考虑地震动谱形影响的钢筋混凝土框架结构抗倒塌能力评估

Seismic design based on collapse probability under intense earthquakes is the main trend in the field of earthquake engineering. This makes it necessary to evaluate the collapse resistant capacity of the structures rationally. The characteristics of ground motion spectral shape influences the evaluation result of collapse resistant capacity as well as the characteristics of strength and stiffness deterioration of structural components. This project will focus on improving the reliabilty of evaluation results of collapse resistant capacity of the structures and the key scientific issues will be studied systematically. First, some qualified records from Wenchuan Earthquake and other earthquake events are chosen to investigate the characteristics of ground motion spectral shape and its influencing mechanism on nonlinear seismic responses of the structures. Second, in order to investigate strength and stiffness deterioration characteristics of structural components and the main governing parameters, a series of experimental and analytical simulation on structural components under complex combined actions will be conducted. Third, based on the aforementioned work, the correlation between the maximum seismic responses of the structures and selected ground motion parameters will be studied via nonlinear dynamic analysis and incremental dynamic analysis in order to propose the sufficient and efficient methods to select and modify ground motion records. Finally, the whole probabilistic procedure to evaluate the collapse resistance capacity of reinforced concrete frames, which can take into account the influence of ground motion spectral shape and the charactersitics of strength and stiffness deteririoration of structural components, will be proposed based on the improvement of the current analytical models, analytical algorithms and collapse criteria. This project can contribute to improving the reliability of evaluation results of collapse resistance capacity. Thus it can also contribute to achieving the stage of seismic design which is based on collapse probability target under intense ground motion and promoting the advances of science and technology in the field of earthquake disaster mitigation.

基于倒塌率目标的抗震设计是结构抗震领域的主要发展方向，这就要求科学合理地评估结构的抗倒塌能力。而地震动的谱形特征及结构构件的强度、刚度退化特征对抗倒塌能力评估结果的影响很大。本项目着眼于提高结构抗倒塌能力评估结果的可靠性，就涉及的关键科学问题进行深入系统的研究，主要包括：选择汶川地震及其它典型地震动记录，深入分析地震动谱形特征及其对结构非线性响应的影响机理；通过复杂受力条件下构件滞回性能试验研究和数值模拟，研究考虑强度和刚度退化特征的构件滞回模型及主要控制参数；在此基础上，采用非线性动力分析和增量动力分析，研究可以考虑地震动谱形影响的地震动参数与结构非线性响应的相关性，提出充分且有效的地震动记录选择与调整方法；最后，通过对现有分析模型、分析方法及倒塌判别准则等的改进，提出考虑谱形影响、反映结构构件强度及刚度退化特征、基于概率的抗倒塌能力评估方法，为实现基于倒塌率目标的抗震设计奠定基础。

本课题以考虑地震动谱形影响的钢筋混凝土框架结构抗倒塌能力评估为目标，分别从地震动特性和结构非线性特性两方面，对影响钢筋混凝土框架结构抗倒塌能力的因素进行系统研究。包括确定反映强度和刚度退化特征的构件滞回模型及主要控制参数，结合填充墙平面内外相互作用，残余位移及节点轴-弯-剪耦合效应，基于静力推覆和增量动力分析，对地震动谱形和持时影响的钢筋混凝土框架结构抗倒塌能力进行评估。研究结果表明，考虑轴-弯-剪耦合的串联模型能较好地模拟钢筋混凝土柱的强度、刚度退化及捏拢效应等，且能够反映钢筋混凝土构件在复杂应力条件下的受力性能。不考虑填充墙平面内外相互作用会明显低估结构的抗倒塌能力。P-Δ效应和高阶模态效应对多层RC框架结构的残余位移响应的平均放大作用均大于其对最大位移响应的放大效应，残余位移响应的离散性也大于最大位移响应的离散性。长持时和长周期地震动输入均会使结构的抗倒塌能力显著降低。由于高阶振型的影响或进入非线性阶段的周期延长效应，仅按单一强度指标如峰值地震动加速度、对应结构基本周期的谱加速度值调整地震动记录对结构进行动力分析，所得结果的离散性较大，而基于改进模态推覆分析的地震动记录调整方法所得结构地震响应分析结果的离散性明显下降。谱形对结构非线性地震反应的影响，随着地面运动强度的增加以及结构非线性程度的提高而增大，反应谱不同区段的谱形对于结构非线性地震反应的影响差异显著。不论是短周期还是中等周期结构，在小于结构基本自振周期区段的地震动反应谱谱形对结构非线性反应基本没有影响，但在大于结构基本自振周期区段的地震动反应谱谱形对框架结构非线性反应影响显著。考虑合理谱形的地震动记录调整方法能够有效减小结构地震响应的离散性，得到很好的响应估计。最终提出了考虑谱形影响的基于概率的钢筋混凝土框架结构抗整体倒塌能力评估方法，为基于倒塌率目标的抗震设计提供依据和建议。