Numerical study of joint behaviour for top-seat flange cleat connection in cold-formed steel structures

Abstract

The use of cold-formed steel for primary load bearing members in low and medium rise buildings has become an increasingly popular form of construction. The design of connections between these members is crucial to the overall structural integrity of such buildings. However, for beam-to-column joint design, recent codes of practice show ambiguity in the mechanical behaviour. Further research is required to investigate the strength, stiffness and ductility prediction of such connections. This paper addresses these concerns by proposing simplified formulas for the moment-rotation behaviour of light steel frames with bolted top-seat flange cleat joints. A finite element study is presented which is validated against laboratory experimental tests on cold-formed steel arrangements. The validated model is used within a parametrical study to investigate several additional geometrical parameters that are not included in the experimental works. An exponential equation has been proposed for large deformation of top-seat flange cleat joint under monotonic vertical load. The predictions using the equations are compared to the design codes (BS EN1993-1-8) and experimental data. From the comparison, the proposed equation can improve the BS EN1993-1-8 prediction from 168.08% difference, compared to experimental results, to 7.09% difference. The new proposed model gives a safe design for top-seat flange cleat joint in cold-formed steel light frame construction.