近断层地震作用下高墩刚构桥抗震性能与减震控制研究

In recent years, hundreds of rigid frame bridges with relatively large pier height between 40m and 200m have been erected in mountainous areas where natural barriers and complex landform are common. However, since seismic zones and faults are widely distributed in China, most rigid frame bridges are inevitability adjacent to faults. Near fault earthquakes which contain a large percent of long-period, large velocity pulse-like and vertical vibration show significant effects on high-pier rigid frame bridges with high piers and long periods while domestic studies on this issue are rarely seen. This project selects typical high-pier continuous rigid frame bridge in mountainous areas as target. Scaled model of typical high-piers and the pier-girder rigid node will be conducted pseudo static tests to obtain the failure modes and hysteretic model of plastic hinges. The original model will also be theoretically analyzed and numerically simulated under near-fault seismic excitations. This study will focus on the different structural parameters such as height of piers, level differences of piers, spans, approach spans, etc. Influences of the characters of near-fault earthquakes on the seismic performance of such bridges are also included in the research scope. The position and mechanism of plastic hinge, seismic performance of pier-tie beam joint core area, damage mechanism of joint part between pier and girder under vertical seismic excitation, damage mechanism of bearings and pounding effect, etc. will be intensively studied. Research results will provide useful suggestions to improve the seismic performance of continuous rigid frame bridges under near-fault earthquakes, which may also be referable for further revising and optimizing on related specifications.

近年来，我国山区40-200m墩高的高墩刚构桥已相继建成数百座，而山区地形地貌复杂、地震带分布广、断层数量多，使得此类桥梁的选址难以避开断层。近断层地震动的长周期成分丰富、脉冲效应、竖向震动分量大等特点，对于此类桥梁抗震性能的影响如何，国内外的相关研究还较为鲜见。鉴于此，本项目拟选取典型山区高墩刚构桥，通过典型高墩结构及墩-梁节点缩尺模型的拟静力试验得到失效模式，进而通过对原型结构的抗震理论分析及数值模拟，研究墩高、墩高差、跨数跨度、引桥类型等结构设计参数及脉冲效应、竖向分量等近断层地震动特性，对高墩刚构桥抗震性能和地震易损性的影响规律，着重分析高墩成铰位置及机理、桥墩-系梁节点抗震性能、竖向地震分量下墩-梁固结区损伤机理、支座破坏机理及梁端碰撞效应等，并提出提高其抗震性能的减震控制方法。本项目的研究成果将为提高近断层山区高墩刚构桥的抗震性能和修订和完善相关规范奠定一定的基础。

随着高墩刚构桥梁在中国的大量修建，其抗震性能也越来越引起重视。本项目以典型双肢高墩刚构桥为主要研究对象，首先基于精细化建模、弹塑性动力时程分析及IDA分析手段，分析了传统设置钢筋混凝土系梁对双肢高墩抗震性能的影响规律，对系梁设计参数及桥墩设计参数的敏感性进行了研究，对比了近远场地震激励下高墩刚构桥的地震易损性；提炼了桥梁碰撞模型，提出了考虑纵向梁端碰撞效应对于桥梁地震动力响应的影响规律，进而提出可更换耗能系梁的概念，并提出了两种不同耗能机制的耗能系梁，其在代替传统钢筋混凝土系梁实现桥梁静力稳定性的基础上，遭受地震时能够起到兼顾耗能的作用，保证双肢高墩的墩身和耗能系梁在地震中均不会遭受破坏，并通过动力弹塑性分析验证了其减震控制能力；由于高墩刚构桥存在墩梁固结、基本周期长等特征，无法采用隔震设计，所以对比了复合式金属阻尼器及粘滞阻尼器等几种不同出力机制的被动控制阻尼器对近断层桥梁的减震控制效果，通过理论分析和试验验证了粘滞阻尼器对近断层桥梁减震控制效果较好，而具有两阶段出力特性的复合式金属阻尼器能够兼具耗能及防落梁功能；随着国内设防烈度不断提高，极罕遇地震动概念的提出，针对目前存在的大量的因配筋率不足、钢筋锈蚀等因素导致桥梁延性性能不能满足现行规范的在役桥梁，开展了基于连续玄武岩纤维布进行抗震加固的拟静力试验研究，得出了玄武岩纤维布缠绕在钢筋混凝土柱塑性铰区，可以提高低配筋柱、钢筋锈蚀柱的延性变形能力。