带暗牛腿-变摩擦耗能预应力自复位混凝土框架的抗震性能与易损性研究

Self-centering prestressed concrete (SCPC) frame is an innovative prefabricated structure with favorable self-centering capability. However, this kind of structure may encounter some critical problems of large lateral displacement and insufficient shear capacity when subjected to strong earthquakes. Hence, with the concept of combining the variable friction energy dissipation, post-tensioned self-centering and hidden corbel vertical-shear-resistance, a SCPC frame with hidden corbel and variable friction damper (HC-VFD-SCPC) is proposed in this research project. The new flag-shaped hysteretic feature including two-stage friction activation and third variable stiffness is achieved. The beam-column connection with self-centering, energy dissipation capacity and sufficient vertical shear capacity are constructed. The key scientific issues of HC-VFD-SCPC frame are investigated, including connection mechanism, structural performance, design method and fragility analysis. Correspondingly, the following tasks are sequentially involved in this research project. Firstly, from the viewpoint of connections, pseudo-static tests and nonlinear finite element analysis will be carried out, as well as the optimization of connection details and the investigation of hysteretic performance. Secondly, based on the nonlinear static and dynamic analysis of multi-story structures, together with the structural experiments, the influences of key hysteretic parameters on structural seismic performance under near-field and far-field earthquake can be investigated. Then, via studying the nonlinear drift ratio spectrum of structures, the direct performance-based design method will be proposed. Finally, via studying the vector intensity parameters which is applicable for probabilistic seismic estimation under near-far-field earthquakes, the fragility evaluation method of HC-VFD-SCPC frames will be built.

预应力自复位混凝土(SCPC)框架是一种具有可恢复功能的新型预制装配式结构，但在强震作用下易产生层间位移角较大、节点竖向抗剪能力较弱等问题。为此，本项目基于“变摩擦(VFD)耗能”、“预应力复位”与“暗牛腿(HC)抗剪”的紧密融合，提出一种带暗牛腿-变摩擦耗能SCPC(HC-VFD-SCPC)框架，形成具有两阶段摩擦启动和第三刚度的新型旗帜形滞回特征，建立具有足够竖向抗剪能力的自复位耗能节点形式。拟针对HC-VFD-SCPC框架的节点机理、结构性能、设计方法和易损分析等关键科学问题开展研究，包括：开展节点拟静力试验和非线性有限元分析，研究节点的优化构造系统和滞回性能模型；通过多层结构非线性静动力分析和试验，分析关键滞回参数对框架近远场抗震性能的影响机理；研究框架的非线性位移比谱，提出结构基于性能的直接设计方法；研究适用于近远场概率抗震评估的向量强度参数，建立框架的易损性评估方法。

预应力自复位混凝土框架(Self-Centering Prestressed Concrete frames, SCPC)作为一种重要的可恢复功能抗震结构，在强震作用下易产生层间位移角较大、节点竖向抗剪能力较弱等问题。项目基于“变摩擦(Variable friction dampers, VFD)耗能”、“预应力复位”与“暗牛腿(Hidden Corbel, HC)抗剪”的紧密融合，提出一种带暗牛腿-变摩擦耗能SCPC框架(HC-VFD-SCPC)，形成具有两阶段摩擦启动和第三刚度的新型旗帜型滞回特征，建立了具有足够竖向抗剪能力的自复位耗能节点形式。研究了抗剪需求小、抗震要求低的“顶底定摩擦耗能自复位混凝土梁柱节点( SCPC beam-to-column connections with Constant Friction Dampers, CFD-SCPC)”和具有更高抗剪能力的“带暗牛腿顶底摩擦耗能自复位混凝土梁柱节点(CFD-SCPC beam-to-column connections with Hidden Corbels, HC-CFD-SCPC)”的滞回机理。分析了复位单元、耗能器单元及梁柱单元对体系承载能力和刚度变化历程的影响机理，优化了定摩擦耗能器，开展了CFD-SCPC节点的多工况拟静力试验和HC-CFD-SCPC节点的多工况拟静力试验，揭示了节点的自复位机理。结合理论分析，提出暗牛腿-变摩擦耗能器连接构造的设计原则。分析了初始预应力、摩擦力和耗能器细部构造等设计参数及加载历程对体系刚度、预应力损失、自复位能力、耗能能力和承载能力等滞回性能的影响。开展了HC-VFD-SCPC节点的拟静力试验，解明了摩擦型自复位混凝土结构体系的失效模式。揭示了坡面滑动段角度、平面滑动段和坡面滑动段距离之比、碟形弹簧组合刚度及复位单元等设计参数对节点消压后刚度、耗能能力和承载能力的控制机理，提出了耗能器二次启动的控制方法。建立了顶底摩擦自复位节点的有限元模型，开展了HC-VFD-SCPC框架基于关键滞回指标的参数化分析。确定了多阶段抗震性能目标，建立了HC-VFD-SCPC框架的抗震设计方法。依据FEMA P-58抗震性能评估理论，利用非线性时程分析中的地震响应结果和易损性分析结果，对自复位框架和传统整浇框架在设防地震水准和罕遇地震水准下的地震损失进行了对比评估。

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