Comparison of near- and far-fault ground motion effects on the seismic performance evaluation of dam-reservoir-foundation systems
28 May 2009
In this paper, near- and far-fault ground motion effects on seismic performance evolution of concrete dams are investigated, considering dam-reservoir-foundation interaction by using demand capacity ratios. Four different types of dam - concrete arch, concrete gravity, concrete faced rockfill and roller compacted concrete dams - are selected for the numerical example. Near- and far-fault ground motion records, which have approximately identical peak ground accelerations, of the Loma Prieta (1989) earthquake are selected for the analyses. The behaviour of the dam, reservoir and foundation is expressed in terms of displacements using the Lagrangian approach, and the foundation is assumed as massless. Dynamic equilibrium equations of motions obtained from the finite element models of the coupled systems are solved by using Newmark’s time integration algorithm. The seismic performance evaluation of the dams for the near- and far-fault ground motions are performed by using demand capacity ratios obtained from linear analyses. Displacements, maximum and minimum principal stresses, are determined using finite element method and compared with each other for near- and far-fault effects. In this study it is concluded that near-fault ground motion is more effective than far-fault ground motion on the seismic responses of dam-reservoir-foundation systems. In addition to this, near-fault ground motion records must be taken into account in the dynamic analysis of dams to obtain more realistic results of responses of dams.
