基于损伤路径的分阶嵌固RC结构强震失效模式及控制方法研究

Building structures supported by stepped foundation are built in accommodation with the slope topography and have been widely applied in mountainous cities. Most of the seismic damage of the RC building structures supported by stepped foundation concentrates on vertical embedded structural members. Thus, the structures would be apt to collapse under strong ground motions. The previous seismic failure mode expectation and control methods, which only focusing on the damage location of building structures, cannot solve the damage concentration problems in vertical embedded members properly. Therefore, a damage path-based control method by considering the damage location, level, and sequence is may be an efficient approach to solving the problem. In this project, expected failure modes of building structures supported by stepped foundation are built based on the damage path identification under strong ground motions. Then, the seismic design method which can realize the expected failure modes of the building structures on stepped foundation is put forward. From theoretical analysis, numerical simulation, and experiment, the law of earthquake damage and internal force redistribution of these building structures is obtained, the method for evaluating an expected failure mode of these structures is established by considering the damage path in these structures, the expected failure modes for these structures are presented based on the damage path, the method to realize the expected failure mode for these structures is put forward, and the method to realize the expected failure mode of building structures supported by stepped foundations is proposed. The research achievements of this project can be used in seismic design of building structures supported by stepped foundation, and can be referred as theoretical basis for further updating of the Design specification for building structure on the slope.

分阶嵌固山地建筑具有坡地适应性而在山地城镇建筑中有较好的应用前景。分阶嵌固钢筋混凝土(RC)结构在强震作用时，其损伤主要集中在嵌固竖向构件而易于发生倒塌破坏。当前所倡导的结构失效模式及其控制方法，因仅关注结构损伤部位而难以解决分阶嵌固RC结构强震损伤集中现象，基于损伤部位、程度和顺序的结构强震损伤路径控制是解决此问题的有效途径。本项目旨在构建基于损伤路径的分阶嵌固RC结构强震预期失效模式，建立可实现该预期失效模式的分阶嵌固RC结构抗震设计方法。项目拟通过理论分析、数值模拟和试验，研究分阶嵌固RC结构的强震损伤演化规律和内力重分布规律；建立基于损伤路径的分阶嵌固RC结构强震失效模式评价方法；构建基于损伤路径的分阶嵌固RC结构预期失效模式集；提出基于损伤路径的分阶嵌固RC结构预期失效模式的实现方法。成果将为多阶嵌固RC结构抗震性能的实现提供理论，为其抗震设计提供方法，为其设计规范编制提供依据。

地基基础位于不同标高的分阶嵌固山地建筑能很好地契合地形、减小环境扰动，可以形成错落有致的具有山地特色的建筑。强震时分阶嵌固混凝土结构容易发生因损伤集中于接地构件的倒塌破坏。目前倡导的预期破坏模式及其控制理论因主要关注结构损伤部位而难以解决这类结构的强震损伤集中现象，基于损伤部位、程度和顺序的结构强震损伤路径控制理论是解决此问题的有效途径。.本项目围绕分阶嵌固RC结构强震失效模式及控制方法完成了以下研究工作：. 1）研究了分阶嵌固RC结构强震损伤特征及失效模式。揭示了掉层和掉脚两类主要分阶嵌固RC结构强震损伤演化规律及主要结构特征参数对其强震损伤的影响规律。掉层RC框架的强震破坏模式为典型的“半层屈服”，其竖向抗侧力构件的破坏路径具有明显的“Z”字形路径。降低吊脚RC框架结构柱间刚度不均匀性可以使梁和柱的塑性铰分布更加均匀，吊脚RC框架结构层刚度比大于或接近1时吊脚短柱的出铰时间较早而易形成局部倒塌，结构的层刚度比宜在在0.75到1.16间。. 2）构建了分阶嵌固RC结构强震失效模式集。构建了屈服类、柱极限弯曲类和柱极限剪切类三种掉层框架结构失效模式。基于割集理论的失效模式判定方法纳入了剪切失效模式，可偏保守地确定分阶嵌固RC结构的抗倒塌能力。基于分阶嵌固RC结构的强震损伤演化规律，提出了防止出现强震时短柱和上接地端首坏后接地端发生连续破坏的强震失效模式。. 3）提出了基于支撑和基于隔震支座的两种分阶嵌固RC结构预期失效模式实现方法。刚度比在3.5-5间的支撑可使分阶嵌固RC结构的薄弱位置由上接地层向上部楼层转移，防止掉层RC框架结构出现上接地层首先破坏的“半层破坏”的模式，防止吊脚RC框架结构底部短柱不先出现塑性铰。合理设计的隔震支座可以调整分阶嵌固结构底层抗侧向刚度的不均匀性，实现分阶嵌固RC结构预期失效模式。