Global Buckling Performance of Cold-Formed Steel Face-to-Face Built-Up Columns

This paper presents an experimental, numerical, and theoretical investigation of cold-formed steel face-to-face built-up columns (CFS-FBC). Twelve global buckling built-up columns with different lengths and screw arrangements were experimentally studied. According to the test results, the load-bearing capacity of CFS-FBC was significantly affected by the arrangement of screws. Decreasing screw spacing from 300[Formula: see text]mm to 200[Formula: see text]mm resulted in a 1–5% increase in load-bearing capacity, while further reducing it to 100[Formula: see text]mm led to an increase of 10–20%. Numerical models were created and calibrated based on compression tests, with parametric analyses conducted to further explore the influence of screw arrangements. It was demonstrated that the most effective method to improve the global buckling behavior of the CFS-FBC was reducing the screw spacing. The theoretical elastic global buckling load of CFS-FBC was derived based on the energy method, taking into account screw arrangements and shearing stiffness. The derived buckling load was compared with the simulation results to validate its accuracy, and then it was introduced into the AISI-S100 design framework to calculate the load-bearing capacity of CFS-FBC. It was found that the proposed method has excellent advantages in accuracy and effectiveness. A reliability analysis was carried out to indicate that the proposed method was on the safety side in predicting the load-bearing capacity of CFS-FBC.