Nonprobabilistic Reliability Evaluation for In-Service Gravity Dam Undergoing Structural Reinforcement

Influenced by many factors such as material performance attenuation, structural defect repair, and reinforcement, the structural reliability of a gravity dam changes in different periods, which are called dynamic effects. Traditional methods are inclined to calculate and analyze the structural probability reliability from the random or fuzzy uncertain characteristics of parameters. However, in practice, it is difficult to obtain the probability distribution of uncertain parameters as well as the performance function, which is too nonlinear to be expressed. In addition, gravity dam failures are low probability events. Thus, a reliability calculation model and method for the gravity dam system considering dynamic effects under the practice of reinforcement are studied by integrating the theory of interval mathematics and nonprobability reliability. First, with the help of the monitoring data, and physical model and numerical simulation results of the gravity dam before and after the reinforcement, we establish a nonprobabilistic reliability (N-PR) calculation model for the gravity dam element and system based on the bounds of uncertain parameters and propose an inversion method for the bounds of uncertain parameters. Subsequently, by combining the response surface method with the central composite design technique, an N-PR index calculation method for gravity dams considering dynamic effects is developed. It turns out that the given model and method can effectively pave the way to avoid falling into the limitations of classical probabilistic reliability analysis of which the uncertain parameters require to be randomly changed and the results are highly sensitive to the parameters. In addition, it can better adapt to the characteristic of gravity dam performance function, which is too nonlinear to be expressed explicitly. When employing this method to analyze the reliability of gravity dam services, we are able to evaluate and predict the changing process and the trend of it more objectively, and have a closer look at the comprehensive influence and contribution of reinforcement to dam service reliability.