Added mass method application for dam-acumulation interaction analysis

Abstract

The aim of this paper is to analyse the influence of modelling the interaction between the dam and accumulation in case of seismic loads using two approaches. A direct transient response analysis was used to solve this type of problem. Theoretical basis of direct transient response analysis as well as the basic equations of Westegaard's added mass and pseudo hydro-dynamic forces method for simulation of the dam-accumulation interaction are shown in the paper. The method of added masses is used to analyse the interaction between dam and accumulation, taking into account that a certain part of the water moves with the upstream face of the structure while the rest of the volume of water remains inactive. The concept of added mass greatly simplifies the analysis procedure considering hydrodynamic effects during earthquakes. The interaction between the dam and accumulation was modelled with two approaches, as pseudo hydro-dynamic forces and added mass. To verify the procedure, simple model of vertical concrete cantilever was used, after which obtained results were compared. Verified procedure of dam-accumulation interaction using pseudo hydro-dynamic forces and added mass method was applied on concrete arch dam "Grančarevo". Results shows that the cantilever response under seismic load is delayed in case of added mass as the cantilever has larger mass compared to cantilever without using hydrodynamic effect. Displacement response of the cantilever for pseudo hydro-dynamic approach in comparison to results for added mass, has the same character of displacement but with increased values. Obtained result of dam crest are consistent with results from simple example. Using added mass method, the dynamic effects that occur during seismic loading are taken into account as opposed to the approach of pseudo hydro-dynamic forces in which the change of acceleration that affect the structure is not taken into account.