Preface 

This is the tenth edition of CSA S16, Design and construction of steel structures . It supersedes the previous limit states editions published in 2019, 2014, 2009, 2001, 1994, 1989, 1984, 1978, and 1974. These limit states design editions were preceded by seven working stress design editions published in 1969, 1965, 1961, 1954, 1940, 1930, and 1924. The 1969 working stress design edition was withdrawn in 1984, from which point the design of steel structures in Canada has been carried out using limit states design principles. The following are the major changes to this edition: a) Minor changes were made to the Scope to bring it into line with the Terms of Reference for the Technical Committee on Design and Construction of Steel Structures. b) The requirement for designers to consider and specify construction live loads has been included for sheet steel deck and structural members supporting the deck. Reference has been made to CSSBI 12M for determining provisions for deck supporting the plastic concrete, with the option of designing structural members supporting the deck in accordance with the loading provisions of CSA S269.1. c) Except for planar frames in low-rise buildings under certain conditions, P-Δ effects are to be taken into account by performing a second-order analysis. The U 2 factor approach only gives accurate results for simple structures when lateral loads and stability effects are uniformly distributed among the frames in the direction of load and the structure has limited torsional response. d) The application of gross and net areas has been clarified for the capacity checks of members and connections in tension, compression, and shear. e) The symbols for effective net area when determining the tension load transmitted by welds have been modified to indicate that shear lag effects are considered. f) The methodology for determining the capacity of concentrically and eccentrically loaded hollow structural section tension members with plates in slotted holes has been unified. As the length of the plate in the slotted hole decreases, the member capacity transitions from the net section fully developed through a reduction due to shear lag to a failure governed by block shear tear-out. g) The default parameter for determining the factored axial compression resistance is n = 1.34. The value of n = 2.24 can be used under certain circumstances. h) Elastic analysis is now used to determine the shear resistance of rectangular and square hollow structural section Class 3 and 4 members and fabricated closed box-shapes for which local wall buckling can occur. i) Shear area definitions are provided for determining the shear resistance of hollow structural section members and concrete-filled hollow structural section members where local wall bucking is prevented. j) Provisions for providing lateral and rotational restraint to beams in Gerber construction have been clarified. Where restraint is provided by bolted connections to the beams, the effect of holes for fasteners on strength is to be considered. k) When combining the factored resistance of fillet welds oriented in multiple directions in the same shear plane, the multi-orientation reduction factor, M w , is used regardless of whether the strength- enhancement factor is applied. l) When determining the capacity of welds for hollow structural section members, the geometric properties are to be determined in accordance with CSA W59. m) In addition to the capacity when modelled as a column, a requirement has been added to check the factored bearing resistance of bearing stiffeners, B r . n) The requirements for determining the combined shear and moment capacity of beams and girders applies to members with or without transverse stiffeners. o) Structural elements of cold-formed shape used for OWSJs may use the effect of cold-forming in accordance with Section A3.3 of AISI S100. Yield levels reported on mill test certificates or determined in accordance with Section K2.3 of AISI S100 are not to be used. p) Clarification has been added that the unified block shear capacity equation applies whether or not a tension plane is present at the block perimeter. q) The scope for concrete-filled hollow structural section members has been revised to allow higher concrete strengths for members subjected to axial compression and bending. An upper limit of 500 MPa has been specified for reinforcing steel yield strength in design calculations. r) The expressions for determining the compressive resistance and bending resistance of concrete- filled hollow structural section members have been revised to include the contribution of longitudinal reinforcing steel to strength. The new expressions are based on the integration of fully plastic stress blocks for the concrete, structural steel, and reinforcing steel. s) For concrete-filled hollow structural section members required to resist both bending moment and axial compression, the coefficient for bending in beam-columns, β, has been revised to be consistent with that used for unfilled hollow structural section members, and the coefficient to determine equivalent uniform bending effect, ω 1 , has been specified. t) A requirement has been added for determining the capacity of concrete-filled hollow structural section members in tension or shear. u) The requirement for determining the capacity of bearing connections with filler plates has been updated to be consistent with provisions adopted by the AISC and RCSC. v) Reference has been made to ASTM F3393 listing acceptable coatings that will not change the mechanical properties of zinc/aluminum coated bolt assemblies. w) For hot-dip galvanized surfaces of slip-critical connections, power wire brushing is not permitted on faying surfaces as indicated by RCSC. x) Requirements for column bases and anchor rods have been revised to harmonize as much as practical with CSA S6 and CSA A23.3, Annex D (on anchorages). The requirements for determining resistances controlled by steel remain in CSA S16 and reference is made to CSA A23.3 for resistances controlled by concrete. Clauses have been added to determine the capacity of anchor rods with both grouted and ungrouted base plates; anchor rods subjected to combined shear, tension, and bending; anchor rods subjected to combined shear, compression, and bending; and shear lugs. y) The design requirements have been updated to include a variable amplitude loading fatigue limit. z) A new requirement has been introduced to determine the fatigue stress range resistance of transversely loaded partial penetration groove welds and transversely loaded fillet welds. aa) The seismic design forces and resistances requirements describing capacity design for yielding elements of the SFRS, non-yielding elements of the SFRS, diaphragms, anchorage of the SFRS to foundations, and the design requirements for foundations have been updated to reflect research over the last decade, improve consistency in the treatment of diaphragms, and address the design of foundations for steel buildings. ab) Special requirements for the seismic design of bolted connections have been limited to the members within the vertical elements of the SFRS. ac) To address new provisions in the NBC, additional performance requirements related to elastic behaviour have been defined for seismic design. ad) For Type D (ductile) moment-resisting frames, the approach for determining column slenderness, limits on gravity-induced axial load, and joint panel design requirements have been updated to reflect new research and supporting analysis. ae) For Type MD (moderately ductile) concentrically braced frames, updated requirements, and definitions for various bracing systems including V, inverted-V, two-storey X-bracing, and multi- tiered bracing have been included. Updated requirements for bracing connections have been added, as well as a new requirement for X-bracing centre connections. Clarification has been added for the additional bending moment to be assumed in braced bay columns. af) For Type LD (limited-ductility) concentrically braced frames, requirements have been updated for the design of multi-tiered bracing and a simplified method was included for designing struts and columns. ag) For Type D (ductile) eccentrically braced frames, the requirements for various link beam systems have been brought forward to a new clause, and new cast modular link provisions have been added. For modular end-plate connected I-section links, the requirements for the link length and inelastic rotation have been updated, and modifications have been made to the provisions for the design of end-plate connections. Clarification has been added for the additional bending moment to be assumed in braced bay columns. ah) For Type D (ductile) buckling restrained braced frames, new requirements and definitions for various bracing systems, including V, inverted-V, two-storey X-bracing, and multi-tiered bracing, have been added. Clarification has been added for the additional bending moment to be assumed in braced bay columns. ai) For conventional construction, substantial revisions have been made to the design provisions, including requirements for diaphragms, reference to the provisions of NBC and CSA A23.3 for the design of foundations, requirements for moment frames, and provisions for concentrically braced frames. aj) In Table 1 for members subject to axial compression, the maximum width-to-thickness ratio for elements supported along one edge has been increased and maximum width (or diameter)-to- thickness ratios have been added for concrete-filled hollow structural section elements. ak) In Table 2 for members subject to flexure or combined flexure and compression, the maximum width-to-thickness ratio for elements supported along one edge has been increased, height-to- width ratios for rectangular hollow structural section members have been included, and maximum width (height or diameter)-to-thickness ratios have been added for concrete-filled hollow structural section elements. al) For the design of members subject to load-induced fatigue, Table 8 has been rearranged to place in sequence new detail figures from CSA W59 that were introduced in the 2019 edition of this Standard. am) The illustrative examples for members subject to load-induced fatigue in Figure 2 have been renumbered in the order presented in Table 8. Some examples have been added for consistency with CSA W59. an) Annex J on qualification testing provisions for seismic moment connections and buckling restrained braces has been revised to include additional requirements for the testing of links in eccentrically braced frames. ao) Annex K on structural design for fire conditions has been revised to include provisions from the latest version of AISC-360, Appendix 4. ap) Annex N on design and construction of steel storage racks has been removed from the Standard. In its place, a new Annex N that addresses the seismic design of Type D (ductile) concrete-filled composite plate walls and Type D (ductile) coupled concrete-filled composite plate walls has been added. aq) Annex P on guidelines for specifying third-party inspection of steel structures has been revised to include steel components used in conjunction with other materials and to indicate that weld inspection requirements for brownfield sites are more frequent than for greenfield sites. ar) Annex Q on additional requirements for castings used as energy-dissipating elements has been added for the specification of castings in seismic applications. as) Annex R, a new informative annex on a quality management system for structures, has been added. A commentary on this Standard, prepared by the Canadian Institute of Steel Construction with contributions from many members of the Technical Committee, comprises Part 2 of the Institute’s Handbook of Steel Construction. This Standard is intended to be used with the provisions of the 2025 edition of the National Building Code of Canada (NBC), specifically Clause 7, which references the NBC for load factors, load combinations, and other loading provisions. Annex K is reprinted with modifications from ANSI/AISC 360, Appendix 4. Copyright American Institute of Steel Construction. Reprinted with permission. All rights reserved. This Standard was prepared by the Technical Committee on Design and Construction of Steel Structures, under the jurisdiction of the Strategic Steering Committee on Construction and Civil Infrastructure, and has been formally approved by the Technical Committee. This Standard has been developed in compliance with Standards Council of Canada requirements for National Standards of Canada. It has been published as a National Standard of Canada by CSA Group. 

Scope and application 

1.1 General 

This Standard provides rules and requirements for the design, fabrication, and erection of a broad range of steel structures based on limit states design approach. The term “steel structures” refers to structural members and frames that consist primarily of structural steel components, including structural steel acting compositely with concrete, and detail parts, welds, bolts, or other fasteners required in fabrication and erection. This Standard also applies to structural steel components in structures framed in other materials. The clauses related to fabrication and erection serve to show that design is inextricably a part of the design-fabrication-erection sequence and cannot be considered in isolation. For matters concerning standard practice pertinent to the fabrication and erection of structural steel not covered in this Standard, see Annex A. For information on the use of quality management systems for the fabrication of steel structures, see Annex R. 

1.2 Requirements 

Other CSA standards cover the requirements for steel structures, such as bridges, antenna towers, offshore structures, and steel storage racks, whereas the requirements for cold-formed steel structural members are given in AISI S100. 

1.3 Application 

This Standard sets out minimum requirements and is expected to be used only by engineers competent in the design and construction of steel structures. It applies unconditionally to steel structures, except that supplementary rules or requirements might be necessary for a) unusual types of construction; b) mixed systems of construction; c) steel structures that i) have great height or spans; ii) are required to be movable or be readily dismantled; iii) are exposed to severe environmental conditions; iv) are exposed to severe loads such as those resulting from vehicle impact or explosion; v) are required to satisfy aesthetic, architectural, or other requirements of a non-structural nature; vi) employ materials or products not listed in Clause 5; or vii) have other special features that could affect the design, fabrication, or erection; d) tanks, stacks, other platework structures, poles, and piling; and e) crane-supporting structures. 

1.4 Other standards 

The use of other standards for the design, fabrication, erection, and/or inspection of members or parts of steel structures is neither warranted nor acceptable except where specifically directed in this Standard. The design formulas provided in this Standard may be supplemented by a rational design based on theory, analysis, and engineering practice acceptable to the authority having jurisdiction, provided that nominal margins (or factors) of safety are at least equal to those intended in the provisions of this Standard. The substitution of other standards or criteria for fabrication, erection, and/ or inspection is expressly prohibited unless specifically directed in this Standard. 

1.5 Terminology 

In this Standard, “shall” is used to express a requirement, i.e., a provision that the user is obliged to satisfy in order to comply with the Standard; “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 Standard. 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.