TECHNICAL USER MANUAL. for STANDARD MODULAR OVERBRIDGES. Standard Detail and Design Drawings

Transcription

1 TECHNICL USER MNUL for STNDRD MODULR OVERBRIDGES Standard Detail and Design Drawings Page 1 of 61

2 Summary This technical user manual is applicable to the standard modular overbridges comprising a composite steel/concrete trough deck. It provides guidance on the selection and application of Network Rail s suite of standard drawings. The standard designs and details within these drawings will generally be used for new-build structures, and part replacement e.g. deck replacement. Summary of Key Deck Components Kerb height varies to suit Main Girder Depth Cross 3m Centres (Concrete Infill Between) Site Splices Main Girder Main Girder Deck Soffit Plate (25mm) Deck Component Deck Slab Deck Soffit Plate (25mm) Cross Girders Main Girders Deck End Trimmers Support Bearings/ Jacking Provision Characteristic Features Spans between cross girders at 3m centres Provides redundancy to main steelwork components cts compositely with Deck Soffit Plate Provides permanent formwork for deck slab Forms bottom flange of cross girders & main girders cts compositely with Deck Slab Spans between main girders Provides U-frame restraint to main girder top flange Spliced at third-points to form Modular Deck Relies on additional support derived from deck slab Spans between deck end trimmers dditional load path provided by deck slab Main girder depth governs kerb height to carriageway Provides support to ends of main girders Spans between proprietary pot bearings above end abutments Proprietary pot bearings below end trimmers Bearings experience dual-curvatures due to trimmer and main girder deformations Critical Design Parameter Provides 100mm concrete cover to cross-girders. Thickness governed by cross-girder depth Principal stresses associated with local bending & main girder/cross girder participation Deck width/skew Depths governed by moments at bolted splices Deck span Depths governed by top flange stresses at mid-span Deck width and span Depths governed by cantilever moments above support bearings Deck width and span Depth available for jack installation above common bearing plinth Page 2 of 61

3 Schedule of Standard Drawings The standard deck details are summarised on twenty drawings. The design of most key deck components has been fully developed, including precamber requirements. limited number of aspects will require site specific assessment, including foundation details, and temporary jacking arrangements. The following table highlights aspects requiring site specific assessment: Drawing No. Drawing Title Items Requiring Site Specific ssessment NR/CIV/SD/2500 General Notes None NR/CIV/SD/2501 Cross Girder Layout for a Range of Spans Intermediate spans/skews may require alternative setting out NR/CIV/SD/2502 Urban Option Cross Sections Highway authority approval of kerb details NR/CIV/SD/2503 Rural ll Purpose Option Cross Highway authority approval of kerb details Sections NR/CIV/SD/2504 ccommodation Option Cross Highway authority approval of kerb details Sections NR/CIV/SD/2505 Cross Girder Splice Details Bolt setting-out for intermediate skews NR/CIV/SD/2506 End Trimmer Details Bolt setting-out for intermediate skews NR/CIV/SD/2507 Trimmer Splice Details Bolt setting-out for intermediate skews NR/CIV/SD/2508 NR/CIV/SD/2509 NR/CIV/SD/2510 NR/CIV/SD/2511 NR/CIV/SD/2512 NR/CIV/SD/2513 Shear Stud Layout and Weld Details Sheet 1 of 2 Shear Stud Layout and Weld Details Sheet 2 of 2 lternative Longitudinal Deck Joint Detail Urban Option Plans, Elevations and Sections (Typical Example) Erection Scheme Layout for Rural ll Purpose and Urban Options Erection Scheme Layout for ccommodation Option Modifications to cross girder rebar holes if lternative Deck Splice adopted Modifications to cross girder rebar holes if lternative Deck Splice adopted Choice of lternative Deck Splice or standard splice detail Choice of parapet system, site specific foundation details Method of placing Pour 2 deck slab concrete beneath main girder top flange to suit highway vertical alignment s above NR/CIV/SD/2514 Bearing Schedule Consideration of bearing/plinth heights to suit sitespecific jacking requirements (Section 4.14) NR/CIV/SD/2515 Typical Deck Reinforcement Details Modifications to cross girder rebar holes if lternative Deck Splice adopted NR/CIV/SD/2516 NR/CIV/SD/2517 NR/CIV/SD/2518 NR/CIV/SD/2519 Reinforced Earth butment and Cill Details Reinforced Concrete Pad Foundations Vertical lignment and Superelevation Details Drainage Details and Service Duct Locations Choice of abutment type, site specific foundation details and jacking clearance requirements Choice of abutment type, site specific foundation details and jacking clearance requirements Choice of normal crossfall or superelevation Highway authority approval of 100mm dia. drainage outlet. Main girder/footpath depth may be increased to suit large diameter services Page 3 of 61

4 Issue record This technical user manual will be updated when necessary by distribution of a complete replacement. vertical black line in the margin will mark amended or additional parts of revised pages. Revision Date Comments Draft 1 July 2010 Draft issue for comment Draft 2 Draft re-issue Form B pproval Page 4 of 61

5 CONTENTS GLOSSRY 7 1 INTRODUCTION TO STNDRD DESIGNS ND DETILS Network Rail s Requirements 9 2 GUIDNCE FOR USE OF NETWORK RIL MODULR OVERBRIDGE DESIGNS pproval of Schemes Using Standard Designs & Details Drawing Selection Flowchart 13 3 MODULR OVERBRIDGE PPLICTION DETILS Scope of pplication Loading Criteria Typical Construction Details Utility Provision on Bridge Decks 17 4 DETILS OF STRUCTURL FORM Geometry and Configuration Span Ranges Skew Ranges Floor Widths Headroom and Lateral Clearances Construction Depths Main Girder Depths and Kerb Details Parapet Options Modular Form of Deck Construction Main Girder Details Floor Type Deck End Trimmers Bearings Deck Jacking rrangements Sub-Structure Options lignment Considerations Guidance for Design of Bespoke Deck Geometries 40 5 INSTLLTION GUIDNCE Deck Steelwork Erection Options Temporary Works Requirements for Modular Deck Installation Steelwork Jointing Details 44 Page 5 of 61

6 5.4 Full Construction Sequence Special Considerations During Deck Installation Trial Erection Installation Tolerances 47 6 GUIDNCE FOR USE OF THE MODULR BRIDGE STNDRD DESIGNS ND DETILS General rrangement Drawing General ssembly Drawings Details Drawings Span and Skew Ranges Considered Concrete to trimmers Deck Surfacing, Drainage and Waterproofing Steelwork Protective Treatment Substructure and ncillary Items Bonding/Stray Current/Insulation 51 7 FBRICTION 52 8 SFETY/CDM ND ENVIRONMENTL 52 PPENDIX PPENDIX B PPENDIX C DESIGN SSUMPTIONS/LODING HIDDEN PRTS STNDRDS Page 6 of 61

7 GLOSSRY Bearing Bridge Cill Cross Girder Deck Designer Filler Beam Floor Impost Main Girder Protective Treatment Scheme SDD The elements on which the deck is supported, via deck end trimmers. deck and its supporting structure (e.g. cill/impost beams, abutments). lternative name for impost. The concrete beam on which the lower part of the bridge bearings are supported. The secondary load sustaining element that spans between main girders and supports the in-situ concrete slab. Comprises an I-shaped beam with a thick, narrow top flange, a vertical web, and a wide, thin bottom flange also forming the exposed soffit of the deck. pair of supporting main girders and floor between. The person responsible for selecting the relevant standard designs and details to suit the specific requirements of a particular scheme. steel and concrete floor arrangement comprising transverse spanning steel sections encased within and acting compositely with a concrete slab. The transverse element that supports the carriageway and footways, comprising steel transverse cross girders, and steel soffit plate acting compositely with the in-situ concrete slab. lternative name for cill. The (usually) concrete beam on which the lower part of the bridge bearings are located. The primary load sustaining element that spans between abutments and supports the floor. Comprises an unsymmetric beam with a thick, narrow top flange, a vertical web, and a wide, thin bottom flange also forming the exposed soffit of the deck. treatment applied to structural elements to protect them from the environment. ny planned work that involves the replacement of an existing bridge or deck. Standard Designs and Details Page 7 of 61

8 Trief Kerb raised precast concrete kerb with a concave recess facing the carriageway designed to protect against errant vehicles by trapping the bulge in tyre sidewalls, preventing wheels from climbing up the kerb and safely redirecting them onto the carriageway in a line dictated by the kerb. Trimmer Beam The first cross member spanning between support bearings. Trimmers extend beyond corner bearings to provide (cantilever) support to the main girders. TUM Two-Stage Pour Technical User Manual Process of placing the in-situ concrete infill in two, separate operations, rather than a single, full depth pour. Concrete allowed to gain sufficient strength between successive pours that primary slab pour acts (partially) compositely with supporting steelwork to reduce overall deflections and locked-in steelwork stresses. Due to large shear flows in (composite) slab, first stage pour would require suitable surface preparation (eg. scabbling, blasting) to ensure good bond with second pour. Waterproofing Measures applied to top surface of concrete deck slab to prevent water infiltration into structural elements. Page 8 of 61

9 1 INTRODUCTION TO STNDRD DESIGNS ND DETILS The development of the Standard Designs and Details (SDD) has been undertaken by Network Rail to improve safety, asset reliability and increase efficiency. Their development is linked to Network Rail s overall business objectives to improve reliability of the railways and reduce the funding requirements for the on-going management and maintenance. The basis of the SDD focuses on two main areas that derive from these issues: Ensuring that the design meets Network Rail s requirements The design is as successful as the designs of previous railway engineers, who built and maintained bridges that have given good service for approaching 150 years. 1.1 Network Rail s Requirements Network Rail s requirements are split between two areas cost effective delivery, and function: Delivery Requirements The SDDs have been taken to a stage where Form s and Bs for each aspect covered (overbridge design, ancillaries etc.) have been submitted and approved. This leads to the following benefits: reduction in the design development timescales and costs. Minimising contractor and sub-contractor costs associated with uncertainties in detailing requirements. Streamlining the technical approval process for commonly used designs and details Functional Requirements The SDD have been designed to ensure satisfactory performance of the asset under both normal operations and abnormal operations (both planned and unplanned). further consideration has been Network Rail s requirement to reduce the volume of maintenance and management costs through the adoption of good practice. This leads to a number key design drivers including: Failure modes critical failure modes should give warning, and alternative load paths should be provided for potential local failures. No hidden details all main structural elements should be visible from at least one side. Robustness it is desirable for elements of the structure to have a degree of robustness so that they are not damaged by unforeseen events disproportionate to the cause. Capability to support load cceptable deformations Page 9 of 61

10 Structure gauge requirements the overbridges have been designed to cater for a range of positions of the structure gauge allowing their wide use. Safe working environment the bridges have been designed to minimise the risk to people on or about the bridge. These and other functional requirements are defined in Network Rail standard NR/L2/CIV/020 (Draft 012) and the requirements therein have been met in designing the Modular Overbridges. Page 10 of 61

11 2 GUIDNCE FOR USE OF NETWORK RIL MODULR OVERBRIDGE DESIGNS The underlying philosophy of this standard is that a single modular overbridge design is provided, together with general details of the other components (i.e. main girders, deck floor, bearings, protective treatment, waterproofing etc.) which go to make up a standard overbridge superstructure. This allows the designer to produce a specific bridge design to suit the particular span, skew, carriageway width, highway geometry, requirements of any particular location with the minimum of design and drawing time, so long as they are within the limits of validity of the standard. The flowchart in figure 2.1 demonstrates the use of the technical user manual and standard drawings. The designer should analyse the constraints and requirements that exist for the specific project site. This information should be used in conjunction with the design advice contained within the technical user manual, to decide which elements can be taken from the suite of standard designs and details and which items, if any, need bespoke design. This designer output and the series of standard drawings can be combined to produce the final Modular Overbridge solution. Specific Site Requirements Technical User Manual Designer Output Standard Drawings Overbridge Design Figure 2.1: Flowchart showing use of Network Rail s Standard Details & Designs This manual describes the 2010 standard for highway overbridges using a half through construction arrangement of main girders with a steel/concrete composite floor. It is intended to be read in conjunction with the set of standard drawings listed on Page 3. This manual is intended to aid the designer in producing an individual bridge design using this standard, or in comparing this standard with other solutions. The manual discusses issues that will need to be covered in a contract specification for a bridge of this type, but is not intended to form part of any contract documentation. Scheme specific design is still required to determine the overall bridge layout. The designer will also have to have to produce survey, proposed general arrangement, substructure details, track clearances and setting out drawings, as necessary. This will include the bridge steel layout and may require consideration of precambers to compensate for deflections during in-situ concreting. Page 11 of 61

12 The deck and other components have been designed to cater for a wide range of spans, skews and highway geometry. For situations outside these parameters, the standard cannot be assumed to be applicable. Equally it will be obvious that the design here, in catering for such a wide range of circumstances, will inevitably involve conservatisms on specific aspects and for specific bridge arrangements. Thus it may be possible to use the existing design in whole or part outside the given limits without modification, or to achieve a less substantial design (e.g. lower weight) within those limits, but again in both cases they will need approval, full re-design, and an appropriate check. If such a course of action is favoured these are matters that will need discussion with the client and with Network Rail s Professional Head of Civil Engineering. 2.1 pproval of Schemes Using Standard Designs & Details The SDDs for each modular overbridge form have been submitted and approved by Network Rail at both Form and Form B stages of the Network Rail approvals process; this has included a Category 3 Check. The flowchart in Figure 2.2 demonstrates the general process of using the SDDs and TUMs. Determine site parameters Does the proposed overbridge fit within the SDD options? NO Bespoke Form and B required for the Overbridge YES Determine Overbridge type Form already approved by Network Rail for SDD Overbridge SDD & TUM Requires Check and Network Rail approval Form B required for non SDD elements e.g. abutment stems, embankments Scheme Specific General rrangements, detail drawings & Reinforcement Schedules Standard Drawings of all other elements Full scheme specific drawings & Form B Figure 2.2: Process using the Standard Drawings and Technical User Manuals Page 12 of 61

13 The designer will need to produce a scheme specific Form for the site under consideration. This Form will detail the site specific parameters and the particular SDDs that will be used. Following Form approval the designer will need to produce general arrangement and general assembly drawings, and any necessary substructure related drawings, including reinforcement schedules, and finishes details. The SDDs have been approved (Form B). Therefore the checking required for each specific scheme will be of the general arrangement and any substructure related drawings, including reinforcement schedules, to ensure they are suitable in meeting the scheme requirements. 2.2 Drawing Selection Flowchart The flowchart presented in Figure 2.3 may assist the designer in deciding the options to select and which drawings to use in detailing a standard modular deck. Page 13 of 61

14 General Notes, Drawing List & TUM ccom. Type of Deck, Span & Skew ngle Urban Kerb Height Governed by Span (may require Highway uthority pproval) Rural P Cross-girder Layouts 2501 Cross-girder Layouts 2501 Cross-girder Layouts 2501 Main Girder Depth Governed by Span Cross-Section 2504/2518 Cross-Section 2503/2518 Cross-Section 2502/2518 Trimmer Details 2506/2507 Cross Girder Depth Governed by Skew Is Construction ccess to Soffit vailable? NO YES Cross-Girder Splices 2505 Cross-Girder Splices 2510 lternatively Consider Non- Standard Fully-Welded Cross Girder Splices if Headroom Critical Deck Shear Studs, Rebar Details and Weld Sizes 2508/2509/2515 Precamber Info V&G V6 Determine Parapet Type Corus P365 Increased Verge/Footpath Widths Minimum Verge/Footpath Widths Long End nchorage Simple End Connection Determine Parapet Fixing Detail 2511 Bearing Schedule 2514 Reinforced Earth Sub-Structure Type Pad Foundation Details 2516 Details 2517 Services and Drainage 2519 Erection Methods 2512/2513 Figure 2.3: Determination of Standard Details for a Modular Overbridge Page 14 of 61

15 3 MODULR OVERBRIDGE PPLICTION DETILS The standard Modular Overbridge design may be used at any suitable location in UK. The standard drawings provide a complete set of details for the superstructure including the bearings and substructure elements. For a particular bridge, the designer needs to determine the specific layout, choose the appropriate drawings, add the necessary dimensions and exercise specific options on these standard drawings. Details are also provided for substructure elements. Substructures comprise reinforced earth, or conventional reinforced concrete abutments (new-build applications) or reinforced concrete cills onto existing masonry abutments (deck replacements). The substructures and approach embankments are intended to provide vertical clearances between the top of rail and the soffit of the deck of 5.2m minimum and 5.7m enhanced for new build situations. Clearances for reconstructions will be determined by existing highway and rail alignments and are to be confirmed by the scheme designer. 3.1 Scope of pplication The drawings cater for spans from 8.5m to 22m (square to abutments) in nine increments and skews from 0 to 30 in three increments (i.e. 0, less than 15 and less than 30 ). Three standard deck arrangements are considered: Designation Carriageway Widths Footway Widths Verge Widths Total Between Parapet Faces Urban 2 x 3.65m 2 x 1.80m (min) n/a 10.90m (min.) Rural ll Purpose 2 x 3.65m 1 x 1.80m (min) 1 x 0.60m (min) 9.70m (min.) ccommodation 1 x 3.65m n/a 2 x 0.60m (min) 4.85m (min.) Table 3.1: Deck rrangements Considered in Standard Details The designer should choose the relevant drawings for the particular bridge type, span and skew range from the full set of standard drawings. Refer to flowchart in Figure 2.2. It is intended that only those standard drawings relevant to the specific contract are issued to the contractor as part of the contract drawings, together with general arrangement drawings particular to the specific bridge. The general arrangement drawing prepared by the designer will specify all principal dimensions and sizes, including material grades. Standard drawings relevant to the particular bridge should be listed on the general arrangement drawing. Page 15 of 61

16 The designer should choose the relevant drawings for the particular bridge type, span and skew range from the full set of standard drawings. The standard drawings were not developed to be used as fabrication drawings. If the designer wishes to produce accurate bridge specific drawings then most views will need adjustment to the dimensions chosen for the particular bridge. 3.2 Loading Criteria The design loading criteria adopted for the standard details is summarised in Table 3.1. Further information is provided in ppendix B. Design Highway Loading Load Models 1 & 2 in accordance with BS EN Special Vehicle Loading Load Model 3 as represented by SV100 in accordance with N to BS EN Footway Loading Load Model 4 in accordance with BS EN Provision for Exceptional Loads (if any) None Standard of Parapet Containment H4(a) in accordance with BS EN 1317 Table 3.2: Design Loading Standards pplicable to Standard Modular Overbridge Designs Other loading standards may require modifications to deck details. 3.3 Typical Construction Details Figure 3.1 illustrates a typical Urban deck cross-section. Road Traffic Design Speed 70mph (max) Design speed dependent on vertical curvature Main Girder Main Girder Figure 3.1: Typical Urban Deck Cross-Section Cross 3m Centres (Concrete Infill Between) The deck comprises a series of regularly spaced cross girders spanning between edge main girders. The main girders span between deck end trimmers supported on proprietary pot bearings. Cross-girders and end trimmers are subsequently encapsulated in in-situ concrete, topped with sprayed waterproofing and mm of highway surfacing. 25 mm steel floor plate is used for all decks. Page 16 of 61

17 half-through form of construction is adopted, with the deck floor below main girder top flanges. This offers a particularly shallow form of construction comparable with traditional filler-beam decks. Typical construction depths measured from the top of roadway centreline to underside of deck soffit are in the range mm (depending on deck type), inclusive of 125mm deck surfacing and waterproofing. Parapets are fixed directly to the top of the main girders. The decks are designed to accommodate two alternative High Containment parapets: 1. conventional Corus post-and-rail system total width 682mm. 2. n alternative Varley and Gulliver V6 system total width 455mm. Varying kerb heights are used to accommodate the variation in main girder depths with span (see Figure 3.2). Increased kerb heights may also be used to accommodate large diameter services. Short-Spans Decks Long-Span Decks Shallow/Narrow Main Girder (Low Kerb Height) Deep/Wide Main Girder (High Trief Kerb) Figure 3.2: Typical Construction Details for Short-Span & Long-Span Urban Decks The standard cross-section incorporates a normal crossfall, although superelevation and vertical curvature can also be accommodated - see Section Utility Provision on Bridge Decks The standard decks have been detailed with service provision in the footway infill, above structural slab level. On short-span decks, footway construction would generally be limited to around 220mm, limiting service provision to around 150mm diameter ducts. However, scope exists for footpath construction to be made deeper if dictated by larger diameter services. Main girder depths would have to be increased to suit, as illustrated in Figure 3.2 above. Standard details for longer-span decks inherently cater for larger service ducts via increased main girder depths. Ducts of up to 450mm diameter could be accommodated in 22m span, skewed decks. Larger ducts could be accommodated via bespoke detailing. Page 17 of 61

18 4 DETILS OF STRUCTURL FORM The basic form of the structure comprises a composite steel and concrete trough deck superstructure supported by reinforced concrete cill units on existing substructures for reconstruction situations, or reinforced concrete abutments for new build situations. continuous steel soffit plate forms the base of the trough and acts as permanent formwork for the deck slab which acts compositely with the steel deck. The soffit plate is profiled to suit the highway vertical alignment and extends over the complete area of the deck acting as the bottom flange of both the cross girders and the main girders. The main edge girders have vertical webs and wide top flanges to minimise construction depths and provide the necessary mounting width for the parapet. Figure 4.1 illustrates some typical cross sections. The overall depth of the structure ranges from 765mm to 1255mm. Figure 4.1: Typical Steelwork Details a) Transverse Cross-Section b) Longitudinal Section (Main Girders not Shown for Clarity) The external steelwork contains the reinforced concrete elements of the composite deck for convenient site casting and to avoid vulnerable external steel/concrete interfaces and crevices. The smooth external profile minimises protruding features or ledges thus avoiding corrosion traps and roosting platforms and is especially efficient for future maintenance. The web plate can be profiled to the highway alignment (including precamber) and will assist with efficient achievement of the necessary headroom clearances. It is arranged to over-sail the bottom flange by 20mm to ensure a good line to the soffit and to act as an effective drip to run off from the outer face. Cross girders, generally spaced at 3.0m centres comprise a steel tee welded to the floor plate. The web of each tee extends to the full distance between the main girder webs and returns upwards to meet the underside of the main girder flange to create a diaphragm/stiffener in the main girder. The cross-girder web also serves as a U-frame restraint to the main girder top flange in the (sagging) bending region. Cross girder flanges are curtailed near to their ends to avoid a slotted detail at the upturn of the web and transverse welding to the main girder web. Cross girders are Page 18 of 61

19 nominally 550mm deep for the widest (Urban) deck but reduce to 345mm for narrower decks. Cross girder spans and composition also vary with deck skew. Deeper end trimmers are provided on the centre line of bearings over the abutments with the floor plate folded down and the main girder webs profiled to follow for neat external appearance avoiding any requirement for check walls on the abutment cills. End trimmers are nominally mm deep (depending on deck width and main girder span). Trimmers incorporate bearing stiffeners approximately 900mm in board from the deck edge to allow bearings to be mounted on abutments of limited width (such as when high containment parapets demand extended deck widths). Proprietary pot bearings are provided at each support location to provide rotation capability about both plan axes to cater for wet concrete and in-service deformations. Trimmers have designated jacking locations for future maintenance provision and for new build situations opportunity exists to re-detail the bridge ends to incorporate semi-integral construction removing the need for expansion joints. On completion of erection, all cross-girders and trimmers are encapsulated in concrete. To limit overall construction depth, the reinforced concrete floor slab provides a minimal 100mm cover to the top of the cross girders to limit corrosion damage, mobilise composite strength and provide a durable top surface for normal waterproofing and surfacing systems. The lower edge of the deck concrete is contained at the end of the deck by the folded floor plate and the web of the trimmer. The top surface of the slab extends over the top of the trimmer and encapsulates the rear face to provide a durable encasement at the expansion joint. Permanent access for inspection of steelwork elements and connections is limited by the presence of the deck slab concrete. However, once the steelwork is encapsulated, there should be little or no reason to inspect these components during their service life. The steelwork soffit and edge girder should be visible for inspection from below, or possibly via road mounted access gantry. The deck end expansion (asphalt plug) joint) is likely to require regular access for inspection and repair. This is accessible from above deck level. 4.1 Geometry and Configuration The designer will need to utilise the following Railway Group Standards (or their successors, where appropriate): GE/RT8073 Requirements for the pplication of Standard Vehicle Gauges. GC/RT5112 Loading Requirements for the Design of Bridges. GC/RT5203 Infrastructure Requirements for Personal Safety in Respect of Clearance and ccess. GC/RT5212 Requirements for Defining and Maintaining Clearances. GE/GN8573 Guidance on Gauging NR/L2/CIV/020 Design of Bridges and Culverts GC/RC5510 Recommendations for the Design of Bridges. Page 19 of 61

20 4.2 Span Ranges Spans have been selected to allow the structure to span single to four track sections of line at skews of up to 30 o. Span ranges vary from 8.5m to 25.4m. The main girders are sized in 2m increments see drawings NR/CIV/SD/2502 to NR/CIV/SD/2504. For simplicity, main girder and trimmer scantlings for each deck type are defined in terms of Longitudinal Bearing Centres, rather than square span as this implicitly caters for any conceivable skew angle. longitudinal bearing spacing of 25.4m is equivalent to a square span of 22m at 30 o skew. Cross girder scantlings remain constant with span but vary with skew angle and deck type. 4.3 Skew Ranges The design skew range, on bearing centre line, is 0 o to 30 o (maximum). 4.4 Floor Widths Floor widths are measured as the clear distance between inner edges of main girder top flanges. Three floor widths have been considered in the standard details: Designation Total Between Parapet Faces No. 3.65m Wide No. 1.8m Wide No. 0.6m Wide Urban 10.90m (min.) 2 No. 2 No. None Rural ll 9.70m (min.) 2 No. 1 No. 1 No. Purpose ccommodation 4.85m (min.) 1 No. None 2 No. Table 4.1: Floor Widths for Varying Deck Types 4.5 Headroom and Lateral Clearances The substructures and approach embankments will be developed to provide vertical clearances between the top of rail and the soffit of the deck of 5.2m minimum and 5.7m enhanced for new build situations. Clearances for reconstructions will be determined by existing highway and rail alignments and are to be confirmed by the scheme designer. 4.6 Construction Depths The construction depth is defined as the depth from the top of carriageway surfacing at roadway centre-line to the underside of steelwork (main girder web downstands) as illustrated in Figure 4.2. Bolt heads at splice positions potentially project to a greater depth, but in instances where headrooms are critical, an option exists for all bolts to be fixed above deck level (see Section 4.9) or to use countersunk HR studs into (thickened) soffit cover plates. The 20mm projection under the main girder webs should therefore generally be critical. Page 20 of 61

21 Construction Depth Main Girder Depth Figure 4.2: Definition of Construction Depth for Modular Overbridges Floor depths vary between deck types, but have been detailed to be independent of the longitudinal span of the deck. constant floor depth is used for each deck type. Increasing spans are accommodated by increasing the size of main girder webs and top flanges. Main girder depths vary from 765mm to 1230mm, depending on deck type. End trimmer sizes also vary with main girder span. ll other steelwork details remain constant. For ccommodation decks (only), a constant 765mm depth main girder is used for all spans. This represents a minimum practicable dimension governed by depths of cross girders, deck slab, and footpaths. Construction depths have been determined assuming 125mm of surfacing and waterproofing. Table 4.2 provides a comparison of Span : Construction Depth Ratios for each type of modular deck with an alternative Precast Concrete Beam deck. Precast concrete decks include a mm allowance for an in-situ topping slab, depending on span. Longitudinal Bearing Centres 8.5m 10m 12m 14m 16m 18m 20m 22m 24m 25.4m CCOMMODTION DECKS Precast Concrete Deck Total Construction Depth 625mm 650mm 750mm 895mm 900mm 1085mm 1165mm 1245mm 1385mm 1385mm Modular Deck Total Construction Depth 590mm Precast Concrete Deck Span : Construction Depth Ratio 13.6 : : 1 16 : : : : : : : : 1 Modular Overbridge Span : Construction Depth Ratio 14.4 : : : : : : : : : : 1 RURL P DECKS Precast Concrete Deck Total Construction Depth 716mm 741mm 841mm 986mm 991mm 1176mm 1256mm 1336mm 1476mm 1476mm Modular Deck Total Construction Depth 781mm Precast Concrete Deck Span : Construction Depth Ratio 11.9 : : : : : : : : : : 1 Modular Overbridge Span : Construction Depth Ratio 10.9 : : : : : : : : : : 1 URBN DECKS Precast Concrete Deck Total Construction Depth 716mm 741mm 841mm 986mm 991mm 1176mm 1256mm 1336mm 1476mm 1476mm Modular Deck Total Construction Depth 846mm Precast Concrete Deck Span : Construction Depth Ratio 11.9 : : : : : : : : : : 1 Modular Overbridge Span : Construction Depth Ratio 10.0 : : : : : : : : : : 1 Table 4.2: Comparison of Span : Construction Depth Ratios for Modular Overbridge Decks and Precast Concrete Beam lternative The modular deck offers a similar construction depth to precast concrete beams for short spans (<12m). Modular decks become considerably more efficient at longer spans construction depths are approximately halved. It should also be noted that modular decks could readily accommodate thinner surfacings for decks where a Page 21 of 61

22 minimal construction depth is critical, subject to the recommendations of IN 96/07, particularly bond strength, deformation and asphalt mixture requirements. 4.7 Main Girder Depths and Kerb Details Main girder depths vary with span but floor depths remain constant for each deck type. Parapet details dictate that footways remain at a constant depth below the main girder top flanges (see Section 4.8). s a result, varying kerb heights are used to accommodate the variable depth of the main girders. Kerb upstands vary in the range mm. Figure 4.3 illustrates the variation in typical construction details for a short and long-span Urban deck. Short-Spans Decks Shallow/Narrow Main Girder (Low Kerb Height) Long-Span Decks Deep/Wide Main Girder (High Trief Kerb) Figure 4.3: Typical Construction Details for Short-Span & Long-Span Urban Decks The longitudinal span of the deck generally dictates the kerb detail used. Main girder depths/kerb heights could be increased further to enhance scope for service provision in the decks. Long span decks generally use a 370mm deep GST2 Trief kerb, which should be sufficient to cater for most large diameter gas or pumped mains. The possible use of Trief kerbs will require Highway uthority approval on a site-specific basis. The use of high kerbs is a consequence of the required depth of main girder, or utility provision. Trief kerbs are not intended to serve as a substitute for H4a parapets. Footway/verge falls provide some tolerance in the selection of main girder depths and kerb heights. Footway falls could vary between 1:60 to 1:20, giving 65mm tolerance. Verge falls could vary between 1:60 to 1:15, giving 38mm tolerance. Page 22 of 61

23 4.8 Parapet Options The decks are designed to accommodate two alternative High Containment parapets: 1. conventional Corus post-and-rail system total width 682mm. 2. n alternative Varley and Gulliver (V&G) V6 system total width 455mm. Both systems satisfy High (H4a) Containment standards in accordance with BS EN The Corus system satisfies working width class W4, the V&G system W3. Further alternatives could also be considered, subject to testing and certification in accordance with BS EN The two systems have different cross-section widths and setting out requirements. The deck cross-sections have been developed to cater for both systems. Figure 4.4 illustrates a typical Urban deck cross-section. Figure 4.4: Footway Setting out Parameters to ccommodate lternative Parapet Types The Varley and Gulliver system is designed to sit flush with the supporting parapet plinth. The Corus system projects 160mm forward from the plinth, potentially impacting upon the available footway/verge width. To cater for this, steelwork is detailed to give a 1960mm offset from the face of kerb to edge of main girder. This allows a minimum footpath width of 1800mm to be maintained for both parapets. It is highly unlikely the alternative parapets would ever be used in combination in this way, but the design ensures future flexibility is retained for parapets to be replaced with alternative systems during the operational life of the structures. Similar setting out parameters are used on Rural P and ccommodation decks to ensure a 600mm (minimum) verge width is maintained for both parapet types. Both parapet systems dictate the underside of parapet/top of main girder must remain within mm of the adjacent back of footpath level to satisfy standard test Page 23 of 61

24 arrangements. The normal (30mm max) bedding grout below parapet posts is omitted with the steel sub-grade, giving a limiting mm offset dimension between back of footway level and top of main girder. Design ranges for crossfalls on footpaths and verges give some tolerances on kerb heights associated with each prescribed main girder depth. However, given the omission of the normal bedding grout, tolerances for parapet installation are potentially very tight - packing allowance is limited to 20mm. Furthermore, main girder deflections during wet concreting of the in-situ deck slab are potentially significant. Final fabrication details for parapets may therefore have to take account of as-built site geometries. The geometries of both parapet systems dictate a minimum 600mm wide top flange. For longer span decks, the flange width increases. For these decks, a full-length anticlimb plate is anticipated to deter trespass and bird roosting. The parapet fixings are restrained by chemical anchors through the main girder top flanges into the in-situ concrete deck. The two parapet systems have differing fixing requirements. The Corus systems requires 4 M33 anchors set-out on a square grid. The Varley and Gulliver system uses smaller M16/M20 anchors as shown on Figure 4.5. Figure 4.5: nchorage Requirements for lternative Parapet Types The concrete edge beam provided beneath the parapet is 490mm wide narrower than the standard 600mm. Torsion calculations indicate a 490mm beam is adequate in this instance. The edge beam also benefits from composite interaction with the main girder webs. Top flange stresses are critical to the sizing of the edge main girders. The holes formed in the top flange potentially increase these stresses. The main girder sizes prescribed on drawings NR/CIV/SD/2502 to NR/CIV/SD/2504 have been derived on the basis of a pair of adjacent 60mm parapet holes to cater for either parapet system. These could conceivably be reduced for V&G parapets, but oversized holes may still be required to accommodate grout venting during concrete placement (see Section 5.5). The two parapet systems also have differing end anchorage details, requiring differing run-on/run-off lengths at the ends of the deck. The Varley and Gulliver system relies Page 24 of 61

25 upon particularly long anchorages - approach lengths of 24m and departure lengths of 18m are generally required. Parapet loads on the approach structures are likely to require the provision of buried retaining structures as indicated in Figure 4.6. The choice of parapet may therefore be constrained by individual site conditions. Figure 4.6: Typical pproach/departure & Retaining Structure rrangements for V&G V6 Parapets Page 25 of 61

26 4.9 Modular Form of Deck Construction The deck steelwork has been detailed to be delivered to site in full span lengths (up to 26.3m long) but divided into transportable widths (or Modules ) across transverse cross-sections. Decks are typically divided into two or three modules, depending on deck widths as illustrated in Figure 4.7. Edge Deck Module Variable Depth with Edge Main Girder Centre Deck Module Constant Depth Edge Deck Module Variable Depth with Edge Main Girder Deck Type Total Deck Width No. of Deck Modules Width of Outer Edge Modules Width of Centre Deck Modules Urban 13020mm (max) Three 4710mm 3600mm Rural ll Purpose 11820mm (max) Three 3510mm / 4710mm 3600mm ccommodation 6970mm (max) Two 3485mm n/a Figure 4.7: Build-up of Typical Modular Units for Various Deck Types Outer modules incorporate edge main girders. For wider, Urban and Rural ll-purpose decks, inner modules comprise constant depth cross-girders and floor plates only. ccommodation decks comprise a pair of Edge Modules only. Each module is made in widths suitable for fabrication, transportation and erection, typically metres. s lengths do not exceed 27m, each module remains within normal STGO vehicle limits. However, special arrangements may be anticipated for access to remote, rural sites. Longitudinal splices between deck sections comprise HR bolts to facilitate site jointing. Cover-plated lapping joints are provided for the deck soffit, cross girder and trimmer web plates and flanges (see Figure 4.8). With this arrangement, most bolting can be undertaken from above only the soffit plate bolts require access from below for installation. n option exists to use countersunk HR studs into (thickened) soffit cover plates in structures with reduced headrooms. n alternative splice detail has also been devised which allows all bolts to be installed from above deck level with no requirement for separate access facilities over the tracks (see Figure 4.9). In both cases, split cover plates are used on all cross-girder top flanges to assist rebar installation in the topping concrete. Page 26 of 61

27 Figure 4.8: Typical Cross-Girder Splice Details long Longitudinal Joints Figure 4.9: lternative Deck Soffit Splice Detail With ll Bolting bove Deck Level lternatively, deck modules could be fully assembled on the ground adjacent to the bridge site, then lifted into place as a fully assembled bridge unit prior to wet concreting (subject to suitable craneage being available). Site pre-assembly also offers the potential to use fully welded joints between deck modules. This could potentially reduce overall construction depths as bolted splices generally govern cross-girder/slab depths. This is discussed further in Section The alternative splice detail originally indicated on the Form drawings was found to be inadequate during detailed design and has been substituted with the above details. Further guidance on deck installation, erection, jointing options and temporary works requirements are provided in Section 5.0. Page 27 of 61

28 4.10 Main Girder Details Main girders comprise unsymmetric fabricated sections with vertical webs and wide top flanges to limit construction depths and provide necessary mounting widths for parapets. Parapet details dictate the deck floor, surfacing and footway construction has to be accommodated within the depth of the main girders. The main girder top flange has to remain within mm of the adjacent back of footpath level, with a minimum 600x40mm top flange. s a result, each deck type has a minimum main girder depth and cross section for short-spans. Minimum and maximum girder sizes and span ranges for each type of deck are summarised in Table 4.3. Deck Type ccommodation Rural P Urban Range of Minimum & Maximum Main Girder Sizes & Overall Depths Top Flange 600 x x 60 Web 20 x x 705 Bottom Flange 25mm Overall Depth mm Top Flange 600 x x 80 Web 20 x x 1075 Bottom Flange 25mm Overall Depth 895mm 1155mm Top Flange 600 x x 80 Web 20 x x 1175 Bottom Flange 25mm Overall Depth 960mm 1255mm Limiting Span Range for Minimum Main Girder 18.0 m 12.0 m 12.0 m Table 4.3: Minimum Main Girder Sizes and Span Ranges Main girder sizes are generally governed by top flange stresses at parapet hole positions. Standard girder sizes allow for two number 60mm diameter holes in all cases. For longer spans, main girder webs and top flanges increase to limit cumulative stresses in the top flange. For Rural P and Urban decks, main girder depths vary by up to 295mm. This is accommodated by varying kerb heights between the roadway and footways transverse floor details remain constant. The edges of the deck the slab are thickened by mm to meet the underside of the main girder flanges and encapsulate the parapet anchorage bolts. This thickening also enhances the stiffness of the composite edge girder. Normal concrete placing is obstructed by the presence of the main girder top flange, but a sound joint is required up to the underside of the steelwork. Forming this upstand may require the use of a Page 28 of 61

29 self-compacting concrete mix and/or a high strength grout placed from the deck ends and vented via the enlarged bolt holes at parapet post positions. Composite shear flows between the main girders and deck slab infill concrete are maintained by shear studs welded to the main girder webs and top flange. Shear studs on the deck soffit plate are also locally enhanced local to main girder webs. Figure 4.10: Shear Stud Provision on Main Girder Web & Top Flange and Local Stud Enhancement on Soffit Plate Local to Main Girders The presence of the top flange shear studs may necessitate the fabrication of main girders as T-sections prior to fixing of shear studs and welding to the deck soffit Floor Type Floors comprise a steel plate, stiffened with transverse cross girders that span between the main girder inner webs through welded end connections. The cross-girder web also serves as a U-frame restraint to the main girder top flange in (sagging) bending regions. Floors are fabricated in units suitable for fabrication and erection, typically metres wide, which are longitudinally bolted together with HR fasteners, through soffit cover plates. The cross girders are subsequently encapsulated in in-situ concrete, topped with sprayed waterproofing and mm of highway surfacing. Trimmer girders are also encased in concrete and connected to the main girders through end welded connections. 25 mm floor plate is used for all decks. This limits cross girder spacings to 3m maximum, primarily due to wet concrete stresses in the floor plate. Floor plate deflections and stresses are potentially at a maximum at the deck ends due to lack of continuity. Cross-girder-to-trimmer centres are locally reduced to 1m at deck ends to cater for this end flexibility. Minimum cross girder spacings may also be applicable in some instances to ensure satisfactory clearances for welds and shear stud installation. Standard cross-girder geometries are shown on drawing NR/CIV/SD/2501. Page 29 of 61

30 The deck soffit plate experiences a complex combination of combined bending and shear stresses. These may be broken down incrementally as summarised in Table 4.4: Stress Component Principal Components Bending Stresses Shear Stresses System I Stresses Soffit plate spanning as (continuous) steel only element between cross-girders Stresses derived almost entirely from wet concrete loads Very Significant Negligible System II Stresses Soffit plate forming bottom flange of cross-girder spanning transversely between main girders. Stresses derived approximately equally between (steel only) wet concrete loads and (composite) live loads Significant Significant System III Stresses Soffit plate forming bottom flange of main-girder spanning longitudinally between abutments. Stresses derived approximately equally between (steel only) wet concrete loads and (composite) live loads Very Significant Table 4.4: Minimum Main Girder Sizes and Span Ranges Significant The cumulative effect of these stress components is complex as critical locations tend not to be coexistent. System II stresses peak at mid-span of the cross-girders (along deck centreline). System III stresses peak beneath main girders (at deck edges). Bending stresses are also mitigated by membrane effects derived from deck end rigidity. ccurate determination of principal stresses in the deck soffit may thus require the use of a 3D FE model. For normal design purposes, deck soffit stresses may be deemed to be adequate on the basis of modelling undertaken for the standard deck layouts provided concrete slab thicknesses (and thereby wet concrete stresses) do not exceed the standard slab thicknesses proposed. Cross girder/floor depths are governed by ULS moments at cross-girder splice positions. Minimum web depths/bolt rows for each deck type and splice are summarised in Table 4.5. Deck Type Minimum Number of Web Bolt Rows Minimum Cross Girder Web Depth Maximum Deck Slab Thickness ccommodation 4 300mm 420mm Rural P 6 430mm 611mm Urban 7 490mm 676mm Table 4.5: Minimum Main Girder Sizes and Span Ranges Page 30 of 61

31 Cross girder splice depths determine corresponding transverse floor depths, and thereby the minimum main girder depths listed in Table 4.3. The deck slab contributes to overall composite strength and stiffness. However, placing the wet concrete also contributes significantly to permanent locked-in steel (System I) stresses. It is therefore crucial to note that deck slab thicknesses should not be increased beyond these limiting values without structure-specific justification. Lightweight concrete or a two-stage pour could also be considered, subject to strength and durability considerations. Shear flows local to cross girder webs would be a critical consideration. Site joints between modules use HR bolts through cover plates to the floor plate soffit and cross girders and trimmers, as discussed in Section 4.7. n option exists to use countersunk HR studs into (thickened) soffit cover plates in structures with reduced headrooms. The cross-girders act compositely with the surrounding concrete infill. Composite shear transfer is achieved via rebar passed through the cross-girder webs at low level. The deck slab also incorporates a top layer of anti-crack reinforcement. Early thermal cracking and composite shear flows dictate the use of B16 rebar at 150mm nominal centres. End trimmer details are similar, but also include shear studs within the girder webs to enhance bond with the deck end concrete (see Figure 4.11). Rebar Fed Thru Cross-Girder and Trimmer Webs Figure 4.11: Composite Shear Flow Provision on Transverse Floor Beams Rebar continuity cannot be maintained at cross-girder splice positions bottom longitudinal bars are locally closed-off with U-bars. t splice positions, transfer shear flow is deemed to be locally maintained by the 19(+) HR bolts either side of the splice centre line. Shear flows are reduced at these (mid-span) positions. Shear studs are also provided along the deck soffit to maintain a consistent bond with the infill concrete. Stud provision is locally enhanced at the deck edges to cater for composite shear flows adjacent to main girders. Deck slab rebar is detailed to cross transverse shear planes associated with each shear stud. The presence of shear studs below cross girders may necessitate their installation prior to cross girder fabrication. For skewed decks, normal cross girder splices potentially clash between web and flange connections. Connections have been detailed to ensure bolts can be installed and tensioned for skews up to 30. Page 31 of 61

32 4.12 Deck End Trimmers ll end trimmers are fabricated sections. Trimmers are nominally mm deep (depending on deck width and main girder span) and incorporate bearing stiffeners approximately 900mm in board from the deck edge to allow bearings to be mounted on abutments of limited width (such as when high containment parapets demand extended deck widths). Trimmers comprise a symmetrical I-Section girder, welded at their ends to main girder webs. Trimmer top flanges follow a consistent profile to the general cross-girders, but have a greater overall depth. The base of the trimmers is welded to the ends of the (25mm) floor soffit plate which is folded down at a 45 slope to tie-in with the underside of the trimmers. Figure 4.12: Typical Deck End Trimmer Steelwork Details The trimmers are integral with the main deck floor and are transversely spliced across adjacent deck modules using HR fasteners, through soffit cover plates. Normal through-bolted connections are considered exclusively for end trimmers as access will inevitably be required adjacent to abutments for bearing installation, etc. Connections have been detailed to ensure bolts can be installed and tensioned for skews up to 30. The trimmers are subsequently encapsulated and act compositely with the in-situ concrete floor. Composite shear transfer is achieved via rebar passed through the trimmer webs at approximately mid-depth. Composite action with the trimmers is important to enhance mid-span stiffness to limit live load deflections along asphaltic plug joints. Shear studs are also provided along the girder webs to prevent debonding of the deck end concrete via segregation above the trimmer web. Page 32 of 61

33 The projection of the trimmer concrete beyond the end of the trimmer steelwork also provides a zone for drainage penetrations through the deck. Surface/Sub-Surface Drainage Provision (100mm Dia.) Max. Short Radius Bend With Rodding ccess Figure 4.13: Typical Deck End Trimmer Rebar, Shear Stud and Drainage Details Drainage outfalls would be limited to 100mm diameter to maintain clearances to deckend trimmer rebar. Highway authorities generally stipulate 150mm diameter gully outlets, so drainage details will require highway authority approval on a site-specific basis. Trimmers have designated jacking locations for future maintenance provision and for new build situations opportunity exists to re-detail the bridge ends to incorporate semiintegral construction removing the need for expansion joints. Page 33 of 61

34 4.13 Bearings Decks are supported on proprietary pot bearings positioned below end trimmer beams, approximately 900mm inboard of the edge main girders. This allows bearings to be mounted on abutments of limited width. s a consequence, bearings experience dualcurvatures associated with combined deflections in the trimmer girders as well as main girders. This prevents the use of fabricated rocker bearings as inward rotations during wet concreting are significant about both plan axes. Outline bearing schedules for each deck type are included on drawing NR/CIV/SD/2514. These have been developed in accordance with the latest guidance in Eurocode EN1337. The scheduled reactions, displacements and girder end rotations are based on the (longest) 22m, 30 skew span decks and should consistently represent worst case values. For completeness, drawing NR/CIV/SD/2514 also includes a schedule of reduced bearing reactions for decks with shorter spans. However, values for girder end displacements and rotations are based exclusively on the longest spans. In the event these prove excessive, benefit may be taken of the reduced end deflections and rotations associated with shorter spans decks. These would need to be derived on a job specific basis. critical constraint in bearing selection is the limited width of the trimmer bottom flange which is a constant 500x40mm section for all deck types and spans. The bearing schedules have been developed on the basis of proprietary PSC Tetron bearings which generally limit the longitudinal width of the bearing top plate to 500mm. Standard Tetron bearings potentially have a top plate width in excess in 500mm for the heaviest Urban and Rural P decks. However, these are designed to accommodate longitudinal movements of up to 100mm. For the modular decks, longitudinal displacements are generally limited to 35mm. However, Eurocode EN1337 includes a blanket requirement to add ±50mm to calculated longitudinal displacements (Cl. 5.4). This is considered excessively onerous for these short-span decks. Furthermore, it is understood that at the time of writing, EN1337 is undergoing substantial restructuring and revision to rectify preliminary errors. Given the anticipated amendments in future editions of this standard, it is not deemed necessary to apply this guideline in full. Partial relaxation of these requirements is sufficient to satisfy the 500mm constraint on top plate width. Cl. 5.4 also includes a requirement to add ±0.005 radians to calculated rotations. This is included in the NR/CIV/SD/2514 schedules, but may exceed typical rotation limits for proprietary pot bearings. The scheduled rotations are based on the (longest) 22m, 30 skew span decks and should consistently represent worst case values. For shorter span decks, job specific evaluation of applied loads, end displacements and rotations should satisfy proprietary bearing rotation limits. lternatively, the validity of the ±0.005 Page 34 of 61

35 radian addition may be questioned if girder end rotations have been rigorously derived. End rotations are greatest in long-span accommodation decks as (relatively flexible) 765mm deep main girders are used for all spans. On skewed decks, bearings should be aligned to suit trimmers, with bearing top and bottom plates aligned to suit the deck ends Deck Jacking rrangements Trimmer girders include internal jacking stiffeners, with an external jack locator and spreader plate, for use in the event of bearing maintenance or replacement. The jacking point is set in-board of the main bearings, but at a short (500mm) offset. This is intended to limit cantilever moments during jacking to enable the decks to remain in-service (at least partially) during bearing replacement operations. Figure 4.14: View on Typical Jacking rrangements Bearing fixing bolts are fixed at shallow depth into cast-in sockets in abutment plinths, and at shallow depth into the deck bearing plates to facilitate easy removal. Jacking heights should normally be limited to around 3-10mm. Figure 4.15: Bolt Removal to Facilitate Bearing Replacement The jacking scheme has been devised with the intention that the bridges could remain open to traffic during jacking operations to minimise temporary highway diversions. To Page 35 of 61

36 prevent overstress in the trimmer cantilevers, live loads will have to be limited/controlled during jacking. It is tentatively estimated that this could be achieved with the following traffic restrictions in place: Deck Type ccommodation Rural P Urban Traffic Restriction During Jacking None possible lane narrowing to avoid direct traffic loading above jacking point Deck narrowed to single lane running with traffic signal control. Operational lane offset relative to jacks. Deck narrowed to single lane running with traffic signal control. Operational lane offset relative to jacks. Table 4.6: nticipated Lane Restrictions During Bearing Replacement Operations Given the proximity of the jacking point to the main bearings, the abutment cills have been detailed to provide a common support plinth to the main bearings and the (temporary) jacks. This potentially limits available jack clearances and spreader plate depths. Drawings NR/CIV/SD/2516 and NR/CIV/SD/2517 indicate available clearances for one particular jacking option using Enerpac Single cting, Pancake Lock Nut Cylinder Jacks. lternative manufacturers may provide greater clearances. Bearing pressures on the concrete plinth beneath jacks could potentially govern live load capacities during jacking. In this event, the following site specific options may be considered: i) Consider operational live load requirements during jacking. ii) Increase thickness of bearing plate above bearing - generally 55mm. iii) Increase grout thickness below bearing. iv) dding supplemental lower or upper subplates to the bearing base plates/top plates. v) Use deeper pot bearings possibly non-standard top/bottom plates. vi) Use high strength concrete for plinth upstands. vii) Use cast-in spreader plate within plinth. viii) Use shallower jacks. ix) Consider possible (local) enhancements to concrete crushing strength due to edge confinement, etc. Options should be chosen on a site specific basis to suit available traffic diversion routes. In some instances, live loading may not need to be accommodated during temporary jacking operations. During any jacking operations, the integrity of longitudinal and transverse restraints to the deck should be carefully considered. For low jacking heights, keep-plates within fixed/guided pot bearings normally remain effective. However, in the event of full bearing removal, alternative means of (temporary) restraint may need to be considered. Page 36 of 61

37 4.15 Sub-Structure Options The decks are designed to be supported on reinforced concrete cills on top of existing abutments in reconstruction situations. Similar reinforced concrete cill units are proposed for new build situations where reinforced earth approach embankments are proposed. Where conventional earth embankments are adopted, the superstructure will be supported on a reinforced concrete abutment with wing walls provided to retain the fill. The size and shape of all sub structure options are the same at bearing shelf level, with plinths sized to accommodate the bearings and jacks (for future bearing replacement). Slopes are provided towards the back of the units to provide drainage from the bearing shelf. The size of the cill unit sitting on an earth embankment is governed by three factors; a) The bearing centreline is located as close as possible to the cill unit centreline to ensure equal pressures b) The nominal dead load pressures are limited to 150kPa under the cill unit c) Desirable for the vertical wall of the reinforced earth abutment to be 2m from the bearing centreline (although this figure can be reduced to 1m). The design of the reinforced earth abutment is part of this scope of works, but advice from specialists should be obtained if this type of foundation is to be used. For the design of a conventional abutment, two sets of ground conditions were assumed to determine soil properties at founding level a) Granular c =0kN/m 2 & Φ =35 o b) Cohesive c =5kN/m 2 & Φ =28 o In BS EN 1997, for every scenario (dead only, dead + live, dead + live + wind etc), two load combinations are considered. The first combination applies factors to the loading, and the second combination applies factors to the material. combination without factors is also considered to determine an overall factor of safety (OFS). This can then be compared with the British Standards. Results from combination 1 and for the OFS give similar utilisations to the British Standard method if the soil parameters given above were taken as design values (i.e mobilisation factors have already been taken into account). However in combination 2, applying a material factor of 1.25 to tan Φ, reduces the angle of shearing resistance from 35 degrees to 29 degrees (in the case of the granular material). This angle is used to determine the bearing resistance factors N c N q & N γ. lthough the reduction in angle is relatively small, there is a large change in these factors (i.e. N γ reduces from 45 to 17). This greatly reduces the allowable bearing resistance and this combination will govern designs to Eurocode 7. Page 37 of 61

38 Results from combination 2 give similar utilisations to the British Standard method if the soil parameters given above were not taken as design values (i.e design values based on applying mobilisation factors). The concrete pad foundations provided on drawing NR/CIV/SD/2517 are based on granular ground conditions by only considering combination 1 of EN 1997, and illustrate the range of base sizes for the different bridge types and spans. No solutions are provided for combination 2 of EN1997 or for the cohesive ground as a pad footing is not appropriate. ll foundations are site specific and are to be designed based on actual soil properties. Varley and Gulliver parapets also require the addition of buried retaining structures for approximately 20m either end of the deck. The substructures and approach embankments are intended to provide vertical clearances between the top of rail and the soffit of the deck of 5.2m minimum and 5.7m enhanced for new build situations. Clearances for reconstructions will be determined by existing highway and rail alignments and are to be confirmed by the scheme designer lignment Considerations Rural P and Urban decks have been detailed to suit alignments with normal crossfalls. Cross girders increase in depth towards mid-span to ensure their (steel-only) construction depths are maximised at intermediate splice positions. Decks with superelevation can also be accommodated. However, it is imperative that deck slab thicknesses do not exceed the limiting values given in Table 4.5 to prevent overstress of steel-only elements during wet concreting. To maintain this limiting slab depth, decks with superelevation have been detailed with a constant slab thickness as illustrated in Figure Tapering sections should not be used on decks with superelevation. Figure 4.16: Decks Details Incorporating Superelevation ccommodation decks are intended to provide a single lane carriageway. These are less likely to adopt balanced crossfalls as standard one way falls are more probable. For these decks, a constant steelwork and slab depth is proposed, consistent with the superelevated deck illustrated above. This is likely to represent the standard installation arrangement for ccommodation decks. lternatively, a normal-crossfall may be accommodated by simply increasing surfacing thicknesses towards the deck centre-line. Page 38 of 61

39 Decks have also been detailed to accommodate alignments requiring vertical curvature. Deck slab thicknesses should not be increased beyond limiting values. It is therefore necessary for the deck soffit steelwork to reproduce any curvature introduced on the deck surface. Decks should not be constructed with a flat soffit and a humped top profile without site specific assessment of resulting steelwork stresses and bearing parameters. Figure 4.17 illustrates this requirement. Figure 4.17: Decks Incorporating Vertical Curvature Page 39 of 61

40 4.17 Guidance for Design of Bespoke Deck Geometries Standard steelwork sizes for each deck type are prescribed on drawings. In the event site conditions dictate the use of alternative deck geometries, construction depths, etc., the following summary of critical design parameters may be useful for preliminary sizing of bespoke details. Note that the list may not be exhaustive normal design procedures should still be used to fully determine and assess critical parameters. Deck Component Deck Slab Deck Plate Soffit (25mm) Cross Girders Main Girders Deck End Trimmers Support Bearings/Jacking Provision Critical Design Location Slab generally not critical thickness governed by cross-girder depth. Do not increase further. Rebar sizes governed by early thermal cracking and composite shear flows from cross girders Soffit plate experiences complex range of principal stresses derived from: Local bending between cross girders Bending stresses and shear flows associated with cross girder bottom flange Bending stresses and shear flows associated with main girder bottom flange Deck soffit stresses derived principally from wet concrete (steel-only) loads. Live load (composite) stresses less significant. Bolted splices at mid-span/third-points. Bolt forces and web plate (principal) stresses at top of web govern. ULS top flange stresses to be limited to around 180 N/mm 2 for acceptable splice stresses. Suggested Method of nalysis nalysis not critical but grillage analysis required to assess loadsharing from cross girders and main girders Finite Element Model. Individual stress components can be estimated manually, but interactions and membrane effects vary considerably at differing locations on plan. Combined interactions best assessed using FE model, possibly limited to steel-only properties for determination of wet-concrete principal stresses. Grillage analysis essential to realistically assess longitudinal support derived from deck slab. Local line beam analysis excessively conservative Note if further reductions in construction depth are required, consideration may be given to site pre-assembly of decks, with fully welded cross-girder connections. This could result in shallower cross girder depths, with subsequent reductions in slab thickness/main girder depths etc. Suitability for site pre-assembly would be dependent on site craneage limits. lso consider thin surfacings to IN 96/07 Mid-span top flange stresses at parapet hole positions Girder depth governs kerb height to carriageway Web principal stresses due to cantilever moments above bearings (combined bending and shear). lso principal stress above jacking stiffener during bearing replacement. Depth available for jack installation above common bearing plinth Grillage analysis beneficial to quantify alternative load path through deck slab Hand calculation using main girder end reactions Table 4.7: Guidance for Design of Bespoke Deck Geometries Consider operational live load requirements during jacking. Consider supplemental bearing baseplates/top-plates to enhance depth available for jacks. Page 40 of 61

41 5 INSTLLTION GUIDNCE The modular decks are designed to be simply-supported or semi-integral above end abutments. It is assumed that road closures are arranged for preparatory works, services diversions, demolition and deck installation. The deck steelwork has been detailed to be delivered to site in full span lengths (up to 26.3m long) but divided into transportable modules across transverse cross-sections. Decks are typically divided into two or three modules, depending on deck widths as illustrated in Figure 5.1. Edge Deck Module Edge Deck Module Centre Deck Module Variable Depth with Edge Main Girder Constant Depth Variable Depth with Edge Main Girder Deck Type Urban Rural ll Purpose ccommodation Total Deck Width 13020mm (max) 11820mm (max) 6970mm (max) No. of Deck Modules Width of Outer Edge Modules Width of Centre Deck Modules Three 4710mm 3600mm Three 3510mm / 4710mm 3600mm Two 3485mm n/a Figure 5.1: Build-up of Typical Modular Deck Units for Various Deck Types Outer modules incorporate edge main girders. Inner modules comprise constant depth cross-girders and floor plates only. ccommodation decks comprise a pair of Edge Modules only. Each module remains within normal STGO vehicle limits. However, special arrangements may be anticipated for access to remote, rural sites. 5.1 Deck Steelwork Erection Options Steelwork for the decks has been designed to be installed by mobile road cranes, either as a series of modular units, or by lifting in complete spans. For modular installation, supplemental temporary works are required. Temporary works requirements are greatly reduced for preassembled decks. Page 41 of 61

42 For modular installation, each module could be erected separately during a short eight hour possession/isolation with permanent connections subsequently made with the environment separated from the track zone by the completed trough. Nominal lifting weights are limited to a maximum of 55 tonnes for the longest spans as summarised in Table 5.1. Deck Type Width of Outer Deck Modules Estimated Craneage Wt. Edge Module 55 tons (approx) 48 tons (approx) 33 tons (approx) Total Steelwork Wt. Pre-ssembled Deck 135 tons (approx) 110 tons (approx) 65 tons (approx) Urban (22m Span, 30 o 4710mm skew) Rural ll Purpose (22m Span, 30 o 4710mm skew) ccommodation (22m Span, 30 o 3485mm skew) Table 5.1: Estimated Craneage Weights for Largest Deck Modules and Pre- ssembled Decks (Steelwork Only) If site craneage allows, pre-assembly of a complete deck could significantly reduce temporary works, minimising the number of possession activities and overall construction time. Fully-assembled decks weigh up to 135 tons. Welded splices between deck modules could also be considered, which may offer further weight and construction depth savings (see Section 4.9). 5.2 Temporary Works Requirements for Modular Deck Installation For modular installation, each deck unit comprises a maximum of one main girder. It is therefore impractical for any individual module to span between end abutments without temporary works. Temporary works requirements are most onerous for centre deck modules. It is proposed these should be erected first, with temporary edge stiffening girders fitted along both edges. These (temporary) girders span the whole length of the deck, providing independent support to the centre module via temporary bearing pads constructed behind permanent bearing cills. Stiffening girders comprise a pair of UBs depending on spans. ll temporary works are installed above deck level to minimise possible impact on the operational railway beneath. Figure 5.2 illustrates proposed erection details for the centre deck module. Page 42 of 61

43 Figure 5.2: Temporary Support Girders for Centre Deck Module Once the centre module is in place and supported on its temporary bearings, outer modules can be craned-in alongside. Outer modules have a (stiff) main girder along one edge, and use a temporary stiffening girder along their in-board edge to balance the section. Stiffening girders comprise UCs depending on deck spans. Calculations indicate the temporary UC edge girders will be sufficient to support the inner edge of the deck panels, provided support cleats are correctly positioned. However, deflections could be much greater than along the opposing edge. s a result, they may be some draping effect when edge panels are offered-up to the pre-erected centre module. Stiff packing plates have been detailed below UCs to oversail the edges of the outer modules such that they also serve as a landing-cleat when erected alongside the centre modules, see Figure 5.3. Figure 5.3: Temporary Stiffening Girder/Landing Cleat for Outer Deck Module This edge draping effect will mean contact will be uneven when panels are first abutted together. This will require careful control of site craneage to ensure a smooth landing is achieved. ccommodation decks have similar erection procedures, but with smaller edge stiffening girders. Full details are provided on drawing NR/CIV/SD/2513. With the deck steelwork in place, all subsequent construction operations are confined above deck level, outside possession. full construction sequence is outlined in Section 5.4. Page 43 of 61

44 5.3 Steelwork Jointing Details Longitudinal splices between deck modules comprise HR bolts to facilitate site jointing. Cover-plated lapping joints are generally provided although an alternative splice detail has also been devised which allows all bolts to be installed from above deck level with no requirement for separate access facilities over the tracks (see Figure 5.4). Figure 5.4: Typical Cross-Girder Splice Details and lternative Deck Soffit Splice Detail With ll Bolting bove Deck Level Both details are suited to early matched assembly at works to ensure fit up at site. End trimmers are also spliced across adjacent deck modules using HR fasteners. Normal through-bolted connections are considered exclusively for end trimmers as access will inevitably be required adjacent to abutments for bearing installation, etc. ll connections have been detailed to ensure bolts can be installed and tensioned for skews up to 30. For sites using full site pre-assembly, fully welded splices may be considered which may offer further weight and construction depth savings. Page 44 of 61

45 5.4 Full Construction Sequence The envisaged sequence of deck erection, is set out below. For less constrained sites, decks may be pre-assembled for a single crane lift of the whole deck. In these cases, Stages 1-10 may be omitted, with the complete deck lowered directly onto the permanent bearings. 1. Deliver central unit to site with erection/stiffening frame pre-attached to cross girder top flanges to control deflection of panel 2. During Possession - Erect central unit with pre-attached erection/stiffening frame and lower onto temporary bearings on or behind abutment walls 3. Deliver first edge unit to site and fit erection tackle and temporary landing cleats to cross girder top flanges to control deflection and permit alignment of holes with central unit 4. During Possession - Erect first edge unit and offer to central unit landing on temporary jacks at designated jacking positions. Jacks and cross girder landing cleats each fitted with adjustment facilities to permit early release of crane 5. Final alignment of first two units to permit alignment of bolt holes and fit/tighten sufficient bolts to permit release of temporary edge stiffening girder. Complete bolting up 6. During Possession - Erect second edge unit and offer to central unit landing on temporary jacks at designated jacking positions. Jacks and cross girder landing cleats each fitted with adjustment facilities to permit early release of crane 7. Final alignment of third unit to permit alignment of bolt holes and fit/tighten sufficient bolts to permit release of temporary edge stiffening girder. Complete bolting up 8. djust to final location, raise deck on jacks till temporary bearings can be removed at ends of centre module erection frame 9. Remove erection frame bearings. Lower jacks till deck rests onto permanent bearings and grout up 10. During Possession - Release erection/stiffening frame and remove from site 11. Fix deck reinforcement 12. Cast first stage concrete slab including shuttered section at deck ends 13. Cast second stage concrete to inside faces of main girders (may require use of self-compacting/self-levelling mix). Good quality/composition of second stage pour essential due to parapet anchorages, main girder shear flows, etc. 14. Cast abutment road slab 15. Waterproof deck 16. Fit services and parapets 17. Surfacing and finishes Page 45 of 61

46 5.5 Special Considerations During Deck Installation The detailed design of modular erection schemes should pay particular attention to the following: Component Edge Support Girders Steelwork Precambers Deck Slab Concreting (Main Pour) Deck Slab Concreting (Secondary pour to main girder top flanges) Support Bearings Suggested Measures to be dopted UBs prescribed for edge girders sized on basis of span lengths shown on drawings and 0.5 kn/m2 construction live load allowance during erection. Loads/spans in excess of these limits will require larger sections. Regular restraints to girder top flanges required via bracing frameworks as shown on drawings. Deck steelwork will experience significant deflections during wet concreting. Steelwork to incorporate longitudinal and transverse precambers to maintain soffit profile proposed. Packing shims below temporary erection frame steelwork sized to suit precambers. Limiting concrete thicknesses for each deck type must not be exceeded to control locked-in stresses. Estimated precambers listed on drawing NR/CIV/SD/2518. If necessary, designer may consider two-stage pour for the deck infill concrete to limit peak deflections. Surface preparation between successive pours should account for shear flows through the infill concrete adjacent to cross- & main-girders. Screed rails (or similar) for deck concreting should be fixed to deck steelwork (not end abutments) to ensure constant deck slab thickness maintained in conjunction with (potentially large) deck deflections during concreting. Concrete to be placed uniformly across entire deck concrete should not be heaped against to individual cross girders or trimmers. Final concrete pour to underside of main girders offers very limited access for concrete placement or compaction. Concrete has to be consistent quality to main deck pour due to composite shear flows from main girders, and parapet anchorage requirements. Consider use of self-compacting/self-levelling mix and/or high strength grout placed from deck ends and vented via enlarged bolt holes at parapet post positions. Bearings experience dual-curvatures associated with combined deflections in the trimmer girders as well as main girders. Inward rotations during wet concreting are significant about both plan axes. Wet concrete deflections will influence final bearing specification. If necessary, consideration may be given to jacking deck following concrete placement to reset bearings such that they have to cater for (far smaller) live load rotations only. Parapet Normal parapet base plate bedding grout omitted - tolerances potentially very tight. Installation lso main girder deflections during wet concreting potentially significant. Parapets details may need to take account of as-built site geometries. Table 5.2: Special Considerations Required During Deck Installation Page 46 of 61

47 No additional stiffening is required if the bridge is erected using the standard elements and standard lifting points but where the bridge is erected as a whole unit or other combination of elements, separate calculations must be carried out in each case to ensure that the elements are not overstressed during erection. Specific calculations may be required to satisfy certain erection methods, but in general the amount of any temporary stiffening is likely to be minimal. Standard lifting cleats should be provided on the temporary lifting beams to suit a crane with 60 maximum sling inclination. The lifting cleats will require valid test certificates for use as lifting tackle. lternative appropriately sized and test certified lifting cleats may be used if proposed by the Contractor. It is envisaged that girders are fabricated and delivered to site full length, but in exceptional cases a site welded or bolted splice could be incorporated to allow delivery in two lengths. design with appropriate design and check certificate for the splice needs to be submitted by the scheme designer (or the Contractor, if he makes the proposal) for approval. ll bearings and anchor plates should be set to the correct relative levels. The bearings, particularly at the free end should be checked for verticality. It is important that some provision for adjustment remains to allow for construction tolerances and distortions due to the full dead loads. 5.6 Trial Erection It is recommended modular overbridges are subject to a full trial erection. This is particularly important given the large precambers required to accommodate wet concrete deflections. The trial erection should include all superstructure elements. ncillary items such as parapets should be excluded from trial erection as fixing points are liable to deflect during wet concreting. During the trial erection all bolts should be at least hand tightened. ny HR bolts that are fully torqued during the trial erection must be marked and discarded after the trial erection. 5.7 Installation Tolerances If the deck is being installed by crane then it has been assumed the decks could be positioned within 10mm of the design position on plan. Vertical positioning tolerance of 10mm has been considered appropriate as it is assumed the highway profile could be locally adjusted on site if necessary. Page 47 of 61

48 6 GUIDNCE FOR USE OF THE MODULR BRIDGE STNDRD DESIGNS ND DETILS 6.1 General rrangement Drawing General arrangement drawings should be produced in line with Network Rail s requirements for the specific site. However it is expected that these drawings should normally include the following: Plan, bridge elevation and a cross-section through the bridge including the elevation of one abutment and the bridge seating arrangement. Geotechnical information, details at services (railway and other) and details at adjacent infrastructure. Principal dimension information such as span, skew, roadway widths, footway widths, clearances from rail to abutments and deck soffit, bearings, bridge soffit, rail, carriageway and deck end levels. List of drawings forming the complete bridge design. 6.2 General ssembly Drawings The setting out and arrangement of cross girders, trimmers and main girders will be unique in most instances and dependent upon many variables including: bridge span, abutment skew, clearance requirements, highway geometry, carriageway widths, and compliance with minimum and maximum spacing requirements of cross girders. For all deck skews, cross girders and end trimmers are designed to remain parallel. 6.3 Details Drawings Details are provided for all spans and skews for the valid range. Details depend on the splice composition proposed (whether access is available below deck level), parapet type, and substructure support details. This section gives guidance on how the required details should be selected Span and Skew Ranges Considered The drawings cater for spans from 8.5m to 22m (square to abutments) in nine increments and skews from 0 to 30 in three increments (i.e. 0, less than 15 and less than 30 ). The main girders are sized in 2m increments. For simplicity, main girder and trimmer scantlings for each deck type are defined in terms of Longitudinal Bearing Centres, rather than square span as this implicitly caters for any conceivable skew angle. Longitudinal bearing centres are measured parallel to main girders. longitudinal bearing spacing of 25.4m is equivalent to a square span of 22m at 30 o skew. Page 48 of 61

49 Cross girder scantlings remain constant with span. Cross girder details vary between deck types and with skew angle. Where the span required (measured as the longitudinal distance between bearings) is not included on the standard drawings, the details for the next span increment are to be used. Similarly for intermediate skews, eg. 17.4º, the details for deck skews between 15º and 30º should be used. 6.4 Concrete to trimmers Reinforced concrete to the rear faces of the trimmers is provided as protection to otherwise inaccessible faces. The concrete also helps support asphaltic plug joints at deck ends. The standard drawings show the concrete outline and indicative reinforcement and these will require tailoring to suit specific floor width and skew arrangements. Production of customised bar bending schedules to accompany the deck drawings is necessary in all instances. 6.5 Deck Surfacing, Drainage and Waterproofing The basic principles are as follows: Deck surfacing and waterproofing should generally be 125mm thick as required by BD 47/99 for durability. The deck structures could readily accommodate thinner surfacings for decks where a minimal construction depth is critical. The design of thin surfacings should take account of the recommendations of IN 96/07, in particular the importance of sub-surface drainage, bond strength and deformation requirements, and limiting air voids in asphalt mixtures. The top surface of the deck slab must be protected by a waterproofing arrangement to prevent any water/chloride penetration into the reinforced concrete deck slab. Deck slabs must incorporate a transverse crossfall and longitudinal fall (or vertical curvature) to assist in water dispersal from the deck and minimise water penetration through the deck surfacing. Deck slabs include provision for surface drainage outlets above deck end trimmers to minimise run-off over deck end expansion joints. In the event of descent gradients being used on the approach to a bridge, standard road gullies should be provided ahead of end expansion joints. Sub-surface drainage outlets should also be incorporated adjacent to end expansion joints. The waterproofing system should comprise an acrylic spray system with an accredited BB HPS Roads and Bridges Certificate. The deck waterproofing should extend to Page 49 of 61

50 the underside of main girder top flanges and should be returned around the rear face of the deck end trimmers. The deck surfacing thickness includes possible provision for a sand-asphalt protection layer when required by the individual waterproofing system. Positive drainage should be provided to all surface drainage outlets. It is anticipated that discharge would be made by connection to the main highway drainage system at opposite ends of the deck. Where sub-surface drainage constraints prevent this, discharge may alternatively be routed towards the track bed down the front face of the abutments. In this instance, pipework would need to be routed down the front face of abutments, which is not desirable and may have implications on clearances/span requirements. Site specific assessment would be required to establish a suitable point of outfall to prevent possible detrimental impacts on foundations. In these instances, it may be preferable to avoid surface drainage outlets at deck level, with surface flows instead routed over end expansion joints. Surface flows should not be allowed to permeate down the abutment face. Sub-surface outfalls should also be positioned near deck ends. Outfalls would be positioned at the base of parapet/main girder upstands. 32mm diameter Honel dripnose outlets are anticipated in each deck corner. Given the limited discharge volumes associated with sub-surface outlets, discharge direct to the main bearing shelves should be acceptable, albeit avoiding direct discharge onto the raised bearing plinths. 6.6 Steelwork Protective Treatment ll steel surfaces permanently exposed in the final structure will receive protective treatment. The use of weathering steel is not considered viable due to the potential vulnerability of certain main girder details, in particular, the drip at the base of the webs, and the in-board edges of the top flanges which may become covered by roadside debris. The standard steelwork protective treatment specified is a type N1 system in accordance with NR/SP/CIV/002. The protective system is omitted in areas where the steelwork is encased in concrete NR/GN/CIV/002. The standard drawings show details in accordance with NR/GN/CIV/002. Where no guidance is provided the requirements of NR/GN/CIV/002 shall apply. Points to note are as include: Where the concrete finishes at underside of main girder top flanges and at the edges of the trimmer bottom flanges, the protective treatment should extend not less than 25mm into the concreted area and a sealant applied in a rebate in the concrete to minimise the risk of water ingress at the steel/concrete interface. Faying and bearing surfaces (e.g. HR connections, trimmer support positions) are blast cleaned and metal sprayed only, to maintain optimum friction conditions Page 50 of 61

51 with minimum protection. Subsequent layers of protective treatment to be stepped back. Joints carried out on site will need completion of protective treatment after bolting up. Concrete surfaces that may be exposed to chlorides may require hydrophobic pore lining impregnant in accordance with Highways gency Document BD43/03 (Note- recent interim guidance from the H suggests this may no longer be required, but this is yet to be formalised in an IN or BD. Latest guidance to be sought from H website on a project specific basis). Protective treatment should be carried out as far as possible in shop conditions to ensure the maximum integrity and quality. Details are shown on the standard drawings of the residual site joint protection involving hand applied protective treatment. It is envisaged that some remedial site painting will be required, to be carried out in accordance with the Network Rail Specification. 6.7 Substructure and ncillary Items The standard details include the following typical substructure elements: Construction Situation Deck Replacement New build Substructure Details Reinforced concrete cills on top of existing abutments Reinforced concrete cills on reinforced earth approach embankments Reinforced concrete abutments with wing walls for conventional earth embankments Where an existing sub-structure is being reused the scheme design should ensure that there is no significant change in the loads or points of application, and also the adequacy of the existing sub-structure. In all cases, the designer should determine the soil parameters and ensure that the maximum design settlement or allowable bearing pressures under substructures is not exceeded. smooth transition from the stiffness of the approach embankments to the stiffness of the bridge deck may require the use of run-on/run-off slabs. The scheme designer should discuss and agree suitable transition arrangement details behind the abutment with the adopting highway authority. Varley and Gulliver parapets also require the addition of buried retaining structures for approximately 20m either end of the deck which could conceivably be made integral with any approach slabs. 6.8 Bonding/Stray Current/Insulation The designer must ensure that suitable details are provided to ensure that the structure is adequately bonded/insulated/protected from stray currents. Page 51 of 61

52 7 FBRICTION The standard details proposed represent a new form of deck design. Precamber requirements and fit-up tolerances along continuous deck joints are expected to be particularly onerous. Composite shear flows also dictate the use of relatively large fillet welds at web-to-flange intersections and shear stud provision. It is recommended that only experienced steelwork fabricators are engaged to carry out fabrication, for which they should be able to determine their own procedures for ensuring the required quality and geometry is achieved. reas requiring particular attention are listed below: voidance of twist/precambering of main girders to ensure horizontal alignment for parapet installation following deck concreting. The presence of shear studs on the underside of the main girder top flanges may necessitate their fabrication as T-sections prior to fixing of shear studs and welding to the deck soffit. The presence of shear studs below cross girders may necessitate their installation to the deck soffit prior to cross girder fabrication. Trial erection of the bridge with its ancillary components is considered essential refer to section SFETY/CDM ND ENVIRONMENTL It is assumed that the scheme contractor is aware of the risks associated with general construction activities in the railway environment. site specific risk assessment will be required by both the scheme designer and the contractor, for example, site-specific considerations, such as the presence of overhead line equipment (OHLE) or vulnerable services. The general (non site specific) risks associated with the bridge design, construction and operation are listed on drawing NR/CIV/SD/2500. primary risk is associated with the modular overbridge design are the works conducted at height above a live railway environment. The design has specifically sought to address this issue through the use of modular (off-site) prefabrication. The deck soffit serves as permanent (participating) formwork, virtually eliminating any requirement for temporary works below deck level. Environmental issues can only be determined on a site by site basis, bridge aesthetics including its colour, should be considered also. The effect of renewing the corrosion protection system on the environment, particularly any watercourses, should be taken into consideration during the selection of the elements of the protection system. Page 52 of 61

53 PPENDIX DESIGN SSUMPTIONS/LODING Structural models Deck components are generally simply supported. However, decks are designed to offer alternate load paths wherever possible, especially for the in-service, composite condition. The deck slab provides additional longitudinal stiffness to the deck, providing an alternate load path to the edge main girders. The deck slab also provides an effective load spreading platform onto the cross girders, reducing mid-span bending effects. The deck slab is considered as un-cracked in accordance with EN Cl Stress checks justify this assumption. Table B1 provides a comparison of live load moments in Urban and ccommodation superstructures for alternative line beam and grillage models. Bridge Type MG Span (m) Skew ngle Main Girder Mid-Span Moments Ratio Line Beam: Grillage Results Cross Girder Mid-Span Moments Ratio Line Beam: Grillage Results ccom Urban Table B1: Comparison of Grillage and Line Beam Live Load Bending Results for Composite Deck Models The alternate load-path provided by the deck slab is particularly apparent for shortspan, wide decks, eg. Urban and Rural P structures. The effect is particularly pronounced in cross-girder results less so for main girders. This redundancy makes the static distribution of loads indeterminate stiffness analysis is generally required. Grillage models should provide a sufficiently accurate representation of the main girder and cross girder live load moments and shears. Figure B1 illustrates a typical grillage layout used for the stiffness modelling of a longspan Urban deck. Page 53 of 61

54 Main Girder Plate/Slab Elements Main Girder End Trimmer Cross Girders End Trimmer Figure B1: Typical Grillage Layout for Composite Deck Model The torsional stiffness of the edge main girder upstands also relieves cross girder midspan moments. Torsional effects are also potentially significant in skewed decks, resulting in uneven end support reactions. Stiffness analysis is therefore critical to the assessment of live load effects. For dead load (steel only) effects, torsional stiffnesses are negligible with no alternate load-paths. For these effects, static line-beam analysis should be sufficiently accurate. Dead load stresses due to wet concrete loads generally contribute between 50-90% of combined stresses in most critical deck components. The accurate assessment of steel-only stresses is therefore just as critical as the assessment of live load effects, but more straightforward. Page 54 of 61

55 Loading The following is a summary of typical design loads derived in accordance with BS EN and BS EN : Permanent ctions Item Density/Load ULS Load Factor (γ G ) Notes Steelwork 78.5 kn/m Ref. EN Table.4 Concrete 25 kn/m Surfacing and Waterproofing 24 kn/m Footway Infill 24 kn/m Ref. EN Table.1 Ref. EN Table.6 N EN requires +55% tolerance on surfacing thickness Preferably lightweight or foamed concrete but density allows possible use of mass 24 kn/m 3 Variable ctions Load Reference ULS Load Factor (γ Q ) Highway Loading Highway Special Vehicle Loading Footways and Verges BS EN Load Models 1 & 2 BS EN Load Model 3 as represented by SV100 vehicle BS EN Load Model 4 Notes 1.35 Load Model 2 discounted - local verifications not critical 1.35 SV100 vehicle 6x165kN axle loads at 1.2m centres. Dynamic amplification factor 1.12(see Table N.2). Characteristic LM3 loads combined with Frequent LM1 loads (Load Group 5) UDL q fk = : 5.0 kn/m 2 Parapets BS EN 1317 H4(a) Containment Transverse BS EN Load Groups 2 & 6 Longitudinal BS EN Load Groups 2 & Load Group 6 using SV100 vehicle marginally more critical based on National nnex parameters 1.35 Load Group 6 using SV100 vehicle marginally more critical based on National nnex parameters Fatigue BS EN n/a Checks generally based on FLM 3 Page 55 of 61

56 PPENDIX B HIDDEN PRTS The standard designs and details have, where possible and practicable, and in accordance with NR/L2/CIV020 (draft 12), minimised the number of structural elements that are considered to be hidden parts, i.e. that cannot be inspected from at least one side. The areas considered as hidden parts on the modular overbridges are listed below, with a description of how the details are protected and how access is provided for inspection. Deck Component Steel floor Steel floor Description of hidden part Shear studs, cross girder webs, top flanges and modular splices Cross girder to main girder connection Main girders Shear Studs Main girders Main girder to trimmer connection Protection provided Encased and protected in concrete. Some redundancy provided in splices by shear transfer through in-situ concrete Encased and protected in concrete. Some redundancy provided by end shear transfer through in-situ concrete Encased and protected in concrete. Encased and protected in concrete. Some redundancy provided by end shear transfer through in-situ concrete ccess provided The bottom flange of the cross-girders is visible from the underside of the deck. No other access The opposite face of the connection is visible from the side elevation of the deck. No other access None. Normal detail The opposite face of the connection is visible from the side elevation of the deck. No other access Trimmers Bearing and Jacking Stiffeners Encased and protected in concrete. Redundancy provided by alternative restraint provided by in-situ concrete None Page 56 of 61

57 PPENDIX C DESIGN STNDRDS Listed below are the standards used in the development of the Modular Bridge. Eurocodes BS EN Road Restraints Systems Part 1 BS EN Road Restraints Systems Part 2 BS EN Road Restraint Systems Part 2 DD ENV Road Restraint Systems Part 4 BS EN 1990: 2002, Issue +1 BS EN : 2002 BS EN : 2003 BS EN : 2005 BS EN : 2003 BS EN : 2005 BS EN : 2006 BS EN : 2003 BS EN : 2004 Terminology and General Criteria for Test Methods (see IN 44/05) Performance Classes, impact test acceptance criteria and test methods for safety barriers (see IN 44/05) Performance Classes, impact test acceptance criteria and test methods for safety barriers (see IN 44/05) Terminals and Transitions (see IN 44/05) Eurocode Basis of Structural Design Eurocode 1: ctions on Structures Part 1.1: General ctions. Densities, self weight, imposed load for buildings. Eurocode 1: ctions on Structures Part 1.3: General ctions. Snow Loads Eurocode 1: ctions on Structures Part 1.4: General ctions. Wind ctions Eurocode 1: ctions on Structures Part 1.5: General ctions. Thermal ctions Eurocode 1: ctions on Structures Part 1.6: General ctions. ctions during Execution. Eurocode 1: ctions on Structures Part 1.7: General ctions. ccidental ctions. Eurocode 1: ctions on Structures Part 2: Traffic Loads on Bridges Eurocode 2: Design of Concrete Structures Part 1: General Rules and Rules for Buildings. BS EN : 2005 Eurocode 2: Design of Concrete Structures Part 2: Concrete Bridges Design and detailing rules. BS EN : 2006 BS EN : 2005 BS EN : 2006 Eurocode 2: Design of Concrete Structures Part 3: Liquid Retaining and Containment Structures Eurocode 3: Design of Steel Structures Part 1.1: General Rules and Rules for Buildings. Eurocode 3: Design of Steel Structures Part 1.5: Plated Structural Elements Page 57 of 61

58 BS EN : Eurocode 3: Design of Steel Structures Part 1.7: General Plated Structures subject to Out of Plane Loading BS EN : 2005 Eurocode 3: Design of Steel Structures Part 1.8: Design of Joints BS EN : 2005 Eurocode 3: Design of Steel Structures Part 1.9: Fatigue Strength BS EN : 2005 Eurocode 3: Design of Steel Structures Part 1.10: Material Toughness and Through Thickness Properties. BS EN : 2006 Eurocode 3: Design of Steel Structures Part 2: Steel Bridges. BS EN : 2005 Eurocode 4: Design of Composite Steel and Concrete Structures Part 2: General Rules and Rules for Bridges. BS EN : 2004 Eurocode 7: Geotechnical Design Part 1: General Rules. BS EN : 2004 Eurocode 7: Geotechnical Design Part 2: Ground Investigation and Testing. BS EN 10025: 2004 Hot Rolled Products of Structural Steels BS :2006 Concrete. Complementary Method of specifying and guidance for the specifier British Standard to BS EN BS :2006 Concrete. Complementary Specification for constituent materials and concrete British Standard to BS EN BS EN 206-1:2000 Concrete. Specification, performance, production and conformity Eurocode National nnexes Doc. No. Issue Date Issue Document Title National nnex to BS June UK National nnex to Eurocode Basis of Structural Design EN1990:2002+1:2005 National nnex to BS EN :2002 December UK National nnex to Eurocode 1: ctions on Structures Part 1.1: General ctions. Densities, self weight, imposed load for buildings. National nnex to BS EN :2003 December UK National nnex to Eurocode 1: ctions on Structures Part 1.3: General ctions. Snow Loads National nnex to BS EN :2005 September UK National nnex to Eurocode 1: ctions on Structures Part 1.4: General ctions. Wind ctions National nnex to BS EN :2003 pril UK National nnex to Eurocode 1: ctions on Structures Part 1.5: General ctions. Thermal ctions National nnex to BS EN : 2005 May UK National nnex to Eurocode 1: ctions on Structures Part 1.6: General ctions. ctions during Execution. National nnex to BS EN : 2006 December UK National nnex to Eurocode 1: ctions on Structures Part 1.7: General ctions. ccidental ctions. National nnex to BS EN May UK National nnex to Eurocode 1: ctions on Structures Page 58 of 61

59 1991-2: 2003 Part 2: Traffic Loads on Bridges National nnex to BS EN : 2004 National nnex to BS EN : 2005 National nnex to BS EN : 2006 National nnex to BS EN : 2005 National nnex to BS EN : 2006 National nnex to BS EN : 2005 National nnex to BS EN : 2005 National nnex to BS EN : 2005 National nnex to BS EN : 2006 National nnex to BS EN : 2005 National nnex to BS EN : 2004 December UK National nnex to Eurocode 2: Design of Concrete Structures Part 1: General Rules and Rules for Buildings. December - UK National nnex to Eurocode 2: Design of Concrete 2007 Structures Part 2: Concrete Bridges Design and detailing rules. October - UK National nnex to Eurocode 2: Design of Concrete 2007 Structures Part 3: Liquid Retaining and Containment Structures. December - UK National nnex to Eurocode 3: Design of Steel Structures 2008 Part 1.1: General Rules and Rules for Buildings. May UK National nnex to Eurocode 3: Design of Steel Structures Part 1.5: Plated Structural Elements November - UK National nnex to Eurocode 3: Design of Steel Structures 2008 Part 1.8: Design of Joints May Eurocode 3: Design of Steel Structures Part 1.9: Fatigue Strength January - UK National nnex to Eurocode 3: Design of Steel Structures 2009 Part 1.10: Material Toughness and Through Thickness Properties. May UK National nnex to Eurocode 3: Design of Steel Structures Part 2: Steel Bridges. December UK National nnex to Eurocode 4: Design of Composite Steel and Concrete Structures Part 2: General Rules and Rules for Bridges. November - UK National nnex to Eurocode 7: Geotechnical Design Part : General Rules. Published Documents Doc. No. Issue Date Issue Document Title PD :2009 December Recommendations for the design of structures to BS EN PD 6687:2006 March Background Paper to the UK National nnexes to BS EN PD :2008 July Recommendations for the design of structures to BS EN :2005 PD :2008 May Recommendations for the design of structures to BS EN Page 59 of 61

60 PD :2009 January Recommendations for the design of structures to BS EN PD :2008 July Recommendations for the design of bridges to BS EN PD :2007 December Background paper to BS EN and the UK National nnex to BS EN Eurocode 4. RILWY GROUP STNDRDS: BRIDGE RENEWLS (Based on Catalogue Issue 4 ug 2009) Code Title Issue Date GC/RT5112 Loading Requirements for the Design of Railway Structures 2 Dec 2008 GC/RT5033 Terminal Tracks Managing the Risk 2 Dec 2007 GC/RT5021 Track System Requirements 3 pril 2007 GO/RT3413 Provision of Information and Signs for ccess on the Railway 1 ug 2008 GC/RT5212 Requirements for Defining and Maintaining Clearances 1 Feb 2003 GE/RT8025 Electrical Protective Provisions for Electrified Lines 1 Oct 2001 GI/RT7012 Requirements for Level Crossings 1 ug 2004 GI/RT7016 Interface between Station Platforms, Track and Trains 2 Dec 2007 GE/GN8573 Guidance on Gauging 2 pril 2008 NETWORK RIL COMPNY STNDRDS: BRIDGE RENEWLS (Based on Catalogue Issue June 2009 to 04 Sept 2009) Code Title Issue Date NR/GN/CIV/001 (Supplements NR/L3/CIV/041) NR/L3/CIV/041 NR/SP/CIV/041 RT/CE/S/041) NR/GN/CIV/002 (formerly Waterproofing of Underline Bridge Decks (compliance date June 2009) 3 ug 2008 Waterproofing Systems for Underline Bridge Decks 3 ug 2008 (compliance date June 2009) Waterproofing Systems for Underline Bridges 2 ug 2001 Use of Protective Treatments and Sealants 5 Mar 2009 (compliance date N/ guidance only) Page 60 of 61

61 NR/GN/CIV/002 pplication and Reapplication of Protective Treatment to 4 Feb 2002 (formerlyrt/ce/c/002) Railtrack Infrastructure (withdrawn 05 Dec 2009) NR/SP/TRK/9003 Installation and Maintenance of Longitudinal Timbers 1 Dec 2005 NR/SP/CIV/003 (formerly Technical pproval of Design, Construction and 2 pril 2004 RT/CE/S/003) Maintenance of Civil Engineering Infrastructure NR/SP/CIV/039 (formerly Specification RT98 - Protective Treatments for Railtrack 4 Feb 2002 RT/CE/S/039) Infrastructure (withdrawn 05 Dec 2009) NR/L3/CIV/040 Specification for the use of Protective Coatings and Sealants (compliance date 05 Dec 2009) 1 Mar 2009 OTHER DOCUMENTS NR/L2/CIV/020 Design of Bridges and Culverts Issue 1(Draft 12) 2008 Page 61 of 61