Study On Isolation Performance Of Wooden Tower In Yingxian Under High Intensity Earthquake

The repair work of the Yingxian wooden tower has been continued since the tower was bulit,but the external forces such as earthquake,snow,war and the decay of the wood itself,which have suffered for a long time,have caused the deformation of the wooden frame system and the local damage of the components to be very serious.In order to ensure that the tower can still be used normally in the future and cope with the damage by high-intensity earthquakes,following the principle of "repair old as old" for ancient buildings,based of summarizing the research work on maintenance and reinforcement of Yingxian wooden tower at home and abroad,this paper applies SPSS statistics software to carry out regression analysis on the dimensions of main large wooden components of Yingxian Wooden Tower,and verifies the rationality that the width and thickness of timber in Song Dynasty is 3:2,the bearing capacity of the bottom members of the wooden tower in Yingxian was checked by using the modern mechanical principles;the three-dimensional finite element model of the wooden tower in Yingxian was established by finite element analysis software Midas,and three different types of isolation bearings are used to simulate the seismic response of the tower structure under the high-intensity earthquake,and the influence of seismic waves of different frequency on the tower structure was analyzed.The main conclusions are as follows:(1)Through the regression analysis calculation of the size of the large wooden components of Yingxian wooden tower,arrive at the ratio of wood width to thickness is 3:2.The modulus system based on the timber reflects the regularity of the dimension,which conforms to the regulations of the width and thickness on ancient wooden building components in China in《Ying-tsao fa-shih》.(2)By checking the bearing capacity of beams,columns and paving layers(materials and gongs),a relatively uniformed structural safety reserve is obtained,that is the safety reserve of beams,columns,paving layers(materials and gongs)and other components is about 2,which indicates that the structural components in yingxian wooden tower are selected reasonably.(3)Under the action of high-intensity seismic wave,the non-isolated structure of wooden tower in Yingxian has a large displacement,and the displacement from bottom to top are gradually increased,reaching 202.88 mm at the top of the tower,The structure does a twisting motion,the maximum inter story displacement angle of the tower structure appears at the top of the tower,reaches at 1/216,the inter story displacement angles of all floors except the first floor exceed the limit of the《Elastic interval displacement Angle criterionr》(1/565);but the isolated tover,although its overall displacement of the tower has increased further after the earthquake,but the overall structure has a rigid and smooth movement,and the displacement from bottom to top isalmost the same,the maximum inter story displacement angle of the tower structure reaches at1/286,only four or more stories exceed the limit,which indicates that the upper part of the tower is relatively weak.(4)After isolation,the first natural periods reaches about 4s,about twice times of that of the structure before non isolation,which shows that the natural periods of the structure after isolation increase significantly,The structural characteristics of the tower are significantly softened.(5)After being strengthened by isolation,under the action of high-intensity seismic wave,the acceleration peak value decreases by 33.99% and the velocity decreases by 29.93% on average,relative to the non isolation structure were significantly lower,shows that after using base isolation technology can significantly reduce the dynamic performance of the tower under the action of earthquake,which can effectively improve the stability of the tower structure.(6)Through comparison of different types of isolation bearings,it is found that the isolation performance of the same type of bearings with cross arrangement is better than that with sequential arrangement;the isolation performance of different types of bearings with mixed arrangement is better than that with single arrangement.