Research On Seismic Behavior Of Precast Rc Structural Walls With Vertical Rebars Spliced By Pressed Couplers

The precast structural wall structure has developed rapidly in recent years,where a reasonable and reliable steel rebar connection method is the key to its seismic performance.As a type of mechanical splicing of steel reinforcing bars,cold forged pressed couplers have the advantages of fast construction speed and stable quality compared to the widely used grouted sleeve couplers,but few researches have been conducted so far.In this paper,cold forged pressed couplers were employed to splice vertical steel rebars in horizontal post-casting joint of precast structural walls,whose seismic performance is studied by means of experiment,numerical simulation and theoretical analysis.This paper aims to promote the engineering application of precast structural wall with vertical rebars spliced by pressed couplers.The main work is as follows:(1)The tensile tests of over 100 original cold forged pressed coupler splicers and 12 damaged splicers without outer concrete were conducted.The design variables include the diameter of connected rebars,the pressed shape,the pressing force,the loading history and the transverse relative angle of connected rebars.Test results shows that when pressed with one indentation at one time and adequate hydraulic force,the cold forged pressed coupler splicer meets the Class I mechanical property stipulations and thus can be employed as reliable connection of vertical rebars in precast structural wall.Meanwhile,it still meet the Class I mechanical strength stipulations after rare earthquake action.(2)The quasi-static tests of five 1:2 scaled,1.18 aspect ratio and 0.3 axial compression level precast structural wall specimens with vertical rebars spliced by pressed couplers and one monolithically cast-in-place control specimen were conducted.The design variables include precast method(cast-in-place or precast),longitudinal reinforcement ratio of boundary elements,web vertical reinforcement connection method(staggered pressed coupler or direct lapping).The test results show that most specimens failed in bending-controlled diagonal compression mode,and the ultimate drift ratio satisfies the stipulated value of inelastic inter-story drift ratio under rare earthquake action;the lateral strength of precast specimen can emulate the cast-inplace counterpart,while the latter have slightly larger dissipated energy and the strength degradation was delayed by the post-casting boundary elements.Increasing the longitudinal reinforcement ratio of boundary elements can enhance the lateral strength to some degree and restrain the stiffness degradation before reaching the peak lateral strength,but it may accelerate the post-peak strength degradation.(3)A detailed finite element model was established with ABAQUS program and validated.The model was then adopted to analyze the influence on seismic performance of variables including aspect ratio,axial compression ratio,concrete strength of post-casting joint,web horizontal reinforcement ratio and thickness ratio of boundary element to web.The analysis result shows that increasing the aspect ratio or decreasing the axial compression ratio has an adverse effect on the lateral strength,but it can slow down the strength degradation after the peak value and improve the deformation ability.Meanwhile,reasonable ranges of the concrete strength of the post-casting joint,web horizontal reinforcement ratio and the thickness ratio of boundary element to web are suggested.(4)The lateral strength of the 6 specimens is evaluated from flexural strength in normal section and shear strength in diagonal section.It is suggested that the positive lateral strength of the specimen controlled by bending failure can be evaluated directly by the formula of flexural strength in normal section,and the contribution to shear strength of horizontal reinforcement and longitudinal steel bar in flange section should be taken into account.