Study On Hysteretic Behavior Of Hybrid Coupled Partially Encased Composite Shear Wall

Hybrid Coupled Partially Encased Composite Shear Wall(referred to as hybrid coupled PEC shear wall)is composed of a steel coupling beam and a Partially Encased Composite Shear Wall(referred to as PEC shear wall).The hybrid coupled PEC shear wall takes full advantage of the strong energy dissipation capacity of steel coupling beams and PEC shear walls.The overall structure remains elastic under small earthquakes,and the steel coupling beams and PEC shear walls have successively entered plastic energy dissipation under the moderate and large earthquakes,which is a two-stage energy dissipation system with excellent seismic performance,and it overcomes the brittle failure of the wall bottom and the concrete coupled beam of the ordinary joint wall structure under earthquake.The method of combining experimental research and finite element analysis is used to study the hysteretic performance of hybrid coupled PEC shear wall.Based on the results,the calculation formula of hybrid coupled PEC shear wall are proposed,which provides a basis for engineering design.In this paper,a piece of hybrid coupled PEC shear wall was selected from an actual project.A specimen was made according to the scale of 2/3,on which a cyclic loading test was performed.Through the analysis of hysteresis curve,skeleton curve and strain,the bearing capacity,ductility and energy dissipation capacity of the structure under reciprocating load were explored.The results show that the hysteretic curve of the hybrid coupled PEC shear wall is plump and there is no obvious pinch and slip.The entire loading process can be divided into the elastic phase,the plastic development phase and the failure phase.In the early stage of loading,the coupling beams play the role of j oints,constraining the two walls to work together,and the cracks first appear at the bottom of the walls.As the displacement increases,the coupling beams begin to yield and consume energy.When the large-area yield of the coupling beam is formed,the restraining effect of the coupling beam on the wall begins to weaken,and the two walls tend to work in a separate cantilever shear wall mode.The concrete cracks width in the tension zone increase,and the flange plates are torn.The concrete in the compression zone is crushed,the web buckling.Then the test specimen is damaged.The finite element software AB AQUS was used to simulate the whole process of the hysteretic performance test of the hybrid coupled PEC shear wall.The accuracy of the finite element model analysis method was verified by comparing with the data obtained from the experimental test.Eight finite elements were established to analyze the effects of coupling ratio CR and axial compression ratio n on the hysteretic performance of hybrid coupled PEC shear wall.The results show that,the size of the coupling ratio determines the working mode and yield mechanism of the hybrid coupled PEC shear wall.Lower coupling ratio(CR<45%)will cause smaller rigidity of the hybrid coupled PEC shear wall.The coupling beam will yield at relatively small displacements,and the lateral displacement between structural layers will be large.Too high coupling ratio(R>60%)makes the axial force of the wall too large,and the wall is prone to brittle failure under the action of earthquake.When the coupling ratio is controlled within the range of 45%～60%,the bearing capacity and initial stiffness of the test specimen increase with the increase of the coupling ratio,and the energy consumption capacity does not change significantly.The yield mechanism meets the double line of defense mechanism of "first beam and then wall".As the axial compression ratio increases,the horizontal peak load capacity of the model increases,the peak displacement decreases,the stiffness degradation rate accelerates,and the ductility and energy dissipation capacity decrease significantly.Excessive axial pressure ratio causes small bias damage to the walls.The"Code for Seismic Design of Buildings" stipulates that when the hybrid coupled PEC shear wall is at an earthquake fortification intensity of 7,8 degrees,the axial compression ratio should not be greater than 0.5.Based on the results of tests and parameter analysis,with reference to the calculation formula for the compression-bending capacity of steel plate shear walls in the“Code for Design of Composite Structures"(JGJ138-2016),the formula for calculating compression-bending capacity of hybrid coupled PEC shear wall were proposed.The theoretically bearing capacity is 1.53%higher than the test value,which agrees well with the test value and provides reference for designing of hybrid coupled PEC shear wall.