Experimental Study On Seismic Performance Of PEC Columns Under Different Axial Load Ratio

H section steel partially encased concrete composite column(PEC column),a new type of composite structure,takes the advantage of shape steel and concrete.PEC column has high bearing capacity,good energy dissipation capacity and good fire resistance.Owing to the prefabricate and assemble ability,PEC specimens are in line with the green building policy of new era and have promising engineering application prospects.At present,China's standards of the PEC structures are still in blank state.So,the study of PEC structures can not only promote the development of its theory,but also provide guidance for practical engineering.In order to study the effects of different axial load ratios on the seismic performance of PEC columns,11 PEC columns made by Q235 and Q345 steel were tested under low frequency reversed cyclic quasi static loading and monotonic loading.The parameters included the axial load ratio,steel strength,section size and loading method.The experiment results show that the hysteresis curve of PEC columns with different parameters are shuttle shape.The main failure phenomena of PEC specimens were the spalling of concrete above the stiffener at the bottom of column,buckling of flanges and the exposing or breaking of transverse tie-bar.The ductility coefficient of each specimen is bigger than 2.49.The ultimate displacement angle which can reach or exceed 1/50 indicated that PEC columns have good seismic performance.When the axial load ratio increases from 0.2 to 0.4,the bearing capacity increases by 14.46% and the ultimate displacement decreases by 49.97%.When the axial load ratio increases from 0.4 to 0.6,the bearing capacity increases by 24.32% and the ultimate displacement decreases by 32.61%.The stiffness and strength of the specimens are different with the difference of cyclic loading displacement.The energy dissipation capacity of PEC columns under different loading method is different.The peak load of specimen with larger difference of cyclic displacement appears later and the energy consumption capacity is worse than other specimens.The finite element simulation test was calculated by ABAQUS.The reliability of the finite element model was verified by comparing with the experiment results.It can be seen that the increase of the axial load ratio can increase the peak load of the specimens,but the peak load decreased while the axial load ratio reached to 0.7.The specimen with Q235 steel has a good ductility coefficient of 4.09 when the axial load ratio is 0.7.The ductility coefficient of the specimen made with Q345 steel is 2.82 when the axial load ratio is 0.4.The reasonable axial load ratio and higher concrete strength should be designed in the anti-seismic design.