设置无粘结钢筋的铁路重力式桥墩抗震性能试验研究

Experimental study on seismic performance of railway gravity bridge piers with unbonded steel BARS

针对铁路少筋混凝土重力式桥墩的延性不足和抗震耗能能力较差的问题,本文提出了一种兼顾改善桥墩延性与强度的抗震措施,即在墩身底部设置局部纵向无粘结钢筋,其余墩身部分的纵向钢筋保持不变。共设计了4个桥墩模型,通过拟静力试验研究了配筋率和粘结方式对少筋混凝土重力式桥墩抗震性能的影响。结果表明:无粘结模型桥墩的破坏形式为弯曲破坏。与完全粘结的模型桥墩相比,未粘结模型桥墩的滞回曲线更加饱满,桥墩的延性性能和耗能能力均得到了显著提高,且采用无粘结方式对于低配筋率模型桥墩的延性及累积耗能的提高更加明显。配筋率对模型桥墩的刚度退化速率影响较大,且高配筋率的无粘结模型桥墩的刚度退化比低配筋率明显。

For the problems of insufficient ductility and poor seismic energy dissipation capacity of railway concrete gravity bridge piers with low longitudinal reinforcement ratio,this paper proposes a combining seismic measure to improve the ductility and strength of the piers-setting local longitudinal unbonded steel at the bottom of the piers and remaining the other portion of the longitudinal steel same. Four pier models were designed,and the effect of reinforcement ratio and bonding methods on the seismic performance of concrete gravity piers with low longitudinal reinforcement ratio is studied by pseudo-static test. The results show that the failure mode of unbonded bridge pier is bending failure. Compared with the fully bonded model piers,the hysteresis curves of the unbonded model piers are plumper,the ductility and energy dissipation capacity of the unbonded model piers are significantly improved,and the improvement of these performances for the unbonded model pier with low reinforcement ratio is more obvious.The reinforcement ratio has a great effect on the stiffness degradation rate of the model piers. And the stiffness degradation of the unbonded model pier with high reinforcement ratio is more obvious than that with low reinforcement ratio.