Research On Seismic Behavior Of Improved Grouting-Anchor Connection Of Precast Shear Walls

The prefabricated shear wall structure is one of the important structural forms of prefabricated buildings.The vertical connection between precast walls is the key to ensure the integrity and seismic performance of the structure.At present,in the prefabricated concrete structure,the technology of grouting-anchor connection and grouting-anchor of corrugated pipe connection of steel bars are widely used by convenient construction,economy and safety.With the practical application of grouting-anchor connection technology in engineering,there also have practical problems,such as excessively long lap length of the steel bars and hole forming defects of grouting-anchor during the manufacturing process.These problems need to be studied and solved urgently.The improved grouting-anchor connection method of preembedded corrugated pipe formation and spiral stirrup restraint(Corrugated Pipe Spiral Stirrup,hereinafter referred to as "CPSS")came into being.In order to ensure the reliability of this type of connection under earthquake action,the research team focuses on the seismic performance of the CPSS grouting-anchor connection of precast shear wall.Based on the research results of the CPSS grouting-anchor connection method,a simplified CPSS grouting-anchor connection method is proposed,4(?)12 rebar replaced with 1(?)25 in the non-edge members,which can reduce the number of connecting reinforcement and solve the practical engineering problems such as complex reinforcement of the precast shear wall and difficulty in construction.In this thesis,the seismic performance of 16 precast shear walls with core-pulling hole of constrained grouting-anchor connection,CPSS grouting-anchor connection and simplified CPSS grouting-anchor connection were systematically tested,numerically simulated and theoretically analyzed.The main research contents and results were as follows:(1)The quasi-static tests on 4 pieces of constrained grouting anchor connection and 8 pieces of CPSS grouting anchor of precast shear wall specimens were carried out.The axial compression ratio,the lap length of reinforcement and the hole formation of grouting anchor were investigated.It reflected the influence rule of the mechanical properties of the CPSS grouting anchor connection,and reveal the failure mode and working mechanism of precast shear wall of CPSS grouting-anchor connection.The thesis gave suggested value of the lap length of precast shear wall specimens with CPSS grouting-anchor connection.Based on the connection of CPSS grouting anchor,a simplified connection form of CPSS grouting anchor was proposed.The pseudo-static test of four full-scale walls were with simplified CPSS grouting anchor connection were carried out.The results showed that the failure mode of the similar to that of the CPSS precast shear wall.(2)Numerical simulations of CPSS precast shear wall were carried out by ABAQUS finite element.The simulation results were well in agreement with the test,the accuracy of the numerical model was valid.On this basis,the extened analysis was carried out by taking axial compression ratio,the lap length,the replacement area of reinforcement and grouting strength.The results showed that the ductility of CPSS specimen with the lap length is 0.9 1a is similar to the shear wall specimen with straight anchor connection.When the lap length of steel bar increased from 0.7la to 1.6la,the bearing capacity of CPSS precast shear wall increased,but the ductility and energy consumption of CPSS precast shear wall decreased gradually.When the reinforcement diameter of the simplified connection was 28mm,which was 1.36 times of the area of the replaced reinforcement(4 bars replaced by a diameter of 12mm),the finite element analysis showed that the connection performance of the simplified connection of CPSS precast shear wall and CPSS wall was equivalent.Increasing with the the grouting material strength did not have a significant influence on the mechanical properties of the CPSS groutinganchor connection and the simplified CPSS connection of the precast shear wall.In actual projects,grouting materials with a strength grade of 60MPa can be used.(3)Combined with the test data and the results of finite element analysis,the calculation methods of concrete structure bearing capacity in domestic and foreign codes were analyzed and compared.The calculation formulas of bearing capacity of normal section,diagonal section and horizontal joint of CPSS precast shear wall were derived.Based on the USFM theoretical calculation model,the shear bearing capacity of the CPSS precast concrete shear wall under the coupling action of compression,bending and shear was calculated and analyzed.(4)Based on the analysis of the influence of the lap length on the bearing capacity of the precast shear wall with CPSS connection,the recommended formula for the calculation of the reinforcement lap length of the CPSS connection was proposed.Combined with the experimental research and finite element analysis results,when the reinforced diameter of the non-edge members of the CPSS precast shear wall with simplified connection was 12mm,the replacement factor of the reinforcement area was proposed,and the design method and construction requirements of simplified connection of CPSS precast shear wall were established and given.