多层次耗能自复位混凝土剪力墙抗震机理与设计方法

In self-centering concrete shear wall, the unbonded post-tensioning tendons arranged from the top to bottom of the wall dominate behavior for returning the wall to its original position, and provide seismic ability together with the steel bars of energy dissipating. Shaking table tests have revealed failure of post-tensioning and rupture of steel bars occurred possibly under strong ground motion, seismic ability of the wall degraded rapidly is very likely prone to sudden collapse. The multi-capacity friction joint of energy dissipating were placed rationally between the bottom of the wall and the foundation and activated progressively to delay or avoid the failure of post-tensioning and steel bars. Because the robustness and structural redundancy were increased by series of friction connection dissipators with various level, the self-centering concrete shear walls with these dissipators hierarchically undergo seismic shaking. For the self-centering wall of hierarchical energy dissipating, firstly, the behavior of elastic restoring energy of post-tensioning tendons is expressed as stress increase during shaking drift. An equivalent spring model is analyzed for the storing energy. The mechanism of post-tensioning tendon is developed to consider its effect for drift capacity and self-centering performance. Secondly, Friction and viscous dissipation due to elongating and shortening movement of tendons during the whole of displacement, deformation dissipation of locating unbonded mild rebar, and radiation dissipation induced by rocking wall shocking foundation are required to carry out qualitatively and quantitatively, multi-performance energy dissipating mechanism and a hysteresis model relating moment and rotation of wall toe are developed. Thirdly, progressively activating strategy of friction connection dissipators, and procedures of predicting seismic capacity and performance-based design are proposed. The investigative objective is to support construction of functional recovery and retrofitting of existing/damaged structures in highly seismic region.

自复位混凝土剪力墙中竖向贯通的无粘结预应力筋主导着自复位行为，并与耗能普通钢筋一起提供结构抗力。已有振动台试验发现，强震下可能发生部分预应力筋失效和耗能普通钢筋断裂，使剪力墙抗震能力急剧退化，易于突然倒塌。在墙与基础间合理布置不同能力的摩擦耗能部件以适应不同地震激励水平，渐进激活后可避免或推迟两类钢筋失效，增加结构鲁棒性和冗余度。本项目以这种多层次耗能自复位剪力墙为研究对象，揭示侧向变形过程中以预应力筋增量效应体现的弹性储能行为，提出预应力筋储能的等效软弹簧模型，分析其对变形和自复位能力的影响机制；揭示多因素影响的各阶段预应力筋伸缩运动的摩擦和粘滞耗能、局部无粘结的普通钢筋拉压变形耗能以及墙－基摇摆辐射耗能的综合机制，提出弯矩－转角滞回模型；获得摩擦耗能部件渐进激活策略，预测剪力墙的抗震能力，给出基于性态的设计方法。项目研究，将有力支持高烈度区可恢复功能结构和既有/震损结构抗震加固。

结合理论分析、试验验证和仿真模拟，既定的研究目标已经基本全部完成。通过常规自复位混凝土剪力墙的拟静力试验，详细分析了预应力筋的应力变化和耗能储能，评估了其对自复位能力的贡献；设计并进行了新型槽栓摩擦夹层耗能部件的滞回性能试验，并将其应用于自复位剪力墙结构，作为常规耗能部件（耗能钢筋）的替代，进行了拟静力试验和自由衰减振动模拟，分析了添加摩擦耗能部件的自复位剪力墙自身的滞回耗能和动力荷载作用下墙-基础的冲击辐射耗能，深入研究了自复位剪力墙的综合耗能机制；通过有限元建模及大量的参数分析，结合自复位结构的旗帜形变形特征，采用单自由度简化模型，着眼于新建自复位剪力墙结构，以及采用自复位剪力墙结构对既有/震损结构进行加固，进行了大量的地震响应分析，获得了对应的最大变形/残余变形反应谱，并结合自复位剪力墙结构的参数静力推覆结果，初步开展了基于不同性态指标的抗震设计方法的研究，并开展了相关的易损性分析工作，形成了多层次耗能自复位剪力墙结构基于性能的设计方法。