Preface
This edition of CSA Standard CAN/CSA-S136-M89 is based entirely on limit states design principles. and supersedes the previous edition published in 1984. The Standard has been prepared for use with SI (metric) units; however, the designer has the option to use any other consistent system of measurement since the applicable expressions are given in a non-dimensional format.
Considerable technical change, reflecting the latest research developments, has been incorporated into this Standard. These changes are based on an increased understanding of the behaviour of cold formed steel structures, members. and elements and of cold formed steel as a structural material. In addition, a number of editorial clarifications have been made throughout the Standard in order to lessen ambiguity and make provisions less liable to misinterpretation.
The major change incorporated into this edition of the Standard is a Unified effective width approach for the design of compressive elements subject to local buckling. The 1984 edition of S136 already contained a common effective width approach for both stiffened and unstiffened compressive elements subjected to uniform compressive stress. However, in the case of members in bending, a reduction in stress for possible web bending had to be used. This is no longer the case in this edition of the Standard since the effective width approach also covers cases under stress gradient; hence making the Unified effective width approach universally applicable to all compressive elements.
The treatment of compressive elements with intermediate and edge stiffeners has also been revised to allow for the partially stiffened case.
This Standard was prepared by the Technical Committee on Cold Formed Steel Structural Members under the jurisdiction of the Standards Steering Committee on Structures (Design), and was formally approved by these Committees. It has been approved as a National Standard of Canada by the Standards Council of Canada.
Scope and Application
1.1
This Standard applies to the design, based on limit states, of structural members cold formed to shape from carbon or low-alloy steel sheet, strip, or plate up to 25 mm in thickness and intended for load-carrying purposes in buildings. For applications other than in buildings, supplementary specifications shall be provided where necessary to account for differences in structural loads and effects, environment, and other service conditions.
1.2
Where a structure consists of cold formed steel structural members, provision shall be made to ensure adequate stability of the structure as a whole, and adequate lateral, torsional, and local stability of all structural parts so as to provide resistance to widespread collapse due to local failure. Supplementary provisions may be required for structures where accidental loads such as vehicle impact or explosion may occur. Where members designed in accordance with this Standard are intended for use in structures where other recognized standards apply, this Standard shall supplement such standards as applicable.
1.3
The resistance factors adopted in this Standard are correlated with the loads and load factors for buildings as specified in the National Building Code of Canada and Clause 4 of this Standard. For other cases, load factors shall be established such that, in conjunction with the resistance factors used in this Standard, the required level of reliability is maintained.
1.4
Where this Standard provides design expressions or dimensional limitations that are not applicable to a specific situation, a rational design may be used if based on appropriate theory, test, analysis, and engineering judgement.
