Finite element analysis on tensile stiffness of cold-formed steel bolted connections

This paper presents a finite element analysis on the tensile stiffness of steel bolted connections, which are fabricated from thin-walled cold-formed steel strips and members. This type of bolted connection is usually used to assemble the diagonal bracing member in the light steel structure. Unlike the architectural steel structure, thin walled steel bolted connection cannot be simplified into a hinge joint due to the weak tensile stiffness of connection. The calculation of tensile stiffness of bolted connection is necessary to accurately evaluate the effectiveness of bracing system in the cold-formed steel structure. Based on the existing test results and analysis results, finite element (FE) models with three-dimensional solid elements were established to investigate the tensile stiffness of bolted connections between cold-formed steel plates under shear. The analysis with non-linear material and contact elements was carried out in order to predict the load-displacement relationships of bolted connections. Furthermore, a parametric study on single-bolted or two-bolted connections with different configurations was performed to study the relationship of connection tensile stiffness and structural parameters such as bolt diameter, plate thickness and steel yield strength. According to the stiffness results from parametric study, six calculating equations for practical design of cold-formed steel bolted connection were proposed. The calculation results of the stiffness equations have a good correlation with those of FE analysis, and the proposed equations are found to provide estimates of tensile stiffness of bolted connections with reasonable accuracy.