Limit States Basis for Cold-Formed Steel Design

Limit states design (in a load factor-performance format) is an option in the 1975 National Building Code of Canada. The code specifies one set of load factors common to all technologies: steel, wood, reinforced concrete, etc. The paper describes the method used to determine the appropriate performance factors (α-factors) for use in cold-formed steel design and embodied in the CSA Standard 8136-1974. Two methods were used independently. The deterministic method was designed to yield the same weighted average safety factor as the given working stress version of the standard. The probabilistic method was designed to minimize the weighted mean square error in the safety index vector from a target vector of safety indices. The results agree for the basic case of yielding limit states.