Unseating Prevention Of Highway Bridge With SMA Restrainers Under Earthquake Excitations

In recent years, with the increase of seismic losing, the investigation on structural seismic has attracted great attentions of the researchers. During the past several strong earthquakes, most of the highway bridge suffered from unseating and pounding damage due to large displacement between the adjacent frames. One traditional approach for mitigating the unseating of the highway bridge is to use restrainers made of steel cables and rods. However, the elastic design demands of the restrainers will induce large additional forces on the structural components of the bridges. Aiming at this important theoretical and engineering issue, this paper investigates the performance of the shape memory alloy (SMA) restrainers for the unseating reduction of the highway bridge, adopting the smart material shape memory alloys as the material of the restrainer, through the analytical model of the structure with pounding effects in conjunction with the SMA restrainers. The main contents include:(1) Cyclic tensile tests on superelastic NiTi SMA wires were carried out. The effects of the different loading conditions, namely: cyclic loading-unloading number, strain amplitude and loading frequency, on the mechanical behavior were examined. A simple constitutive model of superelastic SMAs was proposed.(2) Based on the design method of the traditional restrainer, a improved and more accurate design method was proposed, considering the nonlinear character of SMAs and plastic of the piers. Establish a finite element model of a typical bridge by the large finite element software ANSYS. Through the time-history analysis, the performance of the SMA restrainer for eliminating the bridge unseating and pounding of the highway bridge was investigated.(3) Through the shaking table test of a highway bridge, the performance of the pounding was investigated. Establishing a reduced scale model of a bridge, the pounding response of the model with and without SMA restrainers in the earthquake was simulated. Investigate the performance of the shape memory alloy (SMA) restrainers for the unseating reduction of the highway bridge.