Concrete Filled Steel Tubes for Performance Improvement of Steel Truss Bridges

Abstract

The use of concrete-filled steel tubes (CFST) in engineering structures has become popular because of their excellent seismic resistance structural properties such as high strength, high ductility and large energy absorption capacity. In CFSTs the surrounding steel tube provides effective confinement to the filled-in concrete and in turn the concrete helps to reduce the potential local buckling of the steel tube resulting improved seismic resistant performance. This study aimed at investigating the benefit of CFST members in railway steel truss bridges susceptible to earthquake loads. Since the end frames of truss bridges are mainly subjected to compressive loads CFST is a good alternative for end raker. The steel weight of the rib can be reduced with CFST and hence the method is economically sound. The seismic behaviour of steel truss bridges with steel and CFST end rakers is discussed based on the results of nonlinear time history analyses. Five truss bridges were designed with different types of end rakers namely existing HEB end raker, square hollow end raker, three square hollow CFST end raker bridges with varying concrete grades. Time history analyses were performed for transverse direction using selected past earthquakes and natural frequencies, maximum vertical and lateral deflections, residual vertical and lateral deflections and member stresses were checked. It was found that the use of CFST in steel truss bridges can be effectively utilized to improve the seismic resisting performance.