论文部分内容阅读
2008年5月12日,四川省汶川县发生里氏8.0级地震,造成了巨大的人员伤亡以及工程结构震害。本文基于江油市某RC框架结构的震害调查,分析了该框架结果出现底层“薄弱层”和“强梁弱柱”的破坏机制的主要原因。采用该框架结构附近三个台站的主震加速度记录作为输入开展了非线性地震反应分析。研究表明,填充墙的竖向不均匀布置改变了框架的抗侧刚度分布,造成底层薄弱层的破坏现象。底层柱子的轴压比相对较大,塑性变形能力及耗能能力相对较差,使得底层柱的变形量更容易达到其塑性变形极限而发生破坏。由于现浇楼板对梁刚度和抗弯承载力的增强,框架结构很难出现规范中“强柱弱梁”的破坏机制。结构基本周期对应的加速度反应谱值是决定结构地震反应的主要参数,基本周期加速度反应谱值的增加会导致结构塑性铰的迅速发展,造成结构出现柱铰机构而整体失稳倒塌。建议设计框架结构时,尽量避免填充墙的不均匀布置。适当增加底层柱的截面面积和配筋率,降低轴压比以保证良好的延性。梁端负向抗弯承载力计算时采用T型截面,并考虑一定范围内楼板配筋的影响。
On May 12, 2008, an earthquake measuring 8.0 on the Richter scale hit Wenchuan County in Sichuan Province, causing huge casualties and seismic damage to the structure. Based on the investigation of seismic damage of a RC frame structure in Jiangyou City, this paper analyzes the main causes of the failure mechanism of the bottom “weak layer ” and “strong beam weak column ” in this framework. Nonlinear seismic response analysis was carried out using the mainshock acceleration records of three stations near the frame as input. The research shows that the vertical non-uniform placement of infill walls changes the lateral stiffness distribution of the frame, resulting in the destruction of the underlying weak layer. The axial compression ratio of the bottom column is relatively large, and the plastic deformation capacity and energy dissipation capacity are relatively poor, which makes the deformation of the bottom column easier to reach the plastic deformation limit and destroy. Due to the increase of stiffness and flexural capacity of cast-in-situ floor beams, it is very difficult for the frame structure to appear the failure mechanism of the standard “strong column and weak beam”. The acceleration response spectrum value corresponding to the basic structure periodicity is the main parameter that determines the seismic response of the structure. The increase of the basic periodic acceleration response spectrum results in the rapid development of the structural plastic hinge, resulting in the collapse of the column hinge mechanism and the overall instability. It is recommended to design the frame structure to avoid unevenly packed walls. Appropriate to increase the cross-sectional area of the bottom column and the rate of reinforcement, reduce the axial compression ratio to ensure good ductility. T-section is used for the calculation of the negative bending moment capacity of the beam ends, and the influence of the reinforcement of the floor slab within a certain range is considered.