Global buckling analysis on cold-formed steel built-up box-shape columns at ambient and elevated temperatures

This paper presents a study on the global buckling load of the cold-formed steel built-up box-shape columns (CFS-BBC) at ambient and elevated temperatures. The energy method was employed to calculate the elastic global buckling stress of the CFS-BBC, where screw spacing and shearing-resistance stiffness were incorporated. Numerical models were developed and verified against the test results. Parametric analyses were carried out to verify the effectiveness of the AISI-S100 design method for predicting the global buckling capacity of the CFS-BBC at ambient and elevated temperatures. It was found that when the elastic global buckling load proposed in this paper was incorporated into the AISI -S100 design method, it had a reliable result at ambient temperatures but an unconservative result at elevated temperatures. The coefficient in the AISI-S100 design method was modified based on parametric analyses, and the modified design method was verified against test results. A reliability analysis is performed to indicate the safety of the proposed design method.