Failure Probability Density Evolution Analysis of Gravity Dam Based on ETA Method

Concrete gravity dam response under strong ground motions has a profound impact on the safety assessment and damage failure mode of structures. In this paper, the endurance time analysis (ETA) method was used to generate endurance time accelerations (ETAs), calculate and analyze the probability density evolution process and failure probability of damage evaluation factors subjected by the Koyna ground motion ETAs. The Koyna gravity dam finite element model was established, and the dynamic response and damage process of dam under ETAs was simulated. The plastic dissipation energy, damage dissipation energy, damage volume and normalized damage volume as damage evaluation factors were used. Based on the probability density evolution theory, the generalized probability density evolution model was set. The probability density curves varied with ETA history under different damage evaluation factors were calculated. Selecting two typical moments as moderate damage and severe damage evaluation criterion and combining probability density curves with failure probability, probability curves under different damage evaluation factors and different damage evaluation criterion were compared to realize failure probability analysis and evaluation of dam under different peak ground acceleration. Previous studies showed that damage evaluation index obeys the normal distribution which is just a kind of assumption and no detailed basis. According to the present research, the probability density distribution of damage evaluation index results is similar to normal distribution and has certain deviation compared with PDE method. The studies shows that probability density evolution process based on ETAs has high computation efficiency and precision. Compared with the results of normal distribution, the results of PDE are closer to the true probability distribution. It can be more conservative to represent failure probability of dam when using plastic dissipation energy and damage dissipation energy as damage factors under different ground motion intensity. © 2019, Editorial Department of Advanced Engineering Sciences. All right reserved.