In low-rise steel structures, tension channels are widely adopted for earthquake resistance. Failures of the tension channels at joints with high-strength bolts have three modes: net section fracture, inner tearing fracture, and end fracture. In the current design method, the ultimate strength of the joints is supposed to be examined only for the net section fractures and the end fractures. But, the design values obtained by this method are not always accurate for edge distances and arrangements of bolt holes. Furthermore, as the inner tearing fractures actually occur in tension channels in addition to these other two fracture types, we need to make a design formula for the inner tearing fracture. In this research, we examine experimentally the effects of the bolt-hole arrangement and edge distance of the bolted joints on the ultimate strength of the tension channels and the failure modes. We propose formulas to predict the ultimate strength of joints for the net section, the inner tearing and the end failure modes.
