Research On Seismic Resistant Property Of Adding Steel Stories On Original Buildings With Story Isolation

Adding story reformation is one of the main means to resolve the problem of insufficient housing area in urban core,among many of the adding methods the adding steel story structure rely on light weight,high degree of industrialization,convenient for construction,flexible column grid,high economic benefit and so on,make it widely popularized.But adding steel story structures will inevitably produce much difference in stiffness,and the structure`s damping ratio,period will changes a lot,these will not conducive to seismic performance of the structure.For that matter,the traditional solution is to reinforce the original structure,although this method can improve the component`s bearing capacity,but have not fundamentally solve the essence of "the hard under the soft".However,the technology of story isolation through isolation bearings,extend the structural period,increase the damping ratio,can "indirect" solve such problems.This thesis combining with the real engineering example,using ANSYS,the finite element analysis software,based on current national standards regulations,contrapose to the problem of Seismic performance after steel adding story,add three and three with four kinds of story isolations on four-layer reinforced concrete frame structure for the static and dynamic calculation and analysis,summarize the law.The main objectives include the followings:(1)Use Rayleigh theory to calculate the structural damping based on the structure characteristics,And ultimately determine the damping ratio value is 0.035 for the mixed structure of this topic research,also,illustrates the rationality of the results.(2)Use ANSYS software to the original four frame structure increase three steel layers and three steel layers with four kinds of story isolations set up single common framework model for static analysis,the study show that under the earthquake force,the adding layer directly structure at the top of the horizontal displacement value is much larger than the original structure,and the mainly deformation concentrated in the upper structure,but due to the isolation layer provides the reliable lateral stiffness,so the adding layer with story isolation is relatively stable,the mainly deformationpresent to the isolation layer,ensure the safety of the building.(3)Use ANSYS software set up the original four layers framework structure and directly increase three steel structure,and increase three steel layers with four different isolation bearings,sum to six kinds of 3D model,calculate and analysis by mode-superposition response spectrum method and time-history method under the action of EI-Centro earthquake wave,Taft earthquake wave and an artificial seismic wave,the results show that during the state of frequent earthquake,the isolation layer increase structure compared to the directly add layer structure,the basic natural period of vibration extended by about 60%,the average of structural maximum displacement between layers reduce by about 44%,the maximum interlaminar shear reduce by 45%to 55%,the largest deformation occurred in isolation part,effectively guarantee the safety of the structure under seismic action.(4)Through summarizing the calculated results on six kinds of structures under the action of three seismic waves can be found that,blindly choose a big size,big diameter of lead core isolation bearing will not only increase the difficulty in construction and also can cause the waste of the economy.Based on the reality engineering in this paper,increase three layers of steel structure with 20GZY500-100 type isolation bearing as isolation layer arrangement between the new and old structure,is the most scientific and economic increase layer scheme.(5)Adopts the economic life analysis method to analyze the economical to the isolation layer increasing structure,the calculation results showed that although the initial cost will produce 1.47%(51800 yuan)of the extra cost,but through the whole economic life cycle to calculate,due to the isolation layer,the disaster losses can greatly reduces,remove the maintenance section and the increases in initial cost,the isolation structure still reduce the cost of 460700 yuan,so the economic benefit of introduction story isolation system is obviously.