Ultimate Strength, Ductility and Failure Mode of High-Strength Frictional Bolted Joints Made of High Strength Steel

Abstract

Further structural rationalization of steel bridge such as weight reduction of members is realizable by utilizing high strength steel. However, due to the high yield-to-tensile strength ratio, failure of connected members occur before the members in gross area has been plastic-deformed sufficiently. In this study, tensile tests of frictional bolted joint which varies geometrical configurations and grades of plate and bolts, were conducted to compare failure modes of high strength steel joint and mild steel joint and to investigate the relationship among ultimate strength, ductility and failure mode. From obtained results, failure modes of high strength steel joint were the same as those of mild steel joint and can be almost classified with the respective ratios of net cross-section failure resistance and plate shear failure resistance to bolt shear failure resistance. Ultimate resistance and ductility became highest in the case of split failure mode where these ratios were about 1.0 and they increased as the ratios decreased. Therefore, it’s concluded that these ratios should be less than 1.0 to induce split failure mode for making high strength steel joint be broken after the member has been plastic-deformed sufficiently.