A simple equation for axially loaded steel column design curves

Clause 13.3 of the Canadian Standards Association Standard CAN/CSA-S16.1-M89 "Limit states design of steel structures" utilizes complex five-piece curves to specify the limiting capacity of axially loaded steel columns. A study of these equations shows that they do not fit smoothly together. The resulting curves are scalloped. It has been found that the five-piece curves can be replaced by one continuous equation which never deviates by more than approximately 3% from the S16.1-M89 values. The proposed equation is applicable to all three column curves of the Structural Stability Research Council with only a change in the value of the exponent. The proposed equation has been adopted in the recently published CAN/CSA-S16.1-94 standard.