Experimental Study On The Influence Of The Position Of Vertical Connecting Reinforcement On The Force Transfer Performance Of The Horizontal Joint Of The Precast Superposed Shear Wall

In recent years,prefabricated building technology has developed rapidly in China,and it will shine in the 2020 epidemic prevention campaign.It has completed the construction of Huoshenshan hospital and Leishenshan hospital in more than ten days.The China’s quality and China’s speed are appreciated by people around the world.Supporting the rapid and high-quality construction of projects are the engineering construction standards,and the mission of the researcher is to improve these standards and promote the healthy and orderly development of China’s prefabricated buildings.In "Technical standard for assembled buildings with concrete structure ",the precast superposed shear wall structure system is a semi-prefabricated and semi-in-situ cast system composed of a superimposed wall panel with both precast wall panels and postcast concrete,which is widely used in multi-storey and high-rise buildings structure.The vertical connection steel bars are the overlapping steel bars set in the post-cast core layer concrete at the horizontal joint to achieve the common force of the upper and lower laminated wall panels,and the vertical steel bars in the prefabricated wall panels realizes load transfer by the force transmission mechanism.At present,China’s relevant regulations do not specify the position of the vertical connection steel bars.During the construction process,the vertical steel bar positioning may also be disturbed by the placement of post-cast concrete and the position deviation may occur.The research on the indirect lap force transfer performance of steel bars is still lacking.Therefore,this paper mainly aims at the transfer of the connected steel bars to the horizontal joints of the precast superposed shear walls’ mechanical performance by the tests research and finite element analysis research.The main work and achievements are as follows:(1)According to different vertical connection positions of steel bars and different shear span ratios,11 composite shear wall and 1 cast-in-place shear wall specimens were designed and tested.Various stress performance indexes such as the failure form,bearing capacity,ductility,stiffness degradation,and steel bar strain of each specimen were obtained,combined with the analysis of the whole-field strain data of the specimen surface collected by the digital image correlation method,and the effects of vertical connection steel bar position on the horizontal joint force transmission performance of the precast superposed shear walls were summarized and compared.(2)The experimental research results show that the initial cracks of the precast superposed shear wall specimens appear earlier as the net distance between the connecting reinforcement and the inside of the prefabricated wall panel decreases,and the number of cracks decreases as the shear span ratio increases;increasing the distance between the connecting reinforcements the internal clearance of prefabricated wall panels can improve the bearing capacity of low-span-to-span precast superposed test specimens at various stages,and reduce the bearing capacity of intermediate and high shear-span ratio test specimens.Increasing the initial stiffness of the laminated specimen,but it has a small effect on the rate of stiffness degradation and ductility of the laminated specimen.(3)The abaqus finite element software was used to analyze the force transmission process of the steel bar at the horizontal joint of the superposed shear wall and the influence of the vertical connection of the steel bar position,and the calculation results are in good agreement with the test results.The comparative analysis of the finite element calculation results of the full-scale shear wall specimens and the beam-type specimens verifies that the beam-type test method can be used to study the horizontal joint force transfer performance of the superposed shear wall,which can achieve similar research goals of the full-scale shear wall test and effectively reduce the test workload.In addition,this paper also established a finite element model of a full-scale specimen of a double-sided laminated shear wall with horizontal joints,and explored the influence of axial compression ratio,shear span ratio and the position of the connecting bars on the horizontal joint transmission performance of the superposed shear wall.The design recommendations for the location of the vertical connecting bars of the horizontal joint of the superposed shear wall are proposed.Finally,on the basis of summarizing the results of this study,the questions to be further studied are put forward.