CSA S6:19

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 rei