| In precast concrete members,especially in the connection of beam column joints,the phenomenon of dense distribution of reinforcement is very common.After the reinforcement of beam column joint is bound and put into the formwork,it is difficult to vibrate and ensure the quality of the project due to the dense reinforcement configuration.It can reduce the number of mechanical connection of steel bars,simplify the construction process,reduce the construction difficulty and optimize the assembly performance.At present,it seems that the application and development of large-diameter reinforcement in prefabricated concrete buildings in China is still in the exploratory stage,the research theory is not mature,and the experimental research and numerical simulation results are few,so it is necessary to carry out research on such components.In this paper,a kind of prefabricated composite beam with the diameter of upper and lower longitudinal bars of 40 mm and 32 mm respectively and the diameter of upper and lower longitudinal bars of 32 mm and 25 mm respectively considering the influence of the floor slab is proposed.The strength grade of the reinforcement is HRB500.Through the low cycle reciprocating loading test and finite element simulation,the seismic performance of the beam is studied.The main research contents are as follows:Before the test,the mechanical property parameters of C40,C45 concrete and HRB500 reinforcement with diameter of 25,32 and 40 mm were measured by material test.Observe and record the test phenomenon,crack development and failure form of the specimen during the test.The construction measures such as rough surface manufacturing technology,shear key and grouting sleeve are used to ensure the overall performance of the test piece under the action of low cycle reciprocating load.The experimental results show that the failure mode of the four specimens is bending failure at the end of the beam;the specimens with 40 mm and 32 mm longitudinal bars have larger yield load and peak load,full hysteretic curve,better performance in stiffness degradation,strength degradation,energy consumption,etc.;the specimens with 32 mm and 25 mm longitudinal bars have better ductility under forward loading;the configuration of additional bars has better superposition The mechanical properties of beams have little influence.Compared with the test results of the frame beam without floor slab,the bearing capacity and rigidity of the frame beam with floor slab are greater than those of the frame beam without floor slab before the displacement of the beam end is loaded to 30 mm,and the displacement is loaded to 30mm-120 mm,and their bearing capacity and rigidity degradation trend are basically the same;the energy consumption capacity of the two kinds of large-diameter high-strength reinforced frame beams with or without floor slab is equivalent.The finite element analysis software ABAQUS is used to establish the model of large-diameter high-strength reinforced frame beam under the same parameters.The influence of the floor slab is considered.The results of the finite element simulation are basically consistent with the test results.The analysis shows that the failure mode of the test piece is basically consistent with the stress nephogram calculated by the finite element model,and the peak load error is within 15%.The model in this paper is in the element The selection,constitutive relationship,mesh division,interaction between materials and contact surfaces,boundary strip and loading system are reasonable,which verifies the correctness of using ABAQUS to establish the model of precast large-diameter high-strength reinforced composite beam considering the influence of floor slab. |
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