Design Principles for Tower and Steeple Restoration

Robert Fulmer Fulmer Associates LLC P.O. Box 434, North Conway, NH 03860 Phone: 603-828-2458 • E-mail: [email protected]

S y m p o S i u m o n B u i l d i n g E n v E l o p E T E c h n o l o g y • o c T o B E r 2 0 1 6 F u l m E r • 5 7 Abstract

The contemporary tectonics of analyzing and designing the restoration or construction of architectural towers and steeples can both inspire and confound contemporary design professionals. The effective design of steeples, bell towers, spires, and clock towers requires a multidisciplinary synthesis of technical, aesthetic, and engineering requirements that are unique to tower architecture. In this presentation, the speaker will discuss construction con­ siderations and design problems inherent to tower projects by reviewing recent restoration case histories. The information shared will help designers to produce effective and thorough design processes for architectural tower and steeple projects.

Speaker

Robert Fulmer — Fulmer Associates LLC

ROBERT FUlmER specializes in the analysis and diagnosis of building envelope issues for both historical and contemporary structures. He provides inspection, design, specifica­ tion, and project management services for building envelope projects involving institutional, academic, and ecclesiastical structures. Fulmer is a published author and has lectured on historical preservation and contemporary building envelope topics. He is past president of the New England Chapter of RCi, inc. and currently serves on the board of directors of the National Slate Association and is chair of its Education Committee.

5 8 • F u l m E r S y m p o S i u m o n B u i l d i n g E n v E l o p E T E c h n o l o g y • o c T o B E r 2 0 1 6 Design Principles for Tower and Steeple Restoration

INTRoDUCTIoN 301 A.D. as the first cathedral in the (then) Campanile: An early Italian architec­ The contemporary tectonics of analyzing Kingdom of Armenia. The inclusion of tow­ tural term for a (usually) freestanding bell and designing the restoration or construc­ ers on ancient religious structures was tower, derived from “campa” (meaning bell). tion of architectural towers and steeples can actually predated by and adapted from their The earliest campaniles, dating from the both inspire and confound contemporary original purpose as military towers as early sixth to tenth centuries AD, were plain design professionals. The effective design as 3500 BC. round towers with minimal ornamentation of steeples, bell towers, spires, and clock Clock towers were not an architectur­ near the top. Square campaniles began to towers requires a multidisciplinary synthe­ al component of Christian churches until appear at the end of the tenth century. In sis of technical, aesthetic, and engineer­ approximately 600 AD, when their use was the 19th century, that design inspired the ing requirements that are unique to tower also adapted from military watchtowers. See tower at Westminster Cathedral (by J.F. architecture. While the design requirements Figure 1. Bentley, 1897). The revival of the campanile for tower and steeple restoration can be as At that time, towers were fairly modest in the 19th and 20th centuries included diverse as the structures themselves, there and were constructed separately from the installations at factories, country houses, is a commonality and standard principles principal church building. blocks of buildings, markets, and academic that need to be addressed within the design Some contemporary discussions use the structures as a bell or a clock tower. (See process for each project. architectural terminology associated with Figure 2.) towers and steeples interchange­ BRIEF HIS TORY AND ably. For the purpose of clarifica­ NomENCLaTURE tion, some basic tower terminology Throughout history, towers and steeples is defined below. have been an integral part of our architec­ Bell Tower: A tower that con­ tural landscape. There are numerous docu­ tains one or more bells or is designed mented third- and fourth-century church to hold bells, even if it currently structures with towers located principally has none. A bell tower may be in what is now know as the Middle East, integrated into a church building or such as Etchmiadzin Cathedral, built in serve as a freestanding structure.

Figure 2 – Campanile, Cathedral of Pordenone, Italy.

Figure 1 – Salisbury Cathedral, England, during a lead roof replacement.

S y m p o S i u m o n B u i l d i n g E n v E l o p E T E c h n o l o g y • o c T o B E r 2 0 1 6 F u l m E r • 5 9 Tower Access Once the scope and focus of the inspec­ tion have been determined, access to all levels of the tower must be planned. Whether in the schematic design phase or the construction phase, the logistics of tower access can be challenging. Unlike the construction phase, the requirements for OSHA compliance are less onerous for design inspections. However, personal safety planning is obviously essential. The need to access the full height of a tower for inspection and actual construction signifi­ cantly impacts both the cost and the sched­ ule of all tower projects. The trade aphorism “everything costs more and takes longer when working at height” is a basic principle to be kept in mind (Figure 3). While interior access is normally avail­ able to the belfry or clock level on most towers, accessing the interior space above the belfry level to evaluate cupola, spire, weathervane mast, etc. can be problematic. In certain circumstances, mechanical lifts Figure 3 – Baker Tower industrial rope access inspection. or cranes can be utilized to access the tower exterior. Occasionally, however, “mechani­ Belfry: Defined as an integrated tower “tower” shall be used generically to describe cal access” is not adequate or feasible. component designed to house bells. It is not complete bell tower, clock tower, and steeple For example, recently Dartmouth a freestanding structure. assemblies. College requested a forensic building con­ Steeple: A tall ornamental structure, usually surmounting a tower and ending TOWER SCHEMATIC in a spire. Common on Christian churches DESIGN PHASE and cathedrals, the term generally connotes Just as in the architectural a religious structure. design of each building project, Spire: Defined as a tapering conical or the schematic design phase is the pyramidal structure commonly found on top first step in developing the contem­ of a church tower or skyscraper. The spire porary tower design process. It is originated in the 12th century as a simple, a logical sequence that differs in four-sided pyramidal roof, capping a church some respects from other building tower. Nineteenth-century architects uti­ projects. lized spires prolifically, particularly during Whether the purpose for the the Gothic Revival period of the mid-1800s. tower/steeple restoration is a result Pinnacle: An architectural, vertical of a discovery of water infiltra­ ornament of pyramidal or conical shape, tion, structural damage, a planned crowning a buttress, spire, or other archi­ change in use, or the expiration of tectural member. A pinnacle is distin­ the service lives of structural or enve­ guished from a finial by its greater size and lope materials, this phase begins complexity and from a tower or spire by its with preliminary client discussions smaller size and subordinate architectural to determine the proposed purpose, role. A tower may be decorated with pin­ goals, and budget for the restoration. nacles, each one capped by a finial. The data gathering process in Cupola: A secondary dome-like struc­ this phase is essential and begins ture on top of a building, used to admit light with the building conditions sur­ or provide ventilation, or as ornamentation. vey. The information obtained dur­ This basic glossary of architectural ing the survey is then utilized to tower terminology will assist in clarifying form the initial basis of design the design process in subsequent sections. (BOD) document early in the design Figure 4 – Rope access enables forensic analysis For the purpose of this discussion, the term development phase. and materials sampling.

6 0 • F u l m E r S y m p o S i u m o n B u i l d i n g E n v E l o p E T E c h n o l o g y • o c T o B E r 2 0 1 6 dition survey and structural evaluation of their iconic Baker Library tower as a pre­ cursor to restoration. The square-planned brick tower base is integral to the attached building on three elevations, with one tower elevation extending to grade and housing the main building entrance. The inspection requirements of the 200-ft.-tall tower precluded the use of a crane for access due to the heavy volume of pedestrian traffic at the tower base entrance, as well as landscaping consider­ ations. While inspection of the full tower height is always important to determine existing conditions, document load con­ cerns, inspect weathervane substructure, etc., full tower access was essential in this case. Without a mechanical access option and with the prohibitive cost of staging erection for our inspection, the author utilized our “industrial rope access” option to access the tower (Figure 4). Figure 5 – Baker Tower building conditions survey. Although the use of ropes to access structures has been employed for centuries, forensic inspections due to potential liabili­ content, and other conditions of use. These older techniques were encumbered with lim­ ties, it is important to clarify your forensic data are then utilized in timber-stress grad­ ited lateral mobility and safety issues. needs early in the discussion phase. ing and engineering design value calcula­ The Industrial Rope Access Trade tions as described in ASTM D245 and SEI/ Association (IRATA) was formed in the Building Conditions Survey ASCE11-99. United Kingdom in 1989 to address mainte­ Forensic inspections represent the most The forensic tower inspection then nance access problems within the offshore critical function in the tower design process. becomes a principal design tool and should oil and gas industry. Today, the techniques Prior to the actual inspections, the designer include evaluation of both the interior and developed by IRATA have been adapted for should ideally have obtained and reviewed exterior of each tower section, from below- use in high-rise building surveys, mainte­ any existing construction documents. If grade (if applicable) to the top of the tower. nance, and façade inspections, as well as construction drawings do exist, they often At a minimum, the building conditions fulfilling wind turbine and offshore oil plat­ were produced during an earlier era when survey (Figure 5) should include the follow­ form inspection and maintenance require­ a construction document set contained ing elements: ments. Rope access allows the operator to less information than contemporary docu­ • Determine the applicable code bod­ descend, ascend, and laterally traverse the ments. In addition, as-built drawings are ies to be addressed as a result of rope system with the structure at arm’s rarely available, especially for tower proj­ initial observations and concerns. length, making it ideal for tower inspec­ ects. Therefore, physical inspections of the • Diagram all existing structural com­ tions. complete tower structure are essential. The ponents in-situ, including sizes; loca­ Our firm successfully completed the data obtained from a thorough inspection tions; configurations; truss struc­ Dartmouth tower inspection, utilizing rope process will define the basis of design and ture; and timber species, quality, access techniques as an efficient and cost- scope of work for the project. Structural and grade (if applicable). Document effective alternative to mechanical or scaf­ evaluations during the inspections provide any conditions of structural compo­ fold access. if your firm does not have certi­ essential data to determine existing load nent stress, deterioration, or failure. fied rope access capabilities, it is possible conditions and to define structural upgrade • Note all areas of water infiltration, to train designated employees at one of sev­ requirements for code compliance. along with any structural distress or eral training centers in the U.S. The Society The building conditions survey process deterioration within those areas. of Rope Access Technicians (SPRAT) was should be forensic in nature. While it is • Record any previous repairs or mod­ formed in Pennsylvania in the mid-1990s to essential to examine all structural systems ifications to the structure. provide U.S.-based education and certifica­ and components, the forensic inspection also • Note any areas of “change of use” or tion. If training is not an option, there are provides an opportunity to collect material potential increase of future loads on a number of domestic companies that spe­ samples for hazardous materials testing. in the structure. cialize in industrial rope access inspections the case of wood or timber frame structures, • Document the existing condition of that can be contracted for individual proj­ samples from wood structural components all tower envelope systems and collect ects. As some firms are reluctant to perform can allow species identification, moisture material samples, both inert (i.e.,

S y m p o S i u m o n B u i l d i n g E n v E l o p E T E c h n o l o g y • o c T o B E r 2 0 1 6 F u l m E r • 6 1 ture being evaluated (to facilitate antenna and tower inspections). Under the new rule, small UAS operators are classified as “remote pilots” and are required to obtain a “remote pilot airman certificate with a small UAS rating” in order to operate a drone. The new ruling also expands current pri­ vacy and airspace restrictions and require­ ments. Future FAA regulation is anticipated by the industry.

Basis of Design The American Institute of Architects (AiA) defines the BOD as a document that records how the building systems meet the owner’s project requirements (OPR) and why the systems were selected. The objective of the BOD is to provide information to the design team during each phase of the proj­ ect and document the thought processes and approach as the design evolves. Once completed, the inspection phase Figure 6 – Point Cloud rendering from a laser scan. should provide sufficient data to produce timber frame component samples) alone cannot provide enough data to replace the initial BOD. The preliminary informa­ and potentially hazardous materials a “hands-on” structural or forensic tower tion contained in this document can be used that may require abatement. inspection. throughout the design development and • Note immediate or potential life- As an example, while conducting a construction document phases to develop safety concerns and possible reme­ recent tower inspection, structural damage the project scope, including the identifica­ diation procedures to address those was discovered beneath flat-seam copper tion of governing code bodies, a listing of all concerns. cornice and cupola panels by walking on architectural divisions to be included in the them (while secured by rope access equip­ construction documents, and further refine­ “Scope creep” can occur on any con­ ment). In addition, original construction ments of the project construction budget. struction project, but on tower projects, documents had indicated that the ornate These data are then shared with the project the impact to both construction schedule balustrades and finials at the clock, bell, design staff and owner(s) during the design and the project budget can be substantial and ringing chamber levels were fabri­ development phase. The BOD document and is multiplied by the significant logistics cated in cedar. Our inspection revealed that should be used as a dynamic organizational of working at height. Most often, project those components were spun in 24-oz. cop­ tool that is equally beneficial to the owner change orders are the result of conditions per, and painted. Both anecdotes are brief and the design team and is updated at regu­ that weren’t exposed or observed during the examples of observations that cannot be lar milestones, such as the 30%, 60%, 90%, forensic inspection process. obtained from photos alone. However, dur­ and 100% phases of construction docu­ ing that inspection, a drone was utilized to ment submissions. Misunderstanding the Drones inspect the inaccessible weathervane shaft design intent of a tower project is one of the Within the past 15 years, the quality connection to the weathervane mast. Drone most common project-related challenges. and efficiency of camera-mounted drones use should be considered a tool in the The BOD should reflect a current and clear (quad-copters or small unmanned aircraft inspection process and not the sole means presentation of the OPR and design intent systems [UASs]) has developed significantly. of documenting existing conditions. as the project evolves and is a key commu­ Drones are a common inspection tool uti­ As an update to the regulatory efforts nication component throughout the design lized by various industries, including the surrounding drones, on June 21, 2016, process. construction industry. the Federal Aviation Administration (FAA), Nine U.S. cities require periodic façade with the support of the Aircraft Owners and Laser Scanning and inspections, and drones are an asset in that Pilots Association (AOPA), issued its current Architectural Modeling application. Currently, ASTM’s task group ruling on the use of UASs, which took effect Existing conditions or as-built model­ on façade inspections is developing a “Guide in late August 2016. Known as FAA Part ing has always been a principal design for Visual inspection of Building Façades 107, the new ruling (in part) states that a requirement in tower restoration. The need Using Drones” (WK52572). drone in the small UAS category (weighing to accurately portray or document the exte­ Within the context of tower inspections under 50 pounds) is not permitted to fly rior of a tower is essential in the creation and design, however, drone use should be more than 400 ft. above ground level unless of useful project drawings. Prior to 20 qualified and specific. Visual observations it remains within a 400-ft. radius of a struc­ years ago, without original drawings, the

6 2 • F u l m E r S y m p o S i u m o n B u i l d i n g E n v E l o p E T E c h n o l o g y • o c T o B E r 2 0 1 6 documentation process was arduous and, assurance measures requiring in-situ test­ Romans), wood timbers, and composite sys­ consequently, expensive. The designer was ing are routinely included in the DD phase tems of both to form the structural support required to access the tower in the safest of tower projects. systems for towers. manner possible and measure each exterior Due to logistical complexities of work­ Structural engineering theory was fur­ architectural component as accurately as ing at height, systems testing in-situ and ther advanced in the 1850s when mild possible. The accuracy of the measurements warranty obligations must be verified and steel structural support systems were obtained was key to both the tower load “signed off” prior to staging removal. Any first made possible by English inventor analysis modeling, as well as the replication systems failures or water infiltration issues Sir Henry Bessemer, eventually replacing of architectural details. occurring after staging removal and proj­ both wrought and cast iron as the struc­ In the late 1990s, laser-scanning tech­ ect “close-out” can be difficult and expen­ tural material of choice. Although structural nology (Figure 6) began to develop, creating sive to remediate. Subsequently, these steel was becoming increasingly popular the possibility of an application for mea­ post-construction issues inevitably invoke in Europe, in North America, many of our surement and documentation of existing the “whose responsibility is it?” dialogue. nineteenth- and early twentieth-century buildings. As laser technology improved, it Consequently, these quality assurance pro­ church structures were being constructed was integrated with existing architectural cedures need to be carefully spelled out with timber-frame structural support sys­ modeling software. Currently, there are in the DD phase. Additionally, the design tems. However, engineering of the timber- a number of companies that specialize in process should incorporate systems that, frame trusses was not common until the laser measurement and digital recording while currently performing, may be more mid- to late1800s. Prior to the 1900s, it was of existing buildings. The accuracy of laser cost-effectively addressed while access is in uncommon for designers to address consid­ measurement technology is currently up place. This comprehensive design approach erations such as load duration, materials to 2 mm over a 120-meter span, which reduces misunderstandings from owners moisture content, and other conditions that exceeds most required design tolerances. who were not clear on the complete project are commonplace today. Drawings and models can be quickly and scope. Standardized timber stress-grading accurately created in CAD and Revit in For example, while in the DD phase techniques and design values were not 2-D/3-D, including 3-D BIM modeling. With of an academic tower restoration, the cli­ developed in the U.S. until the mid-1930s, full 3-D modeling, material takeoffs and ent was advised that the tower’s lightning at the time when framing and structural envelope detailing can be generated, along protection system was not UL-compliant, support components of steel (or composite with an array of component schedules. and the tower’s exterior lighting was dated. steel and timber frame) became increas­ Customizable databases can be generat­ Initially, the client declined the additional ingly popularized. in spite of the engineering ed for area calculations, condition assess­ upgrades, citing budget concerns, but was inconsistencies of that period, many of the ments, hazardous material reports, etc. The eventually convinced to incorporate the tower structures created then still function databases can then be exported from Revit work. Positive comments on the aesthetic today. to be incorporated into any other existing improvements of the tower at night were Although structural engineering didn’t management databases. received; but more importantly, the tower take shape as a profession until the The advantages of utilizing the currently was struck by lightning a year later, sus­ Industrial Revolution, the trade has become available technologies in tower documenta­ taining minimal damage. It is important one of the most significant components in tion and design can be significant. However, to effectively convey to the client during tower design. Structural analysis (developed the financial and detail requirements of the design process the cost-effectiveness by Galileo in 1638), load analysis, and cur­ individual projects vary, and a cost-benefit of addressing both compliance issues, and rent code compliance are the engineering analysis should be performed to confirm the work that may require remediation within components that drive contemporary tower feasibility of modeling options required for the near future. project scope and design. each individual project. When evaluated using contemporary aSSESSmENT STaNDaRDS aND engineering analyses and models, many DESIGN DEVELOPMENT PHASE RELEVaNT CoDE BoDIES existing towers fail to meet current struc­ The AIA describes the design develop­ Tower Engineering tural standards. ment (DD) phase as “[t]he predominant Although the documented history of While utilizing the observations, mea­ production phase, expanding upon the rep­ “tower” structural engineering dates back to surements, and data obtained during the resentative work of the schematic design the 27th century B.C., when imhotep first forensic building conditions survey, relevant (SD) phase and prior to the finalization of designed a step pyramid for Pharaoh Djoser, code bodies can be identified and referenced construction documents.” throughout most of ancient and medieval to help frame the engineering analysis and Tower projects require a DD phase that architectural history, the “engineering” and develop the structural remediation scope. is expanded beyond what is normally incor­ construction of towers and religious struc­ But what are the criteria that can trigger porated in traditional construction projects. tures was performed by master trades­ the initial structural assessment? Scope requirements for specifications and men. Since no structural theory for tow­ Structural assessments and upgrades divisions not normally utilized, such as ers existed, construction technique was may not be required unless a change to scaffolding and access engineering require­ based on previous construction experience. the structure alters loads and stresses or ments, niche trade divisions such as bell Tradesmen utilized masonry (including con­ unless structural deterioration, damage, and clock restoration, as well as quality crete technology developed by the ancient or distress is observed. However, building

S y m p o S i u m o n B u i l d i n g E n v E l o p E T E c h n o l o g y • o c T o B E r 2 0 1 6 F u l m E r • 6 3 alterations within the recent past that were rior of the tower of that required for new construc­ perceived as upgrades or efficiencies at the c. The appearance of asymmetrical set­ tion. Components that are dam­ time could now trigger a structural evalua­ tling or positioning of the structure aged less than “substantially” are tion and subsequent remediation require­ d. Areas of excessive roof deflection, permitted to be repaired or restored ments. Several of the most common exam­ including interior areas of load to their predamage condition. The ples of tower “alterations” addressed by the transfer below the tower assembly, iBC then prescribes “strengthening” current codes, are examined below. such as ceilings, interior walls, etc. or replacing the affected structural e. Inspect the roof truss system at the components if additions, alterations, International Existing Building Code tower framing, as steeple loading and/or repairs cause more than a (IEBC) 2015, Chapter 4 / IBC 2015; can have a significant structural 5% increase in design gravity load Alterations and Repairs impact on the adjacent roof truss or more than a 10% increase in the a. Energy upgrades: In an effort to system. demand-capacity ratio for lateral- control energy costs, many churches f. Inspect masonry walls for signs of load combinations. have decreased heating (or cooling) unit deterioration and mortar con­ • IEBC: Provides three separate meth­ days by adding insulation in the dition. look for signs of “bowing” ods of code compliance in refer­ attic or roof system. Such an energy or other deterioration in cavity wall ence to the alteration, repair, change upgrade can increase dead loads construction. of occupancy, or addition to exist­ and/or live loads by increasing snow ing buildings. These include the accumulation on an existing roof While structural evaluations are stipu­ “Prescriptive Compliance method,” and steeple support system. lated in the model building codes, full code “Work Area Compliance method,” b. Reinforcements or repairs of the upgrades are not always required for exist­ and “Performance Compliance tower/steeple structure: The sup­ ing buildings. If a structure has a history method.” it is important to note that port or “stiffening” of the struc­ of performance but is currently noncompli­ only one method may be used for tural components can alter existing ant, most model codes contain prescriptive a single permit. Structural require­ load paths or create asymmetrical options for repair compliance. The purpose ments are generally consistent with loading conditions. This condition of this subjective option is to allow consid­ the iBC specifications noted above. applies to partial sheathing repairs eration for basic safety. • ASCE: Wind load analysis. Types of as well (i.e., replacing deteriorated Both the IBC and the IEBC contain wind forces on towers that require 1-in. horizontal sheathing with ply­ a “Historic Buildings” chapter, allowing calculation: wood). Unless full replacement of potential code exceptions by the “local a. Lateral load: A “pulling and sheathing or structural components authority having jurisdiction” (i.e., building pushing” (horizontal) wind pres­ is planned, repairs should be made inspector, code enforcement officer, etc.). sure “in kind.” While researching code bodies that are b. Uplift load: Pressures from wind c. Envelope material alterations: applicable to a specific project, it is help­ flow that cause “lifting” effects Replacement of the roof or tower ful to begin with a review of the regional c. Wind overturning moment cladding with systems that can governing building codes, as they may have • ASCE 7: Seismic load calculation increase live loads (i.e., replacement adopted specific editions of national build­ • ANSI/AISC 360: Specification for of a copper roof system with cedar ing codes. Which code bodies and versions Structural Steel Buildings (and other or asphalt shingles may increase (years) are applicable depend on the location structures) the dead load but can also alter the of the project. For example, when referenc­ • ANSI/AISC 341: Seismic Provisions live load by replacing the “slippery” ing iBC Chapter 34, “Existing Structures,” for Steel Buildings copper system with materials that the state of Massachusetts directs the user • ASTM D245: Standard Practice for promote snow and ice retention). to the IBEC 2009. Establishing Structural Grades and A review of the following relevant Related Allowable Properties for Structural Distress national code bodies should be performed Visually Graded Lumber. Strength- Some examples of damage, deterio­ to ensure that the engineering analysis ratio analyses to estimate mechani­ ration, or distress to structural compo­ includes all requisite code and design con­ cal properties of timbers. nents, documented by visual observation siderations: • TFEC 2: Code of Standard Practice that could trigger code-specified structural • IBC: Includes compliance provi­ for Timber Frame Structures. Utilize observation(s) and/or special inspections sions for alteration, repair, addi­ for timber frame repairs, joinery, in- per IBC 2015, sections 1704 and 1705, are: tion, and change of occupancy of situ augmentation, etc. a. Obvious deterioration, decay, or existing structures. Strengthening • SEI/ASCE: Guideline for Structural signs of water infiltration within the or replacing structural elements and Condition Assessment of Existing interior framing or exterior steeple systems is generally required when Buildings components those components are “substantial­ b. Failed, split, or otherwise com­ ly” damaged. This is further defined Analysis and application of all relevant promised structural components as “a 20% reduction of capacity, with building codes is a critical step in the engi­ observable from the interior or exte­ remaining capacity less than 75% neering process at the appropriate level for

6 4 • F u l m E r S y m p o S i u m o n B u i l d i n g E n v E l o p E T E c h n o l o g y • o c T o B E r 2 0 1 6 the various phases of the project. The infor­ mation obtained will define the design cri­ teria and project scope in order to produce a compliant and well-constructed tower structure.

Engineering Modeling After recording and interpreting the structural data obtained during the forensic inspections and completing a code review and analysis, the structural design and modeling can begin. While a “hand analy­ sis” of the data is certainly feasible for most tower projects, the design process is signifi­ cantly aided and expedited by the use of 3-D structural analysis and design software, such as RISA-3D by RISA Technologies Inc., Ram Advance by Bentley Systems Inc., etc. Using a CAD-like drawing/editing environment, this software inputs dynamic synchronization between spreadsheets and graphics to produce models rapidly, while Figure 7 – Clock tower restoration, Groton School, Massachusetts. analyzing current code, gravity, and lateral load calculations (among other features). ite materials. The initial request was to requires painting. Due to its low heat One of the principal benefits of the software utilize PVC for all exterior details, including distortion and softening tempera­ is that it allows the designer to analyze a the ornate millwork and railing system. The tures, PVC can only be painted with system of individual components instead of original 1899 cladding and millwork were light-to-medium colors with a light- looking at each member individually. It is made of first-growth eastern white pine. reflective value (lRV) greater than important to remember, however, that the When we began our materials research, we 55. Coatings with an LRV below 55 model produced is only as good as the input found very little non-proprietary information will void most PVC manufacturers’ (a nod to meticulous inspections), so pre­ available. When PVC manufacturers were warranties. cise input concerning support conditions, contacted, we found conflicting information 4. As the clock level of the tower is restraints, etc., is critical for an accurate and vague answers regarding replications of a “square,” the siding and mill- model. the millwork and “turning” of details such work are mitered at each corner. as the urn finials and balustrades. At this Manufacturers’ recommendations to DESIGN CONSIDERATIONS, point, our due diligence led us to conduct accommodate material movement at CASE STUDY #1 our own research and testing. That process the corners varied from a ½- to ¾-in. Groton School is a private second­ provided the following data: gap at the corners (subsequently ary school located just outside of Boston, 1. PVC is an isotropic material; its filled with sealant), depending on air Massachusetts. The school recently retained volumetric thermodynamics are a temperature during installation. the author’s firm to design and manage response to temperature, and move­ the restoration of the campus clock tower ment is omnidirectional (under Based on the data collected, it was (Figure 7). The tower is positioned in the equal pressures). Wood is an aniso­ concluded that PVC is a highly dynamic center of an academic classroom build­ tropic material. Its thermodynamic material. That characteristic is exacerbated ing. The structure was designed in 1898 movement varies between parallel with an increase in volume (such as mill- by noted Boston architects Peabody and and perpendicular to its grain. The work assemblies and ornamental details). Stearns in the Classical Revival Style and expansion coefficient of isotropic Detail assemblies of multiple layers of PVC built in 1899. The tower stands approxi­ materials is three times its linear that varied in thickness would be prone to mately 150 feet above grade and is sup­ coefficient. asymmetrical material movement. It was ported by a timber-frame structural support 2. PVC products have low thermal dis­ determined that PVC would be best utilized system, integral to a timber-frame roof truss tortion (54-80°C or 129.2-176°F) in linear applications with limited volume system. and “Vicat” softening temperatures differential or isolated component locations (92°C or 197.6°F). in addition, PVC (i.e., decorative finials, etc.) Composite Materials can be deformed by a continuous As a result of our research, we conclud­ During the schematic design phase, the application of an exterior force (tem­ ed that while the use of PVC is appropriate Groton School Board of Trustees expressed perature, gravity loads, etc.) for the replication of some millwork details, an interest in restoring the tower to be “low 3. When field cut or routed (“turned”), the geometry and configuration of those maintenance” and inquired about compos- PVC becomes absorptive and details must be carefully considered.

S y m p o S i u m o n B u i l d i n g E n v E l o p E T E c h n o l o g y • o c T o B E r 2 0 1 6 F u l m E r • 6 5 Specifically, PVC was utilized to replicate the railing assem­ bly, including balustrades, moldings, decorative urn finials, and finial boxes. The column capitols and bases were fabri­ cated from cast fiberglass. The egg-and-dart clock bezel and leaf accents were cast in epoxy resin.

Structural Framing During the schematic design phase, a timber-grade quality assessment inspection was conducted with removal of wood samples. While accessing the tower using the industrial rope access method, the author began to remove materials on the bell-level cupola roof and observed evidence of long-term water infiltration Figure( 8). Over time, water infiltration had substan­ tially deteriorated several column support members. The author utilized ASTm D245 strength-ratio analysis to estimate mechan­ ical properties of the white pine timbers. Structural analysis of the steeple framing revealed overstresses under dead load alone. Extensive in-situ capacity augmentation was required through­ out the steeple and adjacent scissor roof truss framing. When two deteriorated vertical posts were replaced with full-height white oak 8 x 8s, steel tension rods were added at the cupola level, and strain gauges were utilized to ensure load sharing and accurate distribution of dead-load forces among reinforcement members. Structural augmentation also included the composite method of adding “sister” and “foot” plates to overstressed members in-situ, after repositioning by jacking them into place.

Millwork The original 1899 cladding and millwork on the clock tower were Figure 8 – Structural made of eastern white pine. During deterioration of the that era, construction timber was belfry dome. mostly “first growth” or naturally grown, which resulted in a dense wood product with low absorption. Today, the majority of our domestic timber is silviculturally grown or “farmed”. The rapid rate of contem­ porary tree growth produces a less dense, more absorptive wood product with a shortened service life when compared to the same species har­ vested a century ago. The original tower pine compo­ nents performed well for 115 years. In order to replicate that service life, an alternative species was select­ ed for the tower envelope. South American mahogany was chosen for all cladding and millwork (Figure 9). Mahogany is a dense wood with low water absorption qualities and good insect resistance. its fine grain also Figure 9 – Mahogany promotes good coating adhesion. millwork, replicating the A millwork firm was chosen for its original pine details. ability to replicate the existing con-

6 6 • F u l m E r S y m p o S i u m o n B u i l d i n g E n v E l o p E T E c h n o l o g y • o c T o B E r 2 0 1 6 figurations of the ornate exteri­ or details, using five-axis CNC equipment. The tower laser scan was utilized to model all millwork details in Revit and deliver them to the millwork firm, which programmed the data into its computer numeric control (CNC) machinery. in order to ensure accuracy and document existing configura­ tions, one tower elevation was hand-measured, providing an information baseline. All indi­ vidual millwork component dimensions were then entered into a spreadsheet database program. All millwork was speci­ fied to be fully primed at the fabricator’s facility after veri­ fying acceptable wood mois­ ture levels, and then partially assembled. The on-site coat­ ing requirements included the priming of all field cuts prior to installation and two coats of a Figure 10 – Structural failure of improperly erected staging, causing ten-day project delay. proprietary epoxy-based coat­ ing that provided a ten-year warranty. fied the configuration of the staging, includ­ unusable. At that point, the staging was dis­ All wood products were compliant with ing a large work platform at tower mid-level. mantled and the contract with the original either the Forest Products Society’s (FPS’s) In addition, scaffold plans from the staging staging company was terminated. A second international Forest Stewarding Council contractor’s engineer and mandatory pull­ company was engaged and new staging (FSC) or the Sustainable Forest initiative (SFi) out tests for the wall anchors were also erected with engineering supervision. The to confirm they were sustainably sourced, specified, as was full netting with applicable end result was a ten-day project delay; how­ and ethically harvested and purchased. wind load testing. ever, no injuries occurred. After the required engineering staging Staging plans were submitted and anchor pullout Exterior Lighting and Lightning The staging component of a tower proj­ tests were conducted, the contractor began Protection ect, while essential, can at times be under- staging erection on the project start date. A tower project provides a cost-effective specified by the project designer. Scaffolding As part of the project management team, opportunity to upgrade the existing electri­ can have a disproportionally large effect on the author was inspecting the staging, when cal systems, as the access logistics are in a tower project, as it can be expensive; and at approximately 30 ft. above grade, deflec­ place. Significant progress has occurred in as the first trade on a project, no other work tions in the upright legs of the steel frames contemporary exterior tower lighting tech­ can begin until the staging is completed, were observed. Further inspection revealed nology. inspected, and has been approved. that the staging was not being erected per Exterior lED systems can provide flood, OSHA sub-part L, section 1926.452, the engineering design and had 50% fewer spot, or “strip” fixtures that are smaller and item (c) (6), states “scaffolds over 125 feet attachment points than specified at the more discreet, with increased efficiencies (38.0 m) in height above the base plates exterior masonry wall (Figure 10). Work was (i.e., lED 24-watt fixtures, operating on 12V shall be designed by a professional regis­ terminated, and the staging condemned and providing 177 lumens). tered engineer and shall be constructed and while a structural investigation began as The Groton clock tower and pedestrian loaded in accordance with such design.” As to whether or not the noncompliant staging access were previously poorly lit. By specify­ is the case with most standards, this repre­ could be remediated. Meanwhile, monitor­ ing lED fixtures at grade, on the roof, and sents a minimum requirement. ing devices were installed to detect move­ on the tower itself, both public safety (at As with most large academic projects, ment with the existing staging assembly. grade) and aesthetics were vastly improved the clock tower restoration had a brief Ongoing horizontal movement (away from (Figures 11 and 12). With an integrated scheduling window, to be completed when the building) was documented, and lateral sensor system, the lighting is program­ most students were not on campus during loading continued until approximately 12 mable and provides automatic duration and the summer months. The author had speci­ steel frames became deformed and were intensity options.

S y m p o S i u m o n B u i l d i n g E n v E l o p E T E c h n o l o g y • o c T o B E r 2 0 1 6 F u l m E r • 6 7 Figure 11 – Roof design to minimize view of tower lighting fixtures.

Figure 12 – Tower lighting mock-up in progress.

and Company in posed to the school. First, an automatic Boston, Mass­ (electrical) winding system was proposed achusetts. It and installed during restoration. Secondly, is an intricate, upon restoration of the clockworks, they antique round- were relocated from the tower clock level to top timepiece with the classroom hallway beneath the tower. a weight-driven The clockworks have antique value and pendulum and form an attractive period timepiece. A large was mechanically glass display case was built in the hall­ wound once every way to protect and display the clockworks. five days. After Mechanical linkage was added, connecting evaluation, while the instrument to its original position, and currently in ser­ it continues to function as a timepiece while viceable condition, operating the bell. the clock was in need of restora­ DESIGN CONSIDERATIONS, tion. Originally, CASE STUDY #2 the clockworks Recently, Dartmouth College, in were housed on Hanover, NH, requested a forensic building the clock level, conditions survey and structural evalua­ directly behind the tion to serve as the basis for a schematic clock face. design of its iconic Baker Library tower as A tower electrical scope should also Additionally, the clock mechanism rang a precursor to restoration. The tower was include a lightning protection system eval­ the single bell in the belfry above on both designed by noted college architect Jens uation by a Ul-certified inspector. Any the half hour and the hour. The bell was Frederick larson to emulate the tower at defects or upgrades required within the sys­ manufactured by the Meneely Bell Co. of Independence Hall in Philadelphia (Figure tem can be cost-effectively mitigated dur­ Troy, New York, in 1899. As the meneely 13). The steel-frame structure was complet­ ing the project. A new lightning protection Bell Co. went out of business in 1956, a bell ed in 1928. The square-planned brick tower system was subsequently engineered and restoration foundry was contacted for res­ base is surrounded by the attached building installed on this project. toration. Within the first week after staging on three elevations, with one tower elevation completion, both the clock and the bell were extending to grade and housing the main Clock and Bell Restoration removed by crane and sent to their respec­ building entrance. The original tower clock installed in tive restoration firms. The tower stands 200 ft. in height, with 1899 was manufactured by E. Howard Two clock scope alternates were pro­ a weathervane mast (spire) extending 28 ft.

6 8 • F u l m E r S y m p o S i u m o n B u i l d i n g E n v E l o p E T E c h n o l o g y • o c T o B E r 2 0 1 6 Figure 13 – Baker Library Tower, Dartmouth College.

above the weathervane cupola and supporting a weathervane that is 7 ft. tall and weighs 600 lbs. (Figure 14).

Bell Restoration Bell systems are integral to many towers and, if present, should be included in the project scope of work. A bell set is defined as either a carillon or a chime. A carillon is a collection of 23 or more bells, which are by defini­ tion “played serially to produce a melody or sounded together to play a chord.” Although contemporary carillons are frequently played by system software, traditionally, they were played mechanically with a keyboard. A chime is defined as a carillon-like instrument comprised of fewer than 23 bells. The term “change ringing” refers to the art of ringing tuned bells in a full circle, allowing the ringers to produce different striking sequences. It is an important design consideration, as the con­ siderable weights of the bells employed in “full-circle ringing” require complete load analyses and inspection of their support structures. Many owners are not aware that as musical instruments, bell sys­ tems require regular maintenance and should be inspected on five-year intervals as both performance and safety considerations. As a result, a conditions assessment was ordered for the Dartmouth chime and performed by a bell restoration consultant. In addition to providing a scope of work for maintenance or possible restoration of the chime, the assessment also provided specific weights of the bell chime for a com­ plete dynamic load analysis of the chime and belfry system. The scope of the inspection included an acoustical analysis of each bell, as well as the belfry chamber. In addition, all bells, striking mechanisms, and associated hardware were measured to ascertain Figure 14 – Baker Tower weathervane, depicting weights for dead load data, and all components were inspected for Dartmouth’s founder, Eleazar Wheelock, in 1769, teaching condition. As a result of the consultant’s inspection, it was learned a Native American.

S y m p o S i u m o n B u i l d i n g E n v E l o p E T E c h n o l o g y • o c T o B E r 2 0 1 6 F u l m E r • 6 9 for a project, they should be con­ tacted with as much advance notice as possible for scheduling.

Security Management Security management systems are an important component of the tower scope of work. Public safe­ ty concerns highlight the need to address and specify systems and pro­ cedures to mitigate public exposure and eliminate unauthorized public access to the tower. For this project, a security threat assessment was performed by a security-consulting firm. As a result, the current security system was upgraded to include keyless entry (card readers), a surveillance system upgrade, and a revised access control Figure 15 – New tower bells prior to the 1928 installation, Baker Tower. system (ACS) to comply with UL 294 and UL 864 standards. In addition, that the bells were cast by the Meneely Bell in East London, England, in 1570 and has all fenestrations were alarmed. Electronic Company, Troy, NY, in 1928 (Figure 15). been continuously in business since that surveillance is currently maintained by Original records were located and stated the date. In the past, they have produced origi­ campus security, as scheduled tower tours largest bell of the chime weighed 4,993 lbs. nal bell records for several projects by the are conducted upon request. These tours The total weight of the 17 bells (exclusive of author’s firm. Their UK location is generally provide interior access to the ringing cham­ the framing and equipment) was 23,351 lbs. not an issue, as they have restoration staff ber level, with exterior access provided A full structural analysis was performed, who work regularly in the U.S. If considered behind railings on all elevations. based on the inspec­ tion data and revealed that while under code- prescribed loads, most of the carriage compo­ nents were within allow­ able stress limits for a full design load. The few timber-frame bell support system components that were overstressed pro­ vided capacity for 75% of the demand. It was then determined that in-situ capacity augmentation could be utilized to reme­ diate the issues (Figure 16). Specifications for the bell restoration and struc­ tural scope of work were added to the project docu­ ments. Bell restoration and casting foundries are a “niche” trade and can be difficult to locate, requir­ ing the designer to search outside of the U.S. The Whitechapel Bell Foundry was established Figure 16 – Tower chime supports required in-situ capacity augmentation.

7 0 • F u l m E r S y m p o S i u m o n B u i l d i n g E n v E l o p E T E c h n o l o g y • o c T o B E r 2 0 1 6 Firestopping and Suppression projects can be even more beneficial than Document with photos and field A thorough analysis of existing fire their involvement on conventional construc­ reports. suppression systems and penetration fire- tion projects. As highlighted in former case • Firestop system installation, per stopping was performed within the tower. studies, construction mistakes do occur. ASTME 2174 and testing per ASTM Testing or installation of penetration fire- if installation defects or water infiltration 814 stops should comply with UL 1479 and issues are not addressed prior to project • Project safety officer, supervised by ASTm E814 requirements, and firestop con­ closeout and staging removal, the reme­ the project manager. tractors should have Fm 4991 approval. diation process can be very expensive. if an existing fire suppression system is Independent inspectors should be involved As a quality assurance measure, inde­ in place, it should be fully inspected and in the submittal approval process, perform pendent inspectors provide value-added tested during the schematic design phase. materials and system testing while work objectivity and safety to a tower project. Both firestopping and fire suppression is in progress, and schedule and over­ systems are critical life safety components see manufacturers’ warranty inspections. SUmmaRY in tower design. In addition, if the tower is Additionally, consideration should be given While there are a number of design attached to a building, 2015 IBC section to hiring an independent safety consultant considerations and problems unique to 1510.5 states that the fire-resistance rating with tower experience who is familiar with tower and steeple restoration, a methodi­ of the tower must be equal to that of the all applicable OSHA regulations. cal, multidisciplinary approach to project attached structure. Some conditions requiring oversight are scope development and code compliance as as follows: described will guide the designer. Although QUaLITY aSSURaNCE • Staging inspection (daily) per OSHA some of the trades and systems in tower Specifying the use of independent standards design are uncommon, engaging in a thor­ inspectors on a tower project could be per­ • Roofing and wall installation (both ough evaluation of all project systems, ceived as burdening what often is an already low-slope and steep-slope), perfor­ engineering, and code requirements will overstressed project budget. However, the mance of in-situ water tests, and produce an effective and comprehensive use of independent inspectors on tower oversight of warranty inspections. project design.

S y m p o S i u m o n B u i l d i n g E n v E l o p E T E c h n o l o g y • o c T o B E r 2 0 1 6 F u l m E r • 7 1 NoTES

7 2 • F u l m E r S y m p o S i u m o n B u i l d i n g E n v E l o p E T E c h n o l o g y • o c T o B E r 2 0 1 6