抬梁式木构古建抗震性能系统化研究

Seismic damage investigation in recent years indicates the Chinese ancient timber structure is usually damaged of different degrees under earthquakes. However systematic researches on seismic behaviors of its constitutions such as tenon-mortise, tou-kung (bracket sets), free-standing column base, roof and so on are still limited. Analytic models of the whole structure which include the constitutions above and roof are still imperfect due to too simply models. In this study, the post and lintel structure which is popular in Chinese northern district is taken as an example. Pseudo-static tests of the cooperation works of energy dissipation of different types of tenon-mortise joints, the cooperation works of seismic resistance of different types of tou-kung are studied; the corresponding mechanisms are further discussed. Then a model is built, which includes all necessary constitutions of Chinese ancient timber building, such as stone base, column, tie beam, tou-kung, beam system, tile roof, filler wall and so on. By shaking table tests, research results by pseudo-static tests are compared and improved; seismic influences of the filler wall to the timber structure, isolation mechanism by swaying motion of free-standing columns and so on are discussed in detail. Finite element analysis considering material properties as well as constitution characteristics of the timber structure is carried out. The analysis results are compared with those of the experiments, based on which perfect analysis model of the whole structure for seismic evaluation is built .

近年震害调查表明地震常常引起木构古建筑不同程度的损伤，而其榫卯节点、斗拱、嵌固墙体、浮放柱底等特性构造的抗震性能研究需系统化，且包含这些构造及屋顶的木构古建筑整体结构性能的分析罕见于文献，仅个例的研究过于简化而使得结论应用受限。本研究以我国北方地区常见的抬梁式木构古建为对象，分别进行构架中榫卯节点协同耗能、不同类型斗拱协同抗震等拟静力试验及机制分析；在此基础之上制作包含柱顶石、柱、大小额枋、斗拱、梁架、瓦顶、墙体等构件的整体模型进行振动台试验，进行单个构造模型与整体模型试验中相应构造的结果对比分析，研究嵌固墙体对木构架的抗震影响机制及损伤破坏时序；详细进行浮放柱底摇晃隔震的试验表象分析和理论研究。完成试验结果与考虑木构材性和构造特征的模型计算结果的对比分析，建立起较为完善的此类古建抗震性能评估的力学分析模型。

近年来地震活动频繁，严重威胁到我国古建筑安全。故宫又名紫禁城，拥有世界上现存规模最大、保存最为完整的古代宫殿建筑群，具有极其重要的历史文化价值，防震保护意义重大。故宫古建筑均属于抬梁式木结构。本项目基于多手段相结合的方法，以故宫古建筑重要构造及结构整体为对象，开展了故宫古建筑传统防震方法、榫卯节点抗震性能及加固方法、斗拱抗震性能、结构整体抗震性能系统化研究，获得了故宫古建筑重要抗震参数，初步解读了故宫古建筑重要抗震构造及结构整体的抗震机制。.本项目的主要研究结论有：(1) 故宫古建筑碎砖—灰土分层基础，有利于上部结构稳定；柱底平摆浮搁在柱顶石上，可产生滑移隔震效果；榫卯节点、斗拱构造均有利于耗散地震能量；梁架低矮，既可避免大尺寸梁截面的使用，还可避免地震作用下产生倾覆。(2) 榫卯节点具有良好的抗震性能；受损的榫卯节点采用不同材料加固时：节点承载力的大小顺序为：CFRP布>钢构件>扒锔子；耗能能力的大小顺序为：CFRP布>钢构件>扒锔子；刚度退化的严重程度为：CFRP布>扒锔子>钢构件。(3) 对于故宫太和殿斗拱而言，其在竖向有良好的承载性能；水平低周反复荷载作用下，斗拱具有明显的滑移特征，自身恢复力较差，耗能能力较强；不同类型斗拱抗震性能并不相同，但恢复力曲线均可用三折线段表示。(4) 故宫古建筑具有优秀的抗震性能；极端烈度地震作用下，故宫古建筑振动形式表现为柱架、斗拱、梁架及屋顶的近似同步往复摇摆；主要震害包括柱底偏移、榫卯节点开裂及拔榫、斗拱偏移及错位、额枋-垫板分离、墙体倒塌等，但承重木构架受损不严重，结构未产生倒塌。其良好抗震性能的原因与古建筑的构造特征密切相关。.本项目的研究成果对于我国古建筑木结构抗震机理研究、抗震性能评估、建筑震害分析、结构抗震加固等工作的开展，提供了详实可靠的科学支撑。