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 (CFSBBC) 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 CFSBBC 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.