Study On Seismic Performance Of Concrete-filled Steel Tube Gravity Column-concrete Core Tube Structure

With the acceleration of urbanization in China,it is urgent to design and develop new highrise prefabricated building structure system.Frame-core tube structure system is widely used in modern high-rise and super high-rise buildings.However,its rigid joints can only be welded,which leads to heavy workload,complex construction and long time-consuming,and reduces the advantages of prefabricated steel frame beams.Therefore,a new type of concrete-filled steel tube(CFST)gravity column-reinforced concrete(RC)core tube structure is developed,that is,CFST column,fabricated steel beam and RC core tube are hinged by bolts.The overall stress of the structure is clear,without considering the shear sharing rate of the outer frame,which effectively avoids the problem of "fat beam and fat column",reduces the design difficulty and construction cost,and its components can be prefabricated in the factory,which significantly improves the construction efficiency.In this paper,the seismic performance of the new structure is studied.The main work and results are as follows:(1)Using the finite element software Canny,3D modeling and Simulation of the shaking table test model and test process completed by the research group are carried out to study the seismic performance of CFST gravity column-RC core tube structure,and verify the reliability and accuracy of the numerical model.(2)Two finite element models,CFST column frame-RC core tube structure and CFST gravity column-RC core tube structure,are established.Through static elastoplastic analysis and elastoplastic time history analysis,the influence of joint connection mode on the seismic capacity of the structure is explored.It is found that the plastic hinge first appears in the coupling beam of CFST gravity column-RC core tube structure under earthquake action,which acts as the first line of defense against earthquake,that is,the core tube itself can build two lines of defense against earthquake,so its comprehensive seismic performance is roughly equivalent to that of the rigid joint frame structure.The new structure can meet the requirements of "Code for Seismic Design of Building" and achieve "no damage in small earthquake,repairable in medium earthquake and no collapse in large earthquake".(3)By changing the height width ratio and the core tube area ratio,16 CFST gravity column-RC core tube structures are designed.The static elastoplastic analysis is carried out by using the exponential lateral loading mode in the positive direction of x-axis,and the performance points and seismic indexes of these examples under 7 degree small earthquake,medium earthquake,large earthquake and 8 degree large earthquake are obtained respectively.The results show that when the core tube area ratio is constant,the natural period,floor displacement,story displacement angle and overturning moment increase and the period ratio and floor shear force decrease with the increase of the height width ratio;when the height width ratio is constant,the floor shear force and overturning moment increase and the natural period,period ratio,floor displacement and story displacement angle decrease with the increase of the core tube area ratio.