In low-rise steel structures, tension angles are widely adopted for earthquake resistance. Failures of the tension angles at joints with high-strength bolts have three modes: net section fracture, end fracture, and outer tearing 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 outer tearing fractures actually occur in tension angles, in addition to these other two fracture types, we need to make a design formula for the outer tearing fracture. In this research program, we examine experimentally the effects of the bolt-hole arrangement and edge distance of the bolted joints on the ultimate strength of the tension angles and the failure modes. We propose formulas to predict the ultimate strength of joints for the net section and the outer tearing failure modes.
