Ultimate strength and ductility of welded box-section compression members

In recent years, many studies have been conducted related to the ultimate strength of steel compression members regarding initial imperfection effects. Most specifications have also proposed the allowable design strength formulations that have considered local and global buckling effects. However, only a few studies that have focused on the ultimate strain and critical area, especially for box-section compression members. Present study investigated the ultimate stress and strain of in-plane compression members related to slenderness and width–thickness ratio and also effective failure length related to local buckling effect. Beam and shell Finite-Element (FE) models regarding initial displacement and residual stress as initial imperfection factors were analyzed using ABAQUS software. Results indicated that local buckling occurred in the compression members with the width–thickness ratio bigger than 0.7, and generally, slenderness has a more significant effect in decreasing the ultimate stress and strain than the width–thickness ratio. Finally, an effective failure length formula was introduced to assess some of critical areas on the steel compression members. The results of the present study are suitable to be applied for bridge or building welded steel compression members.