Reliability analysis of concrete arch dam under stage construction and hydrostatic pressure by MCS and RS methods

The aim of this paper is to conduct reliability analysis of the Pacoima concrete arch dam considering the construction stage. According to the technical literature and codes, the construction stage should be considered in the structural analysis of the concrete arch dams. Structural analysis was done by taking into account the uncertainties in the physical and mechanical properties of the dam body materials and the reservoir water level. Three parameters of normal reservoir water level, the density of dam body materials, and elasticity modulus of dam body material with coefficients of variation of and with normal distribution function are considered as random variables. Linear elastic behavior is assumed for the constitutive law of concrete material in the finite element model. Two load combinations are considered. is an unusual static load combination due to dam self-weight that considers the effects of dead load stage construction. load combination results from stage construction and hydrostatic reservoir pressure at a normal water level. and are the unusual static and usual static load combinations without considering the construction stage. The sensitivity analysis of random variables to the maximum tensile stress of the dam body is investigated, and random parameters with more impact are specified. The results showed that the density of concrete was the most effective parameter in response to maximum tensile stress. Reliability analysis based on the load-resistant model was utilized. The evaluation of implicit functions of load and resistance was performed by the finite element method. Monte Carlo method with 20,000 iterations utilized for simulation and the Latin Hypercube method was used for sampling. The maximum tensile stress in the dam body is considered as a limit state. The values of the probability of failure and reliability index are . The fragility curves are obtained for different load combinations. Considering the construction stages in the finite element analysis has led to a reduction in maximum tensile stresses, especially for the unusual load combination. To avoid high computational costs, the response surface method is used to determine the exact amount of failure probability . The probability of failure and reliability index in response surface methods are . The results showed that the safety of the Pacoima dam was high and had a very low risk of failure.