地震作用下碾压混凝土重力坝的可靠度分析

RELIABILITY ANALYSIS OF ROLLER COMPACTED CONCRETE GRAVITY DAMS SUBJECTED TO EARTHQUAKE

受基岩和坝体材料参数不确定性及地震随机性的影响,复杂地基上高碾压混凝土重力坝在强震作用下的动力响应具有较大的不确定性,坝体在地震下的失效概率和体系可靠度的分析成为难点。考虑混凝土材料、岩体材料和地震动的变异性,采用响应面法得到模拟重力坝极限状态方程的二次多项式,利用可靠度的有限步长法计算体系的可靠度。结合适应谱Push-over方法,改进拟静力法中重力坝地震惯性力动态分布系数的计算方法,将其用于重力坝动力可靠度计算。通过对强震区碾压混凝土重力坝的极限承载能力以及地震作用下可能失效路径对基本功能目标影响分析,研究不同失效路径下重力坝体系的可靠度影响因素,分析对应于坝体失效、地基失效、层面稳定以及闸门启闭的每种失效模式的失效概率和重力坝的体系可靠度,并用系统可靠度理论研究地震动对整个碾压混凝土重力坝体系的失效概率及可靠度影响。研究结果表明,不同的失效路径与各功能目标相联系,重力坝的可靠度需要综合考虑各失效路径的影响;地震作用下结构体系的可靠度受几种失效路径共同决定。

Due to the uncertainty of material parameters and randomness of earthquake, the dynamic response of high rolled compacted concrete（RCC） gravity dam is uncertain. Analyses of the seismic failure probability and aseisrnic reliabilities of gravity dam located at meizoseismal area are difficult. Taking the variability of material parameters and earthquake into account, a quadratic polynomial fitting by using response surface method is used to simulate the limit state equation of RCC gravity dam. The reliability index is calculated by a finite iteration step method. The distribution of effective earthquake forces is ameliorated according to adaptive spectra-based Push-over procedure and used to calculate the gravity dam＇s reliability. The influences of different failure paths on the reliability of RCC gravity dam are studied by analyzing the dam＇s ultimate bearing capacity. Probable seismic failure paths and failure modes corresponding to limit load state and normal operation state are analyzed. The failure probabilities for the different failure modes corresponding to dam, rock, sliding of roller compacted layer and floor are further analyzed. Based on system reliability theory, the dynamic system failure probability and reliability index of RCC gravitv dam are obtained in terms of the correlated and non-correlated failure modes. The results indicate that the reliability levels have relation to various failure paths. The corporate influence of the different failure paths on the system reliability should be considered.