The Research On The Composite Seismic Isolation Pier Finite Element And Semisic Reduction Factor Correction Calculation Method

The base seismic isolation is an effective method to reduce earthquake damagefor building structures. After years of research and engineering practice, thehorizontal seismic base isolation technology not only has been obtained a very bigdevelopment and application,but also has been tested by the real earthquake,whichshowed it’s good performance. However, the earthquake itself moves in alldirections. Especially, in the regions near the area with high seismic intensity andthe epicenter, the contribution of the vertical seismic component to the response ofthe structure is often bigger. Therefore,three dimension seismic isolationtechnology which considers both horizontal and vertical seismic isolation is verynecessary.Though our country is vast,50%of the its land is located at seven degree highseismic intensity.In the vast rural areas,the earthquake resistance of buildingstructures is poor,which leads to serious damage in earthquakes,and it is easy toappear the phenomena of a huge disaster caused by a small earthquake. In thispaper,two kinds of base isolation device---steel asphalt isolation layer andcomposite seismic isolation pier which were put forward and researched by theauthor’s research group, were taken as the study objects. On the basis oftests,theoretical and finite element studies about them were taken.In order to make up for the lack of tests on the composite isolation pier to studymore working conditions which couldn’t be realized in the laboratory,a nonlinearfinite element model of composite isolation pier by using the large finite elementsoftware ANSYS was set up. First,an "orthogonal arrangement " finite elementmodel which was the same with the test condition was created. Modal analysis andvarious working conditions of shaking table test were calculated using the model toverify its correction.In the same time, the performance of the composite isolationpier under real earthquake was learned by inputing2D and3D real seismic waves.Asa contrast, a "paralle model" was established,and calculation was done by inputingseismic waves with the same type and acceleration amplitude with the "orthogonalarrangement "model. By comparing the calculated results of the two kinds of finiteelement model, the damping performance of the composite isolation pier was further learned,and the vertical damping performance and the influence of the spring steel in"U" shape to its horizontal lateral stiffness were showed also.Through the analysis of the test data of rebar asphalt isolation layer, differencesof secmic reduction factor between the test and theoretical values were found.Andthen, by considering the influence of steel-bar skew, asphalt ointment and rebardiameter,the correction formula of the secmic reduction factor was given,whichmade a beneficial exploration to the calculation of of the secmic reduction factor ofrebar asphalt isolation layer.By comparing the fundamental frequency of "parallel arrangement " and"orthogonal arrangement" finite element model,the effect of the spring steel in "U"shape on the horizontal stiffness of composite seismic isolation pier in differentdirections was learned,which is a beneficial exploration for further understandingthe structure and further improvement of it.