Experimental and numerical study on mechanical behavior of high-strength lockbolted friction grip connections

Despite the wide application of high-strength bolts joint in steel bridges, there are still some issues with this jointing technology such as large variation in the bolt preload, looseness of the joint as well as the fatigue problem. In this study, the high-strength lockbolted friction grip (HSLFG) connections were proposed as an alternative and the experimental results indicated that HSLFG connections have comparable mechanical behavior and strength to that of high-strength bolted friction grip (HSBFG) connections. First, the experiments were carried out on four HSLFG connections and four conventional HSBFG connections, in which the mechanical properties of both connections such as the failure modes, load-bearing behavior, and load-strain relationships were obtained and compared. The experimentally results indicate that the preload of the high-strength lockbolts satisfy the requirements of Eurocode3 and JTG D64-2015. Refined finite element (FE) models were established and were verified against the experimental results which proved the FE models could effectively predict the elastic-plastic behavior and positions of rupture of the HSLFG connections. Furthermore, the parametric analysis of FE model was conducted to investigate the effect of element types, friction coefficients on the mechanical property of the HSLFG connections. This research provided a promising strategy for the development requirements of HSLFG connections in steel bridges.