“强梁弱柱”钢筋混凝土框架结构抗震性能评估

Seismic damage of countries indicated that the failure pattern of most reinforced concrete (RC) frames was “strong beam weak column”, which went against the ductility conception of design. It is important to solve the key problems: How to realize the “strong column weak beam” failure pattern? How to assess the existing “strong beam weak column” RC frames? This project is focused on the RC frames with cast in-situ slabs and infills. The study is based on the combination of the experimental, FEM and theoretical methods. The combined action of cast in-situ slabs and infills is investigated intensively. The model for infills and modified strut and tie model for cast in-situ slabs are presented. The failure mechanism of “strong beam weak column” is studied. The measures to avoid the “strong beam weak column” failure are put forward. The seismic damage assessment model considering failure pattern and main influence factors is proposed. The result can not only raise reasonable comments for design, but also be the premise of the strengthening before strong earthquakes. The project is meaningful to engineering.

各国地震震害表明，钢筋混凝土框架结构大多发生“强梁弱柱”破坏，有悖于延性设计原则。如何实现“强柱弱梁”破坏机制以及大量“强梁弱柱”既有结构的评价成为亟待解决的问题。本项目以钢筋混凝土框架结构为主要研究对象，利用试验研究、有限元分析和理论分析三大手段相结合，深入研究影响破坏机制的两大主要因素填充墙和现浇板的共同作用，建立填充墙的计算模型和修正的现浇板拉压杆模型；研究“强梁弱柱”钢筋混凝土框架结构的地震破坏机理，提出避免“强梁弱柱”破坏的措施；建立考虑破坏模式和主要影响因素的地震损伤评估模型。本项目研究成果不仅对待建结构设计提出适用的建议，也是对既有结构进行加固补强的前提，有重要的工程意义。

为揭示强震下填充墙在RC框架中的作用，系统地对RC框架结构抗震性能的影响、填充墙与周边框架相互作用进行研究，首先对填充墙框架进行pushover分析，考察满填、半填填充墙所在平面框架的剪力分配等；对4榀两层单跨带现浇板的框架模型进行了低周反复抗震试验，影响因素主要考虑满填填充墙、窗洞填充墙框架和偏心开洞填充墙框架。试验结果表明，填充墙对RC框架结构强度、刚度、对柱反弯点位置和弯矩图形都有较大影响，填充墙的压杆作用增大柱剪力造成柱端剪切破坏，现有填充墙压杆宽度偏小。提出考虑大开洞和偏心洞口的填充墙模型；提出填充墙框架柱设计建议。.利用已有试验和有限元分析结果，提出现浇板拉压杆模型和现浇板有效翼缘宽度取值；根据填充墙框架试验结果，提出了有填充墙影响的现浇板有效翼缘宽度取值。在计算柱端弯矩增大系数时，梁端弯矩和考虑板有效翼缘宽度可有效降低“强梁弱柱”的产生；柱端弯矩系数的主要敏感因素为柱轴压比，提高柱端弯矩增大系数可避免“强梁弱柱”破坏形态，完全实现“强柱弱梁”不经济。.针对框架结构提出评估方法，该方法考虑现浇板和填充墙影响。对既有结构进行ECC面层加固有限元模拟，ECC面层可有效增大构件的变形能力。提出一种梁与节点管销连接方式；为改善填充墙的不利作用，提出一种可更换的阻尼填充墙，在强震下可通过填充墙耗能保护主体结构。