基于砌体结构合理破坏机制的窗下墙受力机理与抗震性能研究

Due to the lack of researches on mechanical behavior analysis theory and seismic design method of masonry spandrels, it is difficult to reflect the real mechanical properties of masonry structure in the earthquake and hardly to reveal the damage of masonry walls according to domestic structure codes. In this project, the research object is the seismic performance of damaged masonry spandrels, the target is to accomplish the expected damage of masonry structure in the earthquake. By means of earthquake damage investigation, theoretical analysis, numerical simulation and experimental study, stress distribution of masonry structure walls after earthquake is determined in detail, and the failure characteristics and mechanical behavior of spandrels in different modes are revealed emphatically. Besides, some effects that produce different failure modes are analyzed in depth, including span-depth ratio of spandrel，strength of materials and boundary conditions. Moreover, mechanical properties of spandrels, such as hysteretic characteristics, load-bearing capability, deformation behavior and stiffness deterioration law, are studied systematically. According to the effect factors of failure modes, a method to analyze and calculate the bearing capacity in masonry spandrels is established. Based on expected failure mechanism of masonry structure, ductile seismic design method for masonry walls is proposed accordingly. The project research results are expected to promote theoretical study to realize the ductility design and control methods of masonry structure in domestic specification and research system, and to provide technical support for the reconstruction and reinforcement of masonry structures when suffered powerful earthquakes.

针对我国现行规范中砌体结构力学计算模型难以反映地震中结构真实受力性能、内力分析方法难以解释窗下墙震害现象、窗下墙受力分析理论与抗震设计方法研究不足等问题，以实现地震作用下砌体结构合理破坏机制为目的，以震后受损砌体结构窗下墙为研究对象，采用震害调研、理论分析、数值模拟和试验研究等手段，精细模拟地震作用下砌体结构墙体应力分布状态，重点揭示窗下墙地震作用下的破坏特征与受力机理，深入分析窗下墙跨高比、材料强度及边界条件等因素对窗下墙不同破坏形态的影响规律，系统研究窗下墙的滞回耗能特性、承载能力、变形性能及刚度退化规律。考虑窗下墙破坏形态的影响因素，建立砌体结构窗下墙抗震承载力分析和计算方法，提出地震作用下窗下墙先于窗间墙发生破坏的砌体结构抗震设计方法。研究成果将为在我国规范与研究体系中实现砌体结构合理破坏机制和延性设计方法提供理论依据，为砌体结构灾后恢复重建与既有结构改造加固提供技术支持。

本项目研究工作采用震害调研、理论分析、数值模拟及试验研究相结合的研究方法，按照墙体内力数值分析-->窗下墙拟静力试验-->窗下墙承载力分析与计算的技术路线开展研究工作。首先，分析了地震作用下砌体结构窗下墙的受力机理，建立了窗下墙数值分析模型，揭示出了多层砌体结构开洞墙体内任意位置的应力分布状态；提出砌体结构的合理破坏模式，确定不同破坏形态的影响因素。其次，考虑墙肢刚度比和竖向压应力，开展了窗下墙子结构拟静力抗震性能试验，测试不同破坏形态窗下墙试件的极限承载能力、残余强度与变形性能，重点掌握了窗下墙力-位移滞回耗能特性与窗下墙刚度退化规律，着重分析了窗下墙跨高比、材料强度及边界条件对窗下墙抗震性能的影响。最后，建立了砌体结构窗下墙不同破坏形态下的力学分析模型及对应的力学平衡关系，依据窗下墙承受荷载与构件强度分析结果，构建了地震作用下砌体结构窗下墙抗震承载力计算方法，为提出砌体结构合理破坏机制奠定了理论基础。