Reducing extent of cracks and increasing time to failure of concrete gravity dams by optimization of propertiesof layers of concrete

The objective of this paper is to study the improvement in the seismic behavior of concrete gravity dams by optimization of concrete mechanical properties. The criteria to measure the improvement have been: 1) reduction in the extent of cracks and 2) increase in the amount of time dams are able to tolerate earthquakes before failure. The mechanical properties considered have included the density and modulus of elasticity of concrete. The Pine Flat Dam has been selected for this numerical study. During a high intensity earthquake, dams enter a nonlinear phase, where the cracks open and close repeatedly. A smeared crack model has been used for simulation of nonlinearity. For the purpose of optimization, the dam has been divided into horizontal layers, where the concrete is assumed to have the same properties at every point within each layer. The results of this study have shown that by using lower density concrete in upper layers and in the region of the crest of the Pine Flat Dam, it is possible to both reduce the extent of the induced cracks and increase the time to failure of the dam. The same methodology can be applied to other concrete gravity dams.