CSA S6:25

Preface This is the thirteenth edition of CSA S6, Canadian Highway Bridge Design Code . It supersedes the previous editions published in 2019, 2014, 2006 (including three supplements published in 2010, 2011, and 2013), 2000, 1988, 1978, 1974, 1966, 1952, 1938, 1929, and 1922. This Code is based on limit states design principles and defines design loadings, load combinations and load factors, criteria for earthquake resistant design, and detailed design criteria for the various materials. This Code has been written to be applicable in all provinces and territories. There are 17 Sections in this Code: Section 1 ("General") specifies general requirements for applying this Code and includes definitions and a reference publications clause applicable throughout the Code. It also specifies geometric requirements, based in part on TAC’s Geometric Design Guide for Canadian Roads, and hydrology and hydraulic design requirements. There are also general provisions covering design, including highway class, climate change, design life, economics, the environment, aesthetics, construction, geometry, secondary and auxiliary components, drainage, maintenance, and maintenance inspection access. Major changes for this edition of the Code include the requirement to design for current and future climate conditions, updated hydrologic methods of analysis requirements, and hydraulic design updates. Hydraulic design updates include - the introduction of hydraulic structure classification and associated minimum annual exceedance probabilities, backfill, scour, piping and undermining countermeasures, and a service level hydraulic design method; - enhanced minimum structure size, inerodible invert and revetments, substructure and embankment erosion and piping control, and estimation of scour and protection against scour design provisions; and - the movement of buried structure soil-structure focused design provisions to Section 7. Section 2 ("Durability and sustainability") specifies requirements for durability and sustainability applied during the design process for structures located in transportation corridors. Sustainability considerations alert owners and designers to undertake design and decision-making practices that will help to achieve the context specific balance of social, environmental, and economic values. The durability requirements are based on a service life design process that guides the user to make appropriate decisions related to the structural system, structural details, materials, and protection systems. The service life design process starts by assessing the environmental exposure conditions and applicable deterioration mechanisms, which are described in detail, and follows with the application of protective mitigative measures consisting of avoidance, deemed-to-satisfy approaches, or special analysis and testing (including probabilistic modeling) if allowed by the owner. An Annex to this Section describes how to record durability assumptions and lists items that may be requested to be included in a durability plan, if required by the owner. Section 3 ("Loads") specifies loading requirements for the design of new bridges, including requirements for permanent loads, live loads including special trucks and pedestrians, and special loads (but excluding seismic loads). The 625 kN truck load model and corresponding lane load model are specified as the minima for interprovincial transportation and are based on current Canadian legal loads. Design provisions for climatic loadings are provided in the 2025 edition of this Code, including the effects of climate change. Enhanced provisions are provided for the design of wind loads on highway accessory supports and slender structural elements. Ship collision provisions are also included. Section 3 does not specify limits on the span lengths for application of the truck and lane loads. Accordingly, long- span requirements have been developed and appear in Section 3and elsewhere in this Code (these requirements, however, should not be considered comprehensive). Section 3addresses wind tunnel testing for aerodynamic effects. Section 4 ("Seismic design") specifies seismic design requirements for new bridges and evaluation and rehabilitation requirements for existing bridges. In the 2025 edition of the Code, provisions have been reconfigured. Performance-based design (PBD) has been maintained, including strain and deformation- based damage states and related repair and traffic service objectives. Four seismic design approaches have been provided under the PBD philosophy: displacement-based design, seismic isolation, force- based design using an implicit R-factor approach, and strength-based design. Seismic isolation has been streamlined and requirements revised to encourage its adoption as a low-damage system. Sixth- generation seismic hazard has been adopted and seismic performance category (SPC) levels are revised to align seismic design requirements with the new hazard in particular for eastern Canada. Force-based design (FBD) remains permitted for a defined set of special cases. PBD and recommended minimum performance targets have been revised for the evaluation and rehabilitation of existing bridges. FBD approaches for existing bridges are discouraged, while guidance on displacement-based methods has been provided. Strain limits for existing bridges are not defined as they must be tailored to existing bridge details and hence should be defined on a case-by-case basis. Section 5 ("Methods of analysis") specifies requirements for analyzing bridge superstructures. In the 2025 edition of the Code, this Section provides new methods for the simplified analysis of deck slab cantilever overhang due to transverse traffic barrier load, for aluminum deck on steel girders, and for the stability analysis of substructure systems. Improved requirements are provided for nonlinear static push over seismic analysis and for elastic stability analysis of structural systems. Additional guidance related to shear between longitudinally connected beams is provided. Refined analysis is now required for all types of curved bridges. Indications allowing curved slab-on-girder bridges to be analyzed in the same manner as straight bridges have been removed whereas new ones, presenting a broader range of applicability, have been introduced in the Commentary. The use of the equivalent span length for the simplified analysis of superstructures is limited to continuous bridges only and can no longer be applied to rigid frames or integral abutment systems. The simplified method of analysis of pony-truss bridges has been revised for the structures with top chord ends fully supported at the supports. The simplified method of analysis for determining the factored flexural resistance of steel-reinforced concrete barriers to transverse traffic barrier load has been improved. Section 6 ("Foundations and geotechnical systems") follows a risk-based approach to the design of foundations and geotechnical systems (including bridge approach embankments and retaining systems). The risk-based design approach involves using a resistance factor, which captures the uncertainty in the ground properties and in performance predictions, combined with a consequence factor, which adjusts target reliabilities depending on the severity of failure consequences (i.e., depending on the importance of the supported structure), to produce designs that properly account for the level of site understanding and failure consequences. The 2025 edition of the Code provides considerable additional changes, adding entirely new Code provisions dealing with climatic design, embankments, and ground improvement. Also, the Code provisions for deep and shallow foundations have been brought up-to-date, and the provisions for permafrost design have been entirely rewritten to reflect current practice. Geotechnical seismic design requirements have been updated to conform with the updates made in Section 4. Section 7 ("Buried structures") covers structures whose design and performance are heavily influenced by soil-structure interaction. The conduit wall of these buried structures are fabricated from metal (steel or aluminum) or concrete. For metal structures, the conduit wall is made from corrugated plate that fits one of the three industry categories: shallow, deep, or deeper corrugated plate. For concrete structures, the wall is reinforced concrete and can be precast or cast-in-place. This Section provides for a wide variety of structure shapes from closed bottom metal and concrete structures to open bottom low profile metal boxes or three-sided concrete structures to large span open bottom metal or concrete arches. This Section specifies the use of refined methods of analysis for design although some simplified design equations can be used in smaller structures if specific geometric conditions are met. This Section also specifies requirements for determining the properties and dimensions of the engineered soil construction requirements, geotechnical requirements, and foundation design requirements. Major changes to the 2025 edition of the Code include updated hydraulic and durability design provisions, which align with revisions to Sections 1and 2, introduction of evaluation and rehabilitation methods, which align with revisions to Sections 14and 15, and consolidation of construction requirements in a normative Annex. Section 8 ("Concrete structures") covers reinforced, fully prestressed, and partially prestressed concrete components, including deck slabs, made of normal-density, semi-low-density, and high-density concrete of a strength varying from 30 to 80 MPa. Compression field theory is used for proportioning for shear and for torsion combined with flexure. The strut-and-tie approach is used for proportioning regions where the plane sections assumption is not applicable. An informative Annex provides design provisions for tension softening and tension hardening fibre-reinforced concrete, including ultra-high performance concrete. Major changes to the 2025 edition include design provisions incorporating alternative reinforcing steel types and grades; updated development and splice provisions, design provisions for headed bars, new anchorage design provisions including a new Annex that incorporates the concrete capacity design methodology for steel anchors in concrete, and updated concrete durability design provisions. Section 9 ("Wood structures") specifies the requirements for the design of structural wood bridges and bridge elements using solid-sawn and engineered wood members. Where appropriate, properties for materials and fastenings are consistent with CSA O86. In the 2025 edition of the Code, provisions have been reconfigured, and specified strengths revised, to make the application of service condition factors, related to moisture content in members, transparent for the designer. Specified strengths and moduli of elasticity for Eastern Hemlock has been added as a permitted solid-sawn species. In addition, durability provisions have been updated to remove specific treatments from this Code, and instead reference the CSA O80 Series to maintain consistency with changes in preservative treatment technology. Section 10 ("Steel structures") specifies the design and durability requirements for structural steel bridges and highway accessory supports, including requirements for structural steel components, such as tension and compression members, composite and non-composite straight and horizontally curved girders of I-shape or box shape and their connections. It also covers trusses and arch type bridges. The requirements for structural fatigue and fracture control are outlined in Clauses 10.17and 10.23, respectively. The construction requirements for steel bridges are specified in Annex A10.1. Section 11 ("Joints and bearings") specifies the minimum requirements for the design of deck joints and bearings. In the 2025 edition of the Code, a new best practice in construction and maintenance for joints and bearings has been added to Annex A11.1, which includes content from previous editions of the Code and new material . Section 12 ("Barriers and highway accessory supports") specifies the requirements for the design of permanent bridge barriers and highway accessory supports. Revisions for the 2025 edition of the Code include updated requirements for bridge traffic barriers, the removal of crash testing requirements for traffic barriers on low speed urban roadway bridges (provided certain strength and geometric requirements are met), and the introduction of minimum anchor bolt requirements for highway accessory supports. Section 13 ("Movable bridges") specifies requirements for the design, construction, and operation of conventional movable bridges, i.e., bascule, swing, and vertical lift. Although the structural design aspects are based on the limit states design approach, the mechanical systems design procedures follow the working stress principle used in North American industry. This Section provides special loads, load combinations, and load factors that are specific to movable bridges. Section 14 ("Evaluation") provides provisions concerning the three-level evaluation system, evaluation of permit vehicles, evaluation of deck slabs, detailed evaluation from bridge testing, and load posting of bridges. An optional probability based mean load method that uses site-specific load and resistance information for more accurate evaluation is also provided. Evaluation requirements are provided for selected types of components/materials that are no longer addressed by the design sections of this Code. Information is provided on some historical strength of materials. As in previous editions, an approach to determining material grades from small samples is provided. Section 15 ("Rehabilitation and repair") specifies minimum design requirements for the rehabilitation of bridges, with particular emphasis on condition assessment, remaining service life, and rehabilitation design life. This Section also provides guidance on the selection of loads and load factors for rehabilitation that is based on the intended use of the bridge following rehabilitation. In the 2025 edition of the Code, this Section introduces new provisions on assessment of vehicular collision against existing bridge columns, bridge jacking, and repair of prestressed components. Consideration of climate change impacts has been made a mandatory component of all long-term bridge rehabilitation planning, and that rehabilitation design based on a lower return period for climatic parameters requires analysis by qualified professionals and approval by the owner. Section 16 ("Structures with FRP reinforcements") specifies design requirements for a number of structural components containing high-modulus fibre-reinforced polymers. The high-modulus fibres (aramid, basalt, carbon, and glass) are employed in fibre-reinforced polymers (FRPs), which are used for internal reinforcement as replacements for steel bars and tendons or as external reinforcement for retrofit. This Section covers concrete beams, slabs, columns, concrete deck slabs, barrier walls, and stressed wood decks using FRP. This Section also includes design provisions for glass-fibre-reinforced polymers to be used as primary reinforcement and as tendons in concrete. An informative annex provides guidelines for GFRP composite bridges. Section 17 ("Aluminum structures") specifies the requirements for the design, fabrication, and erection of aluminum highway bridges and pedestrian bridges. This Section may also be applied for the design of aluminum highway accessory structures. In the 2025 edition of the Code, major improvements to the design flow for considering local buckling in member design have been introduced, new guidance has been added for the design of deep sections made from welded plate, a construction annex has been created, new detail categories have been added for friction stir welded (FSW) butt joints, Clause 17.19on aluminum bridge decks has been revised to include practical design criteria, and an alternative method has been acknowledged for strength establishment by testing ["Method 2" the American Specification for Aluminum Structures (SAS)]. CSA Group acknowledges that the development of this Code was made possible, in part, by the financial support of the governments of Alberta, British Columbia, Manitoba, New Brunswick, Newfoundland and Labrador, the Northwest Territories, Nova Scotia, Ontario, Prince Edward Island, Québec, Saskatchewan, and the Yukon, Public Services and Procurement Canada, the Federal Bridge Corporation Limited, and Les Ponts Jacques Cartier et Champlain Incorporée. This Code was prepared by the Technical Committee on the Canadian Highway Bridge Design Code, under the jurisdiction of the Strategic Steering Committee on Construction and Civil Infrastructure, and has been formally approved by the Technical Committee. ---------------------------------------------------------------- Section 1 General 1.1 Scope 1.1.1 Scope of Code This Code applies to the design, evaluation, and structural rehabilitation design of fixed and movable highway bridges in Canada. There is no limit on span length, but this Code does not necessarily cover all aspects of design for every type of long-span bridge. This Code also covers the design of pedestrian bridges, bicycle bridges, buried structures, retaining walls, barriers, and highway accessory supports of a structural nature, e.g., lighting poles and sign support structures. This Code considers climate change. This Code does not apply to public utility structures or to bridges used solely for railway or rail transit purposes. This Code does not specify requirements related to coastal effects (e.g., exposure to sea action and icebergs) or to mountainous terrain effects (e.g., avalanches). For structures that can be subject to such effects, specialists need to be retained to review and advise on the design and to ensure that the applicable requirements of other codes are met. For bridges not entirely within the scope of this Code, the requirements of this Code apply only when appropriate. Necessary additional or alternative design criteria are subject to the approval by the owner. 1.1.2 Scope of this Section Section 1 specifies requirements for applying the Code and requirements of a general nature for bridges, buried structures, and related works. These requirements govern basic geometry and hydraulic design. General requirements are also specified for subsidiary components, deck drainage, maintenance, and inspection access. Broad guidelines related to economic, aesthetic, and environmental considerations are also provided. 1.1.3 Terminology In this Code, "shall" is used to express a requirement, i.e., a provision that the user is obliged to satisfy in order to comply with the Code; "should" is used to express a recommendation or that which is advised but not required; and "may" is used to express an option or that which is permissible within the limits of the Code. Notes accompanying clauses do not include requirements or alternative requirements; the purpose of a note accompanying a clause is to separate from the text explanatory or informative material. Notes to tables and figures are considered part of the table or figure and may be written as requirements. Annexes are designated normative (mandatory) or informative (non-mandatory) to define their application. ---------------------------------------------------------------- Section 2 Durability and sustainability 2.1 Scope This Section specifies requirements for durability, sustainability and resilience to implement during the design process in addition to this Code’s requirements for strength and serviceability. The requirements of this Section apply to new bridges as well as to rehabilitation and replacement work. ---------------------------------------------------------------- Section 3 Loads 3.1 Scope This Section specifies loads, load factors, and load combinations to be used in calculating load effects for design. Resistance factors required to check ULS criteria in accordance with Clause 3.4.2are specified elsewhere in this Code. Loadings provisions for evaluation of existing structures are covered in Section 14and for rehabilitation in Section 15. This Section includes requirements related to the vibration of highway and pedestrian bridges. It also includes requirements related to construction loads and temporary structures; these apply to partially completed structures and structures necessary for construction purposes. Snow loads are not specified because in normal circumstances the occurrence of a considerable snow load will cause a compensating reduction in traffic load. ---------------------------------------------------------------- Section 4 Seismic design 4.1 Scope This Section specifies minimum requirements for a) the seismic analysis and design of new bridge structures; and b) the seismic evaluation and rehabilitation (Clause 4.18) of existing bridge structures ---------------------------------------------------------------- Section 5 Methods of analysis 5.1 Scope This Section specifies the methods of analysis for the design and evaluation of bridge superstructures. ---------------------------------------------------------------- Section 6 Foundations and geotechnical systems 6.1 Scope This Section specifies minimum requirements for the design of foundations and geotechnical systems (including highway embankments) under static loading conditions and for requirements pertaining to geotechnical investigations and design reports. This Section includes requirements for investigation to support seismic design, specifies minimum requirements to evaluate seismic resistance of foundations, and provides seismic performance requirements for geotechnical systems. This Section also includes requirements for investigation to support design of buried structures, although design of buried structures falls within the scope of Section 7. Where conflict occurs between requirements in references to other Standards or Codes and Section 6, the requirements of Section 6take precedence. ---------------------------------------------------------------- Section 7 Buried structures 7.1 Scope This Section specifies requirements for the analysis and design of buried structures of the following types: a) soil-metal structures; b) metal box structures; and c) reinforced concrete structures. This Section also specifies construction procedures, properties and dimensions of engineered fill components, and requirements for construction supervision. ---------------------------------------------------------------- Section 8 Concrete structures 8.1 Scope This Section specifies requirements for the design of structural components that are made of precast or cast-in-place normal-density, low-density, or semi-low-density concrete and reinforced with prestressed or non-prestressed steel. The components covered by this Section can be prestressed with pretensioned steel, grouted post-tensioned steel, or both. The provisions in this Section do not apply to concrete placed using the shotcrete process. Annex A8.1includes requirements for the design of structural components that are made of precast or cast-in-place fibre-reinforced concrete with prestressed or non-prestressed steel. ---------------------------------------------------------------- Section 9 Wood structures 9.1 Scope This Section applies to structural wood components and their connections. ---------------------------------------------------------------- Section 10 Steel structures 10.1 Scope This Section specifies requirements for the design of structural steel bridges and highway accessory support structures, including requirements for structural steel components, welds, bolts, and other fasteners required in fabrication and erection. Requirements related to the repeated application of loads and to fracture control and fracture toughness for primary tension and fracture-critical members are also specified. Construction requirements for structural steel are also provided. ---------------------------------------------------------------- Section 11 Joints and bearings 11.1 Scope This Section specifies minimum requirements for the design, selection, and detailing of joints and bearings. ---------------------------------------------------------------- Section 12 Barriers and highway accessory supports 12.1 Scope This Section specifies requirements for the design of permanent bridge barriers and highway accessory supports. It is not applicable to the replacement or rehabilitation of existing structures. ---------------------------------------------------------------- Section 13 Movable bridges 13.1 Scope This Section specifies requirements for the design of conventional movable highway bridges, i.e., bascule (including rolling lift), swing, and vertical lift bridges and deals primarily with the components involved in the operation of such bridges. The requirements for fixed span bridges, as given in other sections of the Code, apply to movable bridges, except as otherwise provided. ---------------------------------------------------------------- Section 14 Evaluation 14.1 Scope This Section specifies methods of evaluating an existing bridge to determine whether it will carry a particular load or set of loads. ---------------------------------------------------------------- Section 15 Rehabilitation and repair 15.1 Scope This Section specifies minimum requirements for the rehabilitation of bridges but is not applicable to the resolution of construction deficiencies of new structures. The requirements specified in this Section relate only to condition assessment, loads, load factors, resistances, and other design criteria relevant to the rehabilitation of bridges. This includes required remaining service life and assessment of ongoing deterioration and its impact on structural integrity. Material specifications, rehabilitation procedures, and maintenance procedures are not covered in this Section. ---------------------------------------------------------------- Section 16 Structures with FRP reinforcements 16.1 Scope 16.1.1 Components The requirements of this Section apply to the following components containing fibre reinforcement: a) fully or partially prestressed concrete beams and slabs; b) non-prestressed concrete beams, slabs, columns, and deck slabs; c) externally and internally restrained deck slabs; d) stressed wood decks; e) barrier walls; f) existing concrete elements with externally bonded fibre-reinforced polymer (FRP) systems and near-surface-mounted reinforcement (NSMR); and g) existing timber elements with externally or internally bonded glass-fibre-reinforced polymer systems (GFRP) or basalt-fibre-reinforced-polymer systems (BFRP) and near-surface-mounted reinforcement (NSMR). 16.1.2 Fibres This Section covers fibre reinforcement in which the fibre comprises one or more of the following: a) glass; b) carbon; c) aramid; d) basalt; e) a low modulus polymer or polymers; and f) steel. 16.1.3 Matrices This Section covers fibre-reinforced composites in which the matrix comprises one or more of the following: a) epoxy resin; b) saturated polyester resin; c) unsaturated polyester resin; d) vinylester resin; e) polyurethane; and f) Portland-cement-based mortar or concrete. 16.1.4 Uses requiring approval Uses of fibre-reinforced polymers in structures or strengthening schemes that do not meet the requirements of this Section require approval by the owner. ---------------------------------------------------------------- Section 17 Aluminum structures 17.1 Scope This Section specifies requirements for the design, fabrication, and erection of aluminum highway bridges and accessory structures.