Preface
This is the eleventh edition of CSA S6, Canadian Highway Bridge Design Code. It supersedes the previous editions published in 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 (1999), 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.
Section 2 (Durability) specifies requirements for durability that need to be considered during the design process and aspects of materials used in the construction of highway bridges, culverts, and other structures located in transportation corridors. The durability requirements for all of the materials are based on common principles applicable to the deterioration mechanisms for each material, the environmental conditions to which the materials are subjected, and the protective measures and detailing requirements needed to limit deterioration to acceptable levels.
Section 3 (Loads) specifies loading requirements for the design of new bridges, including requirements for permanent loads, live loads, 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 covers long-span live loading and 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, the definitions for importance categories have been revised. The approach for determining seismic hazard has been updated and is based on the approach taken in developing the 2015 National Building Code of Canada. Seismic effects from earthquakes having three different return periods are considered. Performance-based design has been introduced with force-based design permitted for special cases. New provisions for damping, effective moment of inertia, hold-down-devices, and shear keys have been added. Modifications were made to some of the response modification factors. Requirements for foundations have been added. Expected material properties for concrete, reinforcing bars and structural steel have been introduced for design. Changes have been made to provisions for the shear design of ductile concrete columns as well as for braces and connections of ductile concentrically braced frames. Design provisions for ductile diaphragms have been added as energy dissipating systems for slab-on-girder bridges in the transverse directions. Performance-based design provisions for seismic isolation have been added, as well as test requirements for these types of bearings. Requirements for the design and testing of shock transmission units are included. Performance-based design has been added for the evaluation and rehabilitation of existing bridges.
Section 5 (Methods of analysis) specifies requirements for analyzing the basic superstructure of a bridge. In its methods for simplified analysis of bridge superstructures, the beam analogy method approach is used and presented in a more concise manner. Distribution factors are expressed according to S/D approach common to the Code prior to the 2000 edition. Based on research conducted during the past five years to validate and supplement work done in the 1990s, some equations have been modified. The new simplified method includes skewed bridges. Simplified elastic methods are included for the analysis of transverse effects. Refined methods of analysis for short, medium, and long-span bridges are also addressed.
Section 6 (Foundations and geotechnical systems) has adopted a reliability-based approach to the design of foundations and geotechnical systems. It includes a risk and consequence based framework to determine the design factors. New to this edition of the Code is a consequence factor, which adjusts target reliabilities depending on failure consequences, combined with a resistance factor whose value slides, depending on the degree of site and model understanding and the specific limit state being designed. The two factors are applied to the characteristic geotechnical resistance at both ultimate and serviceability limit states to achieve consistent system reliability levels while simultaneously improving economies. In this edition, the scope is limited to the static loading condition (the scope will include the seismic loading conditions in the next edition). Other changes to Section 6 include an additional section for foundation design aspects of integral and semi-integral abutments, enhancements to sections on geotechnical investigations to include requirements for seismic design, and revisions to the deep foundations section to improve foundation design aspects and added provisions for lateral resistance of piles.
Section 7 (Buried structures) deals with soil-metal structures with shallow corrugated plates in which thrust is the dominant force in the metal plates as well as soil-metal structures with deep corrugated plates and metal box structures in which flexural effects are also considered in the design of the metal plates. New provisions are provided for the use of plates with deeper corrugations and conditions stipulated for situations when rigorous methods of analysis should be used in lieu of the simplified equations for determining load effects. Section 7 provides provisions for reinforced concrete precast and cast-in-place structures, including pipes, box sections, and segmental structures. Section 7 also specifies requirements for determining the properties and dimensions of the engineered soil and non-soil components and addresses construction supervision and construction procedures for soil components.
Section 8 (Concrete structures) covers reinforced and partially and fully 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.
Section 9 (Wood structures) specifies properties for materials and fastenings that are consistent with CSA O86, Engineering Design in Wood. Section 9 includes data for sawn lumber, glued-laminated timber, and structural composite lumber. Its provisions related to shear load distribution, design factors (in many cases), and laminated wood decks are essentially unchanged from those of the previous edition. The size effect factor for flexural resistance of glued-laminated timber, and the specified negative bending moment strength for two grades of glued-laminated timber, have been updated in accordance with CSA O86. In addition, compression at an angle to grain formula has been revised. AWPA Standards are referenced for pressure preservative treatment of laminated veneer lumber.
Section 10 (Steel structures) specifies the requirements for the design of structural steel bridges, including requirements for structural steel components and their connections. Requirements for fracture control are outlined in Clause 10.23. Construction requirements are specified in Clause A10.
Section 11 (Joints and bearings) specifies the minimum requirements for the design of deck joints and bearings.
Section 12 (Barriers and highway accessory supports) specifies the requirements for the design of permanent bridge barriers and highway accessory supports. Performance level requirements in previous editions have been replaced with test level requirements and crash test requirements for barriers and highway accessory supports have been updated. Additional geometric requirements have been added for side mounted pedestrian and bicycle barriers.
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. Section 13 includes 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, and detailed evaluation from bridge testing. 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, a more conventional approach to determining material grades from small samples is used in place of the Baye's theorem approach, which was used in CAN/CSA-S6-88.
Section 15 (Rehabilitation and repair) specifies minimum design requirements for the rehabilitation of bridges. Section 15 provides guidance on the selection of loads and load factors for rehabilitation that is based on the intended use of the bridge following rehabilitation.
Section 16 (Fibre-reinforced structures) specifies design requirements for a limited number of structural components containing either high- or low-modulus fibres. The high-modulus fibres (aramid, carbon, and glass) are employed in fibre-reinforced polymers (FRPs), which are used as replacements for steel bars and tendons. The low-modulus fibres are used for controlling cracks in concrete. Section 16 covers concrete beams and slabs, concrete deck slabs, 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.
Section 17 (Aluminum structures) specifies the requirements for the design, fabrication, and erection of aluminum highway bridges and pedestrian bridges.
Funding for developing and publishing this Code was provided by 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. This Code could not have been developed without the cooperation of all of these sponsors.
Foreword
In Canada, the legal mandate for establishing design and construction requirements for highways, including highway bridges, lies with the provincial and territorial governments. All provinces and territories, with the exception of Manitoba, have mandated this Code for use under their jurisdictions.
Among the benefits associated with undertaking the development of this Code is the opportunity to establish safety and reliability levels for highway bridges that are consistent across Canada. Adoption of a single code makes it easier for the consulting and producer industries to respond to calls for proposals and eliminates the need for familiarity with the details of several codes. The adoption of a single code also supports the implementation of a national highway transportation system with agreed minimum standards and loadings for bridges on interprovincial highways, thereby encouraging consistency of vehicle weights across jurisdictions and supporting the objective of more cost-effective transportation of goods.
Designers need to be aware, however, that although this Code establishes CL-625 loading as the minimum for bridges that are part of the national highway system, it is within the mandate of the provinces and territories to adopt a heavier or lighter live loading based on local traffic conditions. For example, Ontario requires (as specified in Annex A3.4) the use of a CL-625-ONT loading in the design of new bridges; this reflects the higher average regulatory and observed loads for trucks operating in the province. All of the requirements of this Code applicable to CL-W loading also apply to CL-625-ONT loading. Designers should always obtain approval from the regulatory authority when a live loading other than the CL-625 loading is to be used for design, and should check whether any variations from the requirements of this Code are in effect in the jurisdiction, e.g., for evaluation of existing bridges or issuance of overload permits.
This Code was developed by taking into account the different regulatory structures and standards of Canada's provinces and territories. Overall priorities and objectives were established by the Regulatory Authority Committee (RAC), which also monitored the progress of the Code's development. In accordance with CSA procedural requirements, however, responsibility for the technical content of this Code was assigned to the Technical Committee (TC), as were decisions on how to deal with the priorities and objectives identified by the RAC. Because of the breadth and complexity of this Code, subcommittees (which were required to operate and report on a consensus basis) were established to oversee each section. In addition, task forces were established to handle specific aspects of this Code. The subcommittees and task forces reported to the TC through their Chairs. The extensive use of subcommittees permitted the recruitment of experts with the knowledge needed to address the sometimes highly specialized subjects covered by this Code.
The developers of this Code wish to acknowledge the contributions of the following individuals, who were unable to complete their terms on the TC: Dino Bagnariol (Ontario Ministry of Transportation), Moe Cheung (University of Ottawa), David Cogswell (New Brunswick Department of Transportation), Clifford Lam (Ontario Ministry of Transportation), Peggy Lepper (Canadian Wood Council), Ron Mathieson (BC Ministry of Transportation and Infrastructure), Guy Richard (Transports Québec and Dessau), Bala Tharmabala (Ontario Ministry of Transportation), and Raymond Yu (Alberta Transportation).
This Code is complemented by CSA S6.1-14, Commentary on CSA S6-14, Canadian Highway Bridge Design Code, which provides rationale statements and explanatory material for many of the clauses of this Code.
----------------------------------------------------------------------------------
Scopes
Section 1 - General
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, 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 Approval.
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.
----------------------------------------------------------------------------------
Section 2 - Durability
2.1 Scope
This Section specifies requirements for durability that need to be considered 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.
----------------------------------------------------------------------------------
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.
----------------------------------------------------------------------------------
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.
----------------------------------------------------------------------------------
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 but does not apply to design for seismic loading conditions, which are treated in Section 4, or to buried structures that fall 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.
----------------------------------------------------------------------------------
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 soil 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.
----------------------------------------------------------------------------------
Section 9 - Wood structures
9.1 Scope
This Section applies to structural wood components and their fastenings.
----------------------------------------------------------------------------------
Section 10 - Steel structures
10.1 Scope
This Section specifies requirements for the design of structural steel bridges, 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.
----------------------------------------------------------------------------------
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.
----------------------------------------------------------------------------------
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.
----------------------------------------------------------------------------------
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. The requirements specified in this Section relate only to loads, load factors, resistances, and other design criteria relevant to the rehabilitation of bridges. Material specifications and rehabilitation and maintenance procedures are not covered in this Section but should conform to accepted Canadian good practice.
----------------------------------------------------------------------------------
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, 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.
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.
----------------------------------------------------------------------------------
Section 17 - Aluminum structures
17.1 Scope
This Section specifies requirements for the design, fabrication, and erection of aluminum highway and pedestrian bridges.
------------------------------------------------------------------------------------------
S6.1-14 - Commentary on CAN/CSA-S6-14, Canadian Highway Bridge Design Code
Preface
This is the fourth edition of CSA S6.1, Commentary on CSA S6-14, Canadian Highway Bridge Design Code. It supersedes the previous editions, published in 2006, 2000, and 1990.
Throughout this Commentary, CSA S6-14 is referred to as the Code. Other Codes are always identified in a manner that allows them to be readily distinguished from the Code.
The purpose of this Commentary is to provide background on the design provisions of the Code and thereby to help designers deal with issues not explicitly addressed in the Code.
Each section and clause in this Commentary bears the number of its corresponding section or clause in the Code, with the addition of the prefix C. For example, Section C1 provides commentary on Section 1 of the Code, and within Section C1, Clause C1.1.1 provides commentary on Clause 1.1.1 of the Code. The same approach is used in the numbering of annexes. Tables and figures are numbered sequentially (for example, the first table in Section C3 is Table C3.1, which is followed by Table C3.2, etc.). However, they do not correspond to the tables and figures bearing the same numbers (minus the C) in the Code.
The Code contains many clauses dealing with Approval, meaning approval in writing by the Regulatory Authority having jurisdiction (see the definitions in Clause 1.3.2 of the Code). Where possible, this Commentary provides guidance for Regulatory Authorities consulting such clauses.
