多维性能极限状态随机性及相关性研究

同时考虑性能极限状态随机性及相关性,提出结构系统多维易损性评估方法。开展增量动力分析获取极限状态阈值样本,构造多维性能极限状态方程,创新地提出二维性能极限状态带确定结构失效域,借助区间估计确定某一置信水平下极限状态带上、下界,利用相关系数定量描述极限状态相关程度。开展非线性动力时程分析获取需求参数,建立结构多维概率地震需求模型,以桥梁系统为例计算多维易损性置信区间,开展易损性敏感性分析。结果表明性能极限状态带可较好解决极限状态随机性问题,多维易损性区间长度随极限状态带置信度的下降而变窄;随着极限状态相关系数的增加,极限状态相关性变弱,易损性评估结果偏小,产生非保守估计,不利于结构风险控制。

Investigation of the Multi-dimensional PLS Uncertainty and Dependence

In the light of the uncertainty and dependence of the performance limit state (PLS), a multi-dimensional fragility analysis methodology is proposed. Incremental dynamic analysis (IDA) is carried out to generate PLS threshold sample, and a multi-dimensional PLS formula is constructed. The two-dimensional performance limit state band is proposed to determine the structural failure domain. The upper and lower bound of the band area is identified based on the interval estimation. The correlation coefficient is introduced to describe the PLS dependence level. Multi-dimensional probabilistic seismic demand model (PSDM) is obtained through nonlinear dynamic time history analysis. An RC-bridge is used as an example to illustrate the methodology, and the multi-dimensional fragility confidence interval is calculated. The sensitivity of the fragility is carried out. Results show that limit state band can better solve the PLS uncertainty problem. The fragility confidence interval length becomes narrow with the decrease of confidence level. As the PLS correlation coefficient increases, the PLS dependence reduces. Non-conservative fragility estimation will be generated, which is adverse for risk control.