Study On Seismic Performance Of Existing Frame Structure Buildings After Top Floor Column Remova

In China,new built building and reconstructed building has become equal instead of largescale new building previous in building industry,and reconstructing the existing building has drawn more and more attention.Columns demolishing reconstruction is a technology that can transform building function,enhances service of the existing building and satisfy people’s requirements.Taking demolishing the top floor columns reconstruction of an existing reinforced concrete frame structure teaching building as an example,the seismic performance of existing frame structure after demolishing columns was investigated and the researches were performed as follows:The original structure was built,that verified by PKPM software and the code requirements.Two options were selected for strengthening by increasing the original beam cross-section at the top floor and using the prestressed beam method at the top floor after the frame forces analysis after demolishing columns on the top floor by PKPM software.The beam cross-section and reinforcement of the two strengthening methods were obtained and met the code requirements.Three frame models were established using ABAQUS finite element software for the original frame without demolishing columns,demolishing the columns frame with increased top original beam section,and demolishing the columns frame with the top prestressed beam.In addition,the ABAQUS finite element software was used to establish the framework finite element model from relevant literature and simulate the low cyclic loading the correctness of the modeling methods such as material intrinsic relationship and loading regimes was verified by comparing them with the test results.The ABAQUS finite element software was used to simulate the horizontal low circumferential repeated loading of the three models established above.Obtaining the hysteresis curves of the three models,and analyzing the change patterns of seismic performance parameters such as skeleton curves,ductility coefficients,stiffness degradation,and equivalent viscous damping coefficients.The main analysis results show that the seismic performance of the frame after demolishing columns is lower than that of the frame without demolishing columns;The bearing capacity of the two frames after demolishing columns decreases by 15%-18%;Model ductility decreases by about 5%,etc.ABAQUS finite element software was used to conduct a numerical simulation analysis of the two frames after demolishing columns by repeated horizontal low circumferential loading.Investigating the effects of the three parameters of column volume hoop ratio,column longitudinal reinforcement rate,and column axial pressure ratio on the seismic performance of the frame after top floor demolishing columns and the following analysis results were obtained.With the increase of columns hoop rate and columns longitudinal reinforcement rate,the model bearing capacity increases by 1.99%-5.98%;the model ductility coefficient increases by 63.48% at maximum;the top prestressed beam demolished column frame performs better than the increased top original beam section demolished column frame in terms of ductility and energy dissipation.But does not perform as well as the increased top original beam section demolished column frame in terms of bearing capacity,with a decrease of 3.87%-7.43% under the same conditions.The reinforced models after columns were demolished,under the large axial pressure ratio.The plastic hinge of the extracted column frame model with increased top original beam crosssection appears first at the mid-span position of the top beam,while the plastic hinge of the extracted column frame of the top prestressed beam appears first at the top column end when the reinforced models after columns are demolished under the large axial pressure ratio.And the models’ damage is brittle.