Analytical and experimental study on the seismic performance of cold-formed steel frames

This study aims to investigate the seismic performance of an innovative cold-formed steel (CFS) moment-resisting frame experimentally and analytically. A half-scale CFS moment-resisting portal frame was tested under static monotonic loading until failure. The frame consisted of two box-shaped columns (face-to-face channels connected with inside plates), a back-to-back lipped channel beam section and fully moment-resisting CFS bolted connections. During experimental tests, damage mostly concentrated at the top and bottom of the CFS columns due to the web crippling of the channels close to the connections, while no fracture or obvious slippage was observed at the connection zones. A detailed Finite Element (FE) model was developed using ABAQUS by taking into account the material non-linearity and geometrical imperfections. The lateral load-displacement behaviour, ultimate strength and failure modes predicted by the model were in very good agreement with the experimental results. The validated FE model was then used to assess the effects of key design parameters on the lateral load capacity, ultimate displacement, energy dissipation, ductility, and ductility reduction factor of the frame. It is shown that the proposed system can provide good seismic performance subjected to the appropriate design of the main structural elements. Increasing the axial load ratio of the columns by 50% resulted in 26%, 62%, and 50% decrease in the ultimate lateral load, energy dissipation capacity, and ductility ratio of the CFS frame, respectively. However, the energy dissipation capacity and the ductility ratio of the proposed system increased significantly by decreasing the width-to-thickness ratio of the columns.