Seismic analysis of gravity dams: a comparative study using a progressive methodology

Abstract

In structural analysis, it is widely accepted that simplified methods, that require fewer resources, should produce more conservative results, while more sophisticated methods, which require greater resources, allow the calculation of more realistic results. For gravity dams, (i) pseudo-static methods, (ii) pseudo-dynamic methods, (iii) linear time history analysis, and (iv) non-linear time history analysis are common techniques. The aim of this paper is to investigate the effectiveness of a progressive analysis methodology, using the four mentioned methods (i -iv) for seismic analysis, and define the scope of its applicability. The study of 52 gravity dam models, representing dams with different heights and properties, was performed by this progressive methodology, regarding the stress distribution along the base of the dam, the sliding safety factor (SSF) and the permanent sliding of the dam. The results show that the pseudo-static method gives a good approximation of the SSF, but the stresses are generally lower, when compared with the values obtained by more sophisticated method s. The pseudo-dynamic method gives a good approximation of the SSF and the stresses on the base of the dam, while the linear time history analysis did not give additional information for the dams analysed with SSF > 1when compared with the pseudo-dynamic method. The nonlinear time history analysis confirms the dam behavior against a sliding failure scenario, even after the stress redistribution, giving an actual time-history of the SSF and stress during an earthquake. The results show that the proposed progressive methodology, is a beneficial procedure to conduct gravity dam safety assessment.