Preface
This is the twelfth edition of CSA S6, Canadian Highway Bridge Design Code. It supersedes the previous editions published in 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 the Code and includes definitions and a reference publications clause applicable throughout this Code. It also specifies geometric requirements, based in part on the Transportation Association of Canada’s Geometric Design Guide for Canadian Roads (2017), and hydraulic design requirements, based in part on the Transportation Association of Canada’s Guide to Bridge Hydraulics (2004). There are also general provisions covering durability, economics, environmental considerations, aesthetics, safety, maintenance, and maintenance inspection access. The definitions in Clauses 1.3.2 to 1.3.4 apply to those used specifically in this Section, and new to this edition of the Code, also apply to common definitions used in more than one Section in this Code.
Section 2 (Durability and sustainability) specifies requirements for durability and sustainability that need to be considered during the design process of bridges, culverts, and other structures located in transportation corridors. The durability requirements are based on principles applicable to service life design that consider the environmental exposure conditions, the deterioration mechanisms, the protective measures, and detailing requirements needed to meet the projected service life of structural components. The concept of sustainability considerations has been introduced to 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, and impacts associated with the investment in building new or rehabilitation of existing bridges and other transportation structures included in the scope of this Code. Similarly, local climate change and exposure conditions are brought to the attention of designers and owners.
Section 3 (Loads) specifies loading requirements for the design of new bridges, including requirements for permanent loads, live loads including special trucks, 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. 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 3 and elsewhere in this Code (these requirements, however, should not be considered comprehensive).
Section 3 addresses 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 this edition of the Code, performance-based design (PBD) has been maintained using updated values for damage states in ductile substructures. Additional damage and service definitions have been provided. Minimum performance levels have been revised from three to two seismic hazard levels for all bridges requiring PBD. Force-based design (FBD) remains permitted for a refined set of special cases. Requirements for geotechnical and foundation design have been moved to Section 6. Some provisions for bearing design have been moved to Section 11 with revisions in Section 4 for consistency. Capacity design has been clarified and encouraged for ductile structures using PBD and FBD. Design forces and material properties for PBD, FBD, and capacity design have been clarified. The shear capacity for ductile concrete columns has been revised upwards. Performance-based design 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.
Section 5 (Methods of analysis) specifies requirements for analyzing bridge superstructures. Additional guidance related to longitudinally connected beams and integral abutment bridges are provided. This Section presents new methods for the simplified analysis of longitudinally connected concrete box-beam bridges (previously named shear connected beams), curved steel girder bridges, and steel or aluminum pony-truss bridges. Reductions to limitations for when a curved bridge can be analyzed in the same manner as a straight bridge have been introduced. The robustness and accuracy of the simplified method has been verified by conducting thorough analysis using a large database of simply supported and continuous slab-on-girder bridges. This analysis resulted in shear forces being increased by up to 13% at interior supports for slab-on-girder bridges. In collaboration with Section 3, more specific requirements related to traffic loading are provided with the aim of clarifying the use of refined method of analysis. Revised requirements and guidance for the refined method of analysis have therefore been included. Methods for the design of deck slab cantilever overhang have been updated. Finally, a new simplified method of analysis is provided for determining the factored flexural resistance of steel-reinforced concrete barrier to transverse traffic barrier load.
Section 6 (Foundations and geotechnical systems) adopted a risk-based approach to the design of foundations and geotechnical systems (including bridge approach embankments and retaining systems) in the 2014 edition of the Code. The risk-based design approach involves using a resistance factor, which captures our uncertainty in the ground and in our 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 which properly account for the level of site understanding and failure consequences. This edition of the Code provides considerable additional changes, adding Code provisions in four design areas, three of which are entirely new to this Section, as follows:
• Clause 6.14, on seismic design, brings the geotechnical seismic design content originally in Section 4 into Section 6 and adds up-to-date content;
• Clause 6.10, on shallow foundations, has been brought up to date and its application is now much clearer;
• Clause 6.18, on permafrost design, provides new specifications for geotechnical design in cold climates; and
• Clause 6.19, on mechanically stabilized earth (MSE) wall systems, provides code requirements for MSE wall systems within the LRFD framework of Section 6 and addresses issues based on Canadian experience with these systems.
Section 7 (Buried structures) deals with structures whose design and performance are heavily influenced by soil-structure interaction. The conduit wall of these buried structures can be fabricated from metal, steel or aluminum, or concrete. For metal structures, the conduit wall is made from corrugated plate which 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. Section 7 provides for a wide variety of structure shapes from low profile metal boxes or three-sided concrete boxes to large span metal or concrete arches. Section 7 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. Section 7 also specifies requirements for determining the properties and dimensions of the engineered soil and non-soil components and addresses construction requirements, geotechnical requirements, and foundation design requirements.
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. New to this edition is an informative Annex that provides design provisions for tension softening and tension hardening fibre-reinforced concrete, including ultra-high performance concrete. Other significant changes in this edition include revised provisions relating to the design of slender compression members, the control of cracking, and the use of debonded strands in pretensioned components.
Section 9 (Wood structures) specifies properties for materials and fastenings that are consistent with CSA O86 Engineering Design in Wood. In this 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 spruce, lodgepole pine, Jack pine glued-laminated timber have been introduced. Preservative treatments related to durability have been updated to reflect current industry practices, and design values for structural composite lumber have been removed as such products are proprietary and design values can vary between manufacturers. Finally, glued-laminated decks have been introduced.
Section 10 (Steel structures) specifies the requirements for the design of 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 10.17 and 10.23, respectively. The construction requirements for steel bridges are specified in Annex A10.1. Provisions for hybrid girders have been re-introduced into Section 10 as Annex A10.2.
Section 11 (Joints and bearings) specifies the minimum requirements for the design of deck joints and bearings. The design of elastomeric bearings has been updated from previous editions to be consistent with approaches used in other North American and international standards and codes. Alternative sliding materials (as an alternative to PTFE) comprised of ultra-high molecular weight polyethylene are presented. A testing protocol for such materials is also presented.
Section 12 (Barriers and highway accessory supports) specifies the requirements for the design of permanent bridge barriers and highway accessory supports. New provisions have been added in this edition of the Code to define the extent of the zone of Intrusion behind barriers and for the design of noise barriers. Also, new provisions have been added for designing highway accessory supports at the serviceability and fatigue limit states.
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 load combinations and load factors that are specific to movable bridges.
Section 14 (Evaluation) includes provisions concerning the three-level evaluation system, 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. 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 this new edition of the Code, this Section introduces a new subsection on rehabilitation of structural steel elements to provide guidance on repair and strengthening of steel components and their connections.
Section 16 (Fibre-reinforced structures) specifies design requirements for a number of structural components containing high- modulus fibre-reinforced polymers. The high-modulus fibres (aramid, 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. A new clause also briefly describes the use of the low-modulus fibres which are used for controlling cracks in concrete. This Section covers concrete beams, slabs, columns, concrete deck slabs, barrier walls, and stressed wood decks using FRP. Section 16 also includes design provisions for glass-fibre-reinforced polymers to be used as primary reinforcement and as tendons in concrete. An informative annex is now included to provide 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. Where permitted in Section 12, Section 17 may now also be applied to highway accessory structures. In this edition of the Code, Clause 17.19 on aluminum bridge decks has been simplified and generalized recognizing that aluminum deck products may come in a broad variety of forms. Clause 17.20 on fatigue has been updated to add new local stress approaches, and a new Clause 17.26 on performance assessment by testing has been added.
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, Nunavut, Ontario, Prince Edward Island, Québec, Saskatchewan, and the Yukon, Public Works and Government Services Canada, the Federal Bridge Corporation Limited, and Les Ponts Jacques Cartier et Champlain Incorporée.
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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, retaining walls, barriers, and highway accessory supports of a structural nature, e.g., lighting poles and sign support structures.
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
This Section specifies requirements for applying the Code and requirements of a general nature for bridges, culverts, 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.
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Section 2 - Durability and sustainability
2.1 Scope
This Section specifies requirements for durability and sustainability that shall be implemented during the design process in addition to this Code’s requirements for strength and serviceability. The requirements of this Section apply to the design of new bridges as well as to rehabilitation and replacement work.
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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 ultimate limit states criteria in accordance with Clause 3.4.2 are specified elsewhere in this Code. Loadings provisions for evaluation of existing structures are covered in Section 14 and 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.
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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 (Clause 4.11) and rehabilitation (Clause 4.12) of existing bridge structures.
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Section 5 - Methods of analysis
5.1 Scope
This Section specifies the methods of analysis for the design and evaluation of bridge superstructures.
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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 6 shall take precedence.
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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.
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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.
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Section 9 - Wood structures
9.1 Scope
This Section applies to structural wood components and their connections.
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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.
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Section 11 - Joints and bearings
11.1 Scope
This Section specifies minimum requirements for the design, selection, and detailing of joints and bearings.
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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.
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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, shall apply to movable bridges, except as otherwise provided.
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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.
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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, including 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.
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Section 16 - Fibre-reinforced structures
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) and NSMR.
A non-mandatory Annex is also included on GFRP composite bridges (see Annex A16.3).
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) a low modulus polymer or polymers; and
e) 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.
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Section 17 - Aluminum structures
17.1 Scope
This Section specifies requirements for the design, fabrication, and erection of aluminum highway and pedestrian bridges. Where permitted in Section 12, the contents of this Section may also be applied to highway accessory structures.
