Seismic performance of cold-formed steel bolted moment connections with bolting friction-slip mechanism

Typical cold-formed steel (CFS) moment-resisting connections generally have relatively low ductility and energy dissipation capacity as a result of low local/distortional buckling resistance of thin-walled CFS elements, and therefore, may not be suitable for seismic applications. To address this issue, a comprehensive analytical study is presented on the seismic performance of CFS bolted beam-to-column connections with fiction-slip mechanism aiming to obtain more efficient design solutions suitable for CFS frames in seismic regions. Experimentally validated finite element (FE) models in ABAQUS are used to predict the hysteretic behaviour and failure of a range of CFS connections by taking into account the characteristics of the bolting system as well as nonlinear material properties and geometrical imperfections. The developed models are then used to investigate the effects of CFS beam cross-sectional shape and classification, bolt configuration, and slip resistance on the seismic performance of the connections. It is shown that using bolting friction-slip mechanism can significantly increase (up to 200%) the ductility, energy dissipation capacity and damping coefficient of the connections especially for CFS beams with thinner plates (class 3 and 4). Based on the results, the best design configurations are identified to improve the cyclic response of the CFS connections under strong earthquakes. While conventional bolted moment connections with class 3 and 4 beam cross-sections generally do not satisfy the AISC requirements for intermediate and special moment frames, it is shown that optimum designed connections with bolting friction-slip mechanism can be efficiently used in high seismic regions.