Recommendation on block shear strength equation of double shear four-bolted connection in cold-formed mild carbon steel

In this study, experimental research was performed to investigate the structural behaviors such as the ultimate strength and fracture mode of double shear four-bolted connection fabricated with cold-formed mild carbon steel. It shows that bolted connections failed by either block shear fracture or net-section fracture at test end. Finite element (FE) analysis model was developed to replicate experimental response. After successful verification, it was employed for further analysis such as stress and strain distributions that could not be seen through the physical testing. Three paths on the plate model of bolted connection were established to investigate the critical shear plane and the shear stress distribution on the critical shear plane at ultimate state. A modified block shear fracture strength equation of the bolted connection was proposed considering the shear stress factor (average of ultimate shear stress and yield shear stress) at the critical shear failure plane (midway of gross shear section and net shear section; effective shear plane), and block shear fracture strengths by test and analysis results were compared with those by the suggested equation. It is concluded that the proposed equation is able to provide more accurate prediction in determining block shear strength of double shear four-bolted connection with mild carbon steel.