Preface
This Canadian Highway Bridge Design Code is the ninth edition of CSA Standard CAN/CSA-S6. It amalgamates and supersedes both CSA Standard CAN/CSA-S6-88, Design of Highway Bridges, and the OHBDC-91-01, Ontario Highway Bridge Design Code, Third Edition. Earlier editions of the Ontario Highway Bridge Design Code were published in 1983 and 1979 by the Ontario Ministry of Transportation, Downsview, Ontario. Earlier editions of the CSA Standard were published in 1978, 1974, 1966, 1952, 1938, 1929, and 1922.
This first edition under the title Canadian Highway Bridge Design Code again uses the limit states design philosophy. Based chiefly on the Ontario Highway Bridge Design Code, Third Edition, it has been rewritten to be applicable across Canada, in all provincial jurisdictions. Several design aspects are addressed for the first time in the Code and more detailed treatment is provided in many areas. The new provisions have resulted in some reorganization and new Code Sections, relative to both the CSA Standard and the Ontario Code. The design provisions reflect the most current information available at time of writing.
Section 1, General, gives general provisions, geometrical requirements and detailed hydraulic design specifications. Geometric provisions have been substantially reduced by referring to the Transportation Association of Canada (TAC) Geometric Design Guide for Canadian Roads. Similarly, hydraulic provisions have been abridged by reference to the TAC Guide to Bridge Hydraulics. New provisions include those covering durability, and broad guidelines concerning economics, environmental considerations, aesthetics, safety, maintenance, and maintenance inspection access.
Section 2, Durability, new, consolidates the durability aspects of the materials used in the construction of highway bridges, culverts, and other structures located in the transportation corridors. The durability requirements for all the materials are based on common principles of the deterioration mechanisms for each material, the environmental conditions to which the materials are subjected, and the protective measures and the detailing requirements needed to limit deterioration to acceptable levels.
Section 3, Loads, contains modified live load models compared to both CAN/CSA-S6-88 and OHBDC-91. The Truck model of 625 kN is specified as the minimum for interprovincial transportation and is based on the current legal loads in Canada. There is no longer any limit to the span lengths for application of the Truck and Lane Loads. Ship collision provisions appear for the first time. Earthquake effects and load provisions for evaluation and rehabilitation are located in their own Sections.
With removal of the span length limit from the Code, long span provisions (not to be considered as fully comprehensive in this edition) have been developed and appear here and throughout the Code. Section 3 covers long span live loading and advises on the need for wind tunnel testing for aerodynamic effects. Issues associated with design of long span bridges but appearing elsewhere include, for example, methods of analysis in Section 5, segmental concrete bridges in Section 8, and resistance factors for cables for suspension and cable-stayed bridges in Section 10.
Section 4, Seismic Design, new, provides seismic design requirements for new bridges which are based primarily on the provisions of the American Association of State Highway and Transportation Officials (AASHTO) load-and-resistance factor design (LRFD) Highway Bridge Code. New features of this Section, different from the AASHTO Code, include more explicit treatment of both the importance factor and the response modification factor, new design and detailing requirements for structural steel ductile substructure elements, and design provisions for seismic base isolation. In addition, design provisions for the seismic evaluation of existing bridges are provided along with requirements and guidance on the seismic rehabilitation of existing bridges.
Section 5, Methods of Analysis, incorporates the basic structure of the OHBDC-91. A new format is used for the methods of simplified analysis of bridge superstructures in which the bridge is treated as a single beam and force effects are averaged over the width of the bridge and subsequently amplified to calculate the true intensity. Distribution factors have been developed from both recent and existing research, using variables similar to those used in OHBDC-91 with some modifications.
Simplified elastic methods have been added for the analysis of transverse effects, similar in format to CSA Standard S6-88. Refined methods of analysis are addressed for short, medium, and long span bridges.
Section 6, Foundations, is based on the OHBDC-91 provisions and the continued use of global resistance factors. Employing the limit states design approach, the term “resistance” is applied to the strength or capacity of the soil or rock at the ultimate limit state. Similarly, the term “reaction” is associated with the serviceability limit state and is indicative of a particular deformation. The importance of communication between the bridge structural Engineer and the geotechnical Engineer at all stages of a project is emphasized.
Section 7, Buried Structures, new to the CAN/CSA-S6 Standard, expands upon the “Soil-steel Structures” section of the OHBDC-91. In addition to soil-metal structures in which thrust is the dominant force effect in the metal plates, this edition covers metal box structures in which flexure is the main effect. Provisions have been added for reinforced concrete precast and cast-in-place structures, including pipes, box sections, and segmental structures. It provides requirements for determining properties and dimensions of the engineered soil and non-soil components. It also specifies construction procedures for soil components and for construction supervision.
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 with strength varying from 30 to 80 MPa. The compression field theory is used as a method of 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, makes specified properties for materials and fastenings consistent with CSA Standard O86.1-94. Data for structural composite lumber have been added. The treatment of shear and compression has been brought up to date. The provisions for load distribution, many design factors, and clauses dealing with laminated wood decks are essentially unchanged from the OHBDC-91-01.
Section 10, Steel Structures, presents the majority of the design requirements for steel structures with the exception of some seismic requirements placed in Section 4. Construction requirements that may impact on the resistance factors used in the Section are given in Clause 10.24. Because the Code has been expanded to include long span bridges, the use of cables is now covered and a clause on arches is presented. Durability is addressed much more fully. Clauses that were essentially revised include those on beams and girders, composite beams and girders, horizontally curved girders, orthotropic decks, fatigue, and construction requirements.
Section 11, Joints and Bearings, incorporates features from CSA Standard S6, the OHBDC-91-01, and the new AASHTO LRFD Highway Bridge Code. It covers the most common deck joints and bearings in use across Canada. Tables have been revised to take account of recent research results in this field.
Section 12, Barriers and Highway Accessory Supports, carries forward the crash testing requirements for barriers that appeared in OHBDC-91 and adds crash testing requirements for breakaway highway accessory supports. Crash testing may be waived for barrier and accessory support designs that have a successful in-service performance record. Alternative performance levels to those specified in the Code are permitted if Approved by the Regulatory Authority.
Section 13, Movable Bridges, new within the Code, provides requirements for the design, construction, and operation of conventional movable bridges. It represents a revised version of the old (1960 edition, withdrawn 1977) CSA Standard on movable bridges, CSA S20. The structural design aspects now are based on the limit states design philosophy, but the mechanical systems design continues to follow the working stress principle which is still in current use in the North American industry. The movable bridge specifications of AASHTO and the American Railway Engineering and Maintenance of Way Association (formerly AREA) were reviewed extensively in developing these updated requirements.
Section 14, Evaluation, merges the evaluation systems and approaches of Clause 12 of CAN/CSA-S6-88 and OHBDC. Clause 12 was issued as Supplement No. 1-1990 to that edition of the Standard. Some features found in OHBDC-91-01 have been added, such as Evaluation Level live loads and evaluation of deck slabs. Another category of permit vehicle (PA - permit, annual) has been added. In this edition, the Mean Load Method has been moved from the Commentary to Clause 12 into the Code. The method of determining material grades from small samples is altered from the use of Bayes Theorem in Clause 12 to a more conventional approach in the current Evaluation Section.
Section 15, Rehabilitation, is based on the OHBDC-91. The subject previously was not covered in the S6 Standard. It provides guidance on the selection of loads and load factors for rehabilitation.
Section 16, Fibre-Reinforced Structures, new, provides the design requirements for a limited number of structural components containing either high- or low-modulus fibres. The high modulus fibres, being aramid, carbon, and glass, are employed in fibre-reinforced polymers, which are used basically as direct replacement for steel bars and tendons. The low-modulus fibres are used essentially for controlling cracks in concrete. The Section includes design provisions for concrete beams and slabs, concrete deck slabs, and stressed wood decks.
Funding to cover the costs of developing and publishing the Code was provided by the provinces of Alberta, British Columbia, Manitoba, New Brunswick, Newfoundland, Nova Scotia, Quebec, and Saskatchewan, and by the Federal Department of Public Works and Government Services Canada. A major share of both the financial support and technical support staff were contributed by the Province of Ontario. This Code could not have been developed without the cooperation of all the sponsors and particularly that of the Ontario Ministry of Transportation.
This Code was prepared by the CSA Technical Committee of the Canadian Highway Bridge Code under the jurisdiction of the CSA Strategic Steering Committee on Structures (Design), and was approved by these Committees. It has been approved by the Standards Council of Canada as a National Standard of Canada.
Scope
1.1.1 Scope of Code
The 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 the provisions do not necessarily cover all aspects of design for every type of long span bridge. Provisions are also included for the design of pedestrian bridges, retaining walls, barriers, and highway accessory supports of a structural nature, such as lighting poles and sign support structures.
The Code is not intended to apply to public utility structures nor to bridges used solely for railway or rail transit purposes.
Requirements are not specified for the consideration of coastal effects such as exposure to sea action and icebergs, nor for conditions in high mountain terrain such as avalanche effects. Experienced specialists must be retained to advise on or review the design of structures that may be subject to such effects, and must ensure that all relevant and applicable requirements of other codes are met.
For bridges not entirely within the scope of the Code, its provisions apply only when appropriate. All necessary additional or alternative design criteria are subject to Approval.
Several Sections have Appendices that contain less frequently used or referenced material. These Appendices should be considered as part of the Section to which they are appended.
1.1.2 Scope of Section 1
Section 1 gives provisions for the application of the Code and requirements of a general nature for bridges, culverts, and related works. Its provisions govern basic geometry and hydraulic design. General requirements are given for subsidiary components, deck drainage, maintenance and inspection access. Broad guidelines are provided concerning economic, aesthetic, and environmental considerations.
