低周往复荷载作用下预应力锚索震害特征研究

以地震灾区的震害斜坡为原型搭建锚固工程模型,采用低周往复荷载试验方法,研究预应力锚索在往复荷载作用下的震害特征与变形规律。结果表明:在往复荷载作用下,预应力锚索最先发生破坏且破坏最为严重的是位于模型最上排的锚索,其破坏形式以锚索体自由段根部拉断和外锚头脱落为主,未出现内锚固段黏结力和握裹力失效现象;锚索体应变显著变化的部位集中在锚固段,一处靠近锚固段底部,另一处靠近滑面位置,且尤以靠近滑面处的应变较大;往复荷载比单一的水平推力对锚索的变形影响更大,更容易导致材料的破坏。该成果对地震灾区预应力锚索的健康诊断与震害评估具有一定的参考价值和指导意义。

STUDY ON SEISMIC DAMAGE CHARACTERISTICS OF PRESTRESSED ANCHOR CABLES UNDER LOW FREQUENCY RECIPROCATING LOADS

The study includes an experimental mode constructed based on a real prestressed anchor cable project in the earthquake-stricken zone，where the seismic loading is imposed through low frequency reciprocating loading. The results of the experimental study are summarized. First，the failure of prestressed anchor cables occurs from the upper to the lower part in sequence under reciprocating loading. The top row of cables is the most severely damaged part，where the failure types are dominated by the breakage at the bottom of the cable and the detachment at the head of the cable. No evidence is observed that supports any failure and destruction of bond force and bond stress of the anchoring section. Second，the deformation of cable concentrates on the anchoring section with large strain occurred on the bottom of the section and the part adjacent to the sliding surface. Small strain is found on the free segment. Third，the reciprocating loading imposes greater impact on the prestressed anchor cables in terms of deformation compared to the constant mono-directional thrust or single mono-directional thrust. The reciprocating loading test is the most widely used approach in the experimental study of seismic structural performance，the results obtained in this study provides a mean of systematic evaluation on the safety and quality of prestressed anchor cables during and/or after the earthquake and can be used in comparison with other study on the seismic performance of prestressed cables.