Experimental Study On Seismic Behavior Of Partially Encased Concrete T-shaped Columns

With people’s requirements for architectural function and aesthetics,special-shaped columns have gradually entered the public’s field of vision.Special-shaped column of Partly Encased Concrete（PEC）composite structure retains the advantages of high flexibility of building space,exerting the characteristics of mechanical performance,fire resistance,and higher rigidity and bearing capacity.It is significant to promote the application of special-shaped columns in higher seismic intensity areas.In this paper,three T-shaped PEC columns were designed with the ratio of axial compression as a parameter.The tests were carried out by applying low-cycle repeating load.The failure modes,hysteretic performance,stiffness,ductility and energy dissipation capacity were analyzed.The research results show that the main failure phenomena are the crushing and falling off of concrete at the bottom of the column about a quarter of the height,the bending and exposing of the tie rods,the buckling of the flanges and the bulging of the web.The maximum tensile force is greater than the maximum compression,and dos better in deformation and ductility in the test pulling direction.In the elasto-plastic deformation stage,the hysteresis loops of specimens are in the shape of a shuttle,getting good energy dissipation performance.The bearing capacity degradation coefficients of most specimens are above 0.97,having relatively good bearing capacity stability.As the axial compression ratio decreased from 0.35 to 0.15,the ultimate load of the specimen is reduced by 15.6% and the initial stiffness of the specimen decreased by 31.4%,but the speed of stiffness degradation slow down and the ductility increased by 29.5%,enhancing the energy consumption and deformation capabilities.The FEA model of the specimen was established using ABAQUS,and the analysis results were compared with the test results to verify the reliability.On this basis,an extended study was carried out on the bearing capacity under different axial compression ratios and different steel ratios.The research results show that,when the axial compression ratio is greater than 0.5,the bearing capacity of the column is reduced,more likely to occur small eccentric compression damage.It is recommended that the axial compression ratio should not be greater than 0.5.Both of increasing the thickness of the flange and web can improve the bearing capacity,but increasing the thickness of the flange more obviously.