Experimental investigation on cold-formed steel built-up columns based on modular component method

Abstract

This study aims to investigate the buckling behavior, assembly effects, and ultimate capacity of cold-formed steel columns. The research encompasses five distinct types of cross-sectional columns, namely C-sections, U-sections, modular components, and closed sections, which were analyzed through both experimental and theoretical approaches. The failure modes of the columns were summarized, and the underlying reasons for these failures were elucidated. Compression tests were performed to assess the impact of cross-sectional dimensions, plate assembly effects, and screw spacing. Additionally, evaluations of material properties and measurements of imperfections were conducted. The test results, including the ultimate load, were compared with predictions derived from the current Effective Width Method (EWM) and Direct Strength Method (DSM) design approaches. The results indicate that the EWM tends to be excessively conservative, whereas the DSM presents a marginally unsafe assessment. A novel design method is proposed based on the experimental investigations presented in this paper. This new approach integrates the effects of screw restraint and plate group interactions into the design principles for predicting the ultimate capacity of box section columns, specifically utilizing a superposition method of the modular component. Ultimately, the proposed method was evaluated using test data alongside the EWM and DSM. Reliability analysis demonstrated that the proposed method offers more accurate and safer predictions for ultimate capacity compared to the original EWM and DSM as outlined in the AISI-S100 specifications.