Experimental Study On Seismic Behavior Of Middle Joint In PEC Column Composite Structure

Compared with PEC composite structure and the traditional pure steel structure and reinforced concrete structure have some advantages,such as high precast mineralization,fast construction,high bearing capacity and mechanical properties,good fireproof performance and the economy,and the beam-column joints can be easily arranged,so it got the more and more attention.At present,the domestic has carried out related research.But in recent years the study of the seismic performance of the framework for PEC column-steel beam end plate connection is relatively small.The node failure modes,mechanical performance of the different structure is not enough in-depth,as well as a lack of performance comparison and analysis with other frame structure.So it is necessary to carry out seismic performance of the PEC column-steel beam end plate connection node,and to provide a reference for future design and construction.In this paper,the four nodes specimens in scale framework were designed,including three PEC column-steel beam end plate connection,and one pure steel structure framework of nodes as a reference,the quasi static loading tests were conducted.Based on the experimental research,a three-dimensional parameterized space model of the specimens was established by using finite element analysis software ABAQUS.It has carried on the finite element analysis to the node specimen verification and the related parameters to expand research.The influences by different axial compression ratio,beam section size,and the PEC column combination structure on the performance of nodes in connection were discussed.Through the observation of each specimen failure process and node data processing of the framework,the hysteretic properties of the specimens,the ultimate bearing capacity,stiffness degradation,ductility,energy dissipation capacity and related seismic performance indicators were analyzed.The results show that node failure mode using PEC column and same beam section is the buckling of beam end,which belongs to the ductile fracture,accord with "strong column weak beam","strong node weak component" seismic design requirements.The node failure mode adopted PEC column and different height beam section is shear failure in cross section,it is consistent with the finite element results,the main reason is to change the section height of the beam on one side of the column,resulting in the increase of the input shear force in the joint domain.The node of shear failure model can be reinforced with large diameter tie bar and high strength concrete.The bearing capacity of PEC column composite structures increase by 36% compared with pure steel structure;Axial compression ratio increased from 0.27 to 0.44,the bearing capacity increases by 57.7%;With different height beam section node,specimen capacity increased by 13.6%.The bearing capacity and stiffness degradation of PEC column specimens are relatively stable in composite structure;The ductility coefficient of PEC column node is between 4.47 to 5.30,the average equivalent viscosity coefficient is between 0.36 to 0.45,which is correspond to that of steel reinforced concrete,slightly less than the pure steel structure.The axial compression ratio increase,energy dissipation capacity rise and node ductility will decline.When the failure mode is beam end occurs plastic hinge,the yield strain and order is beam plastic hinge district,end plate and column web from large to small;When the node is shear failure mode,the yield strain and order is column web,beam flange and the end plate,it is consistent with the results of finite element simulation.when using high strength steel to improve the bearing capacity of the node,Q420 steel with the C50 concrete can be elected;The influences on axial compression ratio to bearing capacity is complex,when the axial compression ratio is less than 0.44,the bearing capacity of specimen increase with axial compression ratio rising.