Experimental investigation on strength and curling influence of bolted connections in thin-walled carbon steel

Abstract

Experimental studies regarding the influence of curling on the ultimate strength of cold-formed stainless steel bolted connections have been carried out by Kim et al. Basic data and modified equations for predicting the structural behaviors considering strength reduction due to curling through the finite element analysis method have also been suggested by previous researchers.In this paper, single shear bolted connections fabricated with four bolts and thin-walled carbon steel commonly utilized in light-weight structural members were tested to investigate the fracture mechanism and curling influence on the ultimate strength. Main variables for test specimen are plate thicknesses and end distances parallel to the direction of loading. Curling (out-of-plane deformation in the direction of plate thickness) also occurred in thin-walled carbon steel bolted connections with a large end distance and thinner plate like previous cold-formed stainless steel connections. The curling occurrence reduced suddenly the ultimate strength of single shear carbon steel bolted connections and the influence pattern of curling on strength was affected according to the plate thickness and end distance. Current design specifications for block shear strength with the combination of tensile fracture and shear fracture are summarized and the ultimate strengths of test results are compared to the predicted design strengths. AISI (American Iron and Steel Institute) and EC3 (Eurocode 3) made conservative estimates of ultimate strength for thin-walled carbon steel bolted connections with no curling, whereas AIJ (Architectural Institute of Japan) and SSBA(Stainless Steel Building Association) manuals provided a good prediction for ultimate strength and fracture mode. Modified strength equations were recommended respectively for bolted connections with typical block shear fracture considering shear stress factor and severe curling accompanied by strength reduction.