Prediction of axial-compressive behaviour of bare cold-formed steel studs through a new stud-to-track contact modeling approach

This paper presents a new and accurate finite element contact-modeling approach, to predict the axial compressive behaviour of bare cold-formed steel (CFS) lipped-channel sections (studs) set in tracks under concentric, static axial compressive loading. Detailed finite element analysis (FEA) models of the stud-track assemblies are developed using the ABAQUS software. The new modeling approach is validated against test results and captures stud-to-track gap and contact normal behaviour, which significantly influences studs’ axial compressive performance. Hard contact (HC) has been used widely in literature for its simplicity, although it overestimates axial structural stiffness. Two softened pressure-overclosure relationships, with linear (LSC) and piecewise linear (PLSC) functions, were investigated for the first time in axially loaded bare CFS studs. PLSC best-replicated studs’ axial-compressive behaviour, post-peak response, and failure mechanism under track boundary conditions. PLSC slightly overestimated the axial stiffness by 1 %, underestimating axial shortening and ultimate capacity by 3 % and 6 %, respectively. HC significantly overestimated the axial stiffness by a factor of 3, with a 5 % overestimation of ultimate capacity. LSC failed to predict the accurate failure mechanism for studs having gauge thicknesses less than 3 mm. PLSC scale factors were established and were found to be closely correlated with studs’ non-dimensional slenderness (λ), following bilinear relationships. New predictive equations were developed to determine the PLSC scale factors for λ ranging between 0.49 and 1.2 to enable designers to use accurately calibrated models to capture bare studs’ complex axial compressive behaviour in the elastic and inelastic range.