强震区新型铁路延性构造桥墩抗震性能试验研究

Experiment on seismic performance of new type railway pier with ductile structure in strong earthquake area

关键词:  铁路桥墩  延性构造  损伤行为  破坏机制  抗震性能

Key words:  railway pier  ductile structure  damage behavior  failure mechanism  seismic performance

摘要:

为提升高烈度地震区铁路桥墩的延性抗震性能,降低强震作用下墩底内力,保护桩基础,提出了两种新型铁路延性构造桥墩方案,并对1个原型桥墩及2个新型延性构造桥墩模型试件进行了低周往复加载试验,最后分析了不同桥墩的损伤行为、破坏机制、滞回性能、耗能能力、残余位移、刚度和承载能力退化特性。试验结果表明:铁路常用圆端形空心墩破坏形式主要为弯曲破坏,在墩底塑性铰区域,裂缝大量开展,混凝土剥落、箍筋外露、部分纵筋断裂；而两种延性构造桥墩的破坏形态更接近于摇摆墩柱的边角破坏,破坏区域主要集中在墩底0～20 cm之间,到试验结束为止,墩身仅出现6～9条水平裂缝,墩底边缘混凝土局部压溃脱落；新型延性构造桥墩初始刚度可与原型桥墩保持一致,满足铁路桥墩的刚度需求,保证行车运营安全；新型延性构造桥墩模型2、模型3的等效屈服力分别为原型桥墩的91.31%和77.12%,墩顶极限水平力分别为原型桥墩的72%和65%,在强震作用下新型延性构造墩可以有效降低墩底及桩基础内力,保护桩基础；新型延性构造桥墩的等效黏滞阻尼比超过原型桥墩的50%,有效提高了铁路圆端形空心桥墩的延性抗震性能。

Abstract:

In order to improve the ductility seismic performance of railway piers in high intensity seismic regions, then reducing the internal force at the bottom of piers under strong earthquakes and protecting the pile foundations, this paper presents two new ductile structure schemes for railway pier. And low cyclic loading tests were carried out on a prototype pier model specimen and two new pier model specimens with ductile structure. Finally, the damage behavior, failure mechanism, hysteretic performance, energy dissipation capacity, residual displacement, stiffness degradation characteristics and strength degradation characteristics of different piers were analyzed. The test results show that the failure mode of round-ended hollow pier commonly used in railway is mainly bending failure. In the plastic hinge area at the bottom of the pier, a large number of cracks develop, concrete flake off, stirrups are exposed, and some longitudinal reinforcement fracture. But the failure modes of two new piers with ductile structure are closer to the corner failure of the rocking pier. Their failure area is mainly concentrated in the range of 20 cm at the bottom of the piers. By the end of the tests, only six to nine horizontal cracks appear on the piers, and partial concrete at the edge of the piers bottom is crushed and peeled off. The initial stiffness of the new piers with ductile structure can be consistent with that of the prototype pier to meet the stiffness requirements of railway piers and ensure the operation safety of trains. The equivalent yield forces of the new piers 2 and 3 are 91.31% and 77.12% of that of the prototype pier, and the ultimate horizontal forces at the top of the piers are 72% and 65% of that of the prototype pier. The internal forces of pier bottom and pile foundation in the new piers with ductile structure can be effectively reduced under strong earthquakes, thus protecting the pile foundation. The equivalent viscous damping ratios of the new piers are more than 50% of that of the prototype pier, and the ductility seismic performance of railway round-ended hollow pier is improved through new ductile structure schemes.