| In recent years,the assembly building developed vigorously in China.Our country is focusing on promoting the transformation of the construction mode and upgrading of the construction industry,promoting the development of the construction industry to energy saving,emission reduction and green environmental protection.It is of great practical significance and far-reaching strategic significance to study the assembly structure for promoting the green innovation and development of urban construction.The existing prefabricated assembled concrete frame structure still has some shortcomings,such as poor quality assurance,more wet work and complex connection.In this paper,a new connection method of precast concrete frame beam-column joints with upper anchor and lower bolts is proposed.The concrete method is that the upper longitudinal bar of the beam is connected with the column through the straight thread sleeve,and the lower embedded steel member is connected with the column through the high-strength bolt.In order to optimize the end plate thickness of beam-end steel connectors and study the mechanical behavior of the new prefabricated concrete frame beam-column joints under seismic loads,we carried out the joint tests and finite element analysis.The main research contents and conclusions are as follows:(1)We obtained the end plate thickness suitable for opening U-shaped holes through unidirectional eccentric tension tests on four steel connection specimens designed for beam ends.By doing the pseudo-static test on the new prefabricated concrete frame beam-column joint specimens and observing the whole failure process and failure mode,we analyzed the hysteretic curve,skeleton curve,bearing capacity,deformation,ductility,stiffness degradation and energy dissipation capacity of the joint specimens.We did research on the deformation of the joints and the development law of the strain of the steel bar.The result shows that the beam hinge failure occurs in both the cast-in-place specimen and the assembly specimen.The straight threaded sleeve can effectively transfer the tension.The lower steel member and the high strength bolt can guarantee the reliability of the force.In a word,the new joint connection is reliable.(2)Finite element software ABAQUS is used to refine the modeling and analysis of cast-in-situ concrete frame beam-column joints and precast concrete frame beam-column joints.The constitutive model of reinforcing bar,steel plate and high strength bolt is double-folded line model,and the constitutive model of concrete is plastic damage model.The numerical simulation results are consistent with the experimental results,which proves the accuracy of the finite element model.(3)Based on the experimental results and finite element analysis results,we analyzed the force transfer mechanism of steel connections at the bottom of beams.And we put forward a new design method of precast concrete frame beam-column joint,including the calculation method of end plate thickness of steel connections and the calculation formula of shear capacity of multiple sections of beams.The design method of steel connectors and the formula of shear capacity of beam section presented in this paper both have certain safety reserve. |
