage will be provided per local highway and transportation code requirements. All signage will be installed after construction on the summit site has been completed. Temporary signage will be utilized as required during construction. 7.4 Enclosure Building As telescopes grow in size, with correspondingly more demanding performance specifications, the task of providing an enclosure becomes more challenging. The enclosure structure must adequately protect the telescope from the sometimes extremely severe environmental conditions when closed and sealed. It must also minimize the effects of thermal and wind flow conditions that impact telescope performance during science operations. The structure needs to be large, and yet also needs to rotate at rates comparable to less massive enclosures for smaller telescopes. There are functional requirements associated with servicing the telescope and instruments that have to be satisfied for increasingly complex systems. Ease of erection and the availability of materials and skilled labor in the host country are also considerations. The enclosure represents a significant fraction of the total cost of the project, and must be designed to minimize costs.

Trade studies18 during the initial phase of the project resulted in the decision to use a cylindrical carousel type of enclosure. The carousel was chosen based on the following:

 Efficient use of structural materials and insulated panels  Use of standard and universal construction techniques  Ease of implementing shutter and ventilation door concepts  The ability to accommodate an enclosure crane which is necessary for servicing the primary mirror assemblies as well as other components of the telescope.

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An overall view of the enclosure building is shown in Figure 7-17.

Figure 7-17. GMT enclosure building

The telescope and enclosure are designed to rotate freely and independently from one another. The principal reason for having independent motion between the telescope and enclosure is to allow for greater flexibility in servicing primary and secondary mirrors using handling equipment built into the enclosure.

The enclosure building includes the following major components:  Enclosure  Enclosure Base  Telescope Pier

The enclosure is the large rotating structure that surrounds the telescope. It provides a closed and sealed environment to protect the telescope during the day or in bad weather and an unobstructed aperture for the telescope to observe through during science operations.

The enclosure also has active and passive provisions for ventilation during night-time operations. The active provisions include a forced ventilation systems to flush hot and stagnant air from several areas of the enclosure, enclosure base, and telescope pier. The passive ventilation system includes the use of large doors in the enclosure walls to promote controlled movement of ambient air through the enclosure.

The fixed enclosure base provides support for the rotating enclosure. The enclosure base serves many functions. It acts as a track and foundation for the rotating enclosure, provides the observing floor level for maintaining and servicing the telescope and houses critical ventilation and electrical systems. Within the enclosure base is the reinforced concrete telescope pier. The telescope pier serves as an isolated foundation for the telescope as well as a connection point for telescope related utilities.

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7.4.1 Architectural Design 7.4.1.1 Enclosure Geometry The overall geometry of the enclosure is largely defined by the requirements listed in Table 7-10.

Table 7-10. Geometric requirements for the enclosure (Level 3 requirement) Requirement ID & Title Requirement Notes To optimize synchronized rotation The enclosure z-axis (center of rotation) ENC-0310: Rotation Axis of the enclosure and the telescope shall be coincident with the pier z-axis Centration and avoid the enclosure and within 10mm telescope being eccentric. The enclosure design shall enable the Conceptual studies showed that Telescope to rotate independently and the cost of co-rotating and non-co- ENC-0311: Enclosure Free freely within the telescope swept volume rotating enclosures were similar Rotation defined in drawing GMT-7.3- and the operational constraints on ASY_40216 per ICD GMT-7.0_4.1-ICD- co-rotating enclosures would be 00512 significant To be able to track the telescope in ENC-0398: Enclosure The enclosure shall provide unlimited both directions and for unlimited Rotation Range range of bidirectional rotation in azimuth number of rotations. The enclosure shall provide a minimum Provides clear access to the pier ENC-9078: Enclosure clearance to the ground level of 8.0 portal and main hatch loading Ground Clearance meters. area. The enclosure shall provide the minimum clearances defined on drawing GMT- 7.3.3-ASY_40220 per ICD GMT- To provide a clear aperture ENC-0314: Shutter 7.0_4.1-ICD-00512 between the through the enclosure (with Opening Line-of-Sight projected pupil and the enclosure shutter margin) for all telescope viewing Clearance opening through the full range of angles. telescope elevation.

The enclosure is designed to allow free movement of the telescope, without restriction within the enclosure. This requirement imposes dimensional restrictions on the overall size of the enclosure, the location of the enclosure crane and any fixed structures on the observing floor.

The telescope elevation axis is at a height of 22.5 meters above grade. This height was determined to be adequate to avoid turbulence near the ground level (see Section 7.8 for a summary of enclosure wind tunnel testing and CFD analyses performed to establish adequate wind flow performance). The observing floor elevation is 11.80 meters above finished grade. At this height, there is sufficient room beneath the observing floor to perform all functions associated with handling and transport of primary mirror assemblies and instruments. A cross-sectional view of the enclosure and Telescope is provided in Figure 7-21 for reference.

The swept volume of the telescope includes a 1.5 meter clearance beyond the telescope structure. The clearance around the zenith pointing position of the telescope has been increased to 2.0 meters to provide additional room for secondary mirror handling operations. The telescope requires a clear aperture within an elevation range from zenith down to 30° above horizon. These viewing angle requirements, along with the telescope aperture width, determine the shutter size. The vertical shutters were also inclined 10° in order to clear the telescope’s swept volume. See Figure 7-18 for the telescope swept volume (shown in blue) within the enclosure.

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Figure 7-18. Telescope swept volume

To accommodate optical path clearance requirements, the minimum shutter width has been defined as 26.2 meters. A 1.25 meter clear space on each side of the aperture for access ways has been added to the 26.2 meter aperture width to provide clearance for allowing the enclosure to track telescope motion in a jog mode. These requirements determined the vertical and horizontal shutter lengths and widths and dictate where fixed and moving structural members can be placed. See Figure 7-19 for a sketch showing extent of the telescope viewing angles (shown in blue).

Figure 7-19. Telescope viewing angles

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7.4.1.2 Enclosure Design 7.4.1.2.1 Structural Arrangement The enclosure is the upper rotating portion of the enclosure building and is centered on the azimuth axis of the telescope. The enclosure is supported largely by four super columns with two of these columns framing the vertical shutter opening and the other two at the back of the enclosure. These columns act as anchor points for structural steel and support the horizontal and vertical shutter assemblies. Secondary columns are positioned between the super columns. All columns are attached to the rotating ring girder at the base of the enclosure. Beneath each super column is an azimuth drive bogie. Idler bogies have been provided below secondary vertical structural members to transfer loads to the stationary ring girder. The super columns are massive elements with a closed cross-section. In an effort to minimize the detrimental effects of exposed thermal mass of these columns, they are completely wrapped with galvanized 75mm thick insulated panels and are actively ventilated. Refer to Figure 7-20 for the location of the super columns, secondary vertical structural members, and the rotating ring girder.

Figure 7-20. Enclosure super columns and secondary vertical structural members

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The enclosure has independently movable horizontal and vertical shutter doors. The horizontal shutter is constructed using two door panels and the vertical shutter has three panels. The shutters, when open, provide the telescope an unobstructed view of the sky. The enclosure is 61.75 meters high. This is driven by the telescope swept volume and ground clearance requirements, the structural depth of the horizontal shutters, and the enclosure crane clearance requirements. A cross-sectional view of the enclosure is given in Figure 7-21.

Figure 7-21. Enclosure section

7.4.1.2.2 Mechanical Corridor Mechanical and electrical equipment used to drive a structure of this magnitude inevitably generate a significant amount of heat. To manage this heat, all mechanisms and electrical equipment related to enclosure movement have been isolated from the telescope chamber by implementation of a mechanical corridor. The mechanical corridor is lined entirely with galvanized 75mm insulated panels. The mechanical corridor provides a means for the active ventilation system to capture the heat from these sources and pull it away from the enclosure and telescope optical path. Refer to Figure 7-22 for the location of the mechanical corridor and Figure 7-23 for a sectional view of the mechanical corridor. See Section 7.7.1.2 for further information on the ventilation system for the enclosure building.

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Figure 7-22. Enclosure mechanical corridor location

Figure 7-23. Mechanical corridor section

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7.4.1.2.3 Vertical Shutter Overall requirements for the layout and design of the vertical shutter are listed in Table 7-11. Additional requirements for shutter motion as well as the details of mechanical design aspects of shutter mechanisms to meet these requirements are given in Section 7.4.3.2.

Table 7-11. Overall requirements for the vertical shutter (Level 3 requirement) Requirement ID & Title Requirement Notes The enclosure shall provide the minimum clearances defined on drawing ENC-0314: Shutter GMT-7.3.3-ASY_40220 per ICD GMT- To provide a clear path for the Opening Line-of-Sight 7.0_4.1-ICD-00512 between the telescope through its entire range Clearance projected pupil and the enclosure shutter of motion with margin. opening through the full range of telescope elevation Adequate to maintain daytime ENC-9632: Vertical The vertical shutter panels shall be telescope chamber air Shutter Insulation insulated to an R value of 20 temperature within required limits

The vertical shutter consists of three individual shutter panels. See Figure 7-24 for the location of the vertical shutter panels. The panels are raised and lowered synchronously so that each panel travels together with the other panels until their desired position is reached. Sequencing the shutters in this manner allows the doors to act together as one structural unit. This sequencing is required to properly share the forces necessary to pull the front super columns into their plumb positions should any deformation due to temperature gradients, occur within the enclosure structure.

Each of the three panels is 11.6 meters high by 31.2 meters wide and 1.2 meters deep. They are constructed of out of a series of parallel trusses that are arrayed vertically. The panels are covered by insulated metal wall panels with an insulation R value of 21. The doors are inclined at 10 degrees to stay outside of the telescope swept volume. The estimated weight of each shutter panel is 42,200kg.

Counterweights are provided to reduce the power required to open and close the shutters and a series of winches are utilized to open and close the shutter panels. The winches are sized to accommodate the difference between the weights of the shutter panels and the counterweights in addition to friction forces. A detailed description of the vertical shutter mechanisms is given in Section 7.4.3.3.

An emergency generator is used to provide power to close the shutters in the event that either main commercial power or main backup generator power is not available.

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Figure 7-24. Isometric view of the enclosure showing shutter panels and wind vents

7.4.1.2.4 Horizontal Shutter Overall requirements for the layout and design of the horizontal shutter are listed in Table 7-12. Additional requirements for shutter motion as well as the details of mechanical design aspects of shutter mechanisms to meet these requirements, is given in Section 7.4.3.4.

Table 7-12. Overall horizontal shutter requirements (Level 3 requirement) Requirement ID & Title Requirement Notes The enclosure shall provide the minimum clearances defined on drawing GMT-7.3.3.4-ASY_40220 per ICD ENC-0314: Shutter To provide a clear path for the GMT-7.0_4.1-ICD-00512 between the Opening Line-of-Sight telescope as laser beam with projected pupil (including laser Clearance some margin. launcher) and the enclosure shutter opening through the full range of telescope elevation The enclosure horizontal shutters top ENC-0410: Peaked Roof To control rain run-off and snow surface shall be sloped to promote rain (Horizontal Shutter) melt run-off and snow melt ENC-8081: Enclosure The enclosure shall provide a system to To control rain run-off and snow Rain/Snow Drainage carry away the water away from the melt (Roof) opening above the telescope

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Requirement ID & Title Requirement Notes Adequate to maintain daytime ENC-9631: Horizontal The horizontal shutter panels shall be telescope chamber air Shutter Insulation insulated to a minimum R value of 20 temperature within required limits

The horizontal shutters consist of two individual shutter panels. Refer to Figure 7-24 for the location of the horizontal shutter panels. The horizontal shutter panels are identified as:  Horizontal Upper Shutter  Horizontal Lower Shutter

The two horizontal shutter panels reside on the top of the enclosure, and act as an operable roof above the telescope. Each shutter spans 30.5 meters and is 19.6 meters in length, with a structural depth of 3.5 meters. The two shutter panels open by sliding toward the back of the enclosure. In the open position, the upper panel rests directly above the lower panel, which in turn rests on fixed structure extending beyond the back of the enclosure roof. The horizontal lower shutter panel rides on the enclosure itself, and the horizontal upper shutter panel rides on the horizontal lower shutter and enclosure.

The vertical faces of the horizontal shutter doors are clad with 75mm thick insulated metal panels. The horizontal faces are clad with a standing seam roof over a 100mm thick rigid insulation board, and are fastened to structural decking. These panels are adequate to meet the structural and thermal design requirements. In the closed position, the horizontal upper shutter cantilevers past the front super columns enough to cover and provide a weather tight compression seal against the vertical upper shutter. The roof is sloped to promote runoff of rain and melting snow and ice.

The horizontal shutters can fully open or close in three minutes using a friction drive system. Electrical power and control signals are accommodated via the use of a common collector (“slip ring”) mounted on both shutters. An emergency generator is used to provide power to close the shutters in the event that either mains power or main backup generator power is not available.

7.4.1.2.5 Wind Vents Overall requirements for the design of the wind vents are listed in Table 7-13.

Table 7-13. Enclosure wind vent design requirements (Level 3 requirement) Requirement ID & Title Requirement Notes The enclosure shall provide openings through the wall structure of the ENC-0436: Enclosure To provide adequate flushing and enclosure to promote wind-forced Wind Vents (general) air flow control ventilation of the interior structure for all azimuth rotation angles ENC-0440: Enclosure The enclosure shall provide a secondary To protect the telescope in adverse Wind Vents Emergency means of closing the wind vents in case weather condition in case of a Closure of a primary system failure system failure ENC-9677: Enclosure The enclosure wind vents shall operate in Enclosure maximum operational Wind Vent Operational winds up to 25 m/s wind speed plus margin Wind Speed

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Requirement ID & Title Requirement Notes The enclosure shall provide This is derived from the independently operated wind vents with requirement for active control of ENC-0447: Wind Vent four discrete opening configurations: the vents to regulate air flow Positioning 25% open, 50% open, 75% open, and through the enclosure, but the 100% open. exact positioning is not critical ENC-0444: Enclosure The enclosure wind vents shall have the Best-practices. To optimize the Wind Vent Minimum maximum time to open or close of one total operation time Speed minute.

Thirty percent of the total wall area of the enclosure can be opened and fully controlled to allow for natural ventilation through the enclosure chamber. This amount of ventilation area, as distributed over the enclosure walls, provides sufficient ventilation of all internal areas of the enclosure as demonstrated by wind tunnel testing and CFD analysis (see Section 7.8). This passive ventilation system consists of 116 insulated, coiling roll-up doors provided throughout the enclosure at multiple elevations. Each door can be individually operated resulting in a very versatile ventilation system. Coiling doors were chosen due to their common availability and performance. See Figure 7-25 for images of the wind vents in both the open and closed position.

Some common features of commercially available coiling doors include the following:  Custom insulated hurricane-rated  Insulation Value: R5, insulated with expanded polystyrene foam within the door slats  Curtain: Interlocking galvanized steel slats  Hood: Galvanized steel with vinyl weather baffle  Guides: Formed U-channel steel guides with vinyl weather-strip  Bottom Bar: Two steel angles with vinyl weather-strip

Figure 7-25. Enclosure wind vents

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Several different sizes of wind vents are needed as a result of the geometry of the enclosure structure, door width restrictions imposed by the high wind loading conditions on the site and height restrictions as a result of the required door opening times. The maximum time to open and close the wind vents is one minute. The wind vents are controllable to allow the open positions of 100% open, 75% open, 50% open, and 25% open. This allows the airflow through the enclosure to be optimized for minimal telescope windshake and adequate flushing of the telescope chamber.

The clear opening sizes are as follows:  4.6m x 5.0m (x6)  4.0m x 4.5m (x64)  4.8m x 4.5m (x32)  5.5m x 4.5m (x14)

Other door systems such as large steel bi-folding and fabric folding/stack-up doors were also considered. The large steel bi-folding doors studied for use on the GMT provided superior insulation values and sealing capabilities, but were deemed unsuitable due to their adverse effects on wind through the enclosure and localized uplift effects created when in the open position. The fabric folding/stack-up doors studied for use on the GMT provided great resilience against wind pressures in the fully open and fully closed positions, but were deemed unsuitable due to their lack of stability in partially open conditions and lack of thermal insulation.

7.4.1.3 Enclosure Base Design Specific requirements for the design of the enclosure base are listed in Table 7-14

Table 7-14. Enclosure vase design requirements (Level 3 requirement) Requirement ID & Title Requirement Notes To minimize vibration transmission between the ENC-0553: Enclosure Base The enclosure base shall be mechanically enclosure base and the telescope Telescope Pier Isolation isolated from the telescope pier pier and between the observing floor and the telescope The enclosure base shall include a main For removing a primary mirror hatch through the observing floor as assembly zenith facing with the ENC-0549: Enclosure Base specified on drawing GMT-7.3.1- overhead crane. Telescope parts Main Hatch ASY_40214 per ICD GMT-7.0_4.1-ICD- will be brought through hatch 00512 during construction The enclosure base shall provide a sealed ENC-0551: Enclosure Base To maintain control of telescope interface to the enclosure base elevator Access Airlock chamber air temperature and stairways To provide adequate air flow The enclosure base shall provide open ENC-0554: Enclosure Base below the observing floor, areas below the observing floor to allow Wind Flushing resulting in an improvement in the natural wind flushing under the enclosure enclosure thermal performance This requirement is derived from The enclosure base shall include a sealed the conceptual design to meet the ENC-0538: Enclosure Base wind shield that is isolated from the pier imaging specification for Wind Shield and extends from the observing floor to vibrations caused by windshake the grade level and mechanical vibration.

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Requirement ID & Title Requirement Notes ENC-9694: Temporary The Enclosure Support Structure shall be To provide a high capacity staging Support of Telescope designed to provide temporary support of area for heavy telescope parts Components During telescope components during the erection during the erection of the Assembly of the telescope structure. telescope structure. This is the building code ENC-0537:Enclosure The observing floor shall have the prescribed uniform live load Support Structure Uniform capacity to support a uniform live load of requirement for activities typically Load 488 kg/m^2 conducted on the observing floor. The observing floor shall have the Pallet trucks are used to move ENC-10538: Observing capacity to support 2500 kg capacity relatively light equipment to any Floor Pallet Truck loading pallet trucks area of the observing floor.

The enclosure base is the fixed structure that provides support for the rotating enclosure. It also provides access to the telescope pier and incorporates a wind screen to protect the telescope pier from vibrations induced by direct exposure to the wind. Fixed rails are provided to allow the transportation of mirrors, instruments, and equipment from the telescope pier to the auxiliary building. An overall view of the enclosure base, identifying its major components is given in Figure 7-26.

Figure 7-26. Enclosure base isometric

Access to the observing level as well as upper portions of the telescope pier is provided by a stairwell & elevator shaft located within the southeastern portion of the enclosure base at the enclosure main entrance. The elevator is a 1,815 kg capacity, passenger-type elevator for day to day personnel use and for conveying small equipment and tools. Parking is provided directly adjacent to the entrance. A receiving area which includes a dock lift for lowering cargo to grade level is also provided. An ice canopy constructed from structural steel clad with metal grating is used to protect personnel and vehicles against falling ice that might have adhered to the enclosure during inclement weather.

Enclosure utilities (plumbing, electrical & communications) enter the enclosure base on the north side of the main entrance. An electrical room is accessible from within the entrance at grade level, or via a pair of doors on the north side. The electrical room houses electrical switchgear and distribution equipment, provides a communications termination point, and contains several load

ENCLOSURE AND FACILITIES 7–43 GMT SYSTEM LEVEL PRELIMINARY DESIGN REVIEW December 13, 2013 centers pertinent to smaller loads throughout the facility. A utility chase runs the entire length from grade level up to the observing floor and provides an organized routing location for all enclosure utilities. See Figure 7-27 for a grade level floor plan of the enclosure base.

Figure 7-27. Enclosure base - grade level plan view

The observing floor is located at 11.8 meters above grade and is the stationary floor open to the enclosure structure and telescope. See Figure 7-28 for a floor plan of the observing floor level. The floor consists of stiffened ¼” steel plate decking with a capacity of 488 kg/m². The observing floor is additionally reinforced locally (small area) to satisfy requirements for higher floor loading needed for staging instruments and other activities in specified areas. The decking is insulated underneath to prevent thermal infiltration of heat from the outside. There is a gap between the fixed observing floor and the rotating telescope azimuth disk that incorporates a seal to prevent air infiltration. The observing floor and the top surface of the telescope azimuth disk floor are at the same elevation.

The observing level houses a temporary control room and single-occupancy restroom. The temporary control room is used during telescope and instrument commissioning and engineering activities. Space has also been reserved for the following equipment:  Enclosure base floor hatch (x2 pieces stacked)  Heavy loading/staging space  Fixed boom lift  Telescope main truss

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Figure 7-28. Enclosure base - observing floor level plan

A 10.5 meter square enclosure base hatch is located at the southeast area of the floor. It is flush with the observing level when closed. The floor hatch is sized to accommodate the handling of the primary mirror assemblies during the mirror coating process. All large instruments and equipment in the telescope chamber are hoisted through the enclosure base hatch with a 65-ton capacity enclosure crane mounted at the top of the enclosure structure.

7.4.1.3.1 Enclosure Active Ventilation System The need for an active ventilation system is defined by the following requirement.

ENC-0336: Heat Waste - The enclosure shall trap and remove excess waste heat generated by active sources inside the enclosure.

The enclosure active ventilation system traps and exhausts hot air from several areas within the enclosure building. Heat generated by the enclosure drive systems, as well as latent heat stored in the enclosure’s structure and telescope pier is drawn downward by two fan arrays located within a large air handler outside of the enclosure building. Exhaust air is pulled through two insulated ventilation ducts; a large rectangular duct evacuates air from the mechanical corridor and super columns, while a smaller duct pulls air from the interior of the telescope pier. This air is pulled to an exhaust point approximately 70 meters west of the telescope pier center point. The exhaust point location was determined to be most ideal based on prevailing wind patterns and Computational Fluid Dynamics (CFD) analysis. See Figure 7-29 for a site plan showing the main

ENCLOSURE AND FACILITIES 7–45 GMT SYSTEM LEVEL PRELIMINARY DESIGN REVIEW December 13, 2013 ventilation duct and Figure 7-30 for an image of the isometric view of the ventilation duct and fan array. A detailed description of the ventilation system is provided in Section 7.7.1.2.

Figure 7-29. Ventilation duct location / site plan

Figure 7-30. Ventilation duct and fan array isometric

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7.4.1.4 Telescope Pier Driving requirements for the design of the telescope pier are listed in Table 7-15.

Table 7-15. Telescope pier design requirements (Level 3 requirement) Requirement ID & Title Requirement Notes The telescope pier shall interface to the The pier must interface with the telescope structure and set the vertical ENC-1158: Pier Interface telescope and enclosure position of the telescope per drawing to Telescope subsystems and set the vertical GMT-7.3.1-ASY_40204 per ICD GMT- position of the telescope. 7.0_4.1-ICD-00512 The telescope pier shall have a design modal performance of greater than or ENC-1151: Pier Modal equal to 10 Hz with an infinitely stiff Derived to meet image quality Performance mass representing the telescope and the requirements. expected soil properties of the site considered The telescope pier shall provide an DG instruments are installed opening through the side at ground level using the pier lift located inside and aligned with the summit rail system ENC-3352: Pier Portal the pier. The portal is also sized in accordance with drawings GMT- to allow M1 assembly and GIR 7.3.1-ASY_40208, per ICD GMT- disks to pass through 7.0_4.1-ICD-00512. The telescope pier shall include an opening to allow vertical passage of the DG instruments are installed ENC-1155: Pier Vertical pier lift platform per drawing GMT- using the pier lift located inside Opening 7.3.1.1-ASY_40205 per ICD GMT- the pier. 7.0_4.1-ICD-00512

The telescope pier is the fixed cylindrical concrete structure at the center of the enclosure that supports the telescope. It is physically detached from all other structures to maintain mechanical vibration isolation from the rest of the enclosure building. The telescope pier structural design and modal performance is discussed in Section 7.4.2.7 and Section 6.5.

At grade level, the pier is accessible via a set of double doors in the pier wind screen. This provides access to the inner pier as well as the interstitial space between the pier and skirt as shown in Figure 7-27. Equipment access to the pier is provided by a large folding fabric door through the pier skirt and then through a portal in the concrete pier. The Pier Lift Platform (PLP) is located at the center of the pier. It provides a means for conveying Direct Gregorian instruments to the GIR and equipment to the various levels of the pier. The skirt door and portal were sized to meet the volumetric interface requirements associated with moving primary mirror assemblies, instruments and the GIR structure into the interior area of the pier.

Additional pier workspace above grade is provided at the following locations:  Pier Lower Utility Platform  Exterior Pier Catwalk  Pier Upper Utility Platform

The pier lower utility platform is inside of the pier, one level up from grade level. It serves as an electrical termination point, and provides stairway access to the upper pier upper utility platform. The pier lower utility platform is accessed by the enclosure base stairs or elevator, over an elevated

ENCLOSURE AND FACILITIES 7–47 GMT SYSTEM LEVEL PRELIMINARY DESIGN REVIEW December 13, 2013 catwalk, and through a penetration in the pier. See Figure 7-31 for the location of these access points.

The exterior pier catwalk is located on the outside surface of the pier, at the same elevation as the pier upper utility platform. It serves as a platform for working on and servicing the hydrostatic bearing equipment, telescope azimuth drives and telescope azimuth encoder system. Access to the exterior pier catwalk is from stairs that originate near the catwalk serving the enclosure base stairs and elevator. Equipment and tools too large for maintenance personnel to carry are raised to this level using a jib crane as shown in Figure 7-31 and Figure 7-32.

The pier upper utility platform is located on the inside of the pier, two levels up from grade level and at the same elevation as the exterior pier catwalk. It serves as a platform for working and servicing the hydrostatic bearing equipment, telescope azimuth drives and electronic equipment. The platform also provides support for the telescope azimuth utility wrap and provides an interface for the PLP. The pier upper utility platform is constructed of reinforced concrete to provide additional stiffness to the pier. Access to the pier upper utility platform is from stairs that originate on the pier lower utility platform as shown in Figure 7-31 and Figure 7-32.

Figure 7-31. Enclosure base second level floor plan showing access to the pier catwalk and utility platforms

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Figure 7-32. Pier access isometric

7.4.1.5 Maintenance/Personnel Access The following sections describe design aspects of the enclosure building implemented to meet access requirements.

7.4.1.5.1 Vertical Access throughout the Enclosure Access requirements are defined in Table 7-16.

Table 7-16. Overall enclosure access requirements (Level 3 requirement) Requirement ID & Title Requirement Notes This shall be attached to the The enclosure shall provide a passenger- enclosure and will lift equipment ENC-0352: Enclosure rated elevator with a minimum load and personnel from the observing Elevator capacity rating of 1000 kg to access all floor to the service platforms, levels of the enclosure secondary mirror service platform and catwalks. The enclosure shall provide vertical lift ENC-9083: Equipment systems sufficient to transport any Equipment and tool transport to Transport Systems hardware and/or tools necessary for remote systems maintenance of all enclosure subsystems The enclosure shall provide platforms, ENC-9084: Platforms catwalks, ladders and stairways sufficient Catwalks, Ladders, and for personnel access to all areas of the Safe access for personnel Stairways enclosure that require maintenance and/or inspection

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Vertical access throughout the telescope chamber is provided via a stairwell and elevator located at the back of the enclosure, which travels between the observing floor to the top of the enclosure. A secondary means of vertical egress is provided by ladders and platforms on either side of the vertical shutter doors, on the inside face of the front super columns. See Figure 7-33 for an image of the main enclosure vertical circulation.

Figure 7-33. Enclosure vertical circulation

Personnel and most equipment and materials can reach the various levels within the enclosure using the enclosure elevator. For the high areas around the horizontal shutter and enclosure crane, jib hoists are located as necessary to bring material and equipment to areas not accessible by the elevator.

An elevator provides access between grade level and the observing floor with an intermediate stop at the pier lower utility platform level accessed by a catwalk from the elevator tower.

With most of the access paths within the enclosure at significant height above the observing floor, the design of these paths for safe access is essential. For personnel and equipment protection, all platforms include guard rails and kick plates and all ladders have cages. When necessary, tie-off points are provided for use with additional fall protection equipment. Safety processes and procedures are described in Section 5.11.

7.4.1.5.2 Enclosure Bogies Access Bogie access requirements include (Level 3 requirement):

ENC-9689: Enclosure Bogie Access - The enclosure shall provide access platforms and equipment (e.g., a jib crane) for servicing the enclosure bogie drives.

Access is provided to the azimuth drive and idler bogie assemblies through the mechanical corridor. Several personnel and roll up doors are provided for day to day tasks. For tasks requiring large

ENCLOSURE AND FACILITIES 7–50 GMT SYSTEM LEVEL PRELIMINARY DESIGN REVIEW December 13, 2013 access space, quick-release mounting methods are employed at the interior wall panels and structure at each bogie location, allowing the space to be fully opened to the observing floor. See Figure 7-34 for an image of the mechanical corridor.

Space on the observing floor, adjacent to the bogies, may be utilized for larger maintenance tasks associated with the bogies. Localized areas as shown in Figure 7-28 provided for heavy maintenance activities. Localized hoists and transportation equipment are provided to remove bogie components and place them on the observing floor for maintenance.

Figure 7-34. Enclosure - bogies access

7.4.1.5.3 Vertical Shutter Mechanisms & Drives Access Vertical shutter winches and control sheaves are accessed from the mechanical corridor. Winches and sheaves are located on a platform that rotates with the enclosure within the mechanical corridor and similar to the enclosure drive bogies, are accessible through a number of personnel and roll up doors. A series of hydraulic bumpers are provided on top of the enclosure tie strut, acting as a stop in case of vertical shutter door over travel. These are accessed through an exterior hatch, located on the exterior wall of the mechanical corridor.

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Figure 7-35. Vertical shutter winch and sheave platforms

Figure 7-36. Enclosure tie strut

With the vertical shutter doors in the closed position, the counterweights come to rest at the top of the rotating ring girder, above the enclosure tie strut. Access to these assemblies is provided through a series of bolted hatches on the sides of the super columns. Counterweight sheaves and cabling are readily accessible at the forward ends of any of the catwalk levels. Access to the

ENCLOSURE AND FACILITIES 7–52 GMT SYSTEM LEVEL PRELIMINARY DESIGN REVIEW December 13, 2013 vertical shutter guides is also provided. In the closed position, the top of each vertical shutter panel has a small platform that provides access to the top idler bogies. The same platforms offer access to the bottom idler bogies for the adjacent shutter. Refer to Figure 7-37 for an image of access to these mechanisms. Refer to Figure 7-38 for an enlarged image of a vertical shutter access platform.

Figure 7-37. Vertical shutter mechanism access

Figure 7-38. Vertical shutter mechanism access – enlarged

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7.4.1.5.4 Horizontal Shutter Bogies Access The horizontal shutter bogies are accessible from an access walkway just above the catwalk at elevation 45.3m. Walkways run the entire length of the main enclosure girder on both sides of the enclosure aperture and provide work-level access to all related horizontal shutter mechanisms. Refer to Figure 7-39 and Figure 7-40 for images of access walkways to the horizontal shutter bogies.

Figure 7-39. Horizontal shutter bogie access catwalk

Figure 7-40. Horizontal shutter bogie access walkway

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7.4.1.5.5 Wind Vent Door Access Access to operating mechanisms on the wind vent doors is provided on the rotating ring girder and the three perimeter catwalk levels above it. Half of the door motors and disconnects are easily accessible from the catwalks. The other half of the door motors and disconnects are accessed through small secondary platforms reached by caged ladders from the perimeter catwalks. See Figure 7-41 for an image of the wind vent door mechanism access.

Figure 7-41. Wind vent door access

7.4.1.5.6 Enclosure Crane Access In the stowed position, the enclosure crane is accessible from a ladder near the upper level catwalk (see Figure 7-33). The crane has an integral maintenance platform parallel to the bridge girders. Refer to Figure 7-42 for an image of access to the enclosure crane.

Figure 7-42. Enclosure crane access

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7.4.1.5.7 Rooftop Access In addition to the requirements for service and maintenance access, the rooftop must meet the Level 3 requirement for snow and ice removal as follows:

ENC-0329: Snow Removal - The Enclosure shall be designed to allow snow removal.

Rooftop access is provided in both open and closed positions of the horizontal shutter. In the closed position, the roof is accessible via a door located on the catwalk at elevation 54.2m. A ladder is provided to gain access to the top of the horizontal shutters, as well as the roofs directly adjacent to them. In the open position, ladders provide access for personnel to climb over the horizontal shutter rail and gain direct access to adjacent roofs. Guardrails and tie-offs for lifelines and lanyards are fixed to the roof structure at all locations requiring personnel access. See Figure 7-43 for an image of the rooftop access.

Figure 7-43. Rooftop access in the closed position

The horizontal shutter rooftop idlers are also accessed from the roof through a series of hatches allowing personnel to inspect and maintain these lighter components of the horizontal shutter system. Likewise, the horizontal shutter rails can be accessed for inspection and maintenance from either the horizontal lower shutter roof, or from the traveling walkway also attached to the horizontal lower shutter.

7.4.1.5.8 M2 Service Platform A requirement for a service platform for maintenance of the secondary mirror assemblies is defined as follows (Level 3 requirement):

ENC-9085: M2 Service Platform - The enclosure shall provide an M2 Service Platform per drawing GMT-7.3.3.8-ASY_40218 per ICD GMT-7.0_4.1-ICD-00512.

A platform, located at the second level catwalk around the perimeter of the enclosure is used to provide personnel access to the secondary mirror assembly when the telescope is positioned at an elevation angle of approximately 30 degrees. This area is primarily used for servicing the adaptive secondary mirror system electronics. Personnel, material and equipment reach the service platform using the enclosure elevator and perimeter catwalks. Details of the design of this platform are provided in Telescope Section 6.14.

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7.4.1.5.9 Primary Mirror Assembly Handling Enclosure building requirements for primary mirror assembly handling during the mirror segment recoating process are listed in Table 7-17. The overhead crane is also used in this process and it is described in Section 7.4.1.6.2.

Table 7-17. Primary mirror assembly handling requirements (Level 3 requirement) Requirement ID & Title Requirement Notes The enclosure shall provide a hatch in the observing floor in accordance with For removing a primary mirror ENC-0322: Enclosure Base drawing GMT-7.3-ASY_40214 per ICD assembly zenith facing with the Hatch GMT-7.0_4.1-ICD-00512 for primary overhead crane. mirror assembly handling The enclosure shall provide a clear path between the telescope structure and the enclosure for maneuvering the primary To provide a safe path for ENC-0323: Primary Mirror cells with the enclosure crane in transporting the primary mirrors Assembly Removal Path accordance with drawing GMT-7.3- across the enclosure. ASY_40214 per ICD GMT-7.0_4.1-ICD- 00512

The observing floor includes a hatch for use during mirror handling operations. The hatch is constructed in two pieces and when in place, it is flush with the observing floor surface. Temporary guardrails are placed around the opening when the hatch is removed. The opening in the floor is approximately 10.5 meters square to allow sufficient length and width for the mirror cell assembly to be lowered through. The center of the opening is well within the enclosure crane reach.

7.4.1.5.10 Enclosure Boom Lift A requirement for a boom lift is as follows (Level 3 requirement):

ENC-9690: Enclosure Boom Lift - The enclosure shall provide a boom lift in accordance with drawing GMT-7.3.2.12-ASY_40219 per ICD GMT-7.0_4.1-ICD-00512.

A commercial boom lift, modified to run on electrical power, is fixed to a pedestal attached to the observing floor. The boom provides the capacity for a payload of 250 kg to reach all areas of the telescope for various maintenance activities. When not in use, it is be parked outside of the swept volume of the telescope. The drawing referenced in the requirement details the volume of the enclosure that must be reached by the boom lift.

7.4.1.6 Lifts and Cranes 7.4.1.6.1 Pier Lift Platform The requirement for a high capacity lift between grade level and the Gregorian Instrument Rotator (GIR) is defined as follows (Level 3 requirement):

ENC-1160: Pier Lift Platform - The enclosure base shall include a pier lift platform with a minimum load capacity of 15,000 kg for installing Direct Gregorian instruments.

The pier lift platform is located at the center of the telescope pier. It is used to raise instruments from ground level for installation into the Gregorian Instrument Rotator (GIR). The platform is circular and in its parked position at the observing level floor, it is used to seal the center of the telescope azimuth disk floor. ENCLOSURE AND FACILITIES 7–57 GMT SYSTEM LEVEL PRELIMINARY DESIGN REVIEW December 13, 2013

The pier lift platform is a custom hydraulic platform lift, supported by vertical rails that originate at the base of the telescope pier. These rails are removable in the event that the GIR journal needs to be removed for maintenance or replacement. See Figure 7-44 for an image of the pier lift platform. The lift is also used to bring material and equipment to the two pier utility platform levels.

Figure 7-44. Pier lift platform

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The Pier Lift Platform has the following specifications:

 Type: ...... Custom hydraulic platform lift  Lift Capacity: ...... 15 metric tons  Platform size: ...... 5 m diameter  Vertical Travel:..... 18 m  Lift speed: ...... Variable from 5 to 100 mm/sec

7.4.1.6.2 Enclosure Crane Specific design requirements for the enclosure crane are listed in Table 7-18.

Table 7-18. Enclosure crane requirements (Level 3 requirement) Requirement ID & Title Requirement Notes For installing and removing the The enclosure shall provide a high primary mirrors in their cells into capacity (65 metric ton) overhead crane ENC-0338: High Capacity and out of the telescope and for with coverage as specified in drawing no. Overhead Crane moving them between grade level GMT-7.3-ASY_40214 per ICD GMT- and telescope through the access 7.0_4.1-ICD-00512 hatch in the observing floor. The enclosure shall provide a low capacity For handling the light assemblies (10 metric ton) overhead crane with the ENC-6461: Low Capacity and equipment with access through same coverage as the high capacity Overhead Crane the observing floor to the grade overhead crane and with the same hook level. travel range ENC-9633: Crane Hook The crane hook reach (both the 65 and 10

Reach metric ton cranes) shall be to grade level. The crane bridge shall include a removable access platform per drawing For personnel access to the ENC-9086: M2 Access no. GMT-7.3.3.8-ASY_40217 per ICD secondary mirror assembly while Bridge GMT-7.0_4.1-ICD-00512 for providing the telescope is at zenith. access to the telescope top frame while the telescope is parked at zenith

A large crane is required in order to handle the primary mirror assemblies during the re-coating process (the primary mirror assembly plus rigging is approximately 55 metric tons). The crane is also used to lift and place the secondary mirror assemblies, instruments and other miscellaneous observatory equipment. In addition, the crane is used to assemble the telescope structure during the construction phase. These uses define the capacity and reach requirements of the crane hook(s). The enclosure crane must move freely without regard for telescope position with its hook in the full-up position.

The crane bridge also provides personnel access to the secondary mirror area of the telescope during the installation and/or removal of the assembly. The bridge is equipped with a removable platform, installed for this purpose and removed for normal crane operation.

The crane bridge rails are supported by the main girders running across the top of the enclosure. Bridge travel is from the back of the enclosure to 0.5 meters past the centerline of the telescope. With enclosure rotation accounted for, this allows for full crane reach within a 20.4 meter radius at the observing level. See Figure 7-45 for a sketch showing the enclosure crane hook limits.

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An alternative design allowing the bridge crane to travel the entire distance to the front of the enclosure was also considered. This option was dismissed for the following reasons. First, if the bridge crane traveled to the front of the enclosure, it would be required to handle additional loads due to the skewing of the bridge crane rails as a result of distortion of the enclosure structure. The crane would take additional loads to pull the structure back into alignment. Second, the shortening of the travel distance eliminated additional steel weight in the crane rail. Finally, increased loads at the front of the enclosure would add additional weight to the front super columns and azimuth drive bogies. For these reasons the bridge crane travel was limited to 0.5 meters past the centerline of the telescope. Since the crane hook reach is not limited by this restriction, the operational aspects of crane use are unaffected.

Figure 7-45. Enclosure crane hook limits

Specifications for a commercially available crane meeting the design requirements are listed in Table 7-19.

Table 7-19. Enclosure crane specifications Criterion Description Notes Crane Type Double girder bridge crane 65 metric ton primary, Crane Capacity Required for M1 assembly lift 10 metric ton secondary Trolley Speed Up to 0.4 m/s, variable 65 metric ton Hoist Speed Up to 0.2 m/s, variable Creep slow speed required 10 metric ton Hoist Speed Up to 0.2 m/s, variable Total Lift Height 54 meters To reach grade level Bridge Travel Speed Up to 0.5 m/s, variable Bridge Span 27.3 m Bridge Travel Distance 19.1 m For full floor coverage with enclosure rotation

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Two crane hoists are provided on the bridge assembly. The primary 65 mt and secondary 10 mt hoists allow telescope components of varying scales to be efficiently handled. The two hoists provide the following motions for handling equipment:

 Bridge travel (back-to- center of the enclosure)  Trolley travel (side-to-side in the enclosure across the width of the shutter)  Arc travel (rotate about the enclosure center point utilizing enclosure rotation)  Tilt (differential extension or retraction of the two hoists)  Lift (symmetrical extension or retraction of the two hoists)

7.4.1.6.3 Jib Crane A jib crane at grade level is provided based upon the following Level 3 requirement.

ENC-1211: Enclosure Base Jib Crane - The enclosure base shall provide a 5000 kg capacity jib crane at grade level outside the Pier Portal with hook access to the centerline of the main hatch.

A 5-ton jib crane is provided for off-loading small equipment from trucks and/or transferring loads from carts. The jib crane is located below the enclosure base hatch. Sufficient room is available for vehicles to pull in front of the telescope pier access door for transfer of their respective loads to other means of conveyance. See Figure 7-46 for the location of the jib crane and Figure 7-47 for an image of the jib crane.

Figure 7-46. Jib crane location

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Figure 7-47. Jib crane at enclosure base

The jib crane has the following specifications:

 Capacity: 5 metric ton  Hook limits: 1.45 m to 6.32 m from face of column (reaches to the center of enclosure base hatch)  Rotation: 180 degrees

7.4.1.6.4 Elevators Elevators are provided in both the fixed enclosure base and Rotating enclosure based upon the following Level 3 requirement.

ENC-0352: Enclosure Elevator - The enclosure shall provide a passenger-rated elevator with a minimum load capacity rating of 1000 kg to access all levels of the enclosure

Two elevators are provided in the enclosure building. The first is located within the enclosure base and reaches up to the observing floor. See Figure 7-27 for the location of the elevator in the enclosure base. The second is located within the vertical circulation shaft at the back of the enclosure and reaches from the observing floor to the upper catwalk at elevation 50.55m. See Figure 7-28 for the location of the elevator in the enclosure. Both are intended to be used for personnel as well as lighter equipment. The elevator specifications are as follows:

 Make and Model: ...... Machine-room-less traction elevator  Elevator Type: ...... Passenger type elevator  Rated Capacity: ...... 1,814 kg for enclosure base, 1,361kg for enclosure  Passenger Capacity: ...... 10 persons for enclosure base, 3 for enclosure  Travel Distance: ...... 11.8 m for enclosure base, 32.9m for enclosure  Car Door Width: ...... 1.2 m wide  Speed: ...... 1.78 m/s

A machine-room-less elevator only requires a flush mounted control panel near the top of the elevator. No hydraulic equipment (or dedicated elevator room) is necessary.

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7.4.1.7 Materials Overview Materials used in the construction of the GMT enclosure building were chosen for their performance as well as their availability in the local region. Concrete and steel fabrication and erection are both commonly available in Chile, as is an abundance of skilled labor in these trades.

The enclosure building is clad primarily with 75 mm insulated metal panels for walls. The primary wall panel is a 610 mm wide panel with an off-set double tongue-and-groove joint providing a full thermal break. Panel joints are sealed with a factory installed continuous seal in the groove and field applied sealant on the opposite side of the joint. Girts provide the main structural support for the panels, and are spaced at 1200 mm to react high wind loads.

The panels are 22-gauge with a smooth galvalume finish on both the interior and exterior sides. Panel widths and skin gauges were determined based on the high wind loading requirements. The core of the panel is 75 mm thick foam-in-place polyurethane with an R-21 insulation value.

The roof system consists of standing seam roof panels over 100 mm of polyisocyanurate insulation. The roof panels come in a 305 mm width, with a seam height of 75 mm. The standing seam panels are made of 20-gauge steel covered with reflective aluminum tape to minimize emissivity.

The metal wall and roof panels are precut at the factory and trimmed on site. All panel edges are trimmed with 20-gauge galvalume sheet metal trim and flashing. Both the roof and wall panels are readily available in Chile.

7.4.1.8 Architectural Seals Design requirements for shutter and wind vent seals are listed in Table 7-20

Table 7-20. Shutter and wind vent seal requirements (Level 3 requirement) Requirement ID & Title Requirement Notes To protect the telescope and The enclosure shutters in their closed equipment, provide a 'light tight" ENC-0403: Enclosure position shall seal the observing opening enclosure for daytime calibrations Shutters Sealing in the enclosure against infiltration of rain, and reduce heat load to enclosure snow, dust, and stray light internal environment during the day. The enclosure wind vents shall include To prevent the infiltration of water, ENC-0438: Enclosure Wind light baffles, weather seals and water snow, dust, or stray light when the Vents Sealing drainage features vents are closed

Architectural seals are required between stationary and moving building components. The main function of seals is to protect the interior environment from a wide range of environmental conditions such as water, air, light, and dust. Seals are positioned for ease of adjustment, maintenance, and replacement. Different types of seals that are incorporated into this structure include the following:

 Sweep action brush seals  Extruded rubber compression seals  Sheet metal labyrinth seals  Custom combinations (i.e., rubber seal and neoprene strips for sliding seals)

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Two layers of seals are provided. The first seal stops high wind, light and most precipitation from entering the building. The second seal keeps out moisture. An example of this would be the utilization of a sweep action brush seal as the first line of defense and a rubber compression seal as the second line of defense. See Figure 7-48 for an image of seal types and locations to be used on the enclosure.

Figure 7-48. Architectural seals at the enclosure

Inflatable seals were also studied for use due to their ability to handle higher movement tolerances. Inflatable seals are more expensive than typical compression seals. They are also more costly to repair and more time consuming to replace than typical compression seals. The structural tolerances and distortion across the seal interfaces have been determined to be small and inflatable type seals were not deemed necessary.

The wind vents on the vertical walls are provided with factory installed seals around the sides and along the bottom. A supplemental second layer of seals are to be provided depending on further evaluation of the factory seals.

7.4.2 Structural Design The enclosure is being designed to withstand specific seismic and wind loading criteria defined in the enclosure building design requirements document10. The structure is designed for survival level seismic loading and survival level wind loading. Apart from the survival criteria, additional operational requirements have been established as defined in the design requirements. The following requirement (ENC-0332) states that open structural shapes be selected with a maximum target plate thickness of 20 mm for fast thermalization of the enclosure structural steel during science operations.

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ENC-0332: Thermal Time Constant Structural Members - The enclosure design shall provide rapid thermal equilibration of the steel during nighttime operation. 20mm max plate thickness

7.4.2.1 Building Code and Reference Standards With regard to the implementation of the American building codes outside of the United States, general practice is to design to the more stringent requirement of the International Building Code or the local building code which in this case is the Chilean Norm. The Chilean Norm requirements are covered fully within the reference standards adopted by GMTO19. The enclosure is being designed in accordance with the following building code and reference standards:

 Building Code: International Building Code, 2006 Edition (IBC 2006)  Reference Standard: ASCE 7-05 Minimum Design Loads for Buildings and Other Structures  Reference Standard: American Institute of Steel Construction, 13th Edition (AISC 360-05)  Reference Standard: American Institute of Steel Construction, Seismic Design Manual (AISC 341-05, Supplement No. 1).  Reference Standard: American Concrete Institute, 2005 Edition (ACI 318-05)

The American Institute of Steel Construction’s Seismic Design Manual (AISC 341-05) is the reference standard for steel construction located in regions of high seismicity. The standard is based on the principle of providing controlled system ductility in response to strong ground motion. This is accomplished through specific member and connection detailing requirements. All steel within the Seismic Lateral Force Resisting System (SLRS) is being designed in conformance with AISC 341-05. All other framing is being designed in accordance with AISC 360-05.

7.4.2.2 Design Wind Speeds A wind tunnel test of the enclosure building was performed by CPP Inc. in June of 201120. A scale model of the enclosure, summit support building and surrounding terrain was constructed for this purpose and tested in the CPP wind tunnel. Wind loading information suitable for the design of cladding and structural elements (including mechanisms) was generated. Wind design criteria was provided to CPP for survival level wind loads with the enclosure in the closed configuration and operational level wind loads with the enclosure in the full-open, partially open, and closed configurations. The design wind velocity requirements and are summarized below:

 Survival Wind Load: ...... V = 65 m/s  Max Operational Wind Load: ...... V = 30 m/s  Telescope Max Operational Wind Load: ...... V = 20 m/s  Shutter Max Operational Wind Load (MOWL): ...... V = 25 m/s  Enclosure Rotation Max Operational Wind Load: ... V = 30 m/s

Note: The maximum operational wind load is greater than the GMT maximum operating gust wind speed of 20 m/s to safely allow for increasing wind velocity during enclosure close-down and stow.

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7.4.2.3 Seismic Requirements A site-specific seismic hazard assessment21 was developed by URS Corporation in consultation with GMT, and Simpson Gumpertz and Heger, Inc. The site-specific analysis consists of the development of Operational Level Earthquake (OLE) response spectra and Survival Level Earthquake response spectra. The OLE was developed on the basis of an average 100 year return period determined from a probabilistic seismic hazard analysis. The SLE was developed as two- thirds of the Maximum Considered Earthquake (as specified in the building code12) determined from a deterministic seismic hazard analysis.

Select survival seismic design criteria are as follows:

 Soil Site Class: Soil Site Class “B” (from Geotechnical report, Revision B)  Seismic Design Category: D (from ASCE 7-05)  Spectral Response Acceleration at short periods, Ss = 1.5g (from ASCE 7-05 and the site specific seismic hazard assessment)  Spectral Response Acceleration at a period of 1-second, S1 = 0.6g (from ASCE 7-05 and the site specific seismic hazard assessment)  Seismic Importance Factor, IE = 1.0

The terms Ss and S1 are the maximum considered seismic ground accelerations expressed as a fraction of the acceleration due to gravity. These are typically mapped in the ASCE 7-05 code. For GMT, these values were provided in the site-specific seismic hazard assessment provided by Simpson, Gumpertz & Heger, Inc.21

The soil site class is defined by the ASCE 7-05 code. This coefficient accounts for the way the soil below the building transmits seismic ground accelerations into the structure. Site classes “A” and “B” indicate a building founded on rock, while site classes “C” through “F” indicate buildings founded on granular soils of varying quality. Site class “A” is the best type of soil to found the building on with respect to seismic design accelerations. Site Class “F” is the worst type of soil to found the building on with respect to seismic design accelerations.

The seismic design category is defined by the ASCE 7-05 code. The design category prescribes specific structural detailing requirements for the seismic force resisting systems. Certain structural bracing systems are prohibited by the code for certain seismic design categories.

The seismic importance factor is defined by the ASCE 7-05 code. The importance of a building is based on the potential threat to either human life, or national security. An importance factor of 1.00, like that used on the summit support building, is indicative of a building that does not have an unusual threat to human life, or national security, in the event of a building collapse.

7.4.2.4 Enclosure The enclosure structure consists of a steel carousel rotating on rails supported by a fixed steel structure base. The carousel is roughly 55 meters in diameter and 48 meters high and rotates independently of the telescope.

The enclosure can be broken down into three equally important subsystems, consisting of the super columns, lateral bracing system and the rotating ring girder. The super columns are the primary gravity and lateral load carrying elements, thus forming the backbone of the enclosure. The typical

ENCLOSURE AND FACILITIES 7–66 GMT SYSTEM LEVEL PRELIMINARY DESIGN REVIEW December 13, 2013 cross section dimensions of the super columns are 2 m x 4 m nominal. They are located at each end of the enclosure. The super columns support both the vertical shutters and the story deep truss which supports the horizontal shutters and enclosure Crane. See Figure 7-49 and Figure 7-50 for the locations of the super columns.

The lateral bracing system consists of a set of diagonal structural elements located along the periphery of the enclosure which resist lateral forces (either from wind or seismic) and transfer these loads to the base of the enclosure base. The rotating ring girder is a steel girder fabricated from plates forming a rectangular cross-section and a closed circular shape in its overall extent, supporting the enclosure and resting over idler and drive bogies. See Figure 7-50 for a view of the enclosure lateral bracing system, super columns and enclosure ring girder.

Figure 7-49. Enclosure framing at top showing the story deep truss

7.4.2.4.1 Framing Overview Based on code requirements, the enclosure is being designed as a “non-building structure” (a structure that is not for continuous people occupancy but designed similar to a building). The Seismic Lateral Resisting System (SLRS), that portion of the enclosure’s structure tasked with resisting seismic lateral forces, consists of Special Concentrically Braced Frames (SCBFs) in the “X-braced” configuration. SCBFs are structural frames which rely on structural members spanning diagonally to tie each beam-column intersection to the opposite beam-column intersection of the same frame. The connections at the beam-column intersection are achieved by use of bolted plates called gussets. For the enclosure, Hollow Structural Steel tube sections (HSS) are used for the brace members. This system has been selected in accordance with IBC 2006 and meets the requirements for use in regions of high seismicity due to its high level of ductility. All bays have been braced in an effort to improve the stiffness of the structure and provide redundant bracing in the case of a survival level seismic event.

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Figure 7-50. Enclosure framing

7.4.2.4.2 Enclosure Facets Two configurations for the side facets of the enclosure were studied using the wind pressures reported by CPP. The configurations that were studied were five facet and seven facet (per side) configurations. The key results of this analysis are listed below:

 The quantity of steel required for either option is very similar, when comparing the material for the structural members.  The seven facet option requires more fabrication, connections, structural members, and erection handling. Increases in the above-mentioned areas lead to corresponding increases in cost.  Currently, the azimuth idler bogies are located beneath each building column with the exception of the columns at the personnel elevator. Thus, the enclosure maintains direct load paths from the columns to bogies. An introduction of two additional facets can lead to either additional idler bogies or an increase in the enclosure ring girder size.

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The five facet option was determined to be the optimal configuration for the above-mentioned reasons. Refer to Figure 7-51 for illustrations of the 5 and 7 facets options studied.

Figure 7-51. Enclosure facet comparison

7.4.2.4.3 Super Column Design The enclosure super columns are designed as stiffened hollow box sections and are key components of the enclosure lateral and vertical load resisting systems. The super columns also serve the purpose of housing the counterweights for raising and lowering the vertical shutter doors. See Figure 7-50 for a view of the super columns. Key features of the super columns include the following:

 Each super column carries roughly 15% of the total building load.  Each super column pair carries roughly one-third of the sail area for wind design.  The columns have the ability to function as a deep cantilevered column when the vertical shutter doors are fully open.  The azimuth drive bogies are located at each super column location.

7.4.2.4.4 Rotating Ring Girder The rotating ring girder defines the physical interface between the enclosure and the azimuth bogie mechanisms. All loads, gravity, wind and seismic are transferred through the ring girder. Similar to the super columns, the rotating ring girder is also designed as a stiffened hollow box section. Its dimensions are 3 meters wide by 1 meter deep. The rotating ring girder is shown in Figure 7-50.

7.4.2.4.5 Vertical Shutter Panels Shutter weight and shutter depth were equally important factors in consideration of the structure layout due to their influence on the depth and bending moment of the guide assembly by which the shutters travel. The weight of the counterweight assembly is proportional to the shutter panel weight, so excessively heavy shutters lead to a need for heavier counterweights. Heavier shutters

ENCLOSURE AND FACILITIES 7–69 GMT SYSTEM LEVEL PRELIMINARY DESIGN REVIEW December 13, 2013 also result in increased seismic base shear as well as higher loads on the enclosure bogies. Reducing shutter weight is highly desirable to produce an efficient enclosure structure. Figure 7-52 shows the current framing used for the vertical shutters.

Figure 7-52. Vertical shutter framing

In the early stages of design, three shutter types were explored:

 Aluminum wide flange shapes  Wide flange girder with wind girts  Truss configuration Initially, aluminum appeared to be a feasible design option for framing the vertical shutter panels. Having one-third the weight of steel, aluminum is highly attractive in regard to weight optimization. However, aluminum has roughly one-third the modulus of elasticity of steel and as such the preliminary aluminum shutter designs were significantly deeper than other steel alternatives. Furthermore, allowable flexural stresses for aluminum are significantly reduced when welded, thus facilitating the need for built-up bolted cross-sections. Trade-off studies showed the drawbacks associated with aluminum outweighed the perceived benefits in comparison to the other steel options.

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A wide flange girder concept with wide flange wind girts was studied. This particular design was arguably the simplest of all designs; however it was also the heaviest. Additionally, the thickness of the flanges reached a point at which thermal mass of the shutters doors became a concern. See Figure 7-53 for the two framing schemes (the third is the variant between steel and aluminum wide flanges).

Figure 7-53. Vertical shutter framing

The design selected for further development is a steel truss framing configuration consisting of a series of long span joist girders as shown in Figure 7-53. This configuration has been selected since it is the lightest of all options with a depth of 1.0 m. The joist girders are spaced at 1.2 m on-center, in order to accommodate spanning limitations for the metal wall panel due to the high wind loading at the summit.

7.4.2.4.6 Horizontal Shutter Panels The horizontal shutters consist of two movable shutter panels (upper and lower) which are supported by a fixed lower shutter when the panels are in the fully closed position (see Figure 7-54). The shutters operate in a “piggy-back” configuration. Each shutter carries a portion of each other’s gravity load; however, no single shutter carries the full load of another. Figure 7-55 shows the upper and lower horizontal shutters and the bogies which transfer the upper shutter loads to the lower shutter and in turn to the lower fixed shutter. See Figure 7-55 for an illustration of how the loads are transferred from shutter to shutter.

The framing configuration of the shutters is a combination of steel open web joists, steel joist girders, and castellated steel box girders.

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Figure 7-54. Horizontal shutter framing (isometric)

Figure 7-55. Horizontal shutter framing (section)

Additional Considerations:

 The shutter doors can be tightly nested upon one another due to the scissor truss configuration of each shutter (A scissor truss configuration is that where the top and bottom chords of a truss are sloped, resembling an open pair of scissors with the apex at the top center). Figure 7-55 illustrates this condition.  Independent rails for each shutter panel are mounted on top of each story truss top chord box girder and at the fixed shutter roof.  End-stops are included to ensure the shutter does not over travel due to brake failure.

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Figure 7-56. Horizontal and vertical shutters’ operation sequence

Apart from out-of-plane wind loads, the shutters must be capable of bringing the super columns into plumb during operation due to as-built misalignments, thermal expansion or contraction. The design load of 50 kips [225 kN] was derived initially on the basis of a 150 mm total displacement (75 mm each way) enforced at the top of the super columns. Both the vertical and horizontal shutters, as well as the shutter mechanisms have been designed to accommodate this loading. This loading criterion was included in the design of the shutter panel structure and shutter mechanisms. Figure 7-56 illustrates the operation sequence of the horizontal and vertical shutters (from top left to bottom right):

1) Shutters are in the closed position, where only the shutters overlap the minimum amount required to keep seals engaged;

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2) Shutters begin to open by retracting and increasing the overlap zone, all of which occurring in a simultaneous manner for both the horizontal and vertical shutters; 3) Vertical shutters completely overlap and horizontal shutters overlap over fixed lower shutter; 4) Vertical shutters travel together and overlap with the fixed panel at the low end.

It is possible to independently operate the horizontal and vertical shutters (i.e., the horizontal shutters can be opened without opening the vertical shutters and vice versa). Furthermore, the foremost shutters near the top of the super column serve the additional function of limiting differential deflection at the open end of the enclosure under survival conditions.

7.4.2.4.7 Finite Element Analysis Model A Finite Element Analysis Model (FEA) has been developed for the enclosure using Robot Structural Analysis Professional, version 2013. The model consists of a combination of member elements and shells. The most recent design incorporates roughly 180,000 element nodes. A sufficient amount of time and detail has been dedicated to the modeling of the super columns and the rotating ring girder which are modeled as shells. The structural model has a considerable number of load cases analyzing both wind and seismic loads. By analysis, the structure satisfies allowable member design ratios and deformations. The allowable member design ratios and deformations used to quantify the adequacy of structural members are defined by the building code and reference standards used for this project (refer to Section 7.4.2.1). The design ratios are represented by a number between 0 and 1.0, (1.0 being a member used to 100% of the code allowed capacity) which varies depending on several conditions such as member type and loading conditions. The allowable deformations are defined in terms of the use of the member and the serviceability conditions that the member satisfies under a particular load (i.e., roof members are required to have a maximum deflection not greater than its span divided by 240 under total load). Future design development will give consideration to thermal effects and other transient loadings.

The design of the azimuth drive and idler bogies are not considered in the structural model. Support below the super columns and other building columns are modeled as rigid links. For this level of design, column boundary conditions utilizing rigid links are appropriate. Subsequent design iterations will account for and analyze the axial and lateral stiffness of the bogie assembly.

For the seismic design of the enclosure, the Response Modification Factor R has been taken equal to 2 at the preliminary design stage. The response modification factor R is a non-dimensional number prescribed by the building code, which is a measure of system ductility in the SLRS. In accordance with the building code, the R factor is established on the basis of an increasing scale: An R factor equal to one suggests an ideally elastic response whereas an R factor taken greater than one is indicative of a structure in which some members may enter into the plastic range. AISC 341-0522 requires the connections of bracing members for SCBF frames to be capable of withstanding the yield capacity of the bracing member, in effect making the braces a sacrificial element. The chief advantage of this particular detailing is that brittle fracture is precluded as a failure mechanism and a more controlled system response can be achieved. The bracing members are being detailed as bolted connections for two reasons. The primary reason is that bolted connections are favorable for remote sites where welding typically becomes cost prohibitive. The second advantage is that the in the event of an SCBF brace exhibiting inelastic behavior during a survival level seismic event, the brace can be unbolted, removed and replaced without significantly affecting the operational downtime of the observatory.

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By nature of the structure’s geographic location, the wind demands at the summit are comparable to Florida’s coastal region, whereas the seismic demands are in the order of those common to California. When considering the lateral force resisting system, survival seismic loads govern over survival wind loads. However, this circumstance cannot be considered in isolation. Although, the design of the lateral bracing system is governed by seismic loading, the design of equally important other systems such as the cladding system (i.e., wind girt, metal wall panels, etc.) is governed by wind demands. The design of the horizontal and vertical shutter systems is also dominated primarily by wind loading. These separate, yet essentially competing requirements lead to members which are generally more robust than what one would expect for a structure that was governed by either seismic or wind, but not both. The positive aspect of this reality is that the structure holds an inherently high factor of safety.

The current design includes the inherent factor of safety required by the building code over the ultimate capacity of a structure or portion of it, depending on many different factors such as: application of the member or portion of the structure, importance of the element, load type, material type, reliability on the fabrication of that element, etc.

7.4.2.5 Uplift Restraints The current Enclosure undergoes vertical uplift under lateral seismic and wind load combinations. To mitigate these actions, uplift restraints must be detailed. There are two methods for detailing the restraints: (1) Employ a "claw type" restraint which travels along the azimuth bogie rails, or (2) detail a restraint which engages the underside of the Enclosure Base Ring Girder top flange. Each of these options carries advantages and disadvantages. The major advantage of Option 1 is that the uplift can be resolved directly at the bogie interface and transferred directly to the azimuth bogie rail. The disadvantage associated with this approach is that the splice of the azimuth bogie rail cannot be bolted and must be welded due to interferences created by the uplift restraint. At this stage of the design, a welded bogie rail splice would not be beneficial for the long term performance under the rail under thermal and operational load cases due to rail expansion. Furthermore, in an unforeseen event in which the rail must be serviced and/or removed, a welded rail splice complicates the effort of accomplishing this task.

With regard to Option 2, the uplift forces bypass the bogie mechanism and are transferred directly to the structure. This load path reduces the demands on the bogie and can lead to a more simple mechanism. It also presents the opportunity to introduce bolted rail splices which are more appropriate for an enclosure of this size for the same aforementioned reasons. A particular drawback associated with this option lies within the potential increase in flange thickness of the ring girder in order to accommodate the uplift load.

Upon considering the advantages and disadvantages associated with each option, Option 2 has been chosen for further development and integration. An image of the enclosure uplift restraints is given in Figure 7-57.

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Figure 7-57. Enclosure uplift restraints

7.4.2.6 Enclosure Base The enclosure base is a multistory circular steel structure that supports the enclosure and encloses the telescope pier. The enclosure base has one main level above grade, the observing floor, which supports equipment and provides space for telescope operation and maintenance activities. The overall design of the enclosure base consists of two circular rows of columns spaced evenly around the telescope pier. A secondary (third) row of columns is provided near the telescope pier to provide support for the insulated wall panels that make up the wind shield to protect the telescope pier.

Figure 7-58. Enclosure base framing

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The lateral resisting system is formed by special concentric braced frames and horizontal diaphragm bracing. See Figure 7-58 for an overall view of the enclosure base.

A structural analysis model of the enclosure base has been prepared, using Robot Structural Analysis Professional 2013. The model is used to determine the stresses and deformations on critical structural members and to optimize the location and profile of the lateral force resisting system elements. The model consists of a combination of steel member elements representing the beams and columns, shell elements representing floors as well as the ring girder, and boundary conditions to represent the foundations. The current model incorporates gravity loads derived from the expected materials, instrumentation and code derived loads for the intended use of the building, the wind pressures provided in the wind tunnel test report and the seismic forces derived from a modal analysis incorporated into the model to distribute the seismic forces throughout the structure. The enclosure base meets all code allowable static and dynamic stress and fatigue requirements.

7.4.2.6.1 Enclosure Base Foundations The foundations of the enclosure base consist of isolated footings under each column to support the downward forces. In addition, the uplift forces from the columns and braces are resisted by a rock anchoring system, which has been selected as the most viable option, considering that hard rock is close to the grade elevation, and this system reduces the on-site labor and materials expense compared to a foundation system that relies on its self-weight to counteract uplift (ballasted foundation system).

Figure 7-59. Enclosure base - typical column foundation

In addition, the current design minimizes vibration transmission from the enclosure to the telescope pier with separate structures and the incorporation of isolation materials such as dense polystyrene foam between structure foundations. Figure 7-59 illustrates the separation between structures at the foundation and different floor levels.

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7.4.2.6.2 Enclosure Base Framing Overview Design Options The enclosure base is a single-story circular steel structure in which gravity loads are transferred through the observing level checkered plate floor resting on a polar array of steel beams supported on steel columns. Lateral loads are resisted by horizontal braces at the observing floor level and mid height. Special concentric braced frames are oriented in the radial direction as well as in two circumferential rings around the enclosure base structure. The current configuration of the braced frames has been designed to reduce the un-braced length of the members. Refer to Figure 7-58 and Figure 7-59 for images showing the components of the enclosure base structure.

7.4.2.6.3 Fixed Ring Girder The fixed ring girder is a circular multi-web plate girder that supports the enclosure. It consists of stiffener plates, web plates, and flange plates as shown in Figure 7-59. The reactions from the rotating enclosure are imposed onto the overall enclosure base through the fixed ring girder, which in turns transfers them to the gravity and lateral force resisting systems. The rails for the Azimuth bogies are fastened to the top plate of the ring girder and allow for adjustability in the field during erection. Figure 7-71 shows an image of the rail leveling assembly consisting of a steel sole plate supported over grout. Alternatively, solid steel shim plates can be used in lieu of the grout. With regard to the shim plate alternative, the intent is to provide continuous bearing support under the azimuth bogie rail and the fixed ring girder. One way to achieve this is to introduce steel finger shims. Ideally, the shim packs would be fabricated as tapered and flat with varying gradations and tapers for both types, allowing the field crew to obtain a high degree of vertical alignment. The design may also include a shim allowance at the column cap plate to fixed ring girder interface. As a result, the field crew will be able to set the top of fixed ring girder at a reasonable tolerance prior to final alignment of the azimuth bogie rail.

7.4.2.7 Telescope Pier The Telescope Pier consists of a cylindrical reinforced concrete structure with interior steel platforms that allow access to equipment (see Figure 7-60). A concrete slab at the top level is also provided for access to the base of the telescope and related equipment. The telescope rests on the azimuth track which in turn attaches to the top of the Pier wall. See Figure 7-61 for a view of the telescope to pier interface.

The telescope pier has several openings through its perimeter wall for personnel, equipment and utilities access. This allows access into the telescope pier from different levels of the enclosure base as well access from the observing floor level.

Figure 7-60. Telescope pier

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Figure 7-61. Telescope attachment to pier (cross section)

7.4.2.7.1 Performance Requirements Dynamic performance of the telescope pier is defined by the following Level 3 requirement:

ENC-1151: Pier Modal Performance - The telescope pier shall have a design modal performance of greater than or equal to 10 Hz with an infinitely stiff mass representing the telescope and the expected soil properties of the site considered.

7.4.2.7.2 Design Overview The Pier has evolved from that at the enclosure and facilities Preliminary Design Review. It is approximately 3 meters shorter and has a different geometry for the large portal. The stepped thickness changes that were in the preliminary design have been eliminated and a single thickness pier wall is now the current baseline design. The preliminary design had the pier walls extending underground to the depth of the utility tunnel.

The geotechnical testing of rock at the location of the pier indicates that the modulus of elasticity of the rock at shallow depths (less than 3 meters from the surface) is somewhat low (E = 3,000 MPa). At a depth of 3 or more meters, the rock quality is higher and the modulus reaches a reasonable level (10,000 MPa).

The results of a modal analysis of the pier, founded on rock with a rigid telescope mass, indicate that with a pier depth of 1.2 meters (and a modulus of 3,000 MPa), the fundamental natural frequency is 8.0 Hz, lower than the 10 Hz requirement. Increasing the depth to 3 meters and using a modulus of 10,000 MPa results in a fundamental frequency of 11.3 Hz which meets our requirement. As a result, the current baseline design has the pier to rock interface at 3 meters below grade. Further investigation of the dynamic modulus of elasticity may yield better results and if so, the depth of the pier interface will be reconsidered.

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7.4.3 Enclosure Mechanisms The enclosure mechanisms include the all of the mechanical components necessary to provide the required motion of the enclosure and shutters.

The enclosure mechanisms are designed with the following criteria:

 Utilize off-the-shelf components, when possible.  Incorporate simple, reliable designs and construction methods using common industry practices.  Use common and interchangeable parts where possible.  Use a standard factor of safety of 1.5 for load carrying components. Preliminary stress analyses were performed on all structural elements of the mechanisms using the Autodesk Inventor finite element analysis (FEA) capabilities. The purpose of the preliminary FEA was to validate the preliminary design and to provide design information in regards to material selection, optimization and redundancy.

The design loads used for the mechanisms are equal to the structural loads (provided by the enclosure FEA) with a 1.5 safety factor applied. Commercial components such as bushings, bearings and rollers are selected based on the vendors stated load capacity using these factored design loads.

7.4.3.1 Enclosure Azimuth Rotation Mechanisms 7.4.3.1.1 Azimuth Bogie Requirements The functional and performance requirements for the enclosure bogies are listed in Table 7-21.

Table 7-21. Enclosure rotation requirements (Level 3 requirement) Requirement ID & Title Requirement Notes To be able to track the telescope in ENC-0398: Enclosure The enclosure shall provide unlimited both directions and for unlimited Rotation Range range of bidirectional rotation in azimuth number of rotations. ENC-0400: Maximum The enclosure shall provide the To match the telescope maximum Enclosure Rotational Speed maximum rotation speed of +/- 2.0 deg/s operational rotation speed ENC-0401: Maximum The enclosure shall provide the To match the telescope maximum Enclosure Acceleration maximum acceleration of +/- 0.1 deg/s2 acceleration For closed enclosure maintenance The enclosure drive system shall allow operations and margin for rotating ENC-0390: Enclosure the enclosure to rotate in winds up to 30 the enclosure under drive failure Drive System Wind m/sec with one drive mechanism not in condition. Velocity and Operational Limit service. acceleration requirements need not be met The enclosure drive system shall To keep the enclosure at its parked ENC-0394: Enclosure incorporate a fail-safe brake system that position and avoid any Drive Brakes engages when the electrical power is off. uncontrolled motion. The enclosure bogie system shall limit ENC-0377: Enclosure To reduce image degradation due induced vibration to the lowest practical Bogie Vibration to enclosure vibration. levels when the enclosure is moving. The enclosure bogies shall be designed To meet the reliability and ENC-9498: Enclosure with all features necessary to readily maintenance requirements for the Bogie Alignment allow re-alignment of the bogies. enclosure building

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The enclosure has been designed to have unrestricted rotational motion. The enclosure structure clears the swept volume of the telescope, and electrical and control signal services cross from the fixed base to the moving enclosure through slip rings as described in Section 7.7.6. The drives have been designed to meet the velocity and acceleration requirements.

7.4.3.1.2 Enclosure Bogie layout There are a total of four enclosure drive bogies and eleven enclosure idler bogies as shown in Figure 7-62. Each drive bogie is located directly under an enclosure super column and each idler bogie is located directly under a secondary support column. These columns are the primary vertical load paths within the rotating enclosure structure and are therefore the best location for the bogies.

Figure 7-62. Azimuth rotation mechanisms

7.4.3.1.3 Design Loads Design loads for the bogies are calculated in the structural analysis described in Section 7.4.2. Vertical and lateral and loads are based on the following load combination:

 100% of all material dead loads and floor dead loads.  100% of shutter door counterweights.  100% of bridge crane equipment weight and payload.  100% of all equipment live loads.  20% of the roof and floor live load  100% of lateral and overturning effects due to seismic loading. (The effective seismic mass of the bridge crane payload has not been included in the derivation of the seismic loads as it is not required by the 2006 International Building Code.)

The enclosure bogie design loads are listed in Table 7-22.

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Table 7-22. Enclosure bogie design loads Bogie Type Vertical Load (kN) Lateral Load (kN) Drive Bogies 6900 1600 Idler Bogies 1900 0

As seen in Table 7-22, the enclosure bogie load distribution is not uniform. This is largely due to the presence of the vertical shutter guide structure and its effect on the structural design of the super columns. The maximum loads occur under the 4 super columns where each of the drive bogies supports 15% of the total vertical load. The remaining 40% of the load is shared by the 11 enclosure idler bogies.

7.4.3.1.4 Enclosure Drive Bogies The enclosure drive bogie consists of three major parts; the saddle, chassis and trucks as shown in Figure 7-63 and Figure 7-64. The chassis includes a support saddle that is bolted to the underside of the rotating ring girder. The bolted connection to the ring girder includes provisions for 6 degree of freedom adjustability via slotted holes and shimming capabilities. A Fabreeka pad is used at this interface to facilitate the transfer of loads between the rotating ring girder and the saddle.

Figure 7-63. Enclosure drive bogie assembly

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Figure 7-64. Enclosure drive bogie assembly (exploded view)

The saddle transfers the loads from the bottom of the super column to the chassis through a large diameter radial pivot pin. The chassis is attached to four truck assemblies via bolted connection with slotted holes for alignment and with each wheel pair incorporating a radial pivot pin in its attachment to the chasses. This mechanical arrangement distributes the load equally to each truck and bogie wheel as shown in Figure 7-65.

Figure 7-65. Enclosure drive bogie free body diagram

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Chassis Assembly The chassis includes the chassis and saddle weldments and is anchored to the enclosure ring girder through the saddle. The saddle is approximately 3.25 m wide, 2.5 m long and 1.5 m tall. It consists of two horizontal 80 mm bearing plates, two vertical 80 mm hinge plates and is heavily stiffened by a mesh of 25 mm vertical stiffener plates.

The saddle is connected to the steel plate chassis with a horizontal pin. The 360-mm carbon steel (radially oriented) horizontal pin provides a pitch direction degree of freedom to compensate for the vertical misalignment the rail. This design provides correct load distribution through the chassis, reduces fatigue at the saddle to ring girder interface and allows constrained motion of the chassis with respect to the saddle.

There are two fabrication options for the horizontal pin being considered:

 The saddle has two bushings, one at each end. The horizontal pin fits tight and is attached to the chassis. This allows the saddle to rotate about the longitudinal axis of the horizontal pin while the pin and chassis remain fixed. This design requires bushings of 360 mm inner diameter capable of handling the high loads.  The second option has a lubricated chassis-horizontal pin connection. This option allows the chassis to rotate freely about the longitudinal axis of horizontal pin, while the pin and saddle remain fixed. This option requires a fully machined shaft and lubrication of the chassis. A trade study of these two options will be completed in the detailed design phase.

The chassis is approximately 2.5 m wide, 5.5 m long and 1.25 m tall. It consists of a stiffened box girder structure made up of 80 mm thick outer web plates and 25 mm thick interior stiffeners. The chassis base is a weldment constructed from 200 mm wide flange sections and 80 mm base plate designed to increase flexural stiffness of the chassis and to provide an interface for the bogie truck assemblies.

Truck Assembly

Figure 7-66. Truck assembly

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Each enclosure drive bogie has four truck assemblies and each truck assembly consists of a truck saddle, truck weldment, two wheels and two lateral restraint assemblies. Each truck is attached to the bogie chassis through a truck saddle. The truck saddle is attached to the truck weldment through a (radially oriented) horizontal pin that facilitates equal sharing of the loads between the two wheels. The truck saddle is bolted to the bottom of the bogie chassis. See Figure 7-66 and Figure 7-67 for images of the truck assembly.

The truck saddle is constructed of 25 mm and 30 mm steel plates similar to the chassis and saddle. The truck weldment is made out of 30 mm thick plates and uses a box design to minimize material. The connection between the truck weldment and the truck saddle is through a 270 mm diameter shaft horizontal pin. The weldment pivots about the saddle allowing up to 1 degree of pitch motion.

Figure 7-67. Truck assembly (exploded view)

Each truck assembly has two 900 mm diameter forged steel (flat) wheels connected to the truck weldment using a horizontal pin connection. The use of flanged wheels is not a viable option due to the high lateral loads and unavailability of forged wheels capable of handling such loads. The 270 mm horizontal pin connection provides equal load sharing between the truck wheels by compensating for any vertical rail tolerance. Each wheel is aligned to the center of the rotation of the enclosure and mounted on two pillow block bearings. Vertical and lateral adjustments are provided at the wheel to truck weldment connection and at the bogie chassis to truck connection.

Lateral Restraint Assembly Lateral restraint assemblies are bolted to each truck in the front and back. Each lateral restraint assembly consists of two 250 mm diameter guide rollers on either side of the rail. See Figure 7-68 for an image of the lateral restraint assembly. The rollers are designed to take maximum survival lateral loads and can be adjusted in the x, y, and z directions.

The rollers of the front and back lateral assemblies have a small gap between the roller and rail face to prevent binding and high frictional forces. During a seismic event, both the front and back rollers engage the rail and share the lateral loads.

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The lateral restraint assembly weldment is a simple steel plate structure designed to withstand high lateral loads and bending moments and to transfer the loads from the truck to the rails. The weldment is designed to allow access for maintenance and inspection of the rollers. The rollers are attached to the weldment through a steel sleeve that is connected to the weldment using slotted bolt connections for lateral adjustments. The sleeve can be shimmed to adjust the roller vertically and is designed to reduce the high shear forces in the restraint roller shaft by distributing these forces over entire length of the shaft.

Figure 7-68. Lateral restraint assembly

Power Requirements The maximum rotational velocity and acceleration requirements in the operational wind environment define the power required for the enclosure drive mechanism. The enclosure must also rotate in a 30 m/s wind environment, but it is not required to rotate at the maximum speed in this non-operational case.

Each of the 4 drive bogie include 4 individual drives for a total of 16. During normal operation, all 16 drives are active. To satisfy requirement ENC-0390, which states that the enclosure must operate in up to 30 m/s winds, a total of 14 drives are used to provide the maximum required drive torque. The 16 drives provide additional margin and allow continued operation if 2 drives fail and must be taken out of service.

Under these conditions, the current design requires drives with a minimum total output of 16 hp (each). Each of the four truck assemblies are equipped with one standard 14.92 kW (20 hp) drive. Each drive bogie hence, has 4 drives with 60 kW (80 hp) of power. The drive bogie can rotate in either direction and is equipped with Variable Frequency Drives (VFD) to ensure smooth operation. The drives are mounted directly on the shaft of the drive wheels as shown in Figure 7-67.

Four drives with brakes are placed symmetrically on the enclosure drive bogies, one at the front of each truck assembly for better tracking. The brakes are sized to restrain motion of the enclosure under the survival wind condition.

In the non-operational case, the enclosure rotational speed is approximately 0.7 deg/sec in the worst case enclosure wind torque orientation relative to the wind.

7.4.3.1.5 Enclosure Idler Bogie The design approach for the enclosure idler bogie is the same as that for the enclosure drive bogie. The idler bogie uses a similar truck assembly as shown in Figure 7-69 and Figure 7-70.

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The enclosure idler bogie is assembled with four 700 mm wheels to meet the load requirements. There are two truck assemblies attached to a weldment extending down from the enclosure ring girder. Each truck pivots independently about a (radially oriented) horizontal pin to compensate for the small vertical alignment errors of the rail. Lateral guide rollers are located at each end of each truck assembly similar to the drive bogie trucks.

Figure 7-69. Enclosure idler bogie

Figure 7-70. Enclosure idler bogie assembly (arrangement)

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7.4.3.1.6 Azimuth Rail Design The enclosure bogies travel on two concentric rails separated by 1.5 meters. The inner rail has a radius of 25.95 meters. Two rail options were studied; a standard ‘A’ European rail and North American crane rail (CR). The standard ‘A’ European rail has a low center of gravity and wide web, ideal for high side thrust loads. To meet the vertical and lateral loads, the A150 rail was chosen. The A150 rail is fabricated from 1100 type steel with a minimum tensile strength of 1080 N/mm2 and minimum Brinell hardness of 319. Since an off-the-shelf rail that can handle the lateral and vertical loads of the enclosure is available, the need to fabricate a custom, machined rail is unnecessary.

The rail is typically fabricated with a radial tolerance of ±6 mm and a vertical tolerance of ±3 mm. To accommodate for manufacturing and installation tolerances, a steel sole plate will be used to allow for vertical adjustment of the rails using leveling nuts below the plate. See Figure 7-71 for an image of the rail and sole plate. Once the sole plates are installed and leveled within tolerance, steel shims or grout is added between the enclosure base steel and the sole plate. The rail is anchored to the sole plate with standard rail clips (rated for lateral restraints at 190 kN per clip) spaced at 300 to 450 mm apart providing lateral adjustment to the rail. A standard resilient pad under the rail will be used to increase the contact area and reduce impact and vibration transmission to the supporting structure.

Figure 7-71. Sole plate and azimuth rail

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7.4.3.2 Shutter Design Requirements Overall performance requirements for the vertical and horizontal shutters are listed in Table 7-23.

Table 7-23. Overall shutter mechanical design requirements (Level 3 requirement) Requirement ID & Title Requirement Notes ENC-0423: Shutter Drives The enclosure shutter drives shall To avoid the uncontrolled motion Brakes incorporate drives with fail-safe brakes of the shutters ENC-0427: Drives The enclosure shall provide a safe and To allow manual closure of the Disconnection (Shutter easy means for disconnecting the drives shutters in the event of drive Drives) failure. The enclosure shutters shall provide a ENC-0430: Shutter positioning accuracy of better than 0.1 Best practices. Positioning Accuracy meters at positions between fully open and fully closed The enclosure shall provide limit ENC-0431: Shutter Limit switches at the end of travel to define Mechanical safety Switches shutter position to < 2 cm To protect the Telescope from The enclosure shutter shall have the adverse weather conditions, the 3 ENC-0432: Maximum maximum time of 3 minutes for a shutter minutes criteria was selected Shutter Opening Time to move between any two positions in the based on the expected wind speed range 2% open to 98% open increase rate for the site To protect the Telescope from adverse weather conditions, the 6 minutes criteria was selected The enclosure shutter shall have the ENC-0433: Maximum based on the ENC-0432 maximum time of 6 minutes to stow from Shutter Stow Time requirement and also allowing 3 any position in its range minutes for the initial process of opening/closing the shutters (e.g., locking pins, etc.) To protect the shutters and The enclosure shall provide hard enclosure from possible ENC-0435: Shutter Stops mechanical stops to prevent over travel of mechanical impacts due to the shutters under any circumstances controlled/uncontrolled motion The enclosure shall provide a safety ENC-0417: Vertical mechanism to prevent a vertical shutter Safety and redundancy Shutters Safety Mechanism panel falling in the event of a failure of the lift mechanism The enclosure shall provide a means of ENC-9500: Horizontal Backup means of closure to closing the horizontal shutters after loss Shutter Emergency Closure protect the telescope of main power The enclosure shall provide a means of ENC-0428: Vertical Backup means of closure to closing the vertical shutters after loss of Shutter Emergency Closure protect the telescope main power

7.4.3.3 Vertical Shutter Mechanisms The vertical shutter consists of three panels. The panels are synchronously driven by a winch, sheave and cable system and the panels are counterweighted to reduce drive the power requirements. The shutter panels are laterally restrained by guide rollers running on steel rails mounted to the enclosure structure. Figure 7-72 gives an overall view of the shutter and all of its mechanical components. Hard mechanical stops in the open and closed positions prevent over- travel of the shutters under any circumstances.

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Figure 7-72. Vertical shutter mechanism configuration

7.4.3.3.1 Vertical Shutter Load Review The design lateral and vertical loads for the vertical shutter bogies are based on the following load combinations:

 100% of all material dead loads.  100% of all Main Wind Force Resisting System (MWFRS) wind loads (survival wind load) have been used for sizing the guide rollers and their components.  Operational MWFRS wind loads were used for mechanism horse power determination.  100% of all vertical and lateral seismic effects.

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Each vertical shutter weighs 415 kN (93 kip). The shutters operate at a 10-degree lean angle to the vertical axis required to clear the telescope swept volume and minimize the enclosure interior space. The counterweight cables and drive mechanisms are designed with a high (7+) factor of safety to keep cable forces low. The maximum vertical shutter lateral guide load is 670 kN.

7.4.3.3.2 Vertical Shutter Mechanism Drive System Options & Selection The use of counterweights to operate the vertical shutters greatly reduces the power necessary to operate the shutters. Various options of counterweights were considered, ranging from a 0% counterweight configuration to a 105% counterweight configuration. All options with counterweight percentage less than 100% require power to close the shutters and therefore do not provide a “fail-close” system.

A 0% counterweight configuration means that no balancing counterweights are used. As the total weight of the shutter moves upward against gravity, the cable size, power and winch required to facilitate this operation become very large and the system becomes expensive. Providing adequate space for the size and quantity of these components becomes a challenge. This option also has the shutter remain open in the case of mechanism failure.

Two competing counterweight designs; 105% and 90% were brought to the preliminary design level. The primary feature of the 105% design was that under a failure condition, the shutter would be able to be closed without drive power. Risk analysis determined that unanticipated loads resulting from higher than normal guide roller friction and shutter panel skew require the need to be able to mechanically drive the panels to a closed position. Therefore the 90% counterweighted panels were chosen for the baseline design.

The space within the super columns contains counterweights for the upper and middle shutters. The space adjacent to the super column houses the counterweight for the lower shutter.

7.4.3.3.2.1 Mechanism Operation Each of the three vertical shutters have independent rails, counterweights, cables, sheaves and a winch system on each side of the shutter. The system is designed with redundancy and adequate safety factors to prevent failure modes where the shutter could free fall. All three systems have the same components (sizes and capacities), facilitating common parts for interchangeability and spares. Each winch has a brake and control system that maintains synchronous motion of the two opposite sides of the shutter.

The shutters are connected to counterweights via counterweight cables from above. Winch cables are connected to the bottom of the counterweights. The winches pull the counterweights to operate (close) the shutters. The shutters are opened by the gravity due to their weights. This motion is controlled by releasing winch cables. See Figure 7-72 for an image of the vertical shutter mechanisms.

Due to construction alignments and thermal contraction and expansion, the vertical shutters are sequenced such that the open portion of the enclosure structure is brought back into plumb through the utilization of the vertical shutters. See Figure 7-56 for the sequence of operations of the vertical shutters. This sequence allows the doors and guide rails to realign the rail and jamb structure from their deflected position. The guide rails, lateral restraint rollers, and shutters accommodate the lateral load independently, but having them move together provides a collective, stronger reaction to the lateral load.

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Each shutter has the ability to be locked in place for maintenance or replacement of parts. A sliding bolt or latch is envisioned for this application allowing maintenance personnel to replace a cable or guide assembly without the door moving from its set location.

7.4.3.3.3 Vertical Shutter Rail Design The vertical shutters travel over the custom designed steel rails shown in Figure 7-73. Two rails are provided for each shutter panel on each side of the aperture for a total of six guide rails. The rails restrain motion of the panels in the lateral and normal directions through lateral guides attached to the shutter panels. The lateral guides include rollers that contact the rails, allowing smooth vertical motion of the panels.

Figure 7-73. Vertical shutter rail detail

7.4.3.3.4 Vertical Shutter Counterweight, Cables and Winch The counterweight for the upper and middle shutters fit within the available space of the front super columns. With the same design as the other shutters, the lower shutters counterweight is located adjacent to the front super column. Refer to Figure 7-74 for a view of the counterweights inside and adjacent to the super column. The counterweight is a composite design of lead plates and lead shot fabricated in a steel frame. The objective of the counterweight design is to maximize the weight and minimize the overall dimensions (especially height) of the assembly so that it fits within the available space and is able to move the required distance for operation of the shutter.

Each counterweight weighs 190 kN (42 kips). The lead plates contribute 120 kN (27 kip) and the frame contributes 35 kN (7.8 kip). The balance, 35 kN (8 kip), is filled with lead shot. The lead shots provide adjustability to the counterweight once the shutters and mechanisms are installed. Each lead plate is stacked to achieve the total weight making it easy to install inside the steel frame. The lead plate and counterweight properties are as follows:

 Plate dimension: 815 mm x 1100 mm x 25 mm  Mass of Each Plate: 237 kg  Quantity of Plates Required: 50 plates  Total stack height : 1.25 m

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Figure 7-74. Vertical shutter counterweights within super column

The counterweight travels vertically within the super column and are restrained laterally by two guide roller assemblies located on opposite sides as shown in Figure 7-75. The assemblies provide the lateral restraint required in the event of an earthquake and keep the counterweight from binding. The cables attached to the bottom and the top of the counterweight restrain it from any vertical motion when it is locked in position. Two counterweight cables (32 mm diameter 6 x 37 classification cables) are required to take the vertical acceleration loads due to a seismic event and the design provides a third cable for redundancy.

Figure 7-75. Vertical shutter counterweight, frame and lead plates

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The selected cables have a design safety factor of 7.0 and are supported on sheaves 500 mm diameter. The effective strength of the cables depends on the sheave diameter, so the sheave diameter is selected based on the loads of the cable and available space within the structure.

Each shutter operates using four 11.5 kW (15 horsepower) winches (with brake). Each counterweight is connected to two winches via four cables (12mm diameter 6 x 37 IWRC classification). The winch cables are supported on 300 mm diameter sheaves. Two winch and cable assemblies are required for the operation and two extra assemblies are provided as backup in case of failure during operation.

7.4.3.3.5 Vertical Shutter Guide Assemblies The vertical shutter guide assembly is a simple bogie weldment with eight 100 mm cam-rollers designed to accommodate loads in two opposite directions as shown in Figure 7-76. Each shutter panel has eight guide assemblies, two at each corner. The guides restrain motion of the shutter panel in the lateral and normal directions and provide free motion along the rails in the vertical direction.

Each guide assembly weighs 100 kg. The guide assembly is designed for easy maintenance and assembly. Figure 7-77 provides a view of the guide assembly and rails. Any restraint roller can be replaced without removing the guide assembly. For better access, all the guide assemblies are located near top and bottom of the shutters. A maintenance platform is provided for access to the guide assemblies.

Figure 7-76. Vertical shutter guide

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Figure 7-77. Vertical shutter guide assemblies

7.4.3.4 Horizontal Shutter Mechanisms The horizontal shutter panels operate on a friction drive system with drive and idler bogies fixed to the shutter doors. Power to the shutter drive bogies is via slip rings mounted on the enclosure and on both sides of the shutter door for redundancy. The shutters move horizontally on separate sets of rails. The lower shutter nests below the upper shutter in the open configuration. When fully open, the shutters provide an unobscured viewing opening for the telescope pointing to zenith. The horizontal shutters are controlled independently and may be deployed at intermediate positions to shield the telescope from moonlight. The layout of the horizontal shutter structure and mechanisms is shown in Figure 7-78 and Figure 7-79.

7.4.3.4.1 Horizontal Shutter Load Review The horizontal shutter mechanisms are designed for the maximum loads due to operational and survival conditions based upon the following load combinations:

 100% of all material dead loads.  100% of all roof live loads. (A roof live load reduction based on tributary area has been taken per the 2006 International Building Code).  100% of all Main Wind Force Resisting System (MWFRS) wind loads (survival wind load) have been used for sizing the bogies and their components.  Operational MWFRS wind loads were used for mechanism horse power determination.  100% of all vertical and lateral seismic effects.

The design load for the horizontal shutter drive bogies is 765.6 kN considering all dead loads, live loads, and survival wind and seismic loads. The design load for the horizontal shutter idler bogie is 340 kN considering all dead loads, live loads, and survival wind and seismic loads. Lateral restraint rollers and vertical uplift restraints can accommodate the maximum lateral loads and survival wind loads. As mentioned, the open end of the enclosure will likely be out of plumb.

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Similar to the vertical shutters, the horizontal shutters deploy and stow in a designated sequence and the shutter mechanisms and shutter structure are capable of bringing the enclosure structure back into plumb. The maximum lateral load on the guide roller assembly is 325 kN.

Figure 7-78. Horizontal shutter mechanisms

Figure 7-79. Horizontal shutter mechanisms isometric section

7.4.3.4.2 Horizontal Shutter Rail Design Similar to the azimuth enclosure rail, the European Standard rail A150 is proposed for the horizontal shutter mechanisms. The rail is adjustable in the vertical and lateral directions to meet the required installation tolerances. Each shutter panel travels on independent rails located on each side of the aperture opening. The rails are mounted to the enclosure steel runway with standard rail clips.

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7.4.3.4.3 Horizontal Shutter Drive Bogie The horizontal shutter drive bogie assembly consists of two bogie trucks, uplift restraint assembly, chain drive assembly and steel weldments as shown in Figure 7-80 and Figure 7-81. The saddle, made of 25 mm steel plates is bolted to the shutter structure with a shim allowance and slotted holes for vertical and lateral adjustment. The chassis, also fabricated from 25 mm steel plates, is connected to a saddle through a 150 mm diameter horizontal steel pin that provides a pitch rotational degree of freedom to compensate for the vertical alignment error of the rail. The chassis is bolted to the truck assemblies with shim allowance and slotted holes for proper adjustment.

Each truck assembly includes a weldment made of 20 mm steel plate and a 450 mm diameter forged flat bogie wheel mounted on two 80 mm pillow blocks and tapered roller bearing. A flanged wheel for lateral restraint is not possible due to the high lateral design loading.

The lateral restraint assembly is fabricated from 25 mm steel plate. It mounts directly to the underside of the truck weldment; one assembly at each end. Each restraint assembly has two 100 mm, heavy-duty cam-rollers.

The horizontal drive bogies do not experience any uplift during operational wind speeds. Bogies are equipped with uplift restraint clamps to prevent uplift at survival wind speeds.

Each drive assembly consists of a 14.91kW (20 horsepower) electric gear-motor with brake and a chain & sprocket drive between the drive motor and the bogie wheel. The drive power is based on the shutter closing time requirement, shutter weight and operational wind speed. The composite mechanism creates a compact drive assembly with off-the-shelf components and is easily maintained.

Figure 7-80. Horizontal shutter drive bogie

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Figure 7-81. Horizontal shutter drive bogie (exploded view)

7.4.3.4.4 Horizontal Shutter Idler Bogie The horizontal shutter idler bogies are categorized as two types:  Horizontal Shutter Idler Bogie (with uplift restraints)  Horizontal Shutter Idler Bogie (without uplift restraints)

The idler bogies are identical to the truck assemblies of the horizontal shutter drive bogie, with one set configured with uplift restraints and the other without. Figure 7-82 shows an exploded view of the horizontal shutter idler bogie (with uplift restraints). The idlers with uplift restraints are located along the sides of the shutter panels and ride on the shutter rails.

The horizontal shutter idler bogies (without uplift restraints) are located on the back edges of both the horizontal upper shutter and horizontal lower shutter and provide support for the shutter panels at mid-span between the rails. These bogies ride on the top surfaces of longitudinal girders within the shutter as shown in Figure 7-54. Locations of these idlers within the shutter are shown in the cross-sectional view of the shutter in Figure 7-55. Use of these idlers eliminates the need for a deep structural member at the back end of the shutter panels and therefore results in a more compact horizontal shutter system.

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Figure 7-82. Horizontal shutter bogie truck assembly (exploded view) 7.5 Summit Support Building 7.5.1 Introduction The Summit Support Building consists of the following three buildings:

 Facility Building  Auxiliary Building  Equipment Building

Figure 7-83 gives an isometric view and Figure 7-84 gives a general cross-section showing its 3 building areas. A plan of the lower level of the building is given in Figure 7-85. See the master plan Section 7.3.4 for details about the siting and overall layout of the summit support building.

Figure 7-83. Summit support building exterior

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Figure 7-84. Summit support building section

Figure 7-85. Summit support building overall floor plan - Level 1

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7.5.2 Architectural Design 7.5.2.1 Facility Building The driving functional design requirements for the facility building are listed in Table 7-24.

Table 7-24. Facility building functional requirements (Level 3 requirement) Requirement ID & Title Requirement Notes The facility building shall be located on The facility building is located on FAC-1323: Facility Building the summit site, detached from the the summit for efficient operations Location enclosure and positioned crosswind to the and detached from the enclosure for enclosure thermal considerations. The control room shall be located on the FAC-1205: Control Room This is required to enable efficient west side of the facility building with a Location science operations. view of the enclosure The facility building shall include an This space is required for the FAC-1187: Facility Building electronics room with a minimum square estimated 15 electronics cabinets Electronics Room footage of 50 m2 needed to support operations. The facility building shall provide an This lab is required for servicing FAC-1330: Facility Building electronics lab with a minimum square electronic equipment and Electronics Lab footage of 60 m2 components. This is required for assembling and The facility building shall provide a FAC-1328: Facility Building maintaining detectors in support of detector lab with a minimum square Detector Lab facility and PI Instruments at the footage of 60 m2 summit. This is required for assembling and The facility building shall provide a class FAC-3406: Facility Building maintaining detectors, adaptive 10,000 clean room with a minimum 14 m2 Clean Room secondary mirror systems and laser of floor space plus a 9 m2 gowning room systems The facility building shall provide a wet This is required for instrument FAC-1114: Facility Building room with a minimum 12 m2 of floor component service to support Wet Room space that includes a stainless steel sink facility and PI Instruments at the and counters, and cabinets summit. The offices are provided for the FAC-3176: Facility Building The facility building shall provide a anticipated level of operations Private Offices minimum of 4 private offices managers. The offices are provided for the FAC-3177: Facility Building The facility building shall provide open anticipated level of operations staff Shared Offices office space for 50 people and visitors. The facility building shall provide a A conference room is needed for FAC-1325: Facility Building conference room with a minimum 40 m2 group meetings and Conference Room of floor space teleconferences.

The spaces within the facility building are as follows:

 GMTO staff offices  Visiting scientist offices  Instrument scientist offices  Detector lab & wet room  Electronics lab

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 Clean room  Control room  Electronics room  Medical room  Conference room  Kitchen/lounge  Storage  Lavatories

The facility building is a two-story building within the summit support building with the main entrance on the northwest side. The main entrance is covered and includes a wind barrier to provide protection from strong winds and precipitation. Adjacent to the entry is a staircase and elevator connecting the first and second floors. The first floor includes a combination of office and laboratory spaces. The office space on the first floor is intended for instrument scientists, visitors, and the site manager. A total of 13 offices have been provided to serve these different, high level personnel. The offices may be used interchangeably, as needs and functions may differ during the lifetime of the observatory. The laboratories on the first floor include the electronics lab, detector lab (with wet room), and clean room. The labs have been placed adjacent to each other and in close proximity to the M2 test bay of the auxiliary building. See Figure 7-86 for a floor plan of the first level of the facility building.

The second level is a continuance of office spaces, along with a conference room and kitchen/lounge adjacent to the stairwell and elevator. The control room and electronics room are located on the west side of the building, adjacent to the stairwell and elevator. The control room has windows overlooking the enclosure and is adjacent to an exterior observation deck. The control room and conference room join with a removable wall partition. The conference and kitchen/lounge are both located on the northern face of the building, providing sweeping views of the landscape and the ability to visually locate any weather systems coming from the north. See Figure 7-87 for a floor plan of the second level of the facility building.

The exterior of the summit support building is consistent with the construction and styling of the enclosure and enclosure base, unifying their aesthetics and promoting their operation as one entity. Windows are insulated, double pane glass. Blackout shades are provided for nighttime operation, allowing natural lighting and throughout the daytime.

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Figure 7-86. Facility building - Level 1

Figure 7-87. Facility building - Level 2

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7.5.2.2 Auxiliary Building The driving functional design requirements for the auxiliary building are listed in Table 7-25.

Table 7-25. Auxiliary building functional requirements (Level 3 requirement)

Requirement ID & Title Requirement Notes The coating facility is required to The auxiliary building shall provide a bay apply fresh coating to the M1 FAC-2636: Auxiliary for the mirror coating facility per GMT- segments to maintain throughput Building Mirror Coating Bay 7.2.3_4.2-ICD-00193 and minimize emissivity.

This is required to apply fresh FAC-3367: Auxiliary coating to the M1 segments to The auxiliary building shall provide a bay Building Mirror Washing maintain throughput and minimize for a primary mirror wash station Bay emissivity.

Large work areas are needed away The auxiliary building shall provide two from the telescope for supporting FAC-1278: Auxiliary bays for the assembly, testing, and large science instruments and Building Instrument Bays servicing of large instruments per GMT- assembling primary mirror cells. 7.2.3_6.0-ICD-00472 Required for assembling and The auxiliary building shall provide a 2 servicing science instruments and FAC-1283: Instrument Bay hoist bridge crane with capacities of 15 primary mirror cells in the Crane and 7.5 metric tons with access to all instrument bays Instrument Bays FAC-2637: Auxiliary The auxiliary building shall provide a This is required to assemble and Building Assembly/Staging staging area for handling primary mirror support GMT subsystems. Area assemblies and large instruments Required for installing primary FAC-1305: The assembly/staging area shall provide a mirrors in their cells, supporting Assembly/Staging Area fixed overhead crane with a minimum coating operations, and for lifting Crane capacity of 30 metric tons the structures of major instruments.

The M2 Lab will be a climate controlled area and should be The M2 Test bay shall be located in the positioned so as to not impact FAC-3156: M2 Test Bay auxiliary building, in a bay adjacent to the thermal stability of the enclosure Location clean room and telescope imaging performance.

The auxiliary building shall include an This is required for assembling and FAC-1315: Auxiliary instrument shop for small fitting work maintaining telescope equipment Building Instrument Shop (lathe, mill, drill presses) and mechanical and science instruments. assembly of small subsystems

The auxiliary building provides high-bay space necessary for maintenance of the telescope primary and secondary mirrors and instruments. It is located between the facility building and equipment building, and connected to the enclosure with fixed rails allowing the primary mirrors and large instruments to be efficiently and safely transported. The rails extend through the building to the east wall for access to the instrument and M2 test bays and to allow for future expansion as described in Section 7.3.4.1.4. The spaces within the auxiliary building are as follows:

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 Mirror coating bay  Mirror washing bay  Instrument bay  Staging area  M2 test bay  Instrument shop  Mirror vestibule  Receiving bay

A mechanical mezzanine is located above the mirror washing bay for building mechanical equipment, such as HVAC air handlers.

A floor plan of the auxiliary building is provided in Figure 7-88.

Figure 7-88. Auxiliary building floor plan

The primary mirror cells will initially be assembled in the auxiliary building. This involves assembly of the mirror support system in the cell, testing with a dummy mirror, installation and testing of the mirror ventilation system and finally installation of the primary mirror segment itself. The mirror in its cell is then coated in the coating chamber prior to installing the full assembly in the telescope. The assembly work will take place in the side bays and central corridor and use the fixed 30 metric ton stationary crane for handling the large pieces. A detailed description of the M1 cell assembly, integration and test work is given in Section 5.10.

The auxiliary building houses the equipment for re-coating the reflective surfaces of the primary mirrors. About half of the total area of the auxiliary building is used for this process. A large bay is provided for stripping off aged coatings, a process that involves a wet chemical soak and rinse,

ENCLOSURE AND FACILITIES 7–105 GMT SYSTEM LEVEL PRELIMINARY DESIGN REVIEW December 13, 2013 and washing the bare surface. Staging and a gantry will be provided to bring personnel close to the mirror surface to manually remove the old coating. Effluent produced in this process is collected for proper disposal. See Section 6.13.6 for more information on the mirror washing and stripping process.

The mirror wash area is located directly across from the coating chamber. The chamber is a large two piece vacuum vessel, the largest piece of equipment within the auxiliary building. A sketch showing the coating chamber in the coating bay is given in Figure 7-89. The size of the coating chamber drives the overall shape of the building, determining structural bay spacing and building height. A detailed description of the primary mirror coating facility is given in Section 6.13.7.

Figure 7-89. Coating chamber

Assembly of major science instruments prior to installation on the telescope and routine service that requires removal of the instrument from the telescope will take place in the instruments bay and staging area. Curtains will provide separation between the bays as required for cleanliness and isolation. The service areas have convenient access to the technical offices and labs in the facility building. A dual hoist 15/7.5 metric ton bridge crane with an 8.0 meter raised hook height will provide equipment handling capability in the instrument and M2 test bays.

A series of flush mounted intersecting rails connect the telescope pier to the auxiliary building and the mirror washing bay to the mirror coating bay. These extend out of the auxiliary building to the enclosure to allow primary mirror assemblies, secondary mirror assemblies and instruments to be

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The mirror cells and large instruments enter the auxiliary building through folding fabric doors on each end of the mirror vestibule. The space in the vestibule area is isolated to maintain cleanliness in the work areas and provide a thermal barrier to the outside. The instrument shop is adjacent to the entry vestibule to allow the vestibule to be used as a staging area for materials or equipment needed by the shop.

The M2 Test Bay provides space for the secondary mirror calibration equipment (see Section 8.7.1 for a description of the M2 calibration system). A 5m diameter x 12m deep pit is provided to house the test equipment and optics for the calibration process. The 15/7.5 metric ton bridge crane travels over the M2 test bay and is used for moving the telescope top frame and secondary mirror assembly into their required positions. Access to the bottom of the pit will be provided via caged ladder. Lighting and an exhaust ventilation system will also be provided for workers entering the pit. The depth of the pit will provide a stable thermal environment for testing. Removable guardrails will be provided around the pit for personnel safety.

The M2 test bay (Figure 7-90) is located adjacent to the clean room. This is to facilitate the movement of personnel and equipment between the two common spaces. The M2 test bay is not a permanent clean room, but can be temporarily tented to provide a clean and stable environment for testing purposes. Figure 7-91 shows a floor plan of the test bay and clean room area.

Figure 7-90. M2 test bay

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Figure 7-91. M2 test bay and clean room

Finally, an equipment mezzanine is located above the mirror washing bay. The equipment mezzanine houses HVAC equipment serving the facility building (control room, laboratories, clean room, general building HVAC, etc.). The area is completely enclosed to limit noise, vibration and dust within the auxiliary building. Access to and from the mezzanine is by a ladder. A 1 ton hoist is provided to bring equipment and tools to the mezzanine through a floor hatch.

7.5.2.2.1 Major Equipment at the Auxiliary Building

Bridge Crane A dual hoist 15/7.5 metric ton bridge crane is provided in the auxiliary building, and travels over the instrument bay, staging area and M2 test bay. The bridge crane is intended to help with the assembly and conveyance of telescope instruments along with the telescope top frame and secondary mirror assembly. The second hoist is provided to assist in rotating the vertical orientation of large instruments. The coverage of the bridge crane is shown in Figure 7-88. Specifications for the bridge crane are listed in Table 7-26.

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Table 7-26. Auxiliary building bridge crane specifications Criterion Specification Notes 15 metric ton primary, Sized for instrument handling. Capacity Second hoist for instrument 7.5 metric ton secondary turning

Required for instrument Hook Height 8 m handling

Trolley Speed 0 to 0.33 m/s, variable

Hoist Speed 0 to 0.20 m/s, variable

Bridge Speed 0 to 0.50 m/s, variable

Number of Hooks 2 For instrument turning

Bridge Span 12.5 m

The following movements are possible with the bridge crane:

Bridge travel (NS in the auxiliary building) Trolley travel (EW in the auxiliary building) Lift (extension & retraction of the hoist) Rotation of load (secondary 7.5 mt hoist to rotate load suspended on the 15 mt hoist)

Stationary Hoist A 30 metric ton stationary hoist is provided in the receiving bay of the auxiliary building. The hoist is located at the intersection of the rail systems, as shown in Figure 7-88, to allow primary mirror segments to be installed in cells using either rail system. The hoist is used for the initial integration of the primary mirror segments into their cells. During operation, the hoist will be used as necessary to support primary mirror segment recoating or to offload large and sensitive items such as science instruments. Specifications for the stationary hoist are given in Table 7-27.

Table 7-27. Auxiliary building stationary hoist specifications Criterion Specification Notes Required for lifting M1 segments Capacity 30 mt during M1 cell integration Required for lifting M1 segments Hook Height 11 m during M1 cell integration Hoist Speed 0.002 m/s to 0.033 m/s, variable Creep speed required

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7.5.2.3 Equipment Building The driving functional design requirements for the equipment building are listed in Table 7-28.

Table 7-28. Equipment building functional requirements (Level 3 requirement) Requirement ID & Title Requirement Notes Machinery and equipment in the FAC-10370: Equipment equipment building shall be mounted Minimize vibration transmission Vibration Isolation using vibration isolators Machinery and equipment in the FAC-10371: Equipment equipment building shall be mounted on Minimize vibration transmission Foundations isolated reinforced concrete pads The equipment building is located The equipment building shall be located on the summit for efficient on the summit site detached from the operations and detached from the FAC-1233: Equipment enclosure and positioned crosswind to the enclosure for thermal Building Location enclosure and physically adjoined to the considerations. It is adjoined to the auxiliary building auxiliary building for operations efficiency. The equipment building shall provide 25 FAC-1229: Equipment This is heat generating equipment m2 of floor space for the pumps and heat Building Hydrostatic moved away from the telescope exchangers for the telescope hydrostatic Bearing Skid enclosure. bearing system The equipment building shall provide a set The set provides redundancy for of air compressors, filters and dryers with mission critical systems. The total FAC-1230: Equipment a minimum rating of 60 CFM each per the peak flow rate is 100 CFM per the Building Air Compressors requirements in GMT-SE-REQ-000190 Common Utilities Budget GMT- common utilities SE-DOC-00366. The equipment building shall provide the This equipment is contained in the FAC-1232: Equipment chillers and pumps for the HVAC and equipment building due to heat and Building Chiller Systems telescope chilled fluid systems per GMT- noise generation. SE-REF-00366 Common Utilities Budget The equipment building shall provide 25 Locating coating equipment in the FAC-3411: Equipment m2 of floor space along the wall adjacent equipment building frees up space Building Coating System to the coating chamber for coating plant and removes heat and noise from Equipment equipment per GMT-7.2.3_4.2-ICD-00193 the auxiliary building. FAC-1234: Equipment The potable water system is located The equipment building shall house the Building Potable Water indoors in the equipment building water plant for the potable water system Plant for convenience and cleanliness. Power is delivered to the summit at FAC-1227: Equipment The equipment building shall provide a an intermediate voltage to be Building Service Entrance Service Entrance Supply (SES) for power stepped down and distributed Supply delivered from the support site across the summit. The equipment building shall house the FAC-1228: Equipment Transformers are required to step electrical power transformers for the Building Transformers down the voltage on the summit. summit. The equipment building shall provide a This is required to provide clean UPS with a minimum rating of 400 kVA power for critical instrumentation FAC-3414: UPS Power (TBC) at 220V, 50 Hz for electrical per the Common Utilities Budget equipment in the facilities and auxiliary GMT-SE-DOC-00366. buildings. This will allow the telescope and The equipment building shall include a FAC-6140: Emergency enclosure to be put in a safe state in 120 kVA generator for emergency power Generator the event of a catastrophic main on the summit power loss.

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The building has two levels, with an open mezzanine and monorail crane to lift equipment to the second level. The first level houses an array of mechanical, electrical, plumbing, and mirror coating ancillary equipment. To minimize vibration, equipment will be placed on isolated concrete slabs within the buildings and the equipment itself will be placed on vibration mounts (springs). An opening in the floor slab will be provided in the southwest corner of the building to allow the transfer of utilities to the enclosure base through underground pipe and conduit.

The second (mezzanine) level houses mechanical, plumbing, and coating ancillary equipment. The coating ancillary equipment is located adjacent to the mirror coating chamber in the auxiliary building. First and second floor plans of the equipment building are shown Figure 7-92 and Figure 7-93. A sketch of the interior of the equipment building is shown in Figure 7-94.

Figure 7-92. Equipment building floor plan - Level 1

Figure 7-93. Equipment building floor plan - Level 2

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Figure 7-94. Equipment building interior (looking in from the receiving door)

Electrical equipment consisting of transformers, service entrance switchgear, and the backup generator are located outside of the equipment building. This equipment is all under a metal roof canopy. The backup generator is placed within an exterior rated enclosure. Adjacent and exterior to the building are four large fluid coolers that are associated with the chiller systems. See Figure 7-134 for the location of the fluid coolers on the summit site.

The following is a list of mechanical and plumbing equipment in the equipment building:

 Low temperature chillers and pumps  Standard chillers and pumps  Heat exchanger  Raw water storage  Domestic water purification equipment  DI water equipment  Electric boiler  Air compressors & dryers  Air receiver  Hydrostatic bearing oil equipment  Mirror coating ancillary equipment  Fluid coolers (outside)

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The following is a list of electrical equipment in the equipment building:

 Motor control centers  Distribution panels  UPS equipment  Transfer switch  Fiber optic termination points  Main service transformers (outside)  Service entrance switchboards (outside)  Secondary emergency generator (outside)

Design details for the mechanical equipment in the equipment building can be found in Section 7.7.

7.5.2.4 Vibration Isolation Requirements for vibration isolation flow from the Level 2 image quality error budget requirements as described in Section 7.2.1.2. Individual equipment isolation system will be designed to meet this requirement.

To minimize vibration transmission from internal sources, equipment will be placed on concrete equipment isolation pads that are physically separated from the building foundation. The equipment itself will be placed on vibration mounts (springs). This two-tier approach significantly reduces vibration transmitted throughout the buildings and site. See Figure 7-95 for an image of typical vibration isolation details.

Figure 7-95. Vibration isolation of machinery and equipment

7.5.2.5 Materials Overview Materials to be used in the construction of the summit support building were chosen for their performance as well as their availability in the local region. Concrete and steel fabrication and erection are both commonly available in Chile, as is an abundance of skilled labor in these trades.

The summit support building will be clad primarily with 75 mm insulated metal panels for walls. The primary wall panel is 610 mm wide with an off-set double tongue-and-groove joint providing a full thermal break. Panel joints are sealed with a factory installed continuous seal in the groove and field applied sealant on the opposite side of the joint.

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The panels are galvanized with a 20-gauge skin on both faces. The finish material is a 2-coat fluoropolymer coating. Panel widths and skin gauges were determined based on the high wind loading requirements. The core of the panel is 75 mm thick foam-in-place polyurethane with an R- 20 insulation value.

The roof system consists of standing seam roof panels over 100 mm of polyisocyanurate insulation. The roof panels will come in a 305 mm width, with a seam height of 75 mm. The standing seam panels are made of 20-gauge steel.

The metal wall and roof panels are precut at the factory and trimmed on site. All panel edges are trimmed with 20-gauge galvanized sheet metal trim and flashing.

7.5.3 Structural Design The summit support building is designed as a steel, braced frame structure to house the diverse functions of the building. The design considerations that have shaped the structural design include construction costs, building constructability, vibration requirements, site conditions, availability of materials, and architectural considerations.

Design loads are as follows:

Roofs  Superimposed roof live load: 97.6 Kg/m2 The roof live load is as required by the 2006 IBC12.

Floors  Office: 488 kg/m2 The floor live load requirement for office spaces was designed at 488 Kg/m2 for the preliminary design phase. Per the 2006 IBC, office areas are required to be designed for a 50 lb/ft2+ 15 lb/ft2 partition uniform live load (65 lb/ft2 total) and a 2,000 lb. point load. Vibration of the floors is often the governing criteria for the design of floor members in offices. As the design progresses, the current live load requirement of 488 Kg/m2 (100 psf), will be reduced to code required minimums or until vibration becomes the governing criteria.

 Office corridors, stairs: 488 kg/m2 The floor live load requirement for corridors was designed at 488 Kg/m2 for the preliminary design phase. Per the 2006 IBC, corridors are required to be designed for an 80 psf uniform live load and a 2,000 lb. point load. As the design progresses, the current live load requirement of 488 Kg/m2, will be reduced to code required minimums.

 Stairs Per the 2006 IBC, stairs are required to be designed for a 100 lb/ft2 uniform live load.

 Equipment mezzanine: 610 kg/m2 The auxiliary building equipment mezzanine live load was selected based on the estimated weight of the mechanical and electrical equipment placed on the mezzanine.

 Second floor equipment areas: 732 kg/m2

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The equipment building second floor equipment area live load was selected based on the estimated weight of the mechanical, electrical, and GMT provided equipment placed on the floor.

Cranes  Stationary hoist: 30 metric ton  Bridge crane: 15 metric ton / 7.5 metric ton Wind Load  Maximum considered wind speed = 65 m/s  Exposure “C”  Wind Importance Factor = 1.00 The Wind exposure category and wind importance factor are defined by ASCE 7-0523.

Exposure “C” is a code category defined as open terrain with scattered obstructions. All buildings not in a wind shielded environment (i.e., city environment), or located in an exposed wind environment next to a large body of water, fall into category “C” exposure.

The importance factor is a code descriptor for the use of the structure. The importance of a building is based on the potential threat to either human life, or national security. An importance factor of 1.00, as used on the summit support building, is indicative of a building that does not have an unusual threat to human life, or national security, in the event of a building collapse.

Design wind loads are based on IBC 2006 requirements and the wind tunnel test report by Cermak, Peterka, and Petersen24.

Seismic Coefficients For the maximum considered earthquake the seismic design variables are as follows:

 Sds = 1.00g  Sd1 = 0.40g  Soil Site Class= “B”  Seismic Design Category= “D”  Seismic Importance factor = 1

See Section 7.4.2.3 for a description of the seismic design variables.

7.5.3.1 Foundations The ground floor level of the summit support building consists of a reinforced concrete slab on grade. In the auxiliary building, steel crane rails are embedded in the slab and are supported on continuous concrete footings.

The summit support building columns are designed to be supported and anchored on isolated shallow spread concrete footings. Where uplift loads are placed on the footings in excess of the uplift that can be resisted by 60% of the dead load then the footings are designed to be held down by rock anchors. The rock anchors consist of a 100 millimeter diameter concrete filled borings

ENCLOSURE AND FACILITIES 7–115 GMT SYSTEM LEVEL PRELIMINARY DESIGN REVIEW December 13, 2013 with an epoxy coated steel bar core at the centers. The rock anchors resist the uplift forces applied to them through friction between the anchor and the rock.

Foundations have been designed for allowable downward loads based on the soils report by 25 IDIEM for values of 29,780 kilograms per square meter. The Seismic site class has been determined to be site class “B” and foundations have been designed to be located below the frost depth of 700 millimeters. Rock anchor preliminary sizing is based on an assumed frictional resistance of 176,000 kilograms per square meter.

7.5.3.2 Framing Overview 7.5.3.2.1 Roof Framing Figure 7-96 shows an overall framing plan of the summit support building. The roof is composed of bowstring wide flange beams spaced at approximately 1.8 meters on center. The bowstring beams consist of a beam that is hot rolled into an arch to accommodate the curve of the roof. The beams are supported by wide flange steel girders, with the girders in turn supported by structural steel columns.

The steel beams and girders will be topped with a 20 gauge structural steel deck which will support personnel walking on the roof surface during maintenance operations and also serve as a diaphragm when the building is subjected to wind or seismic loads. Design of the roof framing has been dictated primarily by the wind loads contained in the wind tunnel test report. Wind uplift loading in particular is the governing design criteria for most roof components.

7.5.3.2.1 Floor Framing The second level floors of the summit support building are composed of wide flange steel beams and girders supported by structural steel columns. Headed concrete anchors, 19 millimeters in diameter and spaced at approximately 450 millimeters on center, will be auto welded to the top of the beams through the 18 gauge structural steel deck placed over the wide flange beams. Afterwards, the second floor concrete topping will be placed around the headed concrete anchors to form a composite floor system between the steel and concrete. This type of construction minimizes the amount of steel used, and also reduces floor vibrations that can be felt due to human activities. The code required superimposed live loads are the governing design criteria for floor framing.

Figure 7-96. Summit support building overall framing

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7.5.3.2.2 Mechanical Mezzanine The mechanical mezzanine floor is a composite concrete over steel deck system to minimize noise and vibration. The floor is supported by structural steel beams and girder that are supported in turn by the structural steel columns at the perimeter of the mezzanine. Vibration of equipment will be controlled through the utilization of spring isolators mounted between the equipment and its supporting structure.

7.5.3.2.3 Cranes The 30 metric ton stationary hoist is located at the center of the Receiving Bay and is designed to be supported by the roof framing. This framing has been designed for a maximum deflection of L/650 (where L is the span in inches) when subjected to the crane live load only. The support framing is currently configured such that it is tucked up snug to the bottom of the roof framing to minimize the overall building height. Access to the crane in the event of a hoist breakdown may require unbolting the hoist and lowering it to grade for intensive maintenance operations. Figure 7-97 shows an isometric view of the stationary hoist.

Figure 7-97. Stationary 30 metric ton hoist framing

The 15 / 7.5 metric ton bridge crane is supported on a beam and column system that is separate from the main building column system, except that it is braced back to the main building columns for lateral stability. The bridge beam was assumed to weigh 253 kilograms per meter, and the bridge crane machinery was assumed to weigh 15% of the crane’s lifting capacity. The beams supporting the crane bridge were assumed to be limited to a deflection of length/600 in the vertical direction and length/400 in the horizontal direction. The design of the supporting structural steel will be modified as required to support the final bridge crane design. Figure 7-98 gives an isometric view of the bridge crane.

7.5.3.2.4 Exterior Cladding Framing An exterior insulated metal wall panel forms the exterior skin of most of the summit support building. These metal panels are supported by structural steel girts spanning horizontally between the columns at approximately 1.7 meter vertical spacing at the interior and at half this spacing at the building corners. Wind suction loads are the governing design criteria for most of the wall system members and components.

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7.5.3.2.5 Lateral Stability Framing Lateral stability for the superstructure is provided by special concentrically braced steel (SCBF) frames that are usually referred to as “X” braced frames. Lateral loads applied to the structure are resisted primarily by the axial compressive and tensile strengths of the inclined bracing members. This results in a structure that is very stiff and uses the minimum amount of steel to achieve stability. Figure 7-99 shows an image of an SCBF frame for the summit support building.

Figure 7-98. Bridge crane framing

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Figure 7-99. Special concentric braced frame

7.5.3.2.6 M2 Test Bay Pit The M2 test pit (Figure 7-90) is envisioned as a 5 meter wide x 12 meter deep shaft bored into the rock below the summit support building. A 100 millimeter thick sprayed-on concrete wall will provide a smooth face for the shaft to reduce dust accumulation and for mounting supporting lighting and electrical equipment. 7.6 Support Site Buildings 7.6.1 Architectural Design 7.6.1.1 Utilities Building 7.6.1.1.1 Utilities Building Design Requirements The high level functional requirements for the utilities building are listed in Table 7-29.

Table 7-29. Functional design requirements for the utilities building (Level 3 requirement) Requirement ID & Title Requirement Notes The utilities building shall provide shop Shop space is required for facility- FAC-6191: Utility Building space and equipment to support type maintenance and repair Shops maintenance operations operations.

The commercial power will be delivered to GMTO at the support FAC-1354: Utility Building The Utility building shall provide space site on poles where the voltage will Electrical Power Equipment for the main electrical power equipment be stepped down and distributed to the support and summit sites. The Utility building is located at the connection point to the FAC-1355: Utility Building The Utility building shall provide space commercial utility company and is Power Generators for the main power generator(s). were the main switchgear is located and is the logical location for the main power generators.

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7.6.1.1.2 Utilities Building Architectural Design The utilities building serves as the utility electrical and communications termination and distribution point for the whole site. Electrical power and communications enter the building via overhead lines coming from the northwest. Power enters the site via a pad mounted-switch and transformer. From there it is fed into medium voltage rated switchgear and distributed to other areas of the observatory.

Two backup generators housed in environmental enclosures are located outside and adjacent to the utilities building. The two generators provide power in case of a utility company power outage. They are sized to meet the load of the facility during full operation and adjacent space has been provided for a future third generator to allow for redundancy.

Please refer to Section 7.7.6.1 for more information on the electrical yard and electrical power distribution systems.

Fiber optic cables come to the site mounted to the electrical power utility poles. They terminate in the utilities building and are then routed to all other GMT Observatory connection points.

The building also serves as a fabrication and auto shop. The fabrication shop houses heavier machining tools needed for equipment and vehicle maintenance and provides an area for both parts storage and tool storage. The auto shop is sized to allow work on two vehicles at a time.

Office and bench space is provided for personnel within the utilities building including a dedicated office for two maintenance supervisor and a separate room containing eight work benches for technicians. The bench space is intended for office activities and maintenance work on relatively small parts.

See Figure 7-100 for a floor plan of the utilities building.

Figure 7-100. Utilities building floor plan

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7.6.1.2 Warehouse 7.6.1.2.1 Warehouse Design Requirements High level functional requirements for the warehouse are listed in Table 7-30.

Table 7-30. Warehouse functional design requirements (Level 3 requirement) Requirement ID & Title Requirement Notes

The warehouse shall be sized to

accommodate 4 primary mirror transport

FAC-1345: Warehouse containers. Intermediate support This size is large enough to store Size columns are acceptable provided they four primary mirror cell do not interfere with moving mirror assemblies. containers in and out of the warehouse

This is enough headroom to store FAC-1346: Warehouse The warehouse height shall be no less primary mirror cell assemblies on Height than 4 meters high at its lowest point. carts. The warehouse shall have a minimum of FAC-1347: Warehouse one rollup door with dimensions of no This is enough headroom for a Access less than 11 meter wide by 3.8 meter primary mirror assembly on carts. tall. The warehouse floor shall be designed The primary mirror cells will be FAC-1351: Warehouse to support loads on carts up to 30,000 stored in the warehouse and this Loads kg, supported on 3 points. is the load of a primary mirror cell on a cart. Required for dry storage of FAC-6206: Warehouse The warehouse shall provide a closed supplies and equipment under Environment dry environment controlled conditions (i.e., not exposed to weather, sun, etc.).

7.6.1.2.2 Warehouse Architectural Design The warehouse provides space to store the primary mirror segments in their transport boxes as they arrive on the mountain. As the mirrors are installed in the telescope, the transport boxes will be removed and the bays can be converted to general storage space. Initial integration of the primary mirror assemblies will take place in the warehouse.

The warehouse has a completely open floor plan with no interior columns. It is accessed through a large roll-up door to the central bays. A concrete receiving pad is located outside the main door. Mirror segment transport boxes and mirror cells will be off-loaded onto the concrete pad with a mobile crane and rolled into the warehouse on carts or dollies.

See Figure 7-101 for a floor plan of the warehouse.

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Figure 7-101. Warehouse floor plan (showing 6 primary mirror transport containers)

7.6.1.3 Mid-Level Water Storage Facility The functional requirements for water storage include the following Level 3 requirements:

FAC-1379: Water Systems Distribution - The site infrastructure shall provide potable and waste water distribution systems in all buildings.

FAC-6208: Fire Sprinkler System - The site infrastructure shall include fire sprinkler systems in the buildings as required by code.

The water storage facility is located at the mid-level point between the support site and the summit site. This location was chosen to allow the gravity fed water to the support site to stay within acceptable pressure limits. The facility includes two exterior water tanks and a mechanical room. The mechanical room houses a booster pump and water treatment system. This equipment receives water from the summit site and prepares it for transfer to the support site. Tanks are sized for capacity necessary for code required fire protection systems for the dormitories.

7.6.2 Structural Design The utilities building and warehouse are designed as steel framed structures. Key design considerations for these buildings include construction costs, building constructability, availability of materials, and architectural considerations. Design loads are as follows:

Roofs  Superimposed roof live load: 97.6 Kg/m2 (20 PSF). The roof live load is 97.6 Kg/m2 (20 PSF) as required by the Building Code12.

Wind Load  Maximum considered wind speed = 65 m/s (145 mph)

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The maximum design wind speed is based upon site test data analysis15.

 Exposure category “C”

The wind exposure category is defined by the ASCE 7-05 code23. All buildings not in a wind shielded environment (i.e., city environment), or located in an exposed wind environment next to a large body of water, fall into category “C” exposure.

 Wind Importance Factor = 1.0

The importance factor is defined by the ASCE 7-05 code23. The importance of a building is based on the potential threat to either human life, or national security. An importance factor of 1.0 is indicative of a building that does not have an unusual threat to human life, or national security.

Design wind loads for the cladding and structural members were obtained from the warehouse and equipment building wind analysis report26.

Seismic Coefficients For the maximum considered earthquake the seismic design variables are as follows:

 Sds = 1.00g  Sd1 = 0.40g  Soil Site Class = “C”  Seismic Design Category = “D”  Seismic Importance Factor = 1.0

See section 7.4.2.3 for a description of the seismic design variables.

7.6.2.1 Foundations The ground floor level of the warehouse and utilities building consists of reinforced concrete slabs- on-grade. The utilities building slab will be designed as a vehicular driveway subjected to a 3.6 mt point load, while the warehouse building slab will be designed to support the mirror transportation containers on carts.

The columns at the warehouse and utilities buildings are designed to be supported and anchored on isolated shallow spread concrete footings. The footings are designed to bear below the frost depth of the building site (0.70 m minimum) on compacted native soils.

Footings have been designed for allowable downward loads based upon results provided in the geotechnical testing and analysis report. For the support site structures, allowable bearing pressures are 19,530 Kg/m2 for static loads and 25,875 Kg/m2 for dynamic loading conditions that include wind or seismic forces.

7.6.2.2 Framing Overview 7.6.2.2.1 Roof Framing Figure 7-102 and Figure 7-103 show overall framing drawings of the utilities building and warehouse. For each structure, the roof deck is supported by roof purlins spaced on average of 1.6

ENCLOSURE AND FACILITIES 7–123 GMT SYSTEM LEVEL PRELIMINARY DESIGN REVIEW December 13, 2013 meters apart. These roof purlins run over the top of, and are supported by, the rigid steel frames. Horizontal steel trusses span the rigid frames to provide lateral stability.

7.6.2.2.2 Exterior Cladding Framing An exterior metal wall panel forms the exterior skin of the warehouse and utilities buildings. These metal panels are supported by structural steel girts spanning horizontally between the rigid frame columns at approximately 1.9 meter vertical spacing Wind suction loads are the governing design criteria for most of the wall system members and components.

7.6.2.2.3 Lateral Stability Framing Lateral Stability for the warehouse and utilities buildings is provided by two different types of framing systems.

 Ordinary concentrically braced frames- Where possible the buildings are braced by employing ordinary concentrically braced frames, or “X” bracing. Lateral loads applied to the structure are resisted primarily by axial tension and compression of the “X” bracing members resulting in a structure that is very stiff, and uses the minimum amount of steel to achieve stability.  Ordinary Moment Frames- Where architectural and functional requirements prevent the use of “X” braced frames, ordinary moment frames are used to resist lateral forces. Ordinary moment frames resist the loads applied to them through bending resistance provided by rigid connections between the frame members and the bending rigidity of the frame members themselves.

Figure 7-102. Utilities building framing

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Figure 7-103. Warehouse framing 7.7 Utilities 7.7.1 Heating, Ventilation and Air Conditioning (HVAC) 7.7.1.1 Weather Data Summary Historical weather data recorded from August 2005 to July 200827 has been used to calculate building heating and cooling requirements. This data has been plotted on the psychrometric chart shown in Figure 7-104. The three data points shown are the summer dry/wet and winter design conditions that are used to size air conditioning equipment for the facilities building.

Within the ASHRAE 90.1-2007 Energy Standard for Buildings except Low-Rise Residential Buildings28, the GMT site’s weather data matches Climate Zone 5. For the specified climate zone, the standard sets the minimum insulating values for building components. Insulation used for the GMT facilities meets or exceeds these values.

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Figure 7-104. Psychrometric chart

7.7.1.2 Enclosure and Pier Cooling & Ventilation With the mild daytime environmental temperature swings the enclosure structure is not expected to significantly increase in temperature. The telescope chamber is designed to rapidly thermally equilibrate at the start of the night. Because of this, the enclosure is not cooled during daytime hours.

7.7.1.2.1 Driving Requirements for Enclosure Cooling and Ventilation The specific need for active ventilation of spaces within the enclosure building is driven by a requirement to trap and remove excess waste heat that may otherwise migrate into the optical path as stated below in ENC-0336 (Level 3 requirement).

ENC-0336: Heat Waste - The enclosure shall trap and remove excess waste heat generated from active sources inside the enclosure.

To meet the thermal performance requirements for the enclosure, the air temperature within the optical path must be near that of the outside ambient and it must be relatively uniform. Concentrated heat sources from electronics cabinets and electro-mechanical systems within the enclosure are actively cooled. The waste heat from these systems and the residual heat from massive structural and mechanical elements whose temperatures lag behind that of the ambient is collected in the enclosure active ventilation system and expelled outside and downwind of the enclosure.

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The super columns that run along each side of the shutters and down the back side of the enclosure will not track the air temperature rapidly due to their mass and plate thicknesses. The columns will be insulated to reduce the heat transfer to the inside of the enclosure. At night the super columns and mechanical corridor will be ventilated to remove heat released by the bogie drive motors and other electrical equipment. Residual heat from the enclosure bogie structures and vertical shutter counterweights will also be managed by the ventilation system. Fans mounted to each super column will draw a total of 47,190 l/s (100,000 ACFM) of air through the structure and discharge into the mechanical corridor. See Figure 7-105 and Figure 7-106 for locations of the super column fans. Space is a concern with the back super column fans and so the design may be changed to incorporate multiple smaller fans in order to increase head room as shown in Figure 7-106 and Figure 7-107. The air in the mechanical corridor will be drawn into ducts under the observing floor by a multiple fan array (see Figure 7-109) and discharged to the west through the mechanical corridor Ventilation duct (Figure 7-108). Up to 20% more air will be drawn out of the mechanical corridor relative to the air being moved into corridor by the super column fans in order to reduce exfiltration into the telescope chamber. Even with one fan out of service the multiple fan array (Figure 7-109 and Figure 7-110), will still meet design air flow requirements.

Figure 7-105. Super column and mechanical corridor ventilation (pier ventilation described later)

Two other methods were looked at for removing the heat from the mechanical corridor. The first was to rely on the mechanical corridor’s thermal mass at night and ventilate the space during the day. The concern with this approach was the mechanical corridor was always going to be at an elevated temperature to its surroundings. The other option was to provide an HVAC system that consisted of a chiller, ice storage tanks, chilled water piping and fan coils. During the day the chiller would freeze the water in the ice storage tank but not be operational at night. At night the fan coils would operate and reject the mechanical corridor heat into the ice storage tanks by melting the ice. This system had the advantage of being able to precool the mechanical corridor but was not pursued because of space and system complexity.

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Figure 7-106. Back Super Column Fans

Figure 7-107. Shutter super column fans

Figure 7-108. Mechanical corridor ventilation duct system

Figure 7-109. Example of multiple fan arrays (motor access)

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Figure 7-110. Example of multiple fan arrays (fan inlet)

7.7.1.2.2 Telescope Pier Ventilation System The pier ventilation system as shown in Figure 7-111 and Figure 7-112 will exhaust 7,550 l/s (16,000 ACFM) providing 6 air changes per hour. It will operate at night only to prevent warm air from being drawn in during the day. The air will be removed from the upper corridor around the hydrostatic bearings by vertical ducts terminating within 450 mm of the observing level structure and also through the pier interior. A multiple fan array will discharge its air to the west. Airflow must be balanced between the two exhaust paths to minimize air transfer across the hydrostatic bearing surfaces to limit oil carryover.

Figure 7-111. Pier ventilation system

7.7.1.2.3 Ventilation Air Temperature Rise The motor heat from the fan array and super column fans will cause about a 2.2 C air temperature rise. Passing 47,190 l/s (100,000 ACFM) of ambient air through the mechanical corridor will cool the electrical equipment and increase the air temperature by another 0.89 C. Therefore, the total air temperature rise is 3.09 C. The effects of releasing this heat are acceptable as shown by CFD analysis as described in Section 7.8.

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Figure 7-112. Enclosure/pier ventilation schematic

7.7.1.2.4 Fan Noise and Vibration The fans and motors generate noise under normal operation conditions; the amount depends on the fan static pressure rise and its rotational speed. If this airborne sound energy is loud enough it can cause vibrations within the enclosure structure. Sound data is typically given in 8 octave bands and can be summarized into an overall sound power number. For reference, Figure 7-113 lists representative sound power levels from a variety of sources. For the super column fans the overall sound power level per fan is 79dB. The sound power rating of the ventilation fan array is 103dB. Typical methods for reducing sound transmitted from fans are to add duct liners, sound attenuators or several elbows (bends) in the duct. All of these options are available for the ventilation fan arrays but the super column fans are limited by space constraints in the mechanical corridor. The super column fans are short and coupled on the inlet and discharge directly into the mechanical corridor. To reduce the noise to the maximum extent practical, the largest but quietest fan was selected. In addition the super column fans will be suspended on spring isolators to reduce mechanical vibrations transmitted. The enclosure structure is mechanically isolated from the telescope and pier to minimize mechanical vibrations being transmitted to the telescope structure. Vibration isolation mechanisms for this equipment will be designed to meet the telescope pier vibration requirements as described in Section 7.2.1.2.

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Figure 7-113. Representative sound power levels

7.7.1.3 Building HVAC HVAC will be provided in the areas where staff and visitors routinely work and/or equipment (e.g., computers) required conditioned air. This includes the summit support building and the utilities building. HVAC is not provided in the enclosure building or in the warehouse. The Lodge facilities HVAC design is planned for a later stage.

7.7.1.3.1 Summit Support Building The summit support building has mixed uses including office space, lab and assembly areas, cleanroom, equipment room and mirror re-coating facilities. All spaces need to have stable temperature control for process/occupant comfort. Most spaces will be cooled to 24 C and heated to 22 C. Heating and chilled water will be distributed to air handling units, fan coils and unit heaters and controlled by a building automation system. The office spaces will use a variable air volume air handler supplying air to terminal units. A plenum return will be utilized to reduce the quantity of ducting. Operational staff will be able to use the building automation system to monitor space conditions and improve plant efficiency Ductwork will distribute the air as required; it will be lined to reduce duct-borne noise. Outside air will be provided as required by ASHRAE Standard 62.1 Ventilation for Acceptable Indoor Air Quality29. HVAC schematics are provided in the preliminary design drawing3 set for the summit support building.

At the facility building, the vestibule to the M2 test bay will be filtered to an ISO30 8 cleanroom standard while the clean room will be filtered to an ISO 7 standard. A single AHU will control space temperature and circulate air to these clean rooms. Final air filtration will be by ceiling mounted HEPA filters. These spaces will be maintained at a positive pressure relative to their surroundings.

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Also at the facility building, an exhaust fan in the wet room will be used to remove odors during some operations. The electronics lab will be provided with an exhaust hood mounted on an articulating arm. Both of these fans will be controlled locally by a wall switch.

For the M2 test bay, an exhaust duct has been extended to the pit floor to pull heavier-than-air gasses out. Protocols will be established for pit entry and fan operation as this is an enclosure space. An oxygen monitoring station with warning lights and horn will be placed in the pit.

The auxiliary building will not have any cooling but can be heated to a maximum of 20 C. The lower temperature limit will be limited to 4.4 C to prevent freezing of water pipes. Several unit heaters will be placed at various locations and be controlled through the building automation system.

The equipment building temperature will be limited to 24 C by supplying filtered ambient air and then exhausting it. The lower temperature will be limited to 4.4 C to prevent freezing of water pipes. Exhaust fans located on the ground level discharge the room air to the east.

7.7.1.3.2 Utilities Building The main portions of the utilities building will not be heated or cooled for occupant comfort. Split system heat pumps will be used in the two utilities building office spaces. Spaces subject to freezing will have heaters and the machine shop/auto shop will have propane radiant heaters. The electrical room will have filtered ambient air supplied to it to limit the maximum room temperature to 24 C. HVAC Schematics for the utilities building are provided in the preliminary design drawings4.

7.7.2 Plumbing 7.7.2.1 Chilled Water System Driving Requirements 7.7.2.2 Chilled Water Systems Requirements for the chilled water supply system include the following:

FAC-1232: Equipment Building Chiller Systems - The equipment building shall provide the chillers and pumps for the HVAC and telescope chilled fluid systems per GMT-SE- REF-00366 Common Utilities Budget.

Chilled and heating water will be distributed throughout the summit site to meet the building heating/cooling requirements as well as to support various telescope instrumentation needs. Multiple water cooled standard chillers will provide 7 C water for general purpose cooling. Another set of water cooled low temperature chillers will provide water at -15 C. This water will pass through a heat exchanger to raise the water temperature so it is 8 C below the ambient temperature. It will have a temperature range of -5.6 to 20 C. The ambient tracking Ta – 8 C water will be used to extract heat from systems on the telescope that need to be maintained at a temperature near ambient to prevent local heating of the air where image quality could be impacted. A 25% ethylene glycol solution will be used in all systems to meet the minimum survival temperature, except the low temperature chillers and the ambient tracking system. These systems will use a 40% glycol concentration because of the lower operating temperatures. The mission- critical telescope systems requiring chilled water are summarized in Table 7-31. Summit support building plumbing schematics are provided in the preliminary design drawings3.

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Table 7-31. Telescope mission critical chilled water cooling requirements Ambient Tracking Chiller Telescope System Standard Chiller (7 C) (Ta-8 C) Primary Mirror Thermal System NA 175 kW

GIR Drives NA 16 kW

Main Drives NA 20 kW

Hydrostatic Bearing Oil Cooling NA 16.5 kW

Electronics Cabinets NA 100 kW

Science Instruments 110 kW 56 kW

Adaptive Secondary Mirror NA 14 kW

Wavefront Sensors and Cameras NA 6 kW

Laser Guide Star Facility (LGSF) 18 kW NA

The chiller’s condenser water will be used to heat the summit support building, and an electric boiler will provide backup capacity. Heat not used by the building must be rejected through the four fluid coolers located on the southeast corner of the summit support building where heat will be rejected downwind and perpendicular to the enclosure building. A wet type cooling tower would be a more energy efficient option, but was not selected due to concerns over water use.

7.7.2.3 Water & Waste Design requirements for water supply are derived from System Level Requirements9 related to the supply, distribution and disposal of water for personnel use and for water used in the mirror cleaning and coating processes. The driving design requirements for water are listed in Table 7-32.

Table 7-32. Water systems requirements (Level 3 requirement) Requirement ID & Title Requirement Notes FAC-1234: Equipment The equipment building shall house the Required for continuous site Building Potable Water water plant for the potable water system operations Plant Summit The site infrastructure shall provide Support FAC-1379: Water Systems Required for continuous site potable and waste water distribution Building Distribution operations systems in all buildings FAC-1298: Mirror The mirror washing bay shall include a For mirror wash and detector lab Washing Bay DI Water source of de-ionized water wet room applications. Source The site infrastructure shall include FAC-1380: Septic septic treatment plant(s) for the waste Required for continuous site Treatment Plant water at the summit and at the support operations sites

Water is currently taken from LCO’s well in the valley below the observatory, pumped to the summit site and stored in a below grade concrete storage tank located just north of the summit of Las Campanas. This well provides enough water to supply GMT in addition to LCO. Water is distributed from the storage tank to its points of use throughout the LCO and GMT facilities. GMT will take water from this tank and pump it to the equipment building where it will be stored as ENCLOSURE AND FACILITIES 7–133 GMT SYSTEM LEVEL PRELIMINARY DESIGN REVIEW December 13, 2013 shown in Figure 7-114. This tank will hold four days of untreated water to provide some backup capacity from the well system. A water treatment system with a duplex booster pump will purify and pressurize this water for distribution. Water will also be pumped to the water storage facility water storage tanks for domestic and fire water uses. These tanks have been located at an elevation of 2,440m (8,000ft) allowing all water pressure needs to be met by a gravity feed to the support site. The domestic tank will hold four days of untreated water to provide some backup capacity from the well system. Also by placing the tank at this location the pipe pressure to and from the water storage facility will stay under the pressure rating of common fittings. A similar water treatment system will be used at this location as used at the summit support building. Because of the elevation change between the tank and points of use the duplex pump system will not be needed.

De-ionized (DI) water is needed in the wet room and at the mirror stripping bay. The DI system will be capable of producing 230 liters/day (60 gallons/day) of 18 mega-ohm water. The water will be continuously circulated through the DI resin beds and special high purity piping will be used for distribution to help maintain the water purity.

Figure 7-114. Domestic and fire water schematic

Domestic sanitary waste will be collected and sent through an aerobic waste treatment tank, similar to that shown in Figure 7-115. The tank effluent is then sent to a leach field located in native undisturbed soil. The International Private Sewage Disposal Code31 requires that space must be reserved for a second leach field in case the primary field fails.

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Figure 7-115. Domestic waste treatment tank by MicroSepTec

Chemical waste from the mirror stripping operations and the wet room will be collected and manually neutralized in an underground tank. The drainage piping and storage tank will be of chemical resistant double wall construction to prevent chemicals from entering the native soil. Neutralized tank waste will be pumped into a tanker truck for offsite disposal.

7.7.2.4 Fire Protection Requirements for fire protection include the following (Level 3 requirement):

FAC-6208: Fire Sprinkler System - The site infrastructure shall include fire sprinkler systems in the buildings as required by code.

The code12 does not require the installation of fire protection systems for the enclosure and summit support buildings. Therefore fire sprinklers will not be installed at the summit site. A gaseous fire suppression system will be installed in the electronics room.

For the dormitories, 112,832 liters (30,000 gal) of water will be stored at the water storage facility and gravity fed to the lodge site. Fire suppression water will be allocated for the lodge per the code for purposes of fire sprinklers in the sleeping quarters. There is not a water allowance in the tank sizing for firefighting purposes; tank sizing is just for sprinkler use at the lodge site.

7.7.3 Compressed Air Requirements for compressed air include the following based upon the derived capacity necessary to operate telescope subsystems (Level 3 requirement):

FAC-1230: Equipment Building Air Compressors - The equipment building shall provide a set of air compressors, filters and dryers with a minimum rating of 60 CFM each per the requirements in GMT-SE-REQ-000190 common utilities.

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Two 60 CFM rotary screw air compressors each with an integral 900 l (240 gal) storage tank will be used and will provide redundant capacity for the mission critical air systems (e.g., the primary mirror supports). A single inline (500 gal) tank will increase the storage capacity. Coalescing filters, desiccant drier and filter cartridges will provide clean dry air with a -40C (-40F) dew point. Compressed air will be distributed throughout the facility and support all instrumentation and telescope requirements. A final filter will be used at all points of use. Compressed air will also be provided at the utilities building for typical shop air.

7.7.4 Fueling Station and Tank Yard Design requirements for fuel storage are derived from System Level Requirements for on-site storage of fuel, sufficient to meet the needs of the observatory. The driving requirements for fuel storage are listed in Table 7-33.

Table 7-33. Fuel storage requirements (Level 3 requirement) Requirement ID & Title Requirement Notes The Utility Yard shall include gas and FAC-1352: Fuel Tanks and The fuel tanks/pumps are required diesel fuel tanks and pumps with a Pumps for Vehicles and for refueling vehicles, equipment minimum storage capacity of 20,000L Equipment and generators. each for fueling vehicles and equipment The Utility Yard shall include propane This is required for refueling FAC-1353: Propane Tanks storage tanks and propane fill station equipment, such as forklifts etc.

A tank yard and fueling station is located west of the utilities building. Space is provided for two underground double contained 56,780L (15,000 gal.) diesel storage tanks for backup generator fuel and a smaller underground twin-baffle 45,420L (12,000 gal.) gasoline and diesel tank for fuel for the vehicular dispensing stations. Dispensers for fueling vehicles are located on a containment pad. A fuel management system will monitor the tank level, transfer fuel to the generators, detect fuel leakage and restrict fuel pump dispenser access. Remote monitoring through the internet is possible with this system.

This space far exceeds the requirements and allows for future expansion. Typically, tank yards such as these are constructed, maintained and serviced by local specialty companies in Chile. It is our intent to procure and maintain the yard by contract with one of these companies.

7.7.5 Liquid Nitrogen Bulk Storage The design requirements for liquid nitrogen storage are derived from capacities necessary to operate the coating chamber and instruments (Level 3 requirement).

FAC-8045: LN2 Tank Location - The Liquid Nitrogen Tank shall be located adjacent to the auxiliary building in close proximity to the Mirror Coating Bay.

A concrete pad will be provided adjacent to the auxiliary building to allow a liquid nitrogen (LN2) storage tank to be installed by a contractor after construction is complete. The LN2 pad will be 5m x 5m and designed to support an 11,356L (3000 gal) vertical tank with a total (filled) weight of 18 metric tons. The LN2 pad will be located along the southeast side of the auxiliary building for easy access by trucks and adjacent to the coating chamber to allow direct-plumbed lines to feed the coating chamber for transferring large amounts of LN2 during aluminizing efforts. The LN2 storage tank will also be used as a filling station for transfer dewars to be transported to instruments on the telescope and in test labs.

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7.7.6 Electrical Electrical design requirements are listed in Table 7-34.

Table 7-34. Electrical design requirements (Level 3 requirement)

Requirement ID & Title Requirement Notes The site infrastructure shall provide a FAC-1384: Primary Power primary power transformer to step down This is required to connect to the Transformer the Chilean grid standard 23KV, 50 Hz to commercial power grid. an intermediate 3.3 kV, 50 Hz The intermediate voltage provides The site infrastructure shall distribute the FAC-1385: Intermediate an efficient means of distributing intermediate 3.3 kV power between the Power Distribution large power demands across the support and summit sites and buildings summit. The site infrastructure shall provide power FAC-1390: Facility Power transformers at buildings to step down This is a Chilean standard voltage. Transformers from the intermediate voltage to 380V, 50Hz, 3-phase The site infrastructure shall distribute 380 FAC-1387: 380V Power VAC, 50 Hz 3-phase power in all Standard 3 phase site power buildings and service areas The site infrastructure shall distribute 220 This voltage is need for moderate FAC-1388: 220V Power VAC, 50 Hz single phase power in all power equipment, utility outlets, buildings and service areas lighting, etc.

7.7.6.1 Electrical Power Distribution System Overview Commercial electrical utility power is being provided by Emelat, the local/regional Chilean electrical utility company, to the GMT site via a new 23 kV, 3 phase, 50 Hz overhead distribution pole line extension from an existing overhead pole line at LCO. Currently Emelat serves the Las Campanas Observatory (LCO) site with a 23 kV, 3 phase, 50 Hz overhead distribution pole line and multiple electrical service drops to each of the existing LCO telescope and support facilities. The existing LCO electrical distribution system is not adequate to support the GMT so an upgrade to this system will be completed in order to meet the electrical power needs of both LCO and GMTO. See Section 7.9.3 for more information on the planned upgrade.

A new 23 kV, 3 phase overhead line will be extended from the upgraded 23 kV, 3 phase overhead distribution pole line at LCO to the GMT electrical yard, outside of the utilities building. The new pole line will end at a dead end pole with conduit riser and transition to underground through a cluster of fused cutouts and lightning arresters, terminating at the site’s main pad-mounted service entrance primary switch and transformer. The primary switch and service transformer will be pad- mounted, oil filled type with internal lightning arresters located on concrete containment pads adjacent to the utilities building. The service transformer will step down the 23 kV, 3 phase primary voltage to a secondary voltage of 3.3/1.9 kV, 3 phase, 4 wire which will be used as the site underground distribution voltage serving the entire GMT site. Emelat will provide the service primary switch and transformer. Refer to the electrical one line diagrams found in Section 7.7.6.3 for the electrical distribution system serving each site and associated buildings and facilities.

From the outdoor service transformer to the utilities building, an underground duct bank consisting of a 3.3/1.9 kV, 3 phase, 4 wire rated secondary service entrance lateral is provided to serve the main 3.3 kV (5 kV Class) rated electrical service entrance equipment located at the utilities building in the main electrical distribution room. The main electrical service entrance equipment will consist of a bottom feed incoming section, utility company revenue metering section, main ENCLOSURE AND FACILITIES 7–137 GMT SYSTEM LEVEL PRELIMINARY DESIGN REVIEW December 13, 2013 disconnecting means with integral ground fault protection section, on-site generator source input and paralleling control sections and distribution sections. The on-site generator source input sections are to be specified to accommodate the parallel operation and control of two diesel engine/generator sets. Over-current protective devices, such as the main disconnecting means, generator input source devices, and load feeder devices provided in the distribution section will be fully adjustable type circuit breakers. The circuit breakers will be sized for each generator input source, outgoing load feeders and main service entrance rating as determined by the facility electrical loads being served and the available short circuit current. Short circuit currents are to be calculated using the available fault current from the electric utility company and the on-site generators and the overall electrical power system one line diagrams.

Backup electrical power is to be generated on site using two outdoor diesel-driven engine/generators, each rated at 1,120 kW at 0.8 power factor (1,400 kVA), 3.3/1.9 kV, 3 phase, 4 wire, 50 Hertz, operating in parallel. Provisions for one additional future outdoor diesel-driven engine/generator to match the two baseline generators will be provided. Generator paralleling type source input and controls sections, as part of the main electrical service entrance equipment, will be provided to allow the two initial and one future backup engine/generators to operate in parallel for a total combined initial capacity of 2,240 kW (2,800 kVA), and future capacity of 3,360 kW (4,200 kVA). In addition, the generator paralleling sections monitors and controls the transfer of electrical load from electric utility power source to the backup generator sources during the loss of normal electrical utility power. All engine/generators are proposed to be located in weatherproof rated outdoor enclosures adjacent to the utilities building.

The current rating and capacity of backup engine/generators are based upon current estimates. These will be reviewed and verified as the total electrical loads for the GMT site becomes available during the next design phase. Once final electrical loads and worst case motor starting event(s) are established, the backup engine/generators can be sized accounting for engine/generator de-rating for project site altitude, and diesel fuel source.

From a National Fire Protection Association (NFPA) and National Electrical Code (NEC) standpoint, this on-site backup engine/generator system, located outdoors adjacent to the utilities building, is not being designed to serve life safety type electrical loads. As a result, this engine/generator backup system is proposed to be rated as an “Optional Standby System” per the NEC, Article 702 (2011 Edition)32.

7.7.6.2 Preliminary Load Summary The GMT Project preliminary design electrical load estimate summary is being provided here to establish the current basis for design regarding the site electrical power distribution system configuration, capacity ratings, and physical equipment locations. Table 7-35 summarizes the electrical loads for each of the major areas of the site.

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Table 7-35. Preliminary electrical load summary

Preliminary Load Summary Support Site Space Programming Electrical Loads Space Name Area Area Connected Demand Estimated (Sq. Ft.) (Sq. M.) Load (kVA) Load (kVA) Load (kVA) Cafeteria & Rec Center 14,999 1,393 175.59 109.90 60.35 Facilities II building 8,856 823 110.42 67.17 37.69 Lodge 52,715 4,897 366.17 215.63 98.46 Warehouse & Shops 29,640 2,754 341.13 215.02 133.13 Totals 106,210 9,867 993.31 607.72 329.63

Summit Site Space Programming Electrical Loads Space Name Area Area Connected Demand Estimated (Sq. Ft.) (Sq. M.) Load (kVA) Load (kVA) Load (kVA) Enclosure 3,458 1,998.01 1,535.66 504.33 Auxiliary Bldg. 4,030 558.52 449.57 61.92 Facility Bldg. 1,439 439.43 375.98 249.43 Weather Tower 1.00 1.00 1.00 MASS/DIMM Tower 1.00 1.00 1.00 Equipment Bldg. 2,056 2,056.21 1,615.85 1,359.38 Totals 10,983 5,054.17 3,979.06 2,177.06

GMT Totals 20,850 6,047.48 4,586.78 2,506.69

LCO Summary 283.35

Grand Totals 2,790.04

The following notes apply to the table listed above:  Load Density is defined as volt-amps (VA) per square meter (Sq. M.)  Connected Load in kVA is the calculated load, either VA multiplied by Sq. M. or by using actual known equipment loads.  Load (Demand) Factors are actual demand factors that are allowed by the National Electrical Code (NEC).  Demand Load is the Connected Load multiplied by the Demand Factor. The Demand Load is used to determine the minimum size electrical services and feeders.  The Usage (Duty Cycle) is the estimated percentage of time the load is expected or known to be in use.  The Estimated Load is the Demand Load multiplied by the Duty Cycle to determine power usage. The Estimated Load does not take into account any peak load.

7.7.6.3 One-Line Diagrams The preliminary design electrical One Line Diagrams establish the basis of design regarding the site electrical power distribution system configuration, capacity ratings, and physical equipment locations. One Line Diagrams for the support site, summit support building and enclosure building are given in the preliminary design drawings3,4.

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7.7.6.4 Normal, UPS, and Emergency Power Distribution Electrical power distribution to the support site containing the utilities building, warehouse, and lodge will be provided from the main 3.3 kV rated electrical service entrance equipment, located in the main electrical room at the utilities building, and underground 3.3 kV feeder serving a pad mounted, liquid filled outdoor transformer rated at 1,500 kVA, 3.3 kV to 400/230V, 3 phase, 4 wire. The transformer then serves a distribution switchboard, also located in the main electrical room, rated at 2,000 A, 400/230V, 3 phase, and 4 wire. From multiple feeders fed by the main distribution switchboard, electrical power is provided and distributed throughout the support site serving multiple buildings using distribution and sub-distribution panels.

Electrical power distribution to the summit site containing the enclosure and summit support building, will be provided from the main 3.3 kV rated electrical service entrance equipment, located at the utilities building main electrical room and two underground 3.3 kV feeders, routed up to the summit site along the main access road serving two liquid filled transformers located at the equipment yard outside the equipment building. Both transformers are rated at 2,500 kVA at altitude, 3.3 kV to 400/230V, 3 phase, and 4 wire. Both transformers then serve a dedicated service entrance rated switchboard, also located at the equipment yard, both rated at 4,000A, 400/230V, 3 phase, and 4 wire. One transformer and switchboard primarily serve the summit support equipment, auxiliary and facility buildings. The second transformer and switchboard primarily serves the enclosure building and central UPS system. An outdoor standby diesel-driven generator set rated at 140 kW at 0.8 power factor (175 kVA), 400/230V, 3 phase, 4 wire, 50 Hertz will be located in this equipment yard dedicated for backing up specific loads on the enclosure and telescope. The automatic transfer switches (ATS) for this backup power (1200A for the enclosure and 400A for the telescope) will be connected to this second 4,000A switchboard.

Four buried power feeders, two for backup power, one 500A for UPS power, and one 2,500A for utility power, will be provided from the equipment building to the enclosure base electrical room. One 2500A switchboard in this electrical room will provide utility power to the enclosure base and telescope. One 1200A and one 400A disconnect switches for backup power and one 600A disconnect switch for UPS power will be located in this electrical room also. From these disconnect switches, power will be distributed to the enclosure and telescope. Electrical power will be distributed to the rotating enclosure via a slip ring power conductor rail system at the observing floor level and serving multiple floor levels and areas using distribution, sub-distribution panels, and motor control centers. Power will be distributed to the telescope from distribution panels located on the pier lower utility platform, then to the telescope structure via a cable wrap system.

At the equipment building, three central static UPS’s, each rated at 160 kVA, 400/230V, 3 phase, 4 wire with external maintenance bypass switch are connected for parallel operation using a parallel tie module, for combined capacity of 480 kVA will be provided to serve the telescope, facility and auxiliary areas. Typical loads served from this UPS are mission-critical loads such as rack- mounted electronic equipment, communication computer servers, telescope drive and instrumentation, etc. as identified by the project, and is distributed throughout the areas using distribution and sub-distribution panels.

In addition, at the rotating enclosure level, a small static UPS rated at 20 kVA, 400/230V, 3 phase, 4 wire with external maintenance bypass switch will be provided to serve the enclosure specific UPS loads. This UPS will be fed from enclosure power distribution system.

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7.7.6.5 Lightning Protection Systems Requirements for lightning protection include the following:

FAC-1396: Lightning Protection - The site infrastructure will include interconnected lightning protection systems for all buildings on the summit.

ENC-0305: Enclosure Lightning protection - The enclosure building will provide a Faraday Cage-type lightning protection system per NFPA 780.

During the preliminary design phase, several different Lightning Protection System (LPS) methods were researched and evaluated resulting in the selection and recommendations as follows. For the enclosure LPS, because of physical challenges associated with the enclosure size and shutter door configurations and drive systems, the LPS recommended is the Faraday Cage method. This method provides a fully enclosed metal structure (box) fully bonded and connected to the site overall Grounding Electrode System (GES). As a result, the enclosure grounded metal structure acts as one large air terminal providing a low resistive path to ground to dissipate any direct lightning strike energy to the GES via multiple down conductors and building steel. The down conductors will be transferred from the rotating enclosure to the fixed enclosure through the use of multiple (total of 8) dedicated, spring loaded LPS grounding collector brush locations to a continuous circular grounding bus bar located around the entire enclosure perimeter.

All other buildings such as the summit support building, utilities building, and warehouse buildings will be protected using the NFPA 78033 Rolling Sphere method consisting of an array of aluminum air terminals located on the roof and roof top equipment of each building to direct lightning strike energy down to the GES via dedicated down lead conductors. The air terminal arrays are bonded together using NFPA 780 defined Class I main conductor of 24 strand #14 aluminum type conductor with direct connections to the building buried grounding electrode system (GES) made at a minimum of four to six locations around the building’s perimeter.

7.7.6.6 Grounding Electrode System Code requirements for the grounding electrode system are listed in Table 7-36.

Table 7-36. Grounding electrode system requirements (Level 3 requirement) Requirement ID & Title Requirement Notes This bonds the conductive The Grounding System will include FAC-1397: Building materials of the buildings to electrodes for bonding the metal structure Structure Grounding ground to prevent voltage in the buildings to the ground plane potentials from developing. FAC-6313: Grounding The building grounding systems will use Star grounds are used to avoid System Configuration star ground configurations ground loops. The grounding system will include The perimeter ground ring FAC-6382: Perimeter perimeter ground rings around the provides additional grounding Grounds summit facilities potential to improve performance. FAC-6383: Ufer (concrete The grounding system will include The Ufer ground provides encased) Grounding concrete-encased electrodes in the additional grounding potential to Electrodes building slabs and telescope pier improve performance. The grounding system will connect the FAC-6384: Common This improves the overall perimeter and Ufer grounds from all Ground Plane grounding potential. buildings to a common ground plane

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The enclosure, enclosure base, and summit support building will be provided with an electrical safety Grounding Electrode System (GES) as required by the National Electrical Code (NEC). Each building grounding system consists of a continuous grounding mat/mesh made using 1#3/0 bare stranded copper (SDBC) conductor arranged in 4 meter squares and located directly under the building concrete floor and spread foundations. A continuous 1#3/0 SDBC ground ring is provided around the entire building foundation perimeter with ground rods exothermically connected to ground ring at 15 meter intervals and minimum of one ground test well. In addition, the building structural steel columns and concrete reinforcing rebar is bonded to grounding ring and grid using exothermic type welds. The entire building GES is buried at a minimum depth of 1 meter below finished grade. Both the enclosure and summit support building’s grounding systems are connected/tied together to form an overall summit site GES.

In addition, the utilities building and warehouse, including the main backup generators will be provided with a similar GES as described above.

7.7.6.7 Interior Lighting and Control Interior lighting is provided at all support and summit site buildings using fluorescent and Light Emitting Diode (LED) type lighting fixtures and lamps to achieve multiple light levels depending on each interior space use and tasks being performed. In addition, each interior area lighting level, the number of lighting fixtures required to achieve the level and total lighting power densities will be reviewed during detailed design phase to comply with the International Energy Conservation Code (IECC)34.

In general, the type of lighting fixture and lamp source are as follows. For storage, stairways, inner and outer pier and utility spaces such as mechanical and electrical rooms, two lamp, four foot industrial fluorescent type fixtures are specified. For office, control rooms, and electronics labs, two and three lamp, two by four foot recessed fluorescent troffers are specified. For the enclosure, wall mounted LED flood type lighting fixtures are specified around the chamber perimeter between Level 04 and Level 07, providing general illumination of the telescope chamber. At catwalk areas between Level 04 and Level 08, low level, continuous red LED (rope) type lighting is specified to illuminate walkways for operations and maintenance personnel.

All interior lighting will be controlled by a central, fully programmable lighting control system providing capacity and flexibility to support of current lighting control needs as well as future needs. Other methods of local lighting control, such as double line voltage switches, timer, and motion control switching technology, will be evaluated during the next design phase based on specific area needs and compliance to the IECC lighting control requirements.

7.7.6.8 Life Safety Systems Life safety systems provided for the GMT project and supported by the electrical design include emergency lighting and exit signage, fire alarm monitoring and alarm system, in accordance with the NFPA and NEC. Typically, emergency lighting and exit signage, fire alarm monitoring and alarm system, are served and connected to an Emergency System.

The preliminary design approach is to specify emergency lighting and exit signage complying with NFPA using commercially available, dedicated emergency and exit signage lighting fixtures complete with integral, on-board battery back-up per each fixture type. The fire alarm monitoring and alarm system is equipped with battery capacity to comply with NFPA 7235.

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7.7.7 Controls The enclosure Control System (ECS) shall provide the monitoring and control for all enclosure related functions including: rotation, shutters, wind vents, ventilation, lift platforms, hatches, cranes and building functions, such as HVAC and lighting.

Driving requirements for the design of the ECS are listed in Table 7-37.

Table 7-37. Enclosure control system requirements (Level 3 requirement) Requirement ID & Title Requirement Notes PLCs are easy to use and interface, so assembly and The enclosure systems shall be controlled ENC-0454: ECS integration can be carried out in with an interconnected array of Programmable Controllers advance by the contractor, programmable logic controllers (PLC's) independently of the GMT Control System. The ECS controllers software tools and This ensures consistency among ENC-0455: ECS Controller applications shall be compliant with the systems and improves Standards IEC 61131-3 programming standard. maintenance efficiency. To give consistency, since The ECS shall communicate with the EtherCAT is the standard ENC-0461: Enclosure field devices by means of the communications fieldbus adopted Communications (general) industrial Ethernet based fieldbus for all the Telescope devices at the EtherCAT. field level. This allows Subsystems to be The ECS shall provide Local, Test, and operated from a centralized ENC-0448: ECS Operation Remote operation modes for control and location for operational efficiency Modes monitoring of enclosure Subsystems. and locally for maintenance efficiency. The post delivery integration is easier and the maintenance during ENC-0477: ECS The ECS software shall be structured in operations is efficient, since the Programming Modular different modular units called PLC PLC Applications follow an Units Applications. object-oriented model that is applied throughout the Telescope software design. ENC-0449: ECS Hardware The ECS shall include all the hardware The enclosure Systems must be and Software and software needed to operate the ECS tested long before the rest of the in the different operation modes (the TCS Telescope mechanisms, but later is provided by the GMT project office). integrated to the overall Telescope This includes an additional laptop and Control System. test computer and all the software tools and applications required for developing and testing of the ECS.

The enclosure systems are controlled with a series of PLCs interconnected with the EtherCAT industrial Ethernet fieldbus. All of the PLC software tools and applications are compliant with the IEC 61131-3 programming standard. The PLC system consists of Beckhoff Industrial PCs (IPCs), remote PCs, and remote I/O stations located in the enclosure to allow placement near the devices being controlled. The PCs will be running the TwinCAT PLC/CNC software, so they effectively will be a soft-PLC implementation.

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Figure 7-116. Control systems block diagram

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The ECS communicates with the GMT Telescope Control System (TCS) using the communications standard OPC Unified Architecture (OPC UA). The enclosure device control computer hosts an OPC UA client to send instructions over Ethernet to the OPC UA server running in the Beckhoff IPC.

The preferred media for any fieldbus communications is fiber optic cable to protect from electromagnetic noise being injected on the bus. Twisted pair shielded cable are used when fiber optic is not practical. Wireless communications from the enclosure base to the rotating portion of the enclosure is accomplished using redundant EtherCAT radios. Backup to the radio communication is via the slip rings.

The ECS subsystems are able to operate in Remote, Local, or Test Modes. Remote mode is the normal operation during observation periods. In this mode, the ECS communicates with the TCS to receive commands and transmit status information. Under the Local mode, the ECS operates independently of the TCS, as in the case of maintenance periods or daily checks. The Test mode is the operational mode during assembly, integration and verification of the ECS. The ECS subsystems receive commands from a workstation located in the telescope chamber floor using the same interface as normally used to communicate with the TCS. The operational modes are independently selected for each enclosure subsystem. The ECS includes all the necessary hardware and software to perform in the various modes of operation.

The ECS rotates the enclosure, adjusts the wind vents and opens or closes the vertical and horizontal shutters. The control system consists of a master IPC located in the electronics room (at the facility building) and a series of remote PCs tied to EtherCAT drives and remote I/O terminals located in the enclosure. The IPC will act as the EtherCAT master running TwinCAT software to send instructions to the remote PCs in the rotating enclosure via the fiber optic and redundant Ethernet radio system as indicated in Figure 7-116 below. The remote PCs communicate with the drives and remaining remote I/O systems using the EtherCAT fieldbus. During telescope operation, the TCS will have control of the IPC system to operate the enclosure drive bogies, wind vents, ventilation system and shutters in order to keep telescope at optimal conditions. The control systems block diagram is shown in Figure 7-116.

The enclosure drive bogie Variable Frequency Drives (VFDs), located in the motor control center rooms around the outer perimeter of the enclosure, are controlled using a remote EtherCAT PC and remote I/O’s. See Figure 7-117 for the location of the motor control center rooms on the enclosure. The TCS will send the azimuth positioning demands to the IPC, which is connected via EtherCAT to the wireless radio modems in the enclosure base. The radio modems in the rotating structure will relay the commands to a remote PC that acts over the azimuth motor VFDs. Each of the azimuth motor VFDs will be programmed to implement smooth motion profiles, driving the rotating section of the enclosure during slews or tracking.

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Figure 7-117. Locations of motor control centers on the rotating enclosure

The wind vents are controlled using a remote PC connected to a series of networked drives through the EtherCAT fieldbus. The control system will move the wind vents to regulate the wind flow through the enclosure to maintain thermal control of the telescope while minimizing wind shake.

The vertical and horizontal shutter controllers and I/O will be located at the motor control center area on the platform by the vertical shutters. Each shutter door will be raised and lowered using two VFD controlled motors and cable assemblies. The VFDs will be programmed for smooth acceleration and deceleration of the shutters during telescope operation. The drive sheave for each assembly will have a limit switch to sense cable slack. A rotary encoder will be mounted to the shaft of a non-driven sheave on each drive assemblies to prevent the shutter misalignment during the raising and lowering operation. The rotary encoders will be used for feedback to the VFDs during the telescope operation.

Proximity switches will be used as interlocks to raise and lower the vertical shutters in the proper sequence. The horizontal shutters operate in a manner similar to the vertical shutters, using proximity switches to make sure they open and close in the correct order. The control system will adjust the shutters for optimal telescope utilization.

The Human Machine Interface (HMI) for the ECS located in the control room will allow access to control the azimuth motor drives, ventilation system, wind vents and shutter doors through the IPC installed at the electronics room. To control each of the remote stations in the enclosure and enclosure base, a communications link via EtherCAT between the IPC and a master radio will be established. The master radio will transmit the information to a slave radio that will communicate with the remote stations. Information from each of the remote PCs is transmitted back to the master radio and to the IPC and displayed on the HMI.

The encoder system will send encoder pulse information back to the IPC to keep track of the position of the rotating enclosure. The encoder system consists of an encoder tape that is installed around the inner perimeter of the rotating section. A stationary non-contact optical reader reads the encoder tape and sends the absolute location information to the EtherCAT remote station. The rotation controller then uses this encoder information along with the TCS demands to act over the four drive bogies VFDs sending the enclosure to the requested position. The encoder system will ENCLOSURE AND FACILITIES 7–146 GMT SYSTEM LEVEL PRELIMINARY DESIGN REVIEW December 13, 2013 also be equipped with hard set-points at the North, East, South and West locations. The hard set- points will be read using a second stationary non-contact optical reader that can be used to reset the encoder information in the event of power failure or equipment abnormality.

A mechanical encoder wheel may also be used as a comparator to verify the location of the rotating section. If discrepancies between the encoder tape and the mechanical encoder are found, then a hard reset will be required. The mechanical encoder wheel assembly can be mounted to the bogie wheel frame and contact with the track that the bogie wheel uses. The encoder would not be tied to the bogie wheel itself, so if the bogie wheel slips, the encoder will still have an accurate reading.

The wind vents will open to 25%, 50%, 75% or 100% using VFD motor control and proximity switches located at the four (4) set-points. The control system communicates with the drives over the EtherCAT field bus to keep the proper environmental control of the telescope.

The Building Automation Control Network (BACnet) controller for the building HVAC will be linked to the Beckhoff IPC using fiber optic cable. The BACnet is a stand-alone network that controls heating, cooling, lighting and any other systems that pertain to the individual buildings. The link between the IPC and the BACnet is for future consideration.

An additional Beckhoff remote I/O system station is located in the utilities building. The remote PC there communicates with the IPC using fiber-optic cable. The BACnet controller for the warehouse HVAC system (if implemented) and the water treatment will be linked to the IPC and HMI for monitoring. The fire alarm system for the warehouse, utilities building and water storage facility can be monitored at the HMI through the BACnet controller.

All of the BACnet controllers will be linked together using BACnet Ethernet in addition to being linked to the Beckhoff PCs. 7.8 Performance Analysis 7.8.1 Enclosure and Facilities Thermal Performance Requirements The driving requirements for thermal performance of the enclosure and facilities are listed in Table 7-38 .

Table 7-38. Enclosure and facilities thermal performance requirements (Level 3 requirement) Requirement ID & Requirement Notes Title ENC-9078: Enclosure The enclosure shall provide a minimum To minimize obstruction of air Ground clearance clearance to the ground level of 8.0 flow through enclosure base meters. ENC-0331: Wind Vents The enclosure shall incorporate To allow wind forced ventilation controllable vents covering a minimum of of the interior structure and 30% of the enclosure wall surface. telescope. ENC-0332: Thermal The enclosure design shall provide rapid To reduce the cooling-down time Time Constant thermal equilibration of the steel during of the enclosure to optimize Structural Members nighttime operation. 20mm max plate thickness. image quality. ENC-8080: Passive The enclosure shall provide a minimum Best-practices. To ensure the Ventilation Rate flushing rate of 15 air changes per hour at minimum flushing rate for the low wind speed of 3 m/s. enclosure even in low wind conditions.

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Requirement ID & Requirement Notes Title ENC-0334: Nighttime The enclosure interior air temperature Interior Air Temperature shall be maintained within 0.40 degrees To minimize the enclosure seeing K (Goal: 0.22 degrees K) of the ambient air temperature during nighttime operation. ENC-0336: Heat Waste The enclosure shall trap and remove excess waste heat generated by passive To minimize the enclosure Seeing and active sources inside the enclosure.

“Dome Seeing” is a major factor in blurring images delivered to the focal plane. It is caused by thermally inhomogeneous air pockets in the telescope chamber at differing temperatures from the nighttime ambient. Good thermal design practices will be employed to minimize this effect. These include insulating the enclosure to minimize large thermal gradients at the start of the night, use of reflective coatings around the shutters to minimize the effect of overcooling of the enclosure surface due to radiation to the cold nighttime sky, providing vents in the enclosure walls to maximize wind-driven flushing of the telescope chamber, the use of rapidly thermalizing (low cross-section) structure to promote rapid equilibration, and the trapping and exhausting of heat from active sources.

The enclosure building includes an active ventilation system to remove waste heat and prevent it from migrating into the optical path. This system draws air from various spaces within the enclosure building and exhausts it off the site at a location approximately 70 meters from the telescope.

In addition, the layout of the facilities on the site was chosen to minimize the negative effects of the disruption of air flow across the site. The enclosure and summit support buildings are well separated along a path perpendicular to that of the prevailing wind direction. Space for a future telescope is located along this path as well. Heat generating equipment in the summit support building is located on the south side of the building (the prevailing down-wind side). Residual heat from the building will flow directly away from the site most of the time.

To demonstrate compliance with these requirements, several analyses and tests have been completed. Wind tunnel testing of scale models of the site and facilities were used to determine the characteristics of the wind at the site and the positive interaction of the enclosure building with air flow across the summit. These tests demonstrated that the geometry of the enclosure building is sufficient to keep the turbulent ground layer from entering into the telescope chamber. See Section 7.8.2 for a complete discussion of the wind tunnel testing. Computational Fluid Dynamics (CFD) analysis was used to determine the air flow characteristics within the enclosure (see Section 7.8.4.2) as well as the effects of localized heat sources at various locations (see Section 7.8.4.3) The results of these analyses demonstrate that the wind vent design is adequate to meet the flushing rate requirements and that there are no stagnant areas within the enclosure. Residual heat from sources at the telescope top end, instrument platform, enclosure structure, enclosure ventilation system and several areas around the summit support building raise the air temperature within the optical path less than 0.2 degrees (C) above the surrounding ambient, far less that the 0.4 degree requirement.

For reference, views of the enclosure building in the open and closed configurations are shown in Figure 7-118.

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Figure 7-118. Enclosure with open (right) and closed (left) shutters and vents

7.8.2 Wind Tunnel Testing 7.8.2.1 Terrain Study A wind-tunnel study of the topography around the GMT site36 was conducted to assess the impact of terrain on winds at the top of the mountain. A model of the GMT site shown in Figure 7-119 (Left) was fabricated to a 1:5000 scale and placed on a turntable in the wind tunnel. A traverse with a five-hole pressure probe, as presented in Figure 7-119 (Right), was used to measure the vertical profiles of the mean velocity and turbulence intensity for the wind azimuths influenced by the undulating topography. These data were then used to modify the approach flow for the pressure testing of the 1:200 scale models of the enclosure and summit support buildings and to assist in establishing reasonable boundary conditions for the computational fluid dynamics (CFD) analytical work.

Figure 7-119. (Left) The 1:5000 terrain model used to assess the wind profiles at the mountaintop site and (Right) the five-hole probe used to measure the mean velocity and turbulence intensity profiles at the site. The white circle represents the 1:200 turntable at a scale of 1:5000.

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7.8.2.2 Flow Visualization A flow visualization study was carried out in order to investigate the air flow behavior around and through the enclosure. In this study, air flow across the site was visually observed by injecting smoke into the incoming air stream at various heights above the terrain and noting the path that the trailing smoke followed. The effect of wind direction across the site was assessed by rotating the entire model relative to the incoming wind.

A key result of this test was a visual demonstration that the turbulent ground layer in and around the enclosure base is suppressed. Figure 7-120 shows a typical image of the ground level airflow around the enclosure building. The flow paths shown in these images demonstrates that incursion of the turbulent ground layer into the enclosure has been minimized by locating the enclosure observing floor at a sufficient height above the ground level (observing floor height is about 15m). The air will flow below the telescope chamber and around the pier, resulting in minimum effect on the air inside the enclosure. Note that in the current baseline enclosure design, the observing level floor is approximately 12m above grade. The mezzanine level below the observing level floor however, has been eliminated. Thus the clearance to ground is essentially identical to that used in this test model.

Figure 7-120. Enclosure wind tunnel test flow visualization showing the ground layer flow around the enclosure base 7.8.2.3 Cladding Study A wind-tunnel study of the sealed enclosure and summit support building37 was conducted to determine structural loads and peak cladding pressures due to design-level winds. Scale models of these structures were centered on a turntable in the wind tunnel. The local terrain was constructed as part of the turntable, as shown in Figure 7-121 (Left). Pressure taps were integrated into the models to measure exterior pressures exerted by the wind as shown in Figure 7-122. To determine structural loads on the enclosure, fluctuating pressures were measured simultaneously at a large number of tap locations (660 taps) and spatially integrated over the surface of the sealed enclosure.

Measurements of external pressures were made for each pressure tap location for 36 wind directions (10 degree intervals). The measurements were combined with directional wind statistics to produce external pressures. The external pressures were combined with an internal pressure resulting from infiltration and air-handling systems, to obtain total cladding pressures. Zones of total cladding pressures on the roof are presented in Figure 7-121 (Right). The zones with the highest net pressure were small areas on the roof of the sealed enclosure.

For the sealed enclosure, the most severe negative pressure zone is -14 kPa in small regions on the roof. This is due to the formation of local vortices in these regions. Zones of negative pressures over -9 kPa occur at several areas. Positive pressure zones of +4 kPa are quite common on the

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Figure 7-121. (Left) The 1:200 pressure models of the sealed Enclosure and (Right) Cladding zones on the sealed Enclosure roof (kPa).

Figure 7-122. (Left) The completed Enclosure model for the wind tunnel test with all the pressure taps inserted and (Right) Close-up of the Enclosure base showing the pressure taps.

7.8.2.4 Structural Load Study Forces and moments applicable to design of the structural system for the sealed enclosure were determined from the pressure model test. All loads were analyzed with respect to the building coordinate system shown in Figure 7-123. Static-equivalent shears at the base of the building for the extreme wind event are shown in Figure 7-124. Base moments in a sway mode are represented as Mx and My acting about the x and y axes, respectively; the base shears along the x and y axes are Vx and Vy; the base torque about the vertical axis is Mz. These results include the effect of the dynamic response in the fundamental modes of vibration (corresponding nominally to rotation about the x, y, and z axes respectively). Mean values are plotted using a continuous line, while peak values are plotted using box symbols. Peak values are used for design purposes. The primary intent of the figure is to show the relative effect of wind directions and dynamic building properties.

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NORTH 0° wind 90°

34°

270° 5.6 180° 5.6 Y

18.1

X Z up 18.1

Figure 7-123. Enclosure coordinate system

The response indicated by the ‘base’ natural frequencies provided by the structural engineer was used to examine the structural behavior under wind in the following paragraphs. Figure 7-124 also shows the peak response base shears for two additional sets of natural frequencies, which bound the base values by ±25 percent based upon the expected dynamic performance of the enclosure.

The mean base shears along the x and y axes vary smoothly with wind direction in a near- sinusoidal fashion, completing one cycle of variation in 360 degrees, as shown in Figure 7-124. Referring to the coordinate system shown in Figure 7-123 the x shear is expected to be largest (in absolute value) at roughly 120 or 300 degrees, when the approach wind is along the x axis. This is consistent with a so-called along-wind response, i.e., the primary loading is in the direction of the wind. Similarly, the y shear is expected to be large at directions 30 and 210 degrees, when the approach wind is along the y axis.

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Figure 7-124. Design wind loads (Enclosure base shear and torque values) on the sealed Enclosure for various wind directions (at 124 degree the wind is blowing directly at the Vertical shutters)

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The along-wind-response behavior varies from this ideal sinusoidal mean action response, however, because of the asymmetric shape of the enclosure building, the upwind local terrain geometry and effects of the summit support building. The variation of peak shears with wind direction follows approximately the same pattern as mean shears, with the fluctuating portion (peak minus mean) being roughly constant at all wind directions. At those directions where the mean load is large, this is indicative of a long-wind response due to buffeting by longitudinal turbulence in the approach wind. At wind directions where the mean load is near zero, the peak shears are in a direction roughly perpendicular to the approach wind and are mainly due to buffeting by the lateral component of turbulence in the approach wind and/or organized cyclical vortices generated by the building itself. The dynamic response is due partly to resonance (i.e., response at a natural frequency due to excitation by turbulent energy at that frequency) and partly by quasi-static response to turbulent energy at lower frequencies.

7.8.3 Enclosure Thermal Design 7.8.3.1 Natural Ventilation A series of MathCAD simulations38 were used early in the preliminary design phase to establish the thermal design criteria for the enclosure necessary to meet the performance requirements listed in Section 7.3.1.

The key general assumptions used in those analyses are given below:

 Air temperature: 15 °C  Temperature difference between day and night (difference between initial steel temperature and air temperature): 10 °C  Maximum steel thickness: 20 mm (balance between structural efficiency and thermal performance)  Sky temperature (night sky): -23 °C  Heat transfer coefficient (HTC): Estimated from the CFD results for various wind speeds  Enclosure configuration: 100% open, 3 m/s wind speed, 0 deg wind direction  Enclosure members cooling from both sides. The maximum thickness of the enclosure structural members (20 mm) was determined by considering the desired maximum cooling time of about 2 hours after opening the shutters and vents and prior to observing for low wind conditions and the efficiency of the structure to support the enclosure loads.

The initial calculations showed that even for these low wind conditions, a 1 K temperature difference between the enclosure steel members and ambient air would result in an increase of less than 0.1 K in the air temperature inside the enclosure. This is less than the 0.22 K goal and far less than the 0.40 K requirement defined in requirement ENC-0334.

The curves of temperature difference versus time provided in Figure 7-125 show the cooling-down period for steel beams and columns with various flange thicknesses.in low ambient wind speed condition. It should be noted that the results presented in the figures are conservative because: a) a higher heat transfer coefficient is expected under operating wind conditions on site, b) a lower day and night temperature difference is expected, and c) not all the enclosure steel members will have the maximum thickness. The estimated heat transfer coefficients for the low wind speed condition are shown in Figure 7-126.

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Temperature Difference vs Time [Wind speed (around the members): 3.0 m/s]

10.0 2 mm Thick 9.0 4 mm Thick 8.0 6 mm Thick 8 mm Thick 7.0 10 mm Thick 6.0 12 mm Thick 14 mm Thick 5.0 16 mm Thick 4.0 18 mm Thick

3.0 20 mm Thick

T [Temp Difference(K)] [Temp T Δ 2.0

1.0

0.0 0 15 30 45 60 75 90 105 120 135 150 165 180 195 210 225 t [Time (min)]

Figure 7-125. Temperature difference (between the members and the ambient temperature) vs. Time for the enclosure steel members cooling from both sides for the local 3 m/s wind speed.

Figure 7-126. Heat transfer coefficient estimates (CFD results, enclosure 100% open, 3 m/s wind, and 0-deg wind approach direction).

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7.8.3.2 Enclosure Outer Surfaces In order to reduce and limit the enclosure radiation to the night sky, the exposed surfaces outside the enclosure will be covered by low emissivity aluminum tape or paint. This is to prevent overcooling of the exterior surface producing cold air that is carried by the wind in front of the telescope.

With such coatings, the maximum estimated heat flux due to the radiation from the top surface with full exposure to the night sky is approximately 9 . The temperature change of the outer skin of the insulated roof panels will be about -1.1 °C for low wind condition (assuming a heat transfer coefficient of 8 to the ambient air). The exterior surface temperature depression of the side walls will be less due to a 50% reduced view factor of the sky.

7.8.3.3 Forced Ventilation Enclosed spaces within the enclosure are actively ventilated in order to remove heat from sources such as the drive systems. The enclosure forced ventilation system is described in Section 7.7.1.2.

7.8.4 CFD Analysis 7.8.4.1 Overview of the CFD Analyses CFD Analyses were performed for several reasons including the following:

Preliminary Studies 1. To demonstrate that with the layout of controllable wind vents covering 30 percent of the enclosure walls, there is adequate ventilation of all interior spaces of the enclosure. 2. To obtain wind velocity information across the telescope main truss and top end structural elements for use in developing drag forces for the telescope wind vibration analysis. 3. To obtain pressure loads on the primary mirrors and mirror cells for use in the telescope wind vibration analysis. 4. To calculate convective heat transfer coefficients for use in the thermal design of the enclosure structure.

CFD Thermal Studies 1. To calculate the air temperature within the optical path due to heat sources on the telescope and within the enclosure and demonstrate compliance with requirement ENC-0334 that the air temperature difference between ambient and air in the optical path is less than 0.40 C. 2. To model heat sources outside of the enclosure and demonstrate that these heat sources are at a sufficient distance away from the optical path so as to not impact image quality.

These analyses were completed in two stages as noted above (Preliminary Studies and the CFD Thermal Studies). In the preliminary stage, the CFD analyses provided support for the development of the preliminary designs of the enclosure and telescope. These analyses were performed by CPP, Inc., under contract with GMT. The second stage (CFD Thermal Studies) completed by GMT engineers, focused on the more detailed thermal analyses necessary to demonstrate compliance with image quality requirements.

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7.8.4.2 Preliminary CFD Analyses Fully three-dimensional transient CFD analysis was used to predict velocities and temperatures inside the enclosure. Computations were performed using a commercially available software package, STAR-CD (version 4.14).

The following three enclosure configurations were evaluated in the study.

1. Case B: Enclosure and wind vents 100% open 2. Case C: Enclosure and wind vents 50% open 3. Case D: Enclosure shutter 50% open and wind vents closed

For each configuration, two wind speed cases were run; 3 m/s and 10 m/s and for each configuration two angles of attack of the incoming wind were run; 0 deg. (shutter facing the incoming wind) and 50 deg.

Full scale CFD models of various enclosure configurations were built. The approximate model size (depending upon configuration) was 2.8 million fluid cells. The model of the enclosure was placed inside a virtual wind tunnel, as shown in Figure 7-127. The boundary conditions consisted of the approach velocity profile in the form

specified at the inlet, where U is the approach velocity magnitude (m/s) at height above the ground Z (with Z ranging from 0 m to 500 m at the top of the computational domain), the outlet boundary is specified at the virtual wind tunnel outlet and a symmetry plane (slip wall) is specified at the top of the domain to avoid boundary layer formation. is set at 3 m/s or 10 m/s as appropriate for a specific case under consideration, is set at 10 m and the mean wind speed profile power law exponent is set at 0.13 corresponding to open country approach. Effects of the local terrain are neglected due to the varying viewing angle of the enclosure and the floor of the virtual wind tunnel is modeled as flat. Since the night-time viewing conditions are the focus of the model, the outside air temperature is set at 12.7 °C, while inside air temperature at time equal 0 seconds is set at 20 °C. The time domain simulations ran until steady-state airflow conditions were established inside the enclosure. The time to reach steady state conditions (flush time) is summarized in Table 7-39. Under typical low wind speed conditions, the enclosure shutters and wind vents will be completely opened at sundown in order to assist in thermalizing the enclosure and telescope. Results for configurations 3 and 4 represent the enclosure flushing performance for this typical case. For configuration 4, the flushing time is just over 3 minutes. This demonstrates that the enclosure meets the 15 flushes per hour in a low wind (3 m/s) environment.

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Inlet – Wind Approach Profile (rotated for a given wind approach) = 3 ( )0.13 or 10 = 10 ( )0.13 10

Symmetry Plane (Virtual Wind Tunnel Roof)

Outlet

Outside Air Temperature: T = 285.85 K = 12.7 C Initial Inside Air Temperature: T = 293.15 K = 20 C

Figure 7-127. Enclosure CFD model (50% Open Case) boundary conditions

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Table 7-39. Estimated flushing rates for various enclosure configurations Configuration Wind Speed Wind Direction Flush Time Flush Rate Enclosure Setting No (m/s) (deg) (s) (per h) 1 B: 100% Open 10 0 55 65.5 2 B: 100% Open 10 50 70 51.5 3 B: 100% Open 3 0 110 32.7 4 B: 100% Open 3 50 200 18.0

Reducing the overall surface area of the enclosure that is open to the outside increases the time required to flush the enclosure as expected. An interesting result is observed when re-orienting the enclosure at 50 degrees to the incoming wind for the 25% open case where the flush time was reduced compared to the normal-direction wind approach case (see configurations 9 to 12 in Table 7-39). This is due to the fact that for the 50-degree wind approach case the internal air flow is dominated by the circular air movement region along the inside enclosure walls. This air movement pattern results in locally higher velocities inside the enclosure and therefore reduces required flush times. Representative horizontal vector sections depicting airflow inside the enclosure for various considered configurations are shown in Figures 7-12 through 7-15.

(a)

Figure 7-128. Velocity vectors, 100% open Enclosure, 3 m/s approach wind speed, 0-deg wind approach direction.

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(b)

Figure 7-129. Velocity vectors, 100% open Enclosure, 3 m/s approach wind speed, 50-deg wind approach direction

Figure 7-130. Velocity vectors, 25% open Enclosure, 3 m/s approach wind speed, 0-deg wind approach direction

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(b)

Figure 7-131. Velocity vectors, 25% open Enclosure, 3 m/s approach wind speed, 50-deg wind approach direction

7.8.4.3 CFD Thermal Analysis 7.8.4.3.1 Introduction A CFD (Computational Fluid Dynamics) simulation has been performed to study the effects of heat sources within and around the enclosure. In this analysis, the steady-state air temperature distribution within the telescope optical path resulting from the dissipation of this heat is calculated. The driving requirement, as stated in ENC-0334, is that the air temperature within the enclosure is not greater than 0.40 degrees K above or below the surrounding ambient temperature during science operations.

7.8.4.4 Methodology The following steps were taken for the CFD analysis: 1. The simplified geometries (e.g., enclosure building) were generated in SolidWorks (all the key features were preserved). 2. The simplified geometries were imported in to DesignModeler to be pre-processed. 3. The pre-processed geometries were meshed in ANSYS. 4. The meshed geometries were solved in Fluent once the set-ups were complete. 5. The post processing of the CFD results were carried out in ANSY CFD-Post.

The analysis was carried out in ANSYS CFD.

This CFD configuration represents a worst case with regards to enclosure ventilation. The configuration of the model includes the following:  The enclosure vertical shutter faces downwind (incoming wind to the back of the enclosure). The wind direction is from the NNE (primary wind direction).

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 Shutter and wind vents are fully open.  The mean wind speed is 3 m/s at 10 m above the ground.  The model includes the enclosure, telescope (at a 30 deg zenith angle) and summit support building.  Features within these structures that act as heat sources include the telescope top end, instrument platform, enclosure ventilation duct, enclosure bridge crane, fluid coolers and transformers. A description of the heat sources is given below.  The topography is not included in the model.

The geometry setting and CFD domain are shown in Figure 7-132. Figure 7-133 through Figure 7-135 show the close-up images of the 3D model parts.

Heat sources used in the simulation include the following (a summary of heat sources is given in Table 7-40):

1. Enclosure building (1 ºK above air temperature) - Applied to inner surfaces (including the Overhead Crane). This is in line with the air temperature drop rate over night and the air maximum volumetric heat capacity under the low wind conditions. 2. Summit support building (0.5 ºK above air temperature) – Applied to the roof of the building. Estimated temperature increase on the roof for the worst case scenario due to the heat sources inside the summit support building. 3. Telescope (1 ºK above air temperature) – Applied to the C-rings and the instrument platform. Although the telescope mirrors and mirror cells will be actively cooled, the telescope C- rings and other components could have a temperature above the ambient air temperature due to the air temperature change overnight. 4. Telescope top-end (heat rate: 875 , heat flux of 42 ) – Applied to the top face and side surfaces. 5. Fluid coolers (total heat rate: 989200 10.5 ºK above air temperature, 3.0 m/s) – Applied to the south side surface of each cooler. 6. Transformers (10 ºK above air temperature) – Applied to the back panels (south side surface). 7. Ventilation duct exhaust (2.9 ºK above air temperature, 2.7 m/s) – Applied to the exhaust surface.

The heat waste from the enclosure building will be exhausted away from the enclosure via the ventilation duct. The air exiting the ventilation duct will have a higher temperature than that of the ambient air. This could affect the telescope image quality if the air temperature rise is significant.

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Table 7-40. Heat source summary Heat Sources Quantity Surface Input (CFD Model) ENC 1 Inside 286.85 K OC 1 All 286.85 K TEL 1 C-rings, IP 286.85 K TE 1 Top and Sides 42 (W/m^2) TF 2 Back Panel (south side) 295.85 K FC 4 Exhaust (south side) 3.0 m/s, 296.35 K SS 1 Top 286.35 K VD 1 Exhaust 2.7 m/s, 288.75 K

Figure 7-132. Geometry setting – flow domain. The primary wind direction is along the Y axis (-Y)

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Figure 7-133. Geometry setting – enclosure, telescope, top end and enclosure crane model

Figure 7-134. Geometry setting – support facility, fluid coolers and electrical transformers model

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Figure 7-135. Geometry setting – enclosure ventilation duct model

7.8.4.5 Results The extensive amount of data generated by the CFD simulations can be used to improve the design and ultimately enhance the telescope performance. The results summary for parameters such as velocity and temperature are given in this document in order to study the flow behavior and to review the heat transfer analysis accordingly.

7.8.4.5.1 Velocity The flow behavior around and through the buildings on the summit site can be seen in the following Figures. The velocity contours for various sections of the domain are given in Figure 7-136 through Figure 7-143.

7.8.4.5.2 Temperature The results for the thermal analysis of the buildings and major equipment on the summit site are presented in this subsection. The temperature contours for vertical and horizontal planes of the domain are given in Figure 7-148 through Figure 7-156.

7.8.4.6 Conclusions The key findings are summarized below:

 The overall temperature increase in the telescope field of view due to the enclosure-Air temperature difference is within the required range of 0.40 K. See Figure 7-148.  The overall temperature increase in the telescope field of view due to the telescope top end- air temperature difference is within the required range of 0.40 K. See Figure 7-148.  The telescope field of view will not be affected by the hot air exhausted from the ventilation duct. See Figure 7-149 and Figure 7-156.  The effect of the heated top of the summit support building on the local telescope field of view is negligible. See Figure 7-150.

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 The telescope field of view will not be affected by the hot air exhausted from the fluid coolers. See Figure 7-141 through Figure 7-145, and Figure 7-156.  The effect of the transformers on the local telescope field of view is negligible. See Figure 7-156.

Figure 7-136. Velocity contours - vertical cross-section through enclosure centerline

Figure 7-137. Velocity contours - Vertical cross-section through the enclosure ventilation duct

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Figure 7-138. Velocity contours - Vertical cross-section through the summit support building

Figure 7-139. Velocity contours - Vertical cross-section through fluid coolers

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Figure 7-140. Velocity contours - Vertical cross-section through electrical transformers

Section Location

Figure 7-141. Velocity contours - Horizontal cross-section through enclosure near telescope top end

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Figure 7-142. Velocity contours - Horizontal cross-section through the enclosure

Figure 7-143. Velocity contours - Horizontal cross-section just above grade level

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Figure 7-144 and Figure 7-145 show the streamlines for the number of points located vertically and horizontally in the domain. The streamlines show the sample particles path.

Figure 7-144. Velocity streamlines – Vertical

Figure 7-145. Streamlines – horizontal

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The change of direction in the flow path and generated eddies can be observed in the following Figures. The velocity vectors are shown in Figure 7-146 and Figure 7-147 for vertical and horizontal planes accordingly.

Figure 7-146. Velocity vectors - Vertical cross-section through enclosure centerline

Figure 7-147. Velocity vectors - Horizontal cross-section through enclosure near telescope top end

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Figure 7-148. Temperature contours - Vertical cross-section through enclosure centerline

Section Location

Figure 7-149. Temperature contours - Vertical cross-section at ventilation duct exit

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Figure 7-150. Temperature contours - Vertical cross-section through summit support building

Figure 7-151. Temperature contours - Vertical cross-section through fluid coolers

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Section Location

TEL beam lower limit

Figure 7-152. Temperature contours - Vertical cross-section at 15m distance from the vertical shutter. The intersection between the horizontal and vertical planes shows the Telescope beam lower limit at 15m distance. (Top image). Temperature contours – Front View - Vertical cross-section at 15m distance from the vertical shutter. The horizontal line shows the Telescope beam lower limit at 15m distance. (Bottom image)

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Section Location

TEL beam lower limit

Figure 7-153. Temperature contours - Vertical cross-section at 45m distance from the vertical shutter. The intersection between the horizontal and vertical planes shows the Telescope beam lower limit at 45m distance. (Top image). Temperature contours – Front View - Vertical cross-section at 45m distance from the vertical shutter. The horizontal line shows the Telescope beam lower limit at 45m distance. (Bottom image)

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Section Location

Figure 7-154. Temperature contours - Horizontal cross-section through enclosure near telescope top end

Figure 7-155. Temperature contours - Horizontal cross-section through enclosure and telescope

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Figure 7-156. Temperature contours - Horizontal cross-section at site near grade level 7.9 Construction Planning Construction of the enclosure and facilities will require significant planning and coordination. It is anticipated that 5 large procurements will be required to fabricate and deliver all parts and construct the facility. In addition, site power needs to be brought in from the Chilean electrical grid. The LCO water infrastructure needs to be upgraded to supply the needs of GMT and a construction camp will need to be built to accommodate up to 200 workers during the peak construction periods.

The enclosure and facilities construction schedule is described in section 4.4.7. It is built around a set of project milestones associated with the need for certain facilities to be completed in order that other critical path activities in the overall GMT schedule can start on time. These milestone dates include the following:

 The warehouse will be completed and ready for initial integration of M1 Cells by the fourth quarter of 2017.  The auxiliary building will be completed and ready for the installation of the coating facility by the third quarter of 2017.  The enclosure will be completed and ready for the installation of the telescope by the third quarter of 2018.

Work on site begins with the establishment of the construction camp. Facilities at LCO will be utilized and expanded as necessary to meet the construction force needs. Work at Las Campanas Peak will begin with the site work and grading followed by construction of the telescope pier and building foundations. In parallel with this site work, contracts will be let for the fabrication of the enclosure and facilities steel and enclosure mechanisms. Delivery of the steelwork will be sequenced with the completion schedule of the various foundations beginning with the telescope

ENCLOSURE AND FACILITIES 7–177 GMT SYSTEM LEVEL PRELIMINARY DESIGN REVIEW December 13, 2013 pier and enclosure base and to meet the project milestone dates described above. A steel erector will be contracted in time to begin the assembly of the structural steel, wall and roof cladding for all of the buildings, and the enclosure mechanisms. A final contract will be let for the completion of the facilities. This work involves the architectural finishes and the installation of plumbing, electrical and mechanical equipment. Much of the material necessary for the completion work will be purchased by GMTO, shipped to the site and provided as customer-furnished equipment to the completion work contractor.

7.9.1 Site Leveling Las Campanas Peak rough grading has already been completed in preparation for construction of the GMT. This work included the controlled blasting and excavation of rock from the site. The summit has now been graded level at an elevation of 2,518m with a total usable area of approximately 25,495 square meters. Figure 7-157 shows the Las Campanas peak prior to grading the site. The picture was taken at a location on the site near where the telescope will be located, looking east. Environmental test equipment used to characterize the site is shown to the left of the picture and a temporary access road is shown to the right.

Figure 7-157. Las Campanas peak prior to site grading

Figure 7-158 shows a partially graded site with a small amount of rock still remaining and ready to be removed. Low spots were graded flat with compacted, engineered fill material.

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Figure 7-158. Summit peak during site grading

Figure 7-159. Summit site borings and test pit locations

7.9.2 Geotechnical Engineering Once the site leveling had been completed, geotechnical studies necessary for establishing the soil and rock characteristics for foundation designs began. This program included the extraction of core samples near key foundations at both the summit and support sites to examine the rock quality at depth and for laboratory testing to determine mechanical properties of the rock and soil. Test pits

ENCLOSURE AND FACILITIES 7–179 GMT SYSTEM LEVEL PRELIMINARY DESIGN REVIEW December 13, 2013 were dug in several areas to determine the depth and characteristics of granular soil above rock. The locations of borings (B-#) and test pits (CSO-#) are shown in Figure 7-159 for the summit site and in Figure 7-160 for the support site. Several dynamic tests were also performed to measure subsurface properties over extended areas. The summit peak after site grading and during geotechnical testing is shown in Figure 7-161. A drilling rig used for obtaining subsurface test samples is also seen in the figure.

Figure 7-160. Support site borings and test pits

Figure 7-161. Summit peak after site grading and during geotechnical testing

The results of the geotechnical study are being used in the structural design of the building foundations and the civil engineering associated with the design of roadways and retaining structures. Elastic properties of the rock in the area of the pier are incorporated into the performance modeling of the telescope.

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7.9.3 Utilities and Infrastructure 7.9.3.1 Electrical Power and Communications Electrical power and communication infrastructure upgrades are described in Section7.7.6.1. This upgrade will be performed by subcontract with the work coordinated with ongoing activities at LCO. A preliminary design for the upgrade and feed to the GMT site has been completed. The design study included estimates of cost and schedule as well as an implementation plan that limits the disruption of electrical power to LCO.

7.9.3.2 Water A large water storage tank for LCO is currently located just off the summit site. Supply for this water is from a spring on LCO property at a lower elevation. The water is pumped to the storage tank in stages. GMT will make use of this water supply for its fresh water needs. Additional infrastructure and upgrades necessary to bring this water to the summit and support sites will be constructed. During construction, water will be brought in by tanker truck and stored in temporary containers on site.

7.9.3.3 Construction camp GMT will make use of an existing construction camp at LCO, approximately 5 km from the GMT site. This camp has a capacity of approximately 50, so it will need to be expanded substantially to meet the peak GMT construction needs. The camp will provide dormitory and dining hall space for all construction workers and supervisory personnel. It is expected that space for 80 will be required for the construction of the site-work and foundations as well as the erection of the structural steel and cladding. During the completion phase, the peak work force will approach 200. Permanent upgrades to the LCO facilities as well as the use of rented temporary housing facilities are being considered.

7.9.4 Procurement Overview The details of the enclosure and facilities procurement plan are provided in the management section of this report Section 4.7.1 and an overview is provided here.

At the conclusion of the detailed design phase, sets of construction documents will be prepared for the release of Requests for Proposals (RFP’s) for the following work:

 Site-work and foundations – includes roadways, underground utilities infrastructure, grounding systems, telescope pier, building foundations, miscellaneous foundations for generators, transformers, weather tower, etc. and finish grading. The construction documents for this work will include drawings and construction specifications and shop drawings for concrete reinforcing steel.  Fabrication of the structural steel for the enclosure and support buildings – includes all of the structural steel for the rotating enclosure, enclosure base, enclosure shutters, summit support building, warehouse and utility building. This work will likely include the factory preassembly of the enclosure base ring girder, the rotating enclosure ring girder and super- columns to make sure that these structures meet overall assembly tolerances prior to leaving the factory and thus reduce the time-consuming need for field fit-up of complex joints.  Fabrication of the enclosure mechanisms (bogies, etc.) – includes the preparation of fabrication drawings for all parts, fabrication, factory assembly and limited testing of selected mechanisms. ENCLOSURE AND FACILITIES 7–181 GMT SYSTEM LEVEL PRELIMINARY DESIGN REVIEW December 13, 2013

 Erection of the structural steel, enclosure mechanisms and roof & wall panels – includes the site work associated with the erection of the structural steel for the enclosure and facilities buildings and the installation of the enclosure mechanisms and enclosure crane.  Completion of the enclosure and support buildings – completion of the architectural finishes, plumbing, electrical and mechanical equipment.

7.9.5 Site Work and Foundations Site work must begin as soon as possible following approval for construction. Construction documents are scheduled to be ready for release of an RFP for this work in late March, 2014. Work is being planned assuming that the project will receive GMT board approval to start the work in July, 2014.

7.9.5.1 Roads and Grading The existing access road to the Las Campanas summit from the LCO access road will be improved and include a more generous turning radius at the intersection of the Las Campanas peak and LCO access roads. New roads and developed areas will be graded for the support site including one area for the lodge and dining hall and another for the utility building and warehouse. A third developed area will be for water storage and supply for the support site, approximately midway between the support and summit sites.

At the end of the construction phase, the final site grading and finishing will include the installation of a gravel surface at the summit site, the installation of guardrails and signage. If budget allows, the road between the support site and the summit will be paved.

7.9.5.2 Underground Utilities The work includes all the installation of underground utilities infrastructure including conduit for electrical and communications wire and fiber optic cables, and piping for chilled water, compressed air and hydraulic oil. A main conduit run spans between the equipment room at the summit site and utility building at the support site. Another run, including chilled water and compressed air piping connects the equipment room to the enclosure base. A third run includes water lines from the summit water tank to the summit support building, water storage facility and support site.

7.9.5.3 Foundations Reinforced concrete foundations include a massive structure for the telescope pier, spread footings for the enclosure base columns and spread footings with slabs on grade for the summit support building. The utilities building, warehouse and water storage facility at the support site have slabs on grade and spread footings for the structural steel columns.

The site work will begin with the installation and testing of the electrical grounding system for the enclosure followed immediately by the construction of the telescope pier and enclosure base column footings. It is critical to complete the pier and enclosure base foundations as soon as possible. Construction of the auxiliary building and equipment building foundations will follow next. The foundation for the facilities building will begin at the conclusion of the erection of the enclosure steel and cladding in order to provide additional area on site for the construction of the enclosure.

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7.9.6 Steel Fabrication 7.9.6.1 Enclosure and Facilities Steel Fabrication The construction documents for the fabrication of the steel for the enclosure and all of the facilities buildings will include complete sets of shop drawings and specifications for the structural steel components and the fabrication contract will be structured as build-to-print.

It is anticipated that there will be a limited amount of factory pre-assembly for the enclosure steel. Some items such as the enclosure base ring girder, enclosure ring girder, super columns and story truss are assemblies of many individual components. Tolerances for these elements will likely drive the need to modify or shim joints so that the geometric tolerances on the final assemblies can be achieved. It is far easier to make these modifications or shims at the factory than in the field. Decisions on what parts will require factory pre-assembly will be made during the detailed design phase of the work.

A delivery schedule for various packages will be included in the work in order to compress the construction schedule and limit the amount of material that is stored on site. The phased delivery of parts will likely include the following packages, delivered in the order listed:

1. Enclosure base steel 2. Enclosure steel 3. Auxiliary building and equipment building steel 4. Utilities building, warehouse and water storage facility steel 5. Facilities building steel

7.9.6.2 Enclosure Mechanisms Fabrication The design of the enclosure mechanisms will be completed to a detailed design level and include piece part and assembly drawings and specifications. The completion of fabrication drawings will be left for the fabricator since some fabrication processes will be specific to the facilities and equipment available to each potential fabricator. Fabrication drawings will be reviewed and approved by M3 Engineering and GMT prior to fabrication of the parts. Mechanisms included in this work include the following:

1. Enclosure drive bogies 2. Enclosure idler bogies 3. Horizontal shutter drive bogies 4. Horizontal shutter idler bogies 5. Vertical shutter guides 6. Vertical shutter cable drums, winches, sheave assemblies and cables

The delivery of the mechanisms will be scheduled to coincide with the erection of the enclosure steel. The steel erection contractor will install the mechanisms.

7.9.7 Erection of the Structural Steel, Roof and Wall Panels A contract will be awarded to a steel erector to erect all steel for the enclosure and all facilities buildings. The work will also include the installation of the enclosure mechanisms, enclosure crane and the installation of all roof and wall panels for all of the buildings.

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The sequence of the work for the enclosure building will be structured to assure completion of construction in time to meet required schedule date for the start of the assembly of the telescope structure. The general construction sequence for the enclosure building is as follows:

1. Erection of the enclosure base steel 2. Installation and alignment of the enclosure bogie rails 3. Installation of the enclosure bogies and vertical shutter drive mechanisms 4. Erection of the enclosure steel (on false work above the bogies) 5. Installation of the vertical shutter panels (temporarily bolted in place) 6. Installation of the horizontal shutter bogies 7. Installation of the enclosure crane 8. Installation of the horizontal shutter panels (temporarily bolted in place) 9. Installation of the enclosure wall and roof panels 10. Installation of the wind vent doors 11. Removal of the enclosure construction false-work

The schedule for the erection of the steel for the summit support facilities will be built around milestone dates for the installation of the coating facility and the start of the integration of the primary mirror cell assemblies. The sequencing of these activities is more fluid and will depend largely on the delivery schedule of steel parts for the various structures and the resources available to the steel erection contractor. A schedule emphasis will be placed on the completion of the auxiliary building, equipment building and warehouse as these buildings are needed for early telescope work.

7.9.8 Completion Work A separate contract (or multiple contracts) will be made for the completion of the interior spaces, architectural finishes, plumbing, mechanical and electrical systems. These contracts will include all activities associated with the assembly, installation, testing and commissioning including the testing and commissioning of the enclosure mechanisms.

The scheduling of the work will be driven by the same project milestone dates described above for the start of the telescope assembly, coating facility and integration of the primary mirror cell assemblies. Completion work will begin following acceptance of the structural steel, wall and roof work.

GMT plans to procure and deliver to the completion contractor, much of the material and equipment to be installed by the contractor as a part of the work. The procurement of these items will follow the standard GMT procurement process which includes competitive bidding, formal down-select, issuance of contract or purchase order and shipment. GMT personnel in Chile will assist in importing the material, transport to the site and storage until handover to the completion contractor.

7.9.9 Construction Phase Infrastructure All construction phase infrastructure provided for the GMT will take into account the remoteness of the project site. The location of the project site will require workers to be housed near the project, and will also require additional considerations such as a temporary concrete batch plant. Along with these challenges, adequate space for laydown and storage must be provided without disturbing additional site area not planned for construction.

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7.9.9.1 Construction Utilities Common utilities such as water, power, and fuel must also be accounted for during the construction phase of the GMT. Water will be piped from the exiting water storage tank into temporary portable storage tanks for use at all of the building sites. Portable fuel tanks will also be provided to power the temporary construction generators around the project site.

7.9.9.2 Concrete Batch Plant With the large volume of concrete and remoteness of the site, the most economical way to construct such foundations is with a temporary batch plant constructed on-site. Raw materials will be trucked to the site and stockpiled at the batch plant. The concrete will then be mixed as needed during construction. The batch plant will likely be located at the east side of the summit site since the largest quantities of concrete are for the enclosure base and telescope pier.

The concrete batch plant will be a “central mix” type batch plant. This type of plant combines water with the materials at a central location. The nearby location of the water storage tank will accommodate this type of plant. See Figure 7-162 for the location of the concrete batch plant.

Figure 7-162. Concrete batch plant

7.9.9.3 Enclosure Building Laydown and Material Storage Areas The construction of the enclosure building will require a large laydown area on the summit site. The laydown area at the summit site will accommodate the storage of steel and a short-term staging area for steel to be prepared and transported for enclosure building erection. To accommodate this requirement, a large area on the southeast of the summit site has been reserved as shown in Figure 7-163. In addition areas are required for material storage. Figure 7-163 also identifies several off- summit sites available for temporary storage of equipment and materials.

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Figure 7-163. Laydown and material storage areas

Along with providing laydown space, adequate space must be reserved for small vehicle parking and construction trailers used as offices by the construction contractors. A detailed view of the summit site, showing office trailers, parking space, laydown area and overall dimensions is shown in Figure 7-164.

Figure 7-164. Enclosure building laydown area

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7.9.9.4 Crane Pad Locations The height of the enclosure building requires erection cranes to be located at multiple points around the building. Three pad locations, to accommodate a mobile crane, will be provided to access all components of the enclosure building. Along with these three locations, space has been provided for crane maneuvering and travel. See Figure 7-165 for potential enclosure building crane pad locations and travel paths.

Figure 7-165. Enclosure building crane pad locations

7.9.9.4.1 Crane Capacity and Reach The erection of the enclosure building requires the use of a high capacity crane with a long reach. The following crane properties are anticipated based upon the size of the enclosure building.

 Crane Type: Mobile Crane  Maximum Lifting Capacity: 350 mt  Telescopic Boom Length: 70 meters  Lattice Jib: 78 meters

The utilization of a tower crane will also be investigated for feasibility and availability in Chile. Along with the utilization of a large crane for enclosure steel and wall panel installation, multiple smaller cranes will be utilized as necessary for erection of the summit support building and the buildings at the support site.

7.9.9.4.2 Waste Management Temporary toilet facilities will be provided at the summit site and support site for both construction workers and GMT personnel. Single occupant, free standing stalls with hand washing stations will be provided based upon the maximum number of construction workers anticipated. All waste will be collected at shipped off site at frequent intervals.

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7.9.9.5 Construction Power Temporary construction power will be provided by portable generators located throughout the site. Generator sizing will be based upon the anticipated construction power loads. After construction is complete, power will be connected via the overhead power feed from the utility company. 7.10 Enclosure and Facilities Risks 7.10.1 Summary of Current Enclosure and Facilities Risks The enclosure and facilities risk analysis follows the GMTO-wide approach described in Sections 4.6 and 12. Figure 7-166 illustrates the top risks in a risk exposure matrix. Numbers in the figure are the risk ID numbers (per Table 7-41) in their appropriate likelihood and impact coordinate cell. The most significant risks are listed in Table 7-41. Italics are used to indicate those mitigation strategies that are already planned and/or implemented.

Impact

1 2 3 4 5

5

4 92

3 5,7 9,6 Likelihood

2 4,8

1

Figure 7-166. Risk exposure matrix

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Table 7-41. Enclosure and facility risk register Primary Risk Risk Description Consequence Likelihood Rating Mitigations Comments Type RISK0092: Enclosure design is complex Cost 4 - Significant 4 - Probable 15 MIT0188: Include cost Cost estimates provided Cost Enclosure and site assembly challenging. contingency from several independent exceeds budget Costs may well exceed budget MIT0189: Value sources. engineering RISK0009: Problems encountered as a Technical 5 - Significant 3 - Possible 15 MIT0018: Acceptable Preliminary design Bogies and result of the challenging engineering analysis of completed. Loads Track design design and the mechanical and addressed and analysis installation/alignment of the structural designs using demonstrates that stress bogies and tracks due to the maximum loads and levels are acceptable extremely large loads on the appropriate factors of bogies and at the track/ bogies safety. wheel interface. High loads MIT0019: Bogies on the lateral bogies could Assembly acceptance test. result in failure of the lateral Periodic inspection. side thrust rollers Effects: Bogie wheel and track failure.

RISK0006: Reliability of the shutters may Technical 5 - Moderate 3 - Probable 15 MIT0012: Acceptable Preliminary design Shutters be a concern due to the engineering analysis of completed. Loads challenging design resulting the mechanical and addressed and analysis from the large enclosure structural designs using demonstrates that stress opening, high wind loads and maximum loads and levels are acceptable thermal effects. appropriate factors of Effect: Telescope down time safety. during operations, higher MIT0013: Shutters operational costs, telescope Assembly acceptance test. being unprotected if shutters seize up.

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Primary Risk Risk Description Consequence Likelihood Rating Mitigations Comments Type RISK0007: Sealing the enclosure against Technical 3 - Moderate 3 - Possible 9 MIT0014: Selection of the Preliminary design Seals infiltration of dust, water, and seals based on previous completed. Two layers (openings and snow during high wind events experience and best of seals typically used; sliding will be a major challenge practices for similar large outer brush seal and interfaces) especially with the number of telescopes. inner compression seal seals associated with the large MIT0179: Using where possible. Wind number of ventilation inflatable seals. vent jambs in channels to openings. MIT0184: Seals reduce light leaks. Effects: Decreased Assembly acceptance test performance (or increased maintenance costs) as reflectivity of optics reduces faster due to increased scattering from dust accumulation. Rain could cause problems with electronics or cause safety hazard from slipping on walkways and catwalks RISK0005: Inside temperature of the Technical 3 - Moderate 3 - Possible 9 MIT0010: CFD and wind Wind tunnel testing and Structure Enclosure could vary tunnel tests to be CFD analysis for (thermal) significantly at different undertaken to study the enclosure ventilation places as a result of various thermal behavior of the completed with thicknesses of the Enclosure Enclosure and the flow acceptable results. CFD members. Key factors: a) inside and around the thermal analysis Heavy steel structure at the Enclosure in order to ongoing. top of the Enclosure, b) study the wind effects on Overhead crane, c) Thin walls the Enclosure air (for max heat transfer), d) temperature. Wind flow and speed, and e) MIT0011: Day-time Radiation. thermal control. Effects: Enclosure seeing. MIT0017: Accept lower performance of the telescope.

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Primary Risk Risk Description Consequence Likelihood Rating Mitigations Comments Type RISK0008: Flow uncertainty inside the Technical 4 - Significant 2 - Unlikely 8 MIT0017: Accept lower Wind tunnel testing and Wind Vents Enclosure. Key factors: a) performance of the CFD analysis for Wind vents partially open. telescope. enclosure ventilation Effects: Enclosure seeing. MIT0010: CFD and wind completed with tunnel tests to be acceptable results. CFD undertaken to study the thermal analysis ongoing thermal behavior of the Enclosure and the flow inside and around the Enclosure in order to study the wind effects on the Enclosure air temperature. RISK0004: More strict new seismic codes Technical 4 - Significant 2 - Unlikely 8 MIT0008: Advanced Preliminary design Structure and the size and mass of the seismic calculations completed. Seismic (seismic) enclosure may drive the (FEA) to be carried out by design requirements met design towards needing base the contractors to support using site specific design isolation. the proposed design. environments and Effect: High cost of base GMTO defined design isolation. Higher relative criteria motion between the enclosure observing floor and the telescope

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7.10.2 Risk Mitigation Strategies The risk mitigations identified in the risk register generally fall under categories that include preliminary and detailed analysis as well as testing prior to reaching the site. Analytical means were used to mitigate several risks in the months following the Enclosure and Facilities PDR. Factory preassembly and testing of several components prior to shipment is still an option if further analysis does not produce convincing results.

7.10.3 Risk Mitigation since the Enclosure and Facilities PDR 7.10.3.1 Enclosure Bogie and track Design (Risk0009) Analyses of fabrication and installation tolerances that can be achieved for the enclosure azimuth track were completed soon after the Enclosure PDR. In addition, improvements made to the design and installation procedures of the track on the enclosure base ring girder will provide more flexibility to adjust the height and radial position of the rail. Further work by M3 Engineering since the Enclosure PDR has led to a more efficient design that distributes the bogie forces more uniformly. With these design improvements, the likelihood for this risk was dropped from probable to possible.

7.10.3.2 Enclosure and Facilities Costs (Risk0092) Following the completion of the preliminary design of the enclosure and facilities buildings, several steel fabrication companies, steel erection companies and large machine shops were approached to provide estimates for the cost of various portions of the work and also schedule information. In addition, recommendations regarding cost savings from the PDR committee as well as internal GMT considerations were evaluated during a value engineering exercise. This process resulted in significant cost savings and more reliable cost and contingency estimates. However, the enclosure design is complex and the construction site is remote. Any construction work in Chile competes with ongoing mining industry activities for local resources. The enclosure steel work will be bid worldwide. The likelihood for this risk is kept at possible and the severity remains at significant.

7.10.3.3 Reliability of the Shutters (Risk0006) The shutters are complex mechanisms, particularly the vertical shutters with their cable driven and counterweighted designs. Improvements to the shutter design since the Enclosure PDR include a redesign of the vertical shutter counterweight system to counterbalance the shutter panel loads at a level of 90% of the shutter panel weight. The shutters open by gravitational force, therefore the shutter drives need to drive the panels closed. The drive mechanisms can be designed to overcome large friction forces that may occur if the panels get misaligned. A less complex cable management system for the vertical shutter was also developed. As such, the likelihood for this risk was reduced from probable to possible.

7.10.3.4 Enclosure Seals (Risk0007) The enclosure will use two layers of seals where possible such as sweep action brush seals and compression seals. This is consistent with best practices for large telescope enclosures. Wind vent doors will have factory preinstalled side and bottom seals as well as channel and possible brush seals along the sides to reduce infiltration and minimize light leaks. With these design considerations, the likelihood for this risk was reduced from probable to possible.

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7.11 Recent Design Activities 7.11.1 Preliminary Design Review A PDR for the Enclosure and Facilities was held at the GMTO offices in Pasadena on January 16– 18, 2013. Comments brought up by the review committee generated improvements to various areas of the designs. Several suggestions both from this review committee and by others resulted in a value engineering phase between February and July 2013, where many elements of the enclosure and facilities buildings were re-engineered to reduce costs. A detailed summary of the value engineering effort is provided in section 7.11.2. The enclosure and facilities designs described in this report are the value engineered PDR designs and are referred to as the current Baseline enclosure and facilities designs.

7.11.1.1 Enclosure and Facilities Preliminary Design Review Design information was presented at PDR by GMT and M3 Engineering personnel to GMTO management and to an external review panel. The review panel consisted of the following group of experts in the design, construction and operation of telescope facilities and enclosures:

Mark Warner (ATST/AURA) [chair] Jeff Barr (CTIO/LSST/AURA) Enrique Figueroa (CTIO/LSST/AURA) Heather Marshall (ATST/AURA) Frank Perez (Magellan/OCIW)

The panel was specifically asked to evaluate the enclosure and facilities design requirements, design approaches and trade studies, particular aspects of the enclosure bogies and track, shutters, crane and wind vents, interfaces and interface management, risks and safety. Information presented at the review covered the master plan, structural, architectural and mechanical aspects of the summit support and enclosure buildings, utilities, risk management, safety and schedule. In addition, the committee was asked to make recommendations of changes or considerations where they thought that cost savings could be made.

The review was considered a success with no significant problems or concerns voiced by the committee. A comprehensive committee report was submitted to GMT following the review.39 This report includes detailed comments and recommendations for selected items and design areas. GMT and M3 Engineering provided a response to all committee actions and recommendations40.

As stated in the executive summary of the committee’s report:

“The GMTO project office presented an impressive quantity and quality of work product. In general, the drawings, analyses, and supporting documents were detailed appropriately for this phase of the design effort”.

7.11.2 Enclosure and Facilities Cost Reduction Studies 7.11.2.1 Enclosure and Facilities Value Engineering Following the PDR, recommendations from GMT personnel, the enclosure and facilities PDR committee and M3 Engineering regarding cost-reduction measures were considered and reviewed during several focused sessions. The result of this work was a set of proposed design changes that would result in little or no impact to the performance of the enclosure and facilities, but result in the potential for significant cost savings.

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The following sub-sections provide an overview of these activities. The current baseline design includes all of the features described herein.

7.11.2.1.1 Survival Wind Speed Requirements The survival level wind speed was reduced from 70 m/s to 65 m/s. This decrease in wind speed corresponds to a 13% load reduction on the walls and roofs of the enclosure and summit support buildings. Subsequent refinement of the structural design of secondary framing members for the roof and wall elements resulted in a decrease in steel.

7.11.2.2 Enclosure Height Reduction The height of the rotating enclosure was reduced by 1.7 meters. This reduction resulted primarily from a reduction in the telescope swept volume clearance requirements after the telescope preliminary design was completed and the structure re-balanced. In addition to the updated swept volume, the enclosure overhead bridge crane was optimized, resulting in a reduced bridge crane girder depth. Figure 7-167 and Figure 7-168 give “before and after” enclosure cross-sections showing this height reduction.

Figure 7-167. Enclosure height (before value engineering)

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Figure 7-168. Enclosure height (after value engineering)

7.11.2.3 Telescope Pier Height Reduction The telescope pier height was reduced by 3.0 meters. This reduction was accomplished by optimizing the infrastructure and procedures for Direct Gregorian (DG) instrument handling resulting in a reduction in clearance requirements. The optimized clearance requirements also allowed the large opening (portal) in the telescope pier to be reduced in height and width. Figure 7-167 and Figure 7-168 give “before and after” Telescope Pier height dimensions. This change resulted in a significant savings in reinforced concrete.

The overall clearance between grade level and the underside of the observing floor was essentially unaffected by this change because the mezzanine level, below the observing floor, was eliminated (see Section 7.11.2.6)

7.11.2.4 Enclosure Base Height Reduction and Optimization The enclosure base height was reduced by 3.0 meters as shown in Figure 7-167 and Figure 7-168. This corresponded directly to the telescope pier height reduction. The reduction in height also allowed for further optimization of structural column spacing and bracing member sizing due to the reduction in column height.

7.11.2.5 Control Building and M2 Lab Relocation The Control Building and M2 lab were relocated to the summit support building. These spaces previously resided within the enclosure base. After a thorough review of operational needs, it was determined these spaces could be relocated and joined with the summit support building. The relocation of these spaces greatly simplified the enclosure base structural framing and thus reduces construction costs. In addition to a simplified structural framing system, the relocation of the spaces allows wind to move freely under the enclosure, providing more efficient passive ventilation. Figure 7-169 and Figure 7-170 give “before and after” images of the control building area of the enclosure base.

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Figure 7-169. Control building prior to relocation to the facilities building

Figure 7-170. Enclosure base after removal of the control building

7.11.2.6 Enclosure Mezzanine Elimination The enclosure mezzanine level was eliminated. This area housed HVAC and electrical equipment associated with the control building and M2 lab. Space within the mezzanine, not used by the HVAC or electrical equipment, was designated for storage. Due to the relocation of the control building, the mezzanine only served as a storage function. The construction costs associated with creating an entire level for storage purposes only, and negative thermal effects created by storing equipment under the telescope, led to the elimination of the this area. The elimination of the mezzanine also allowed for the elimination of the mezzanine ventilation system. Figure 7-167 and Figure 7-168 show “before and after” images of the enclosure mezzanine level. 7.11.2.7 Site Utility Tunnel Elimination The site Utility Tunnel running between the enclosure base and summit support building was eliminated. Utilities running between the two facilities will now be directly buried with concrete encasement as required to withstand traffic loads. The costs of excavation and construction of a tunnel that could be safely occupied by staff, considering lighting, ventilation, emergency exits, confined space considerations etc., were expensive. Future installation of utilities will be

ENCLOSURE AND FACILITIES 7–196 GMT SYSTEM LEVEL PRELIMINARY DESIGN REVIEW December 13, 2013 accommodated with spare conduits and reserved space adjacent to conduits. Hydrostatic bearing oil lines will be accommodated adjacent to the concrete foundation and rails utilized for the transportation of mirrors and equipment between the enclosure and summit support building. The hydrostatic bearing lines will be placed within an accessible concrete trench with a removable cover plate. Figure 7-171 and Figure 7-172 give “before and after” images of the utility transfer methods between the enclosure building and summit support building.

Figure 7-171. Site utility tunnel prior to value engineering

Figure 7-172. Location of direct bury utilities after value engineering

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7.11.2.8 Enclosure Ventilation Building Redesign The enclosure Ventilation Building, previously designed to house electrical and ventilation equipment, has been eliminated. In lieu of a building, an exterior rated “self-contained” fan array unit will be placed on the summit edge. All electrical equipment housed in the enclosure ventilation building has been relocated to the summit support building. The transition of this space from an occupied building to a “self-contained” piece of equipment reduced the overall costs associated with ventilating the enclosure. In addition, the ventilation fan sizing has been reduced due to the elimination of the enclosure mezzanine ventilation system. Figure 7-173 and Figure 7-174 show “before and after” images of the enclosure ventilation building.

Figure 7-173. Enclosure ventilation building prior to value engineering

Figure 7-174. Enclosure ventilation building after value engineering

7.11.2.9 Summit Support Building - Building Area and Height Reduction The area and height of the summit support building were slightly reduced due to updated functional and operational requirements. The reduction in area also accounts for enclosure base functions that were relocated to the summit support building (i.e., control room, computer room, M2 lab, etc.). ENCLOSURE AND FACILITIES 7–198 GMT SYSTEM LEVEL PRELIMINARY DESIGN REVIEW December 13, 2013

The majority of the office spaces at the facility building were changed from “private” offices to “open” offices. This allowed a reduction in area, while supporting the same number of personnel. The number of structural bays in the auxiliary building was reduced from 9 bays to 6 bays. In addition to reduced building areas, the roof design and structural orientation of the building have been optimized based upon functional requirements of the building. Figure 7-175 and Figure 7-176 give “before and after” floor plans of the summit support building.

Figure 7-175. Summit building floor plan prior to value engineering

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Figure 7-176. Summit building floor plan after value engineering

7.11.2.10 Summit Support Building - Fire Protection Elimination Active wet sprinkler fire protection requirements were eliminated at the summit support building due to a reduced overall building area. After reductions in building areas, a building code review revealed that sprinklers were no longer required by code. After meeting with GMTO property insurers, it was concluded that fire sprinklers could be eliminated if a fire wall was provided between the equipment building and auxiliary building.

7.11.2.11 Summit Support Building - Reduced Crane Size The capacity of the stationary hoist in the auxiliary building was reduced from 65 metric tons to 30 metric tons. This reduction was achieved by redesigning the mirror coating facilities to eliminate the need to lift primary mirror cell assemblies during the coating process. See Section 6.13 for a description of the primary mirror coating facilities.

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7.11.2.12 Utilities Building The Utilities building area was reduced by 35%. This was accomplished by placing the backup generators (x2) outside the building within exterior rated enclosures. Other interior areas of the building were also optimized to achieve the reduction in area. In addition, the siding material changed from insulated metal panels to a typical uninsulated metal panel with draped batt insulation to reduce overall material costs. Figure 7-177 and Figure 7-178 give “before and after” floor plans of the utilities building.

Figure 7-177. Utilities building floor plan prior to value engineering

Figure 7-178. Utilities building floor plan after value engineering

7.11.2.13 Warehouse Building The warehouse area was reduced by 35%. This was accomplished by reducing the number of structural bays from 8 to 6. The area was further reduced by eliminating “small parts” storage and restroom facilities. A restroom is available at the adjacent utilities building. The siding material changed from insulated metal panels to a typical uninsulated metal panel with draped batt insulation to reduce overall material costs. The number of large roller doors (10M width) was reduced from four to one. Figure 7-179 and Figure 7-180 give “before and after” floor plan images of the warehouse.

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Figure 7-179. Warehouse floor plan prior to value engineering

Figure 7-180. Warehouse floor plan after value engineering

7.11.2.14 Summary of Cost Savings Achieved Costs from the value engineered design (current baseline design) are compared with those of the preliminary design in Table 7-42. The costs were derived from material take-offs from the system level design models, scaled by unit costs. All costs are in 2012 dollars. Contingency is set at 20% of the total cost for both designs.

Approximately $21.0M in cost savings was achieved in this process (with contingency included).

Additional costs, covered in the current baseline summary, but missing from the PDR design are listed in Table 7-43. The geotechnical study concluded that the bearing capacity of the rock was somewhat lower than was assumed in the preliminary design. The study also recommended a rock anchor solution for uplift forces on the foundations. These two items add approximately $2.5M to the cost of the foundations, not covered in the preliminary cost estimates. Moving the M2 lab to the auxiliary building resulted in the elimination of the M2 test tower, but also the need to excavate a pit for the M2 test optics in the auxiliary building. The cost of the pit is approximately $0.5M. Other architectural features added since the PDR marginally increased the cost as well.

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Table 7-42. Comparison of preliminary design and current baseline design costs

Total Project Savings 1 DIVISION 1 GENERAL CONDITIONS $ 6,266,286 2 DIVISION 2 SITEWORK $ 313,579 3 DIVISION 3 CONCRETE $ (1,621,256) 4 DIVISION 4 MASONRY $ - 5 DIVISION 5 METALS $ 4,868,552 6 DIVISION 6 WOOD & PLASTIC $ (57,910) 7 DIVISION 7 THERMAL & MOISTURE $ 3,099,181 8 DIVISION 8 DOORS & WINDOWS $ 693,954 9 DIVISION 9 FINISHES $ 388,240 10 DIVISION 10 SPECIALTIES $ (1,462) 11 DIVISION 11 EQUIPMENT $ 384,250 12 DIVISION 12 FURNISHINGS $ (277,171) 13 DIVISION 13 SPECIAL CONSTRUCTION $ - 14 DIVISION 14 CONVEYING SYSTEMS $ (440) 15 DIVISION 15 MECHANICAL $ 4,158,862 16 DIVISION 16 ELECTRICAL $ 2,756,618 Total with Contingency $ 20,971,284

Contingency $ 3,495,214 Total w/out Contingency $ 17,476,070

Table 7-43. Summary of additional costs since the PDR, not covered in the PDR cost estimate Item Added Cost 1 Enclosure Base Concrete $ 1,765,052 2 Enclosure Base Rock Anchors $ 741,995 3 Summit Support Building Rock Anchors $ 131,564 4 M2 Pit Excavation $ 471,272 5 Blackout Shades $ 325,915 6 Jib and Monorail Cranes $ 36,032 Total Added Scope $ 3,471,830

7.11.3 Alternate Enclosure Shutter Study In addition, conceptual studies of alternate enclosure shutter designs began in July 2013, primarily to develop better structural and mechanical designs and to achieve better performance that could lead to significant cost savings. These alternate shutter designs are only at a conceptual level for the purposes of estimating performance and cost. They are only mentioned here as a potential for design and development as an upgrade to the existing design and do not represent the current baseline design.

Several alternate shutter concepts were evaluated. A promising candidate is a shutter consisting of separate horizontal and vertical elements, where the vertical shutter doors are curved and move on circular, horizontal tracks as shown in Figure 7-181. The concept has a 2 piece horizontal shutter that is similar to that of the baseline enclosure. The horizontal shutter acts as a weather seal when the enclosure is closed, provides protection for the telescope in high winds during operation and also acts as a moon roof. The vertical shutter has ventilation doors that line up with vents in the enclosure walls resulting in good enclosure ventilation performance. A vertical wind screen would

ENCLOSURE AND FACILITIES 7–203 GMT SYSTEM LEVEL PRELIMINARY DESIGN REVIEW December 13, 2013 have to be included with this design to protect the telescope from high winds during operation. Several potential advantages are evident with this design including:

 A significant reduction in steel (and thermal mass) near the shutter opening  The ability to redesign the main structure of the enclosure using space trusses consisting of open steel cross-sections instead of the built-up plate sections in the baseline design. This would result in a significant weight savings and eliminate the need to ventilate the closed structural sections  Simplified mechanisms for the shutter doors. The cable driven system in the baseline design with its winches, sheaves and counterweights would be replaced by relatively simple bogies running on horizontal tracks  A more uniform distribution of enclosure bogie reaction forces to the enclosure base resulting in a weight savings in the enclosure base structure and a far simpler enclosure bogie design  An opportunity to fix the bogies to the enclosure base (with wheels pointing up). Advantages to this include less electrical power across the slip rings, easier maintenance and service access and easier bogie drive and motor heat management  A reduction of the rotating enclosure mass by approximately 700 tons  Substantial cost savings

All aspects of this study are still at the conceptual level and not included in this documentation. If the alternate enclosure shutter conceptual design studies lead to a desire to change the baseline design, additional formal review of these designs will occur at the appropriate time.

Figure 7-181. Alternate shutter design, currently being reviewed at a conceptual level

If the alternative shutter concept proves to be viable, an additional $5-7M in cost savings may be realized.

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References

1 J. Teran et al., M3 Engineering, Package 1 - Site Grading, Utilities & Improvements (Value Engineering) 26-July-2013. 2 J. Teran et al., M3 Engineering, Package 2 - Enclosure, Enclosure Base & Telescope Pier (Value Engineering) 26-July-2013. 3 J. Teran et al., M3 Engineering, Package 3 - Summit Support Building (Value Engineering) 26- July-2013. 4 J. Teran et al., M3 Engineering, Package 4 - Utilities Building, Warehouse & Water Storage Facility (Value Engineering) 26-July-2013. 5 J. Teran et al., M3 Engineering, Material & Equipment Literature - Preliminary Design (Value Engineering) 26-July-2013. 6 J. Teran et al., M3 Engineering, Calculations - Preliminary Design (Value Engineering) 26-July- 2013. 7 P. McCarthy, Science Requirements Document, GMT-SCI-REQ-00001, 2013. 8 P. McCarthy, Operations Concept Document, GMT-SCI-DOC-00034, Rev 10, 2013. 9 M. Johns, System Level Requirements, GMT-SE-REQ-00027, Rev C, 2013. 10 M. Sheehan, GMT Enclosure Building Requirements, GMT-ENC-REQ-00109, Rev 7.0, 2013. 11 M. Sheehan, GMT Facilities and Site Infrastructure/Utilities Requirements, GMT-FAC-REQ- 00090, Rev 7, 2012. 12 International Building Code, IBC 2006, 2006. 13 R. Racine, Mirror, Dome and Natural Seeing, Publication of the Astronomical Society of the Pacific, 1991. 14 J. Maiten, GMT Environmental Conditions, GMT-SE-REF-00144, Rev B, 2012. 15 D. Chen, Wind Climate Analysis for the Giant Magellan Telescope, 2013. 16 D. Sawyer, Maintenance Time Budget, GMT-SE-DOC-00420, 2013. 17 D. Sawyer, GMT Proposed Chile Based Operations Staffing, GMT-PM-REF-00626, 2013. 18 M. Johns et al., GMT Report, GMT-ID-01479-Chapter_14_Enclosure, 2006. 19 D. Sawyer, GMT Compliance to Regulations, Codes and Standards, GMT-SE-REF-00229A, 2012. 20 Cermak, Peterka, and Petersen, Final Structural Report (GMT Sealed Enclosure) 2011. 21 Simpson, Gumpertz & Heger, Inc., Site Specific Seismic Hazard Analysis of the Proposed Giant Magellan Telescope Site, Las Campanas Peak, Chile, 2012. 22 Seismic Design Manual, Supplement 1, ASCE 341-05, 2005. 23 Minimum Design Loads for Buildings and Other Structures, ASCE7-05, 2005. 24 Cermak, Peterka, and Petersen, Report No. 5610, 2011. 25 C. Panilla, IDIEM, Report No. 807.436, 2013. 26 Cermak, Peterka, and Petersen Report, Task 6: Design Loads for Warehouse and Equipment Buildings, 2012. 27 M. Johns, GMT Site Testing at Las Campanas Observatory – Final Report, GMT-TEO-DOC- 00114, Rev A, 2011. 28 Energy Standard for Buildings except Low-Rise Residential, ASHRAE 90.1, Buildings, 2007.

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29 Ventilation for Acceptable Indoor Air Quality, ASHRAE 62.1, 2010. 30 Clean Room Standards, ISO 14644-1, 1999. 31 International Private Sewer Disposal Code, ICC IPSDC, 2012. 32 Optional Installation of Fuel Fired Generators for Emergency and Standby Power, NEC 702, 2011. 33 Standard for the Installation of Lightning Protection Systems, NFPA 780, 2014. 34 International Energy Conservation Code, IECC, 2000. 35 National Fire Alarm and Signaling Code, NFPA 72, 2013. 36 Cermak, Peterka, and Petersen Report, Wind Tunnel Tests for the Giant Magellan Telescope Terrain Study, 2011. 37 Cermak, Peterka, and Petersen Report, Final Cladding Report for the Giant Magellan Telescope Study, 2011. 38 A. Farahani, A. Kolesnikov, L. Cochran, C. Hull, M. Johns, GMT Enclosure Wind and Thermal Study, SPIE 2012 (Astronomical Telescopes and Instrumentation), Amsterdam, Netherlands, SPIE 8444-29, July 1-6, 2012. 39 M. Warner, Enclosure and Facilities Preliminary Design Review Committee Report, 2013. 40 M. Sheehan, GMT Response to the Enclosure and Facilities Preliminary Design Review Committee Report, 2013.

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