土结相互作用对框架结构倒塌的影响研究

在结构的强震倒塌研究中, 结构底部土体的变形会影响上部结构的非线性性能和倒塌机制。该文以一10层钢筋混凝土框架结构为例, 利用纤维梁模型模拟梁、柱的非线性反应, 并根据ATC-40的土体弹簧模型分别考虑软弱土、中软土、中硬土的影响。分析表明, 考虑土结相互作用后, 结构顶点位移变大, 由此产生的结构侧移会加大结构的整体二阶效应, 同时结构的变形明显集中于首层, 对结构反应不利；从结构的破坏形态来看, 不考虑土结相互作用, 结构的破坏始于首层柱底, 而考虑土结相互作用后, 首层柱顶首先屈服破坏, 在上部结构塑性性能未充分发挥前, 结构底层发生倒塌破坏, 结构的抗倒塌能力降低。

RESEARCH ON THE INFLUENCE OF SOIL-STRUCTURE INTERACTION ON THE COLLAPSE OF FRAME STRUCTURE

In the research on the collapse of the structures under strong earthquake, the nonlinear dynamic behavior of tall reinforced concrete (RC) structures is influenced by the characteristics of the foundation soil. The assumption of a fixed-base model for this type of structure might not adequately represent their seismic response. Therefore, the seismic performance evaluation should take into account the soil-structure interaction (SSI). In this study, the seismic performance of a 10-story RC frame with fixed-base and flexible-base conditions is evaluated. The characteristics of the flexible-base models cover three types of soils, namely, soft soil, medium soft soil and medium hard soil. The ATC-40 spring model is adopted to represent the soil condition. The analysis results reveal that the roof displacement will be magnified when considering SSI. The inter-story drift angle in the first story will be increased obviously, and will be smaller in the second and above stories compared with the fixed-base model. The failure point will change from the bottom to the top of the column in the first story compared with the fixed-base model, while the distribution of plastic hinges will be concentrated in the lower stories, which reduces the capacity resistance of the frame.