Elastoplastic Seismic Response Analysis For Cooling Tower Including Soil-structure Interaction

With continuous expansion of power plants in China,cooling tower structure tends to be large or even super-large.The seismic capacity is one of the key issues concerned in the design process of the large diameter and high height cooling tower.Therefore,it's necessary to study the influence of soil-structure interaction,site type and other factors on the elastic-plastic time history analysis of cooling tower structure in seismic response.Based on an actual cooling tower structure project,this paper adopts the finite element method to establish a numerical model of the structure,to discusse the influence of soil-structure interaction,site type and other factors on the elasto-plastic time history analysis of the cooling tower structure in the seismic response and analyze the structure dynamic elastic-plastic response of different laws rigid between foundation assumption model and interaction model based on viscoelastic artificial boundary in the action of multiple earthquake,region' s earthquake and rare earthquake.It's expected to provide certain references and suggestions to this kind of engineering structures'seismic response analysis and site selection through this paper research.The main contents and results of this paper are as follows:(1)Based on a cooling tower engineering example and choosing ABAQUS program which is suited for this article elastoplastic seismic response analysis,the finite element numerical model of cooling tower under the rigid foundation assumption and based on the viscoelastic artificial boundary considering soil-structure interaction under the influence is completed.The upper structure is used for elastoplastic constitution model,the lower part of pile foundation is used for simplified pile-soil equivalent complex model as well as Mohr-Coulomb constitution model for soil.(2)Dynamic characteristics of cooling tower under the models of rigid foundation and interaction of soil-structure interaction are analyzed respectively.It is found that the natural vibration frequency of cooling tower structure under the two models is small,and the first 500 order frequency is lower than 10 Hz.The basic mode of vibration is located in the front,and there is aggregation,which is all the mode of partial vibration of the upper tower cylinder.The overall mode of vibration is distributed discretely and in the back.In comparison,considering the interaction effect,the frequency of cooling tower structure decreases,the natural vibration period is prolonged,and the overall vibration mode appears earlier than the rigid foundation model.(3)The elastoplastic time-history analysis of cooling tower under the models of rigid foundation and interaction of soil-structure interaction under the action of multiple,region's and rare earthquakes is respectively carried out to obtain the damage,acceleration and displacement response of the structure.lt is found that there is no obvious damage in the elastic stage of the structure under the action of frequent earthquakes.Therefore,the damage development and damage factor variation rule of the cooling tower model under the action of prevention and rare earthquakes are mainly studied.It is found that:under the action of earthquake prevention,the inclined strut of the structure shows strong nonlinear and begins to appear damage;Under the action of rare earthquake,the tower shell and pillar parts appear obvious damage.it can be considered that the pillar is the weak part of the whole cooling tower structure.Under the two models,the acceleration response and displacement response of the cooling tower structure have the same rules:in the rigid foundation model,the response of the pillar increases with the increase of the structural elevation,while that of the tower tube decreases with the increase of the height;Under the interaction model,the strut response increases with the elevation of the structure,and the tower tube response increases with the height.Therefore,the interaction between soil and structure cannot be ignored under the action of earthquake.(4)Considering the influence of site type on soil-structure interaction influence model of cooling tower,Compare the elastoplastic responses of four kinds of structures under different site conditions with the results of acceleration and displacement.It is found that this kind of structure is sensitive to the effect of type IV site,which is not conducive to its seismic resistance.It is suggested that the site selection of practical engineering should avoid soft soil layers such as type IV site.It is hoped that the above research results and conclusions can provide some references and suggestions for the seismic design and site selection of cooling tower structure.