Bracing requirements for a semi‐rigidly connected column considering column lateral stiffness and initial curvature

This paper theoretically assesses the required brace stiffness and strength for a semi‐rigidly connected column with a lateral brace at the mid‐height, by introducing a half‐length column model and adopting the concept of storey‐based buckling. Unlike that in Winter's model, column lateral stiffness and initial curvature associated with column initial out‐of‐straightness are accounted for. A coefficient, which is a function of applied load and column end connection stiffness, is introduced to characterize the effect of column initial curvature on bracing requirements. By comparing the results obtained from the analytical method and current structural steel and cold‐formed steel design standards, it has been found that the required brace strength stipulated in these standards are generally conservative in various degrees for design loads; however, the required brace stiffness should be increased if the effect of column initial curvature is considered. The results obtained from the proposed approach are verified against the finite element analysis, indicating that the proposed approach provides an accurate evaluation of required brace strengths for semi‐rigid columns and is recommended to be adopted for engineering practice.