Local buckling of cold-formed high-strength steel hollow section columns at elevated temperatures

Abstract

A numerical investigation is conducted on the local buckling behavior of cold-formed square hollow section (SHS) and rectangular hollow section (RHS) columns made of normal and advanced high-strength steels at elevated temperatures. Shell finite element models validated against experimental results are used in a parametric numerical study to evaluate the local buckling strength at ambient and elevated temperatures of SHS and RHS columns fabricated with G450, dual-phase, and martensitic steels. The modeling uses recent experimental data on the elevated temperature behavior of advanced high-strength steels. The numerical results are compared with the design strengths calculated by the Direct Strength Method in AISI S100. Results show that the current method in AISI S100 consistently captures the trend but overestimates the ultimate capacity of G450 cold-formed columns both at ambient and elevated temperatures by about 10% for the SHS columns and 6% for the RHS columns. The current Direct Strength Method also yields higher estimates of capacity than the finite element models for advanced high-strength steel grades. Therefore, a modification to the method for local buckling capacity is proposed for these sections. The modified Direct Strength Method proposed herein can be used to evaluate the local buckling strength of cold-formed SHS and RHS columns made of normal and advanced high-strength steels at temperatures up to 700 °C.