Dynamic Damage Analysis Of A Powerhouse At Dam Toe Considering The Oblique Incidence Of Seismic Waves

In recent years,China's large-scale hydropower project construction sites are mostly located in the southwest seismic zone.Thus the seismic fortification of hydropower station is always a priority for all hydropower projects.For a large building such as a hydropower station,the radiation damping effect of semi-infinite foundation and the traveling wave effect must be considered in the seismic calculation.The traditional way to consider these two aspects is to check the dynamic response of the structure subjected to seismic waves incident vertically from the bottom of the foundation.This assumption is reasonable for the site far from the seismic source.However,for the site near the source,the impact of the incident angle of seismic wave on the dynamic response of the structure cannot be ignored.In this thesis,the viscoelastic boundary is adopted to simulate the semi-infinite foundation.Based on the cylindrical wave theory,the mechanical parameters of the normal and tangential viscoelastic boundary in plane are derived.Meanwhile the oblique incident seismic waves are transformed into equivalent nodal forces and applied on the viscoelastic boundary.In order to consider the dynamic damage of the powerhouse at dam toe under the action of oblique incident seismic waves,the concrete elastic damage model is adopted to describe the stress-strain relationship under dynamic load.Also this constitutive relation is embedded in the oblique incidence code of seismic wave by APDL language.Based on the case of Longkaikou hydropower station,the finite element model of the non-spillway section is established in ANSYS.Then the elastic analysis of the whole finite element model is carried out.According to the structural dynamic analysis,the upstream and downstream walls of the powerhouse at dam toe are the control areas of stress and displacement.And materials in this area are simulated by the concrete elastic damage model.Furthermore,the materials in rest parts of the finite element model are assumed to be elastic.After calculation and analysis,the following conclusions are obtained:(1)Under the action of P and SV wave oblique incidence,the displacement and stress of the upstream and downstream walls of the powerhouse are different from the results of vertical incidence.(2)The larger the incident angle of SV wave,the lower the horizontal displacement amplitude of the uppsteam and downsteam walls and the higher the vertical displacement amplitude;the larger the incident angle of P wave is,the higher the horizontal displacement amplitude of the uppsteam and downsteam walls will be,and the lower the vertical displacement amplitude will be.(3)Under the action of oblique incidence of P and SV waves,the damaged areas located at the bottom of upsteam wall and downsteam wall,as well as the upsteam wall at elevation of 1260.4m.(4)At elevation 1260.4m,the dynamic stress amplitude of the upstream wall increases suddenly due to the apperance of concrete damage elements.(5)The propagation direction of P and SV wave has a certain influence on the dynamic response of the powerhouse at dam toe.The conclusion of this paper proves the necessity and feasibility of considering the oblique incidence of seismic waves.It can be used as a theoretical reference for the seismic analysis of the powerhouse at dam toe in China.