Efficient design of cold-formed steel bolted-moment connections for earthquake resistant frames

Ye, Jun and Mojtabaei, Seyed Mohammad and Hajirasouliha, Iman and Pilakoutas, Kypros (2020) Efficient design of cold-formed steel bolted-moment connections for earthquake resistant frames. Thin-Walled Structures, 150. 105926. ISSN 0263-8231 (https://doi.org/10.1016/j.tws.2018.12.015)

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Cold-formed steel (CFS) sections can be designed in many configurations and, compared to hot-rolled steel elements, can lead to more efficient and economic design solutions. While CFS moment resisting frames can be used as an alternative to conventional CFS shear-wall systems to create more flexible space plans, their performance under strong earthquakes is questionable due to the inherited low local/distortional buckling of thin-walled CFS elements and limited ductility and energy dissipation capacity of typical CFS bolted-moment connections. To address the latter issue, this paper presents a comprehensive parametric study on the structural behaviour of CFS bolted beam-to-column connections with gusset plates under cyclic loading aiming to develop efficient design solutions for earthquake resistant frames. To simulate the hysteretic moment–rotation behaviour and failure modes of selected CFS connections, an experimentally validated finite element model using ABAQUS is developed, which accounts for both nonlinear material properties and geometrical imperfections. Connection behaviour is modelled using a connector element, simulating the mechanical characteristics of a bolt bearing against a steel plate. The model is used to investigate the effects of bolt arrangement, cross-sectional shape, gusset plate thickness and cross-sectional slenderness on the seismic performance of CFS connections under cyclic loading. The results indicate that, for the same amount of material, folded flange beam sections with diamond or circle bolt arrangements can provide up to 100% and 250% higher ductility and energy dissipation capacity, respectively, compared to conventional flat-flange sections with square bolt arrangement. Using gusset plates with the same or lower thickness as the CFS beam may result in a premature failure mode in the gusset plate, which can considerably reduce the moment capacity of the connection. The proposed numerical model and design configurations can underpin the further development and implementation of CFS bolted-moment connections in seismic regions.