Study On U-shaped Overlapping Performance Of Reinforcement In Precast Wall

In recent years,China has strongly advocated the greens environmental protection development.Compared with the traditional cast-in-situ structure,the assembled building has the advantages of reducing the consumption of materials,shortening the construction period and improving the quality of the building,for which the assembled building has a broad space for development.The assembled shear wall structure is one of the common forms of the assembled structure with the advantages of large lateral stiffness and small lateral displacement.The diameter of distribute reinforcement is relatively small in the shear wall structure.If the reinforcement sleeve grouting connection mode is adopted,the large diameter reinforcement bar will be used,which will cause waste of materials,and the fabrication errors and other factors will make the actual construction operation inconvenient,so the overlapping connection mode should be adopted.Based on the above analysis,a shear wall structure with U-shaped distributed reinforcement lapping connection is proposed.The force transmission mechanism of this overlapping mode is different from that of ordinary reinforcement in the code.Through full-scale test and finite element simulation,the force transfer mechanism was studied deeply.The main works and achievements are as follows:(1)Sixteen specimens with U-shaped bar lapping connection were tested.The main parameters include:the diameter of U-shaped bar,the lap length,the diameter of horizontal inserted reinforcement and the position relation of U-shaped reinforcement.The crack initiation,failure process,failure mode,load value of each characteristic point,deformation value and variation law of steel bar strain in joint area were studied by experiment.The test results showed that there were two failure modes in the specimens:if the lap length was enough,the U-shaped reinforcement was pulled apart;if the lap length was insufficient,the concrete of the specimens were sheared in the joint area,and the horizontal reinforcements were sheared or buckled.The horizontal inserted reinforcement played an important role in the force transfer mechanism of U-shaped distributed reinforcement lapping connection.(2)The finite element software ABAQUS was used to numerically simulate the shear wall with U-shaped distributed reinforcement lapping connection.In the model,plastic damage model and double broken line reinforcement model are used respectively to consider the non-linearity of concrete and reinforcement.The simulation results were in good agreement with the experimental results,which proved that the finite element model was reasonable and effective.Based on the validated model,the variable-parameter analysis was carried out.The parameter was the lap length and the diameter of horizontal inserted reinforcement.The analysis results showed that the higher the lap height of u-shaped distributed reinforcement was within a certain range,the greater the axial tensile capacity of the specimen was;while the certain range was exceeded,the bearing capacity was no longer increased;the bearing capacity of the specimen with horizontal splicing bar was greater than that of the specimen without splicing.Horizontal splicing played an important role in transferring force.(3)Based on the experimental results and finite element analysis,the force transfer mechanism of U-Shaped splicing joint was analyzed.the calculation formula of bearing capacity of u-shaped splicing joint under axial load and non-axial load was proposed and the validity of the formula is verified with the test results and finite element analysis results.On the basis of the calculation formula,the theory of joint length design of U-Shaped distributed bar splicing joint is presented.