Technical Note No. TN01 Loading for Structures

Surface Transport Master Plan Addendum 3 – Transit Corridor Safeguarding Mott MacDonald Technical Note May 2009

Loading for Tram Structures

Issue and Revision Record

Rev Date Originator Checker Approver Description

A 31-03-09 S. Luke T. Watson J. Forbes First Issue – for Comment

B 27-05-09 J. Gomez B. Duguid S. Luke Second Issue

This document has been prepared for the titled project or named part thereof and should not be relied upon or used for any other project without an independent check being carried out as to its suitability and prior written authority of Mott MacDonald being obtained. Mott MacDonald accepts no responsibility or liability for the consequence of this document being used for a purpose other than the purposes for which it was commissioned. Any person using or relying on the document for such other purpose agrees, and will by such use or reliance be taken to confirm his agreement to indemnify Mott MacDonald for all loss or damage resulting therefrom. Mott MacDonald accepts no responsibility or liability for this document to any party other than the person by whom it was commissioned. To the extent that this report is based on information supplied by other parties, Mott MacDonald accepts no liability for any loss or damage suffered by the client, whether contractual or tortious, stemming from any conclusions based on data supplied by parties other than Mott MacDonald and used by Mott MacDonald in preparing this report.

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Technical Note No. TN01 Loading for Tram Structures

Contents

Ch Section/Title Page

1 INTRODUCTION 3 1.1 Purpose of the Technical Note 3 1.2 Source data 3 1.3 Definitions & Acronyms 4

2 STANDARDS 6 2.1 Technical Standards 6 2.2 Abu Dhabi Tramway Planning Guidelines 6 2.2.1 Lighting Requirements Error! Bookmark not defined. 2.2.2 Geometric Requirements 6 2.2.3 Electrical Requirements 7 2.2.4 Drainage Requirements 7 2.2.5 Ducting and Utilities 7 2.2.6 Trackform 7 2.3 Technical approvals 9

3 TRAM LOADS 10 3.1 Vertical loads from passenger 10 3.1.1 Review of LRVs 10 3.1.2 Summary of vertical loads 11 3.2 Horizontal loads from passenger trams 12 3.2.1 Lurching 12 3.2.2 Nosing 13 3.2.3 Centrifugal 13 3.2.4 Summary of horizontal loads 13 3.3 Longitudinal loads from passenger trams 14 3.3.1 Deceleration 14 3.3.2 Acceleration 15 3.3.3 Summary of Longitudinal Traction Loads 16 3.4 Fatigue loads for passenger trams 17 3.4.1 Load intensity 17 3.4.2 Load frequency 18 3.5 Accidental loads for passenger trams 18 3.5.1 Vertical loads from derailed LRV 18 3.5.2 Horizontal loads from derailed LRV 19 3.5.3 Horizontal loads from impact of other vehicles 20 3.6 Loads from freight trams 20 3.6.1 Vertical loads for freight trams 21 3.6.2 Horizontal loads for freight trams 21

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3.6.3 Longitudinal loads for freight trams 21 3.6.4 Fatigue loads for freight trams 21 3.6.5 Accidental loads for freight trams 21

4 MAINTENANCE AND CONSTRUCTION VEHICLE LOADS 22 4.1 Vertical loads for maintenance and construction vehicles 22 4.1.1 Assumed vehicles 22 4.1.2 Summary of vertical loads 24 4.2 Horizontal loads for maintenance and construction vehicles 24 4.3 Accidental loads for maintenance and construction vehicles 25

5 OTHER LOADS 26 5.1 Highway vehicles 26 5.2 Pedestrian loading 26 5.3 Wind loads 26 5.4 Temperature loading 26

6 REFERENCES 27

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Technical Note No. TN01 Loading for Tram Structures

1 Introduction

1.1 Purpose of the Technical Note In September 2007 the Abu Dhabi Government published “Plan Abu Dhabi 2030: Urban Structure Framework Plan”, also known as Vision 2030, which is a plan for the development of the City of Abu Dhabi to guide planning decisions for the next quarter of a century. In February 2008, Mott MacDonald was appointed by the DOT to prepare the STMP. This was to develop the conceptual transportation strategy outlined in Vision 2030 into a detailed master plan and prepare the implementation programme. The STMP includes an ambitious plan to introduce over 340km of tramway into Abu Dhabi. Some elements of the tram system will be retrofitted into the existing urban fabric whilst other elements will be provided within new development areas. In these new development areas the tramway might be implemented in parallel with, earlier or later than other development. In all instances however it will be necessary for the functional requirements of the tramway to be provided. One aspect of this is that any new or existing structures that interface with the tramway should take into account the loading and other design criteria related to the tram system. The objective of this Technical Note is to detail the required considerations for tramway structures and other structures integrated or related to the proposed and likely alignment. The Technical Note considers vertical, horizontal, fatigue and accidental loadings, and design criteria including headroom clearances, deflection and vibration. The Technical Note will propose appropriate standards for the system. Loading and design criteria for structures other than tram structures are not covered by this Technical Note. Text in bold type is intended as a mandatory requirement and all structures supporting the tramway must demonstrate compliance.

1.2 Source data The information consulted in preparation of this Technical Note comprises, but is not limited to the following documents: • Design Manual for Roads and Bridges (DMRB) – UK Highways Agency publication (Ref. 1); • Roadway Design Manual – Road and Bridges (Abu Dhabi Municipality) (Ref. 2); • Load appraisal report for , Mott MacDonald, 2004 (Ref.3); • Design loads & spatial parameters – Technical Note. Cross River Tram, Mott MacDonald, 2008 (Ref. 4); • Report on loading and design criteria for tram structures. Nottingham Express Transit, Mott MacDonald, 2008 (Ref. 5); • Manufacturer specifications and publish data for information on low floor trams. Collated in May 2009 by Mott MacDonald.

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1.3 Definitions & Acronyms

DKE Developed Kinematic Envelope, defined as per the UK’s Office of Rail Regulation (ORR) “Guidance on Tramways” (Ref. 6), clause 107: “The DKE should be established by enlarging the kinematic envelope to take into account all the possible effects of curvature, including superelevation of the track, and end and centre throw of the tram. It too is speed dependent, but is unique to the particular location at given speed.” Refer to additional Clauses 108-109 for further information.

DoT Department of Transport

ESZ Area within which, there may be a risk of electrocution from the OLE.

LRT Light Rail Transit

LRV Light Rail Vehicle

OLE Overhead Line Equipment

RL Reduced loading for use on passenger rapid transit systems on lines where main line locomotives and rolling stock do not operate.

RU Standard railway loading and allows for all combinations of vehicles running or projected to run on railways in the UK.

STMP Surface Transport Master Plan.

TCS Transit Corridor Safeguarding.

Tramway As per the ORR “Guidance on Tramways” (Ref. 6), clause 16: “…a system of transport used wholly or mainly for the carriage of passengers, employing parallel rails which provide support and guidance for vehicles carried on flanged wheels, and in respect of which: the rails are laid in a place to which the public have access; and on any part of the system, the permitted speed of operation of the vehicles is limited to that which enables the driver on any such vehicle to stop it within the distance he can see or be clear ahead…” Refer to additional Clauses 108-109 for further information.

Tramway Path As per the ORR “Guidance on Tramways” (Ref. 6), clause 85: “…the area reserved for a moving tram in its environment. It is derived from the DKE by adding the minimum appropriate clearance as specified within this document…It therefore depends upon the DKE and upon the nature of the operational environment and the structures and features within it.” Refer to Clause 86 for further information.

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UIC Union Internationale des Chemin de Fer or International Union of Railways.

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2 Standards

2.1 Technical Standards A number of different technical standards are routinely used in the United Arab Emirates (UAE) for various purposes. For example, British Standards are used in building design, and AASHTO standards for road and bridge design. There are no recognised national or international standards for LRT structures. In the UK, the Highways Agency’s Design Manual for Roads and Bridges (DMRB) (Ref. 1) together with UIC 776-3R (Ref. 7) are often combined for LRT Structures. We have developed on other schemes a set of LRT structures requirements and recommend a similar approach is adopted for STMP-TCS. However, it should be open to developers to use other standards where they can demonstrate that the requirements of this Technical Note will be fully satisfied. In particular, structures supporting both LRV and highway loads may need to comply with the Abu Dhabi Municipality Roadway Design Manual (Ref. 2), which incorporates AASHTO Standards. Structures supporting the tramway shall be designed in compliance with the Highways Agency’s Design Manual for Roads and Bridges (DMRB) (Ref 1), with the addition of UIC 776-3R (International Union of Railways) (Ref. 7) to address vibration issues and deflection constraints. Alternative standards may be adopted subject to prior demonstration that they are at least equivalent to these standards, and that their use shall satisfy the other requirements set out in this Technical Note.

2.2 Abu Dhabi Tramway Planning Guidelines

The DoT have commissioned the preparation of Tramway Planning Guidelines and this Technical Note should be read in conjunction with these guidelines.

2.2.1 Geometric Requirements Provision for sufficient height clearance to the OLE will be required (the desirable minimum wire clearance is 6.2m above top of rail). If a tram only section runs under a structure, this may be locally reduced to an absolute minimum height of 5.2m above platform/street level providing that there is sufficient longitudinal separation to the nearest section of on-street track to achieve the minimum clearance of 6.2m at that point. An absolute minimum of height of 4.8m and 4.2m shall apply to off street and subway sections where there is no public access. The Electrical Safety Zone (ESZ) extends 2m beyond the outer rails of the tramway once the tramway is operational. Buildings shall be located and designed such that areas physically accessible to occupiers are a minimum 2.75m clear of the ESZ to reduce the risk of electrocution. The layout of the development boundaries should allow for maintenance of the development without the need for possessions of the tramway. It should be noted that possessions of the tramway could have significant cost implications.

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No obstructions shall be placed within the tram DKE. Obstructions greater than 0.5m in length shall additionally be located at least 0.9m beyond the DKE to allow clear space for evacuation of passengers in an emergency.

2.2.2 Electrical Requirements Stray current issues stem from the fundamental design of electrified rail transit systems. Electric current from the OLE is returned to substations via the running rails. The magnitude of stray current flow in the ground conductor will increase as its resistivity decreases. Steel reinforcement to concrete and any metallic structure buried in ground of this nature will also tend to “attract” stray current. The risk of corrosion to the metallic elements is therefore increased. Stray current monitoring and management are therefore required to prevent structural damage of structures. Structures supporting the tramway shall be electrically isolated from the trackform. For example, an electrically inert membrane shall be placed on any structural floor slab below the proposed tramway trackform (see below). Developers shall have regard to the possibility of electromagnetic interference with sensitive equipment (e.g. computing and communication equipment) placed in the close vicinity of the tramway’s electrical system. Measures to address such interference are the developer’s responsibility (e.g. relocation of equipment).

2.2.3 Drainage Requirements All new or altered drainage should direct surface water away from the tramway. Proposals to drain water onto, or connect into, the tramway track drainage shall not be permitted. Tramway drainage is expected to be incorporated into the trackform, comprising longitudinal drain channels and carrier drains. On long structures, developers may be required to provide for tramway drainage outfalls at suitable intervals, to be incorporated into the structure’s design.

2.2.4 Ducting and Utilities

Provision shall be made for tramway related ducting. The location of utilities shall take into account the requirements of the Tramway planning Guidelines.

2.2.5 Trackform Various track forms are currently in use on modern tram schemes. These are: Ballasted track, without stray current collection measures but incorporating insulated rail fastenings. Ballast-less paved track, with the rails flush with the road surface and continuously supported by and embedded in an elastomeric insulating material.

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Ballast-less non-paved track, with discrete rail supports incorporating full insulation as part of the rail fastenings. Grass-track which is a modification of one of the ballast-less track forms (generally not proposed for Abu Dhabi because of watering requirements). Typical Ballast-less paved track slab arrangement adopted in the UK is shown in Figure 1. For situations where the track slab is placed directly onto a podium, it would be expected that reinforced concrete elements of the track slab could be placed directly onto the podium structure, with electrical separation. Developers shall allow in their designs for the dead weight of the tramway track slab and platforms where required including all ancillary fixed items (e.g. OLE support columns, platform shelters and the like).

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Figure 1: Typical track slab detail

2.3 Technical approvals We recommend that the Department of Transport obtains assurance from developers and contractors that their structures and other design features comply with this Technical Note and Tramway Planning Guidelines, prior to commencement of construction. In other jurisdictions, this assurance is obtained by means of a Technical Approval process whereby designers submit their proposals for “Approval in Principle” at the preliminary design stage. While this offers the greatest assurance that developments will be compliant, it requires the approval body to have appropriate technical expertise and devote considerable resources to technical review of design proposals. Typical UK Standards for such a Technical Approval process include: • BD 2/05 – Technical Approval of Highway Structures (Ref. 8); • NR/SP/CIV/003 – Technical Approval of Design, Construction and maintenance of Civil Engineering Infrastructure (Ref. 9). • 1-538 – Underground (Ref. 17) The fundamental objectives of the Technical Approval procedures are to give increased assurance for the required construction, refurbishment or demolition so that the proposals are safe to implement. Also, that any new structures procured are serviceable in use, economic to build and maintain, comply with the objectives of sustainability, have due regard for the environment, and that they satisfactorily perform their intended functions. Additionally, Technical Approval gives the Department of Transport the assurance that structures built by others can safely support the future tramway with a minimum of alteration. Developers shall submit preliminary details of their structural proposals, and an accompanying design statement demonstrating how their design meets the requirements of this Technical Note and Tramway Planning Guidelines. The developer shall obtain the Department of Transport’s acceptance of this submission before finalising the design of the structure.

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3 Tram Loads

3.1 Vertical loads from passenger trams

3.1.1 Review of LRVs There are currently no national or international standards for tram loading. Therefore, information on low floor (full or partial) trams was collated in May 2009 from manufacturer and published data. This data has been reviewed and the relevant results are shown on Table 1. This information is preliminary and may not reflect all LRVs on the market satisfying the requirements set by the Abu Dhabi Surface Transport Masterplan on tram characteristics. We are aware that trams have historically tended to become heavier as improvements are made and extra pieces of equipment added. For example, different manufacturers may choose to deal with the temperature extremes of Abu Dhabi in different ways, adding solar gain shields, additional fans or additional air-conditioning units among the possible solutions. Therefore, it would seem prudent to add a margin for future flexibility and location specific requirements.

Vehicle Loaded Equivalent Loaded Equivalent Vehicle Vehicle Location Length 2 Weight Crush UDL-6p Crush UDL-8p Maker Type (City) (m) 1 (Empty) (6pass./m 2) (kN/m) (8pass./m 2) (kN/m) Tramways

CAF Streetcar Edinburgh 45.850 55.8t 79.040t 16.91 84.920t 18.17

Flexity Bombardier Berlin 40.550 51.5t 74.005t 17.90 79.780 19.30 Outlook Flexity Bombardier Brussels 43.394 52.5t 76.160t 17.22 82.320t 18.61 Outlook

3 Combino Siemens Almada 36.360 50.5t 72.270t 19.50 77.800t 20.99 Plus Guided Buses Tram-on- Bombardier Nancy 24.500 25.5 39.710t 15.90 43.280t 17.33 Tires

Table 1 Comparison of Low-floor Light Rail Vehicle Loads

We have compared the above vehicle loads against reference standards for light rail loading. Chapter 8.0 of the design code BD 37/01 (Ref. 10) describes two types of railway loading, RU and RL loading. RL loading is a reduced loading for use on passenger transit railway systems where mainline

1 Vehicle weight (empty) does not include cooling units or similar. 2 Assumed passenger weight is 70kg per person 3 Siemens provides a second version of the Combino Plus tramway for Budapest, with a vehicle length of 53.990m; however, at the time of the production of this Technical Note, we do not have tare weight data for this model.

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Technical Note No. TN01 Loading for Tram Structures locomotives and rolling stock do not operate, and can be used for LRV loading, although this is conservative. In accordance with clause 8.2.2 of BD 37/01, the most onerous of the following is used for nominal (un-factored) RL loading: • A single 200 kN concentrated load coupled with a uniformly distributed load (UDL) of 50 kN/m for loaded lengths up to 100 m, and for loaded lengths in excess of 100 m a UDL of 50 kN/m for the first 100 m reducing to 25 kN/m for lengths in excess of 100 m; or • Two concentrated loads of 300 kN and 150 kN, spaced at 2.4 m along the track, placed at a point along the deck to give the most severe result. With the exception of the two concentrated loads of 300 kN and 150 kN, which are deemed to include dynamic effects (clause 8.2.2 of BD 37/01), a dynamic factor for RL loading shall be taken as 1.4 for un-ballasted tracks and 1.2 for ballasted tracks (clause 8.2.3.2 of BD 37/01) (Ref. 10). Mott MacDonald has previously carried out research work in the UK, investigating both LRVs and maintenance vehicles. Our load appraisal reports for Merseytram (Ref. 3), Cross River Tram (Ref. 4), and Nottingham Express Transit (Ref. 5), concluded that a value of 0.5 x RL was generally suitable to represent current and future tram loads on those schemes. The tabulated UDLs range between 17.33 kN/m and 20.99 kN/m and would be within a proposed loading of 0.5 x RL, which equates to 25 kN/m. This provides a margin typically 20% above the most onerous tram considered for this load model. Latest developments in tram technology include ground-powered trams using the PRIMOVE (Bombardier) and APS (Alstrom) systems. We have no evidence to anticipate that the load imposed by these systems is much more onerous than the vehicles explored in Table 1. Other technologies, such as Bombardier’s MITRAC system, for storing energy released when braking, can add to the empty weight of vehicles by approximately one tonne. This increase to the tare weight has minimal effect on the equivalent UDL, hence, the proposed 0.5 x RL remains acceptable. In a climate such as Abu Dhabi, we have estimated conservatively that for a 7 section, 40 metre long tram, 2 drivers cab air conditioning modules would be required (1 module per cab), combined with approximately 7 separate saloon air conditioning modules (1 in each vehicle section). These modules would increase the tare weight of vehicles by approximately 2.5t. The tabulated UDLs range would then be between 18.70kN/m and 21.66kN/m. Under this loading, the proposed 0.5 x RL provides a margin typically 15% above the most onerous tram and, therefore, still acceptable. We recommend that the design should allow for a maximum static axle load of 12.5 tonnes. This would result in a revised load model of two 175 kN axles, spaced anywhere from 1.6 m to 1.9 m, whichever is most onerous.

3.1.2 Summary of vertical loads To summarise, the proposed design vertical LRV loads for Abu Dhabi tramway shall be as follows:

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• 0.5 x RL for normal vertical loading. This comprises a uniformly distributed load (UDL) of 25 kN/m with a concentrated load of 100 kN for loaded lengths up to 100 m, both of which shall be increased with a dynamic factor of either 1.2 for ballasted track or 1.4 for non-ballasted track. or • Two 175 kN axle loads spaced 1.6 m to 1.9 m apart to represent the likely maximum concentrated load of current or planned trams. These loads are illustrated in Figure 2.

Proposed Condition No. 1 100 kN

25 kN/m

Up to 100m

Proposed Condition No. 2

175 kN 175 kN

1.6m to 1.9m

Figure 2: Proposed nominal vertical LRV loads

3.2 Horizontal loads from passenger trams

3.2.1 Lurching Lurching is an effect that results form the temporary transfer of part of the live loading from one rail to another, whilst the total load remains unaltered. Clause 8.2.7 of BD 37/01 provides the following factors to account for lurching, which results from the temporary transfer of part of the live loading from one rail to the other with the total track load remaining unaltered. 0.56 of the track load shall be considered to act on one rail concurrently with 0.44 of the track load acting on the other. The total load per track will continue to be based on 0.5 x RL UDL loading. The effect of lurching will only be considered on one track where structural members support two tracks.

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3.2.2 Nosing The nosing effect is caused by discontinuities on the rails. The gaps between the rails and the wheel flanges due to lateral construction tolerances will cause the vehicles to apply a lateral force onto the rails. Clause 8.2.8 of BD 37/01 provides an allowance of 100 kN for lateral loads applied by trains to the track. Where elements support more than one track a single load is deemed sufficient to represent this effect. The origin of this value is unclear, however the structural design shall include provision for this 100 kN horizontal load applied at right angles to the track. The vertical effects of this load on secondary elements such as bridge bearings shall also be considered.

3.2.3 Centrifugal Clause 8.2.9 of BD 37/01 provides an equation for calculating centrifugal forces, only applicable to tracks which are curved in plan. The centrifugal force is dependent on the greatest speed envisaged on the curve, the radius of the curve and the static equivalent uniformly distributed load for bending moment when designing for RU loading. In this clause, a value of P for static uniformly distributed load of 40 kN/m is given for RL loading. However for the reasons given in section 3.1.1 of this Technical Note, we propose to use 0.5 x RL, i.e. 25 kN/m, for calculating centrifugal forces. For the purposes of these calculations, we propose that the speeds for Abu Dhabi Tramway are limited to 80 km/h generally, with 30 km/h restrictions at sections with adjacent passenger walkways or platforms. Different speeds may be adopted at individual structures with prior approval from a competent technical authority to suit site specific restrictions.

3.2.4 Summary of horizontal loads To summarise, the proposed design horizontal LRV loads for Abu Dhabi tramway shall be as follows: • For lurching effects, 0.56 of the track load shall be considered to act on one rail concurrently with 0.44 of the track load acting on the other. The total load per track will continue to be based on 0.5 x RL UDL loading. The effect of lurching will only be considered on one track where members support two tracks. • For nosing effects, a single nominal load of 100 kN, acting horizontally in either direction at right angles to the track at rail level and at such point in the span as to produce the maximum effect in the element shall be applied. • The centrifugal load shall be calculated with the following equation: 2 25 × (vt +10 ) Fc = ; where the centrifugal load (Fc)is given in kN/m, the greatest speed 127 × r

(vt) is given in km/h and the radius (r) is given in metres.

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3.3 Longitudinal loads from passenger trams

3.3.1 Deceleration Tram braking systems are often composed of 3 different types of brakes. These are dynamic, disc and magnetic, and are designed especially for service braking, parking and emergency braking respectively. • Service braking is often via the regenerative use of the AC traction motors. It is common for them to provide a retardation rate of about 1.3 m/s2 from the maximum permitted speed of operation. This braking force will be applied at the powered bogies. • The friction brake is used when the tram is in a park position. • Trams are normally required to have hazard brakes fitted to provide a retardation rate of at least 2.5 m/s 2 and a maximum instantaneous retardation rate of between 3 and 4 m/s 2. This is achieved through the use of electromagnetic braking. In this situation a 'shoe' either side of a bogie, can apply over 5 tons of pressure onto the track, causing rapid deceleration. Magnetic track brakes are intended to be primarily used for emergency applications. Not all the types of braking systems are located on all bogies. Regenerative/rheostatic electric brakes are often located on the motorised bogies, although electromagnetic emergency brakes are often located on all bogies. As the emergency braking gives the critical braking loads it will be assumed for Abu Dhabi Tram that the brakes are located on every bogie. This means that the braking load has been assessed relative to the entire tram loading. The most severe braking forces are produced when the emergency braking is applied. This is often achieved through a combination of the available braking methods. The magnetic brakes are applied to all axles and are used as an emergency brake. Due to the effectiveness of magnetic brakes and the lightness of the tram vehicles, the rates of acceleration and deceleration are often higher than for other rail vehicles. For this reason, the longitudinal loads are assessed specifically for tram vehicles.

(a) Braking efficiency In BD37/01, both the RL and RU longitudinal braking loads are calculated as 25% of the load on the braked wheels. As force is a product of mass and acceleration, the deceleration that occurs from a braking system of 25% can be calculated as 0.25g = 2.453 m/s 2. Therefore, BD37/01 assumes a rate of deceleration of approximately 2.5 m/s 2. The maximum braking speed allowed for trams by the Railway Safety Principals and Guidance (Ref. 11) is 4 m/s 2. Estimates have been made that the maximum permissible emergency deceleration is 0.47g for forward facing seated passengers, and 0.41g for side-facing seated passengers (Ref. 12). These are equal to 4.61 m/s 2 and 4.02 m/s 2.

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Service Braking Hazard Braking Location (m/s 2) (m/s 2) Nottingham Express Transit 1.3 - Edinburgh-Proposed prototype 1.5 3.3 Sheffield -Stagecoach Supertram 1.5 3 1.3 3.93 Croydon 1.2 3.15

Table 2 Rates of retardation achieved on British tram systems

The maximum deceleration rates of trams are currently around 3m/s 2. Table 2 shows some examples of braking systems that are in use or have been proposed in Britain. As braking systems are constantly being developed and improved, it is assumed that the tram braking system is only limited by human factors. Therefore the loads will be calculated assuming a deceleration rate of 4m/s 2. This value takes into account possible future developments in braking technology.

(b) Adjusted Braking Loads A new set of braking loads shall be calculated for the tram loading using the following assumptions: • Vertical loading = 0.5 x RL, limited to a maximum tram length of 80m • Load on braking wheels is equal to total vertical loading over loading length • A deceleration rate of 4m/s 2 Longitudinal Force = Total mass acting on loading length x Acceleration = (0.5 x RL loading / 9.81) x 4

Loaded Length RL Loading RL Braking Load Tram Braking Load Up to 8m 400 kN 64 kN 150 kN From 8 to 15m 50 kN/m 8 kN/m 150 kN From 15 to 80m 50 kN/m 8 kN/m 10 kN/m From 80 to 100m 50 kN/m 8 kN/m 800 kN Over 100m 5000 kN 800 kN 800 kN

Table 3 Calculation of RL braking loads and Adjusted Tram braking loads

A minimum braking load is set for short spans to allow for the possible case where only a single braking bogie is supported by the structure.

3.3.2 Acceleration

(a) Driving units The standard tram designs have a set of 4 motors fitted to the two, two axle power bogies at the outer ends. The central bogies are generally un-powered. As the topography in Abu Dhabi is relatively flat

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Technical Note No. TN01 Loading for Tram Structures and the tramway planning guidelines have placed limits on the tramway vertical gradient it has, therefore, been assumed that only the front and back bogies will be powered. The document BD 37/01 uses a reduced value for the weight on the driving wheels. This is to allow for the fact that not all the bogies have motors. As it will be assumed that some of the bogies will be un-powered, the reduction factor used in BD37/01 RL Traction loading will be used in the evaluation of Tram traction loading.

(b) Rate of acceleration The assumed rate of acceleration for the tram under full RL loading used in BD37/01 may be calculated in a similar way to the rate of retardation, using a factor of 0.30 Longitudinal traction force = Load on driving wheels x 0.30 Therefore assumed acceleration = 0.3 g = 2.943m/s 2

Location Rate of acceleration (m/s 2) Nottingham Express Transit 1.3 Edinburgh-Proposed prototype 1.5 Sheffield -Stagecoach Supertram 1.3 Manchester Metrolink 1.3 Croydon Tramlink 1.2

Table 4 Rates of acceleration achieved on British tram systems

Current rate of acceleration for trams tend to range from about 1 m/s 2 to 1.5 m/s 2. Therefore, this is safely within the values taken in BD37/01. Acceleration capabilities are constantly being developed. A potential development is that it may be possible to develop electromagnetism further so that it can be used to enhance both the acceleration and the deceleration. It may be that acceleration capabilities increase so that the maximum acceleration is governed by human comfort factors. As mentioned in the previous section, humans can take accelerations up to 4 m/s 2. However, it is only intended for a value this high to occur in emergency braking and not in general use. Therefore, a maximum acceleration of 3 m/s 2 is an acceptable value to be assumed for tram loadings.

3.3.3 Summary of Longitudinal Traction Loads The above concludes that a higher rate of retardation should be used when calculating braking loads for trams. New values of these longitudinal loads have been calculated using a deceleration rate of 4 m/s 2. These are summarised in Table 5. The following longitudinal loads shall be used in design of structures supporting the tramway. It shall be assumed that traction can occur on one track simultaneously with braking on any one other track.

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Loaded Length LRV Braking Loads LRV Traction Loads Up to 15m 150 kN 112.50 kN From 15 to 80m 10 kN/m 7.5 kN/m Over 80m 800 kN 600 kN

Table 5 Adjusted values for Braking and Traction Longitudinal Loads

3.4 Fatigue loads for passenger trams All steel structures will be designed for fatigue loading in accordance with BS5400: Part 10 (Ref. 13). Clause 9.0 provides two methods for assessing fatigue and the choice of method depends on the information available. In this case, the information available for loadings and loading frequency enables the use of Miner’s summation (clause 9.3.1) to be used for assessing fatigue.

3.4.1 Load intensity Axel load distribution is particular to each tram design and number of bogies on each car. The typical axle loads depend on the extent of passenger loading under the following conditions: • Typical off peak period – AW1 (all seats occupied) • Typical peak period – AW2 (4 persons/m 2 standing) • Crush laden – AW3 (6 persons/m 2 standing) Note that an occupation of 8 persons per square metre is assumed for strength design, but this extreme condition would not be appropriate for consideration of cyclic loading. The typical axle loads can be applied to the structure to calculate the worst load effects and therefore the maximum stress in any given section of the structure. The weight of the vehicles studied for the purpose of this report show a likely axle load under the following load conditions:

Loadcase Maximum bogie axle load AW1 (all seats occupied) - Typical off peak period 7.675 t AW2 (4 persons/m 2 standing) - Typical peak period 9.145 t AW3 (6 persons/m 2 standing) - Crush laden 9.880 t

Table 6 Axle loads

The Abu Dhabi design LRV has not been confirmed and the tram fleet is likely to change during the design life of the structures. Therefore, we recommend allowing flexibility for alternative trams with potentially heavier loading and modifications due to extreme temperatures as described previously. Unlike the maximum static axle load (12.5 t) which would be an extreme case, the fatigue loading considers everyday service operation. A reasonable cyclical loading margin to apply would be a 25% increase on the most onerous tare (empty) load form the reviewed trams for this study and this is assumed in the following calculations.

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Loadcase Maximum bogie axle load AW1 (all seats occupied) - Typical off peak period 9.419 t AW2 (4 persons/m 2 standing) - Typical peak period 10.890 t AW3 (6 persons/m 2 standing) - Crush laden 11.624 t

Table 7 Adjusted axle loads

3.4.2 Load frequency The proposed peak operational service for the Abu Dhabi tramway system is to be 30 trams per hour per direction, operating during approximately 19 hours per day, from 05.30 am to 00:30 am the following morning. A frequency breakdown of peak and non-peak hours has not been provided at the time of issuing this Technical Note, therefore, we have assumed that all trams, conservatively, carry the full AW3 load at all times and on all lines. For fatigue design, the following loads and frequencies will be applied: • 19-Hour Peak Period (30 trams/ hour/ direction) 19 Hours AW3 loading = 19 x 30 = 570 trams/ day at AW3 per track The total tram movements over 365 days per year are • 208,050 trams at AW3/ year (365 x 570) per track The axle load to apply is 125kN. Assume 8 axles per LRV for passenger trams.

3.5 Accidental loads for passenger trams Derailment of LRVs can occur in several circumstances, including a steering mechanism failure, a fault or wear in the rails, or vehicle collision. In the case of collision, it can occur between LRVs or with other road vehicles, where the road is shared. The support structure needs to be designed for the vertical load imposed by the LRV in its derailed location, and barriers to contain the LRVs require to be designed to withstand the appropriate collision forces. Building structures in close proximity to the tramway may be affected in the derailed condition and as such, they must be designed to withstand such collision forces as well.

3.5.1 Vertical loads from derailed LRV In the UK, Clause 8.5 of BD 37/01 (Ref. 10) outlines three conditions to be taken into account to ensure the stability of the structure under vertical derailment loads. These three conditions below shall be considered separately and are based on the RL loading specified in Clause 8.5.2: Condition (a) – For serviceability limit state, derailed coaches or light wagons remaining close to the track shall cause no permanent damage.

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Condition (b) – For the ultimate limit state, derailed locomotive or heavy wagons remaining close to the track shall not cause collapse of any major element, but local damage may be accepted. Condition (c) – For overturning or instability, a locomotive and one following wagon balancing on the parapet shall not cause the structure as a whole to overturn, but other damage may be accepted. The loading applied for each of these conditions shall be as follows: Condition (a), either a pair of vertical line loads 15 kN/m each, 1.4 m apart, parallel to the track and applied anywhere within 2 m either side of the track centre line, or an individual concentrated load of 75 kN applied anywhere within 2 m either side of the track centre line. Condition (b), for ultimate limit state, four individual concentrated vertical loads each of 120 kN arranged at the corners of a rectangle 2 m long by 1.4 m wide applied anywhere on the deck. Condition (c), for overturning or instability, a single line vertical load of 30 kN/m over a 20 m length applied along the parapet or outermost edge of the bridge anywhere along the span.

3.5.2 Horizontal loads from derailed LRV The Railway Safety Principles and Guidance (RSPG), Part 2, Section G, Guidance on Tramways published by the HSE (Ref. 11) has been reviewed for general recommendations for derailment loads. Although, no specific loads are provided in RSPG to represent the effects of a derailed tram, the document recommends adequate derailment containment including the provision of longitudinal pits or drainage channels to contain a stray wheel. It can be assumed that the trackform will incorporate such derailment containment channels, or alternative wheel restraint such as a robust structural up-stand or keep rail. Developers shall assume that derailment imparts a 100kN lateral point load to the trackform, to be transmitted to the tramway support structure, and applied in conjunction with normal accidental vertical loads. Parapets or balustrades do not generally need to be designed to restrain a derailed tram but may be designed for pedestrian or highway vehicle impact where appropriate. It is anticipated that the Abu Dhabi tramway will be supported upon podium structures design by developers, and structural elements from other sections of the buildings will be located near the tram corridor. Guidance on containment barriers is given in the text book “Bridge Loads” (Ref. 15). The magnitude and line of action of a horizontal derailment load on a barrier element is dependant on several factors including the lateral clearance from the track to the obstacle, and the friction coefficient between the LRVs and the surface of the physical barrier. There is little or no published guidance on impact loads from a derailed tram where the primary derailment containment (channel or up-stand) has been ineffective. The American Concrete Institute Committee Report ACI 358.1R-92 (Ref. 16) states in lieu of a detailed analysis to adopt a load equal to 50% of the tram’s total weight, and we propose that this be adopted for particularly vulnerable structures.

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Designers shall assess and identify any structural elements within the vicinity of the tramway, which, if they were to fail under LRV impact could lead to disproportionate collapse or loss of life. These would typically include column supports to bridges over the tramway, or to adjacent building structures. All vulnerable structural elements located at or closer than 4.5 metres from the running edge of the track shall be designed for impact loading to resist a point lateral force equivalent to 50 per cent of a single LRV, acting at a height of 1 metre above floor level, and in any horizontal direction. For the purposes of this clause, the tram weight may be assumed to be 25kN/m, over a 40m LRV, i.e. 1000kN, giving a 500kN impact force.

3.5.3 Horizontal loads from impact of other vehicles The local effects of road or rail vehicle collision with supports to the tramway structure (including piers and columns) and also the tramway deck superstructure require consideration. Vehicle collision loads on supports to the tramway shall be considered for the design as secondary live loads. This load shall be applied in combination with the permanent loads and the appropriate primary live loads associated with it. Clause 6.8.1 of BD 37/01 (Ref. 10) provides highway vehicle impact loads with their direction and height of application, acting horizontally on the supports or superstructure. These are appropriate to high-speed road vehicle impact e.g. where the tramway passes above a public highway. Heavy rail impact loads shall be as agreed with the appropriate technical authority and applied where the tramway passes above a heavy rail line. Designers shall identify elements of the tramway superstructure or substructure that are vulnerable to impact due to limited headroom (superstructure) or proximity to traffic (substructure), and design these for appropriate collision loads. Alternatively, suitable barriers may be located to protect the structure against impact. In the case of multi-level carriageways, such as those encountered in multi-storey car parks, the collision loads are to be considered for each level of carriageway separately, not together. Different methods to determine the collision loading may be adopted at individual structures to suit site-specific restrictions, subject to prior agreement with Department of Transport.

3.6 Loads from freight trams At the time of writing this Technical Note it is not clear whether freight trams will run on the system, and if so, on which parts. Worldwide, few freight tram systems exist, and we have based what follows on information from the Dresden system summarised in Table 8.

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Vehicle Location Length Vehicle Weight Loaded Crush Equivalent UDL Vehicle Type Maker (City) (m) (Empty) (Fully laden) (kN/m)

Freight Tramways Schalke CarGoTram Dresden 59.400 90t 158t 26.09

Table 8 Freight tramway vehicle loads

3.6.1 Vertical loads for freight trams Due the limited information available on freight trams at the time of writing this Technical Note and observing the data collected in Table 8, we conclude that LRV loading (i.e. 0.5 RL) is insufficient to allow for freight trams; particularly if some redundancy is desirable for technological advances in tram systems and location specific requirements on freight trams such as cooled units. A detailed review of the tram network usage should be carried as soon as possible in order to identify the sections where it would be desirable to provide for freight tram operation. To cover freight vehicles and allow flexibility, we propose a loading of typically 50kN/m to be appropriate, i.e. RL. For track carrying freight trams we recommend the use of BD37/01 (Ref. 1) for light rail lines (RL loading). The design of tramway structures supporting or providing access to freight trams shall allow for vehicle load equal to full RL loading to BD37/01. RL loading on any two tracks simultaneously shall be applied to these sections of track.

3.6.2 Horizontal loads for freight trams For sections of track loaded with RL, the appropriate RL horizontal loads from BD 37/01 will be applied.

3.6.3 Longitudinal loads for freight trams For sections of track loaded with RL, the appropriate RL longitudinal loads from BD 37/01 will be applied.

3.6.4 Fatigue loads for freight trams Designers shall consider what further analysis for fatigue is required beyond that already stated for passenger trams.

3.6.5 Accidental loads for freight trams Derailment loads shall be the same as for RL in accordance to BD37/01. Accidental loading of a derailed freight tram shall be full RL loading applied as two line loads 1.4m apart anywhere within 2m either side of the track centre line, including consideration of the alternative RL axle loads (300kN and 150kN) where this gives an effect worse than the uniform load (50 kN/m).

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4 Maintenance and Construction Vehicle Loads

4.1 Vertical loads for maintenance and construction vehicles

4.1.1 Assumed vehicles Information on vehicles to be used to construct or maintain the tramway is not yet available. We have therefore drawn on our experience elsewhere in proposing the following requirements. A more detailed review of system construction and maintenance requirements should be carried out as soon as possible. For track sections not involving ballast or access to ballast track, designers may assume maintenance vehicles are restricted in weight to be no more onerous than passenger trams. Therefore no further consideration is required. Rail mounted maintenance could be carried out using a modified LRV, however the loads would be less than those for a fully laden passenger tram and will therefore not be a governing case. Maintenance can also be carried out using road/rail vehicles which again give lesser load effects than a fully laden tram. We have assumed that in non-ballasted areas all heavy maintenance plant will cross the bridges on rails and be limited to the loading conditions of a crush laden tram. Non rail access will be limited to LGV class maintenance vehicles with 2 axles and less than 7.5 tonne gross vehicle weight. For ballasted track, we have made reference both to BD37/01 (Ref. 1) for light rail lines (RL loading) and to typical ballast wagons and tamping plant operated in the UK. Heavy rail ballast wagons (e.g. “Skako” type) impose loads up to 3 or 4 times that of the passenger trams. We believe it is not economic to design the tramway for this loadcase, and therefore only restricted plant can be permitted. RL loading covers maintenance vehicles such as those shown in Figure 3, showing the layout and axle configuration for work trains covered by RL loading. The 20 t hopper is a 7.88 m long vehicle with two axle loads of 16.3 t (160 kN) at 3.96 m spacing, equating to a UDL of 41 kN/m. The tube battery car is 16.85 m in length and applies a total axle load of 62.7 t (615 kN), equating to a UDL of 36 kN/m. The steam crane applies a total axle load of 63.2 t (620 kN) over a length of 16.77 m, a UDL of 37 kN/m. The diesel electric crane applies a UDL of 30 kN/m (total axle load of 46.6 t (457 kN) over 15.63 m). In addition to these vehicles, allowance for typical tamping plant such us those in Figure 4 are also likely to be required. Therefore, designing the structure to a capacity of 0.5 x RL design load would exclude the use of all the work trains described here.

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Figure 3: Extract from BD37/01 showing works trains covered by RL loading

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Equivalent UDL 20.1 kN/m

Equivalent UDL 21.7 kN/m

Figure 4: Typical tamping plant configuration

4.1.2 Summary of vertical loads To cover all the vehicles in section 4.1.1 and allow flexibility to also operate alternative plant, we propose a loading of typically 50kN/m to be appropriate, i.e. RL. However, we propose to adopt full RL loading on one track coexistent with LRV loading on the other track as this restriction can readily be implemented during maintenance operations and may lead to some economy in the design. The design of tramway structures supporting or providing access to ballast track line shall allow for maintenance vehicle load equal to full RL loading to BD37/01. RL loading on one track coexistent with LRV loading on any one other track shall be applied to these sections of track.

4.2 Horizontal loads for maintenance and construction vehicles For sections of track loaded with RL, the appropriate RL horizontal loads from BD 37/01 will be applied.

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4.3 Accidental loads for maintenance and construction vehicles Derailment loads shall be the same as for the LRV i.e. 100kN applied horizontally. Accidental loading of a derailed maintenance vehicle shall be full RL loading applied as two line loads 1.4m apart anywhere within 2m either side of the track centre line, including consideration of the alternative RL axle loads (300kN and 150kN) where this gives an effect worse than the uniform load (50 kN/m).

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5 Other Loads

5.1 Highway vehicles Where tramway structures can additionally provide access to highway vehicles, they shall be designed for both loads. Generally, design highway loads are given in Abu Dhabi Municipality Roadway Design Manual (Ref. 2). Design shall assume whichever of the following gives the most onerous case: • Highway loads only • LRV loads only • Mixed loads but LRV loads not shorter than 40m Longitudinal and horizontal loads from highway vehicles and LRVs shall be considered simultaneously.

5.2 Pedestrian loading All public footways shall be designed for BD 37/01 pedestrian loads. Emergency, cess and evacuation walkways shall be designed for the same loading unless agreed otherwise in individual cases.

5.3 Wind loads The wind loading required to be applied on a structure depends on the geographical location and structure characteristics. Factors such as the topography and terrain of the surrounding area, and the horizontal dimensions and cross-section of the structure or element under consideration determine the loading to be applied. The method described under BD37/01 or an agreed equivalent standard shall be used to determine the wind loading to be applied. For wind load coexistent with live load, designers shall assume trams to be 4m high. Apply wind load to an assumed 4m high side face over the full length of the structure. This shall be assumed to be transmitted to the deck by appropriate horizontal and vertical forces applied at each rail. Further guidance for wind velocity values can be found in Abu Dhabi Municipality Road Design Manual (Ref. 2) Part 3: clause 201.6, appropriate for this geographical location.

5.4 Temperature loading Temperature loading on all structures shall be applied in accordance with Abu Dhabi Municipality Road Design Manual (Ref. 2) Part 3: clause 201.8. Any structures with an unjointed length greater than 100m shall require special discussion, as thermal effects may lead to the need for unusual track joints and create difficulties for the future design of the track and trackform

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6 References 1. Design Manual fro Roads and Bridges (DMRB), The Highways Agency, HMSO, February 2009. 2. Roadway Design Manual: Road and Bridges, Abu Dhabi Municipality, 2009. 3. “Load appraisal report for Merseytram”, ref 205066/205066/L1/STR/00/A, Mott MacDonald, July 2004 4. “Design Loads & Spatial Parameters”, ref 221214/TNXX, Mott MacDonald, January 2008 5. “Report on Loading and Design Criteria for Tram Structures”, ref 241592/000/REP/003/B, Mott MacDonald, August 2008 6. “Guidance on Tramways: Railway safety publication”, Office of Rail Regulation, UK, November 2006. 7. UIC Code 776-3R “Deformation of Bridges”, International Union of Railways, 1989. 8. BD 2/05 “Technical Approval of Highway Structures” DMRB Volume 1 Section 1 Part 1, 2005. 9. NR/SP/CIV/003 “Technical Approval of Design- Construction and maintenance of Civil Engineering Infrastructure”, 2004 10. BD 37/01 “Loads for Highway Bridges”, The Highways Agency, HMSO, August 2002. 11. “The Railway Safety Principles and Guidance, Part 2, Section G, Guidance on Tramways”, HSE, 2005 12. “Transportation Research Record: Effects of deceleration and rate of deceleration on live seated human subjects”, Transportation Research Board Business Office, USA, 1977. 13. “Steel, concrete and composite bridges Part 10 – Code of practice for fatigue”, BS 5400 Pt 10, British Standards Institution, 1980 14. “Recommendations for the Design of Bridges”, GC/RC5510, Railtrack, August 2000 15. “Bridge Loads”: O’Connor, Colin and Shaw, Peter, SPON Press, 2000, pg 255. 16. “Analysis and Design of Reinforced and Prestressed Concrete Guideway Structures”, Report ACI 358.1R-92, American Concrete Institute Committee, 1992. 17. “Assurance” Report 1-538 Issue A1, , 2008.

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