Performance of New Connections for Robustness Design of Cold-Formed Steel Structures

This paper presents a new cold-formed steel (CFS) connection designed to increase the horizontal tying in CFS structures aimed at robustness design and progressive collapse mitigation, as traditional CFS connections are typically designed to resist shear forces and bending moment but fails to resist significant tension forces (membrane forces) resulting from large catenary action under stud wall removal scenarios. The paper first presents six sub-assembly tests with varying configurations to investigate the effects of two new elements, i.e. stiffener and bottom plate, on increasing the capacity of tension forces, referred to as tying force, to resist appreciable membrane forces. The bottom plate, showing significantly enhancement of tying force, is incorporated to the proposed joist-to-joist bottom plate connection (JBPC). Next, the paper describes the parametric study to investigate the behaviour of JBPC and its influencing factors, based on the validated finite element model. A mechanical model is also presented for determining the tying force of the JBPC, expressed as a function of the membrane force capacity and its corresponding vertical displacement. A conversion between vertical concentrated load and line load is also presented.