Experimental and analytical study on fatigue behavior of composite truss joints

In order to fully understand the performance of composite joints in a truss bridge with double decks, fatigue tests of three composite joints with different connectors such as headed studs, concrete dowels and perforated plates under constant repeated loading were carried out, and the responses of displacement, strain distribution, crack development, relative slip between concrete and steel were observed after different loading cycles. The experimental results showed that the deflection increased almost linearly with applied load even after certain repeated loading cycles, but the stiffness reduced gradually with the repeated loading cycles. No serious damage occurred except tiny cracks at the steel–concrete interface caused by slip after 2 million repeated loading cycles, which means all three composite joints have good fatigue performance. Based on experimental works, three dimensional finite element models of composite joints were established. The results from finite element analysis were consistent with those from tests in terms of strength and stiffness. Finally, the fatigue details involving reinforcing bars, welding seams and shear connectors were evaluated according to related specifications. The presented overall investigation may provide reference for design and construction of composite joints in composite truss bridges.

► Fatigue behavior of composite joints was experimentally investigated.
► Effects of connector type on fatigue performance were studied.
► Numerical models of composite joints were established and verified.
► Fatigue details were evaluated based on related specifications.