Study On Mechanical Behavior Of Prefabricated Prestressed Steel Reinforced High Strength Concrete Composite Frame Structure

A new frame structure system with green assembly construction,reasonable structure and superior seismic performance is proposed,that is,the high-strength concrete composite column with built-in concrete-filled steel tube core column is used as the frame column,and the built-in H-shaped steel prestressed high-strength concrete composite beam is used as the frame beam.The frame column and the frame beam are rigidly connected with the integral steel joint,and the integral high ductility joint is formed by post-pouring engineered cementitious composites（ECC）.In view of the fact that the mechanical properties of assembled prestressed steel reinforced high strength concrete composite frame（PSRCF）have not been reported,this paper has carried out the following three studies to provide technical support for the practical engineering application of this kind of composite frames.1.The finite element software ABAQUS is used to select a reasonable material constitutive model.Considering the interface contact between steel tube,concrete and beam-column joint,a three-dimensional finite element model of assembled prestressed steel reinforced high-strength concrete composite frame is established.Compared with the existing experimental data,the maximum error is not more than 9.65%,which can verify the rationality of the modeling method.2.Based on the reasonable modeling method,the static analysis of 17 PSRCF under monotonic horizontal load are carried out.The results show that the increasing of the diameter of the core column（d）,the strength of the beam and the outer concrete(f_co),the stirrups ratio（λ_v）and the axial compression ratio（n）of the column can improve the ultimate bearing capacity of the specimens,and the increasing of d and f_co can improve the initial stiffness（K）,but the increasing of n andλ_v can reduce K.Joints by pouring ECC can significantly improve the ductility of composite frames.Through the static analysis of the single-layer single-span PSRCF frame,it is found that the plastic hinge of the frames firstly appears at the end of beam,then appears at the right column foot and the left column foot respectively.There is no shear failure in the core zone of the joint,which well reflects the concept of strong column,weak beam,and strong joint.Finally,the plastic hinge length formula of the beam and column of this kind of composite frame is fitted and regressed by 1st Opt software.3.The pseudo-static simulation analysis of 17 PSRCF frames under low-cycle repeated horizontal displacement is carried out.The results show that the P-Δcurves of the PSRCF frames exhibit arched and are full.Whenλ_v and f_co increase and joint by pouring ECC is adopted,the pinch effect of hysteresis curves can be improved.Withλ_v increasing,the shape of hysteresis curves gradually change from arch to spindle,which has good seismic performance.Under the action of low-cycle repeated horizontal displacement,PSRCF pouring by ECC still maintains good integrity when it is destroyed,and the ECC joint can improve the failure mode of this kind of composite frames under earthquake action.Based on the skeleton curves of seventeen PSRCFs,the skeleton curves models of this kind of frames are regressed by 1st Opt software.