Research On Seismic Design Method Of Multi-high Story Building With New-type Precast RC Diaphragm

The new-type precast RC diaphragms(for short,new-type diaphragm)have many advantages,such as factory standardized processing,fast construction speed,high labor efficiency and less wet work.Due to the limited stiffness in the plane of precst diaphragm,significant in-plane deformation and even structural damage will occur under horizontal earthquakes.Such type of diaphragm is defined as semi-rigid diaphragm in domestic standards and a simple averaging method is adopted during the internal force distribution in seismic design.However,research shows the method has large errors and safety hazards.In order to reveal the dynamic characteristics and seismic response law of the building with new-type diaphragm and propose a seismic design method for the building with the new-type diaphragm,in this paper,the pseudo-static test of the in-plane deformation of the new-type diaphragm is carried out,and the seismic analysis model of the building structure considering the in-plane stiffness of the new-type diaphragm is established,and the dynamic characteristics and seismic response analysis of the high-rise building with the new-type diaphragm are carried out.The main contents are as follows:(1)The quasi-static test of force performance in the plane of the new-type diaphragm and the correction of the calculation method of the in-plane stiffness were carried out.The hysteresis curve and skeleton curve of the diaphragm,the in-plane deflection and the shear distribution at the joint are obtained through the analysis of the in-plane mechanical performance of the new-type precast RC diaphragm with the hairpin-cover(HP-CPC)connector.The test results show that the deflection of the new-type precast RC diaphragm under horizontal load is close to that of the simply supported beam under uniform load,which provides a test basis for calculating the in-plane deformation of the diaphragm using the equivalent beam theory method.On the basis of the experiment,the correction calculation method of the in-plane stiffness of the new-type diaphragm is proposed.The calculation result of this method is in good agreement with the experimental measurement value,and can be used to calculate the in-plane stiffness of the new-type diaphragm in the elastic stage.(2)A seismic analysis model for multi-high story buildings with the new-type diaphragm was established.For the multi-high story buildings with the new-type diaphragm,due to the limited stiffness in the plane of the diaphragm,the “series multi-mass system” seismic analysis model assumed by rigid diaphragm cannot be used.Therefore,based on the research content(1)calculation method of the stiffness in the plane of the diaphragm,a seismic analysis model of "serial-parallel multi-mass system" considering the actual stiffness in the plane of the new-type diaphragm is proposed,and a case study is carried out.The method of establishing shear wall,frame and floor stiffness matrix is elaborated,and the matlab calculation program for solving structural vibration equation(reaction spectrum and time history analysis method)is compiled.Through debugging and case verification,it is proved that the calculation program can be used for seismic calculation of multi-high story buildings with the new-type diaphragm.(3)Dynamic characteristics and seismic response analysis of multi-high story buildings with the new-type diaphragm were carried out.In order to verify the research content(2)the calculation accuracy of the theoretical seismic analysis model and the difference with the "series multi-mass system" seismic analysis model,the finite element program is used to build a multi-high story building model with the new-type diaphragm and the cast-in-place diaphragm of the same size.Through analysis,the response law of the structure’s natural vibration period,vibration mode,displacement,internal force and acceleration is obtained.The conclusions are as follows: 1)The theoretical analysis results are in good agreement with the finite element analysis results,indicating that the theoretical seismic analysis model is more accurate for structural seismic analysis;2)Due to the flexibility of the diaphragm,the natural vibration period of the structure is significantly larger than that of the cast-in-place structure;3)Under the horizontal earthquake,the floor cover has significant in-plane deformation,and the lateral displacement of each lateral force structure is greatly different;4)Seismic shear force distribution has also undergone major changes,and the framework will assume greater seismic shear;5)The acceleration response of each floor also changes significantly,and the frame will produce a larger acceleration response.(4)Analysis of seismic response parameters of multi-high story buildings with the new-type diaphragm were conducted.By adjusting the number of vibration modes,the stiffness of the diaphragm and the number of building layers,the seismic response law of multi-high story buildings with the new-type diaphragm is obtained.The conclusions are as follows: 1)The influence of the high-order mode on the shear wall is significantly larger than that of the frame,and the effect on the middle opening of the floor is greater than that in the end;2)When the stiffness of the floor is small,the change of the stiffness of the diaphragm will cause the seismic shear force of the structure to change drastically.When the stiffness of the diaphragm is large,even close to the cast-in-place diaphragm,the impact of the stiffness of the diaphragm on the seismic shear of the structure become weak,and the distribution of seismic shear forces between the shear wall and the frame gradually shifts toward the shear wall;3)The increase in the number of building layers will reduce the horizontal seismic shear force of the diaphragm,which means that new-type precast RC diaphragm can be used for high-rise structures without causing additional seismic internal forces.Finally,the paper summarizes the research results and existing problems,and proposes the seismic design method and design suggestions of multi-high story buildings with new-type precast RC diaphragm,and prospects for the subsequent research of the subject.