| With the rapid development of contemporary society,prefabricated building has become more and more a construction production mode in the construction industry.Prefabricated buildings have the characteristics of green environment protection,less wet work on site,and fast construction speed.At present,most of the researches on prefabricated buildings at home and abroad still focus on the connection between frame structures,the shear wall structure and the frame-shear wall structure.Therefore,this paper uses this connection method to analyze the mechanical properties of the research framework.Under the strong support of the national science and nature foundation project(No.51678375),based on the experimental results of the existing beam-column joints,ABAQUS finite element software is used to simulate the beam-column joints.The simulation results are extracted and compared with the experimental results.The results show that the load-displacement curve of numerical analysis is fuller than the experimental curve and shows greater stiffness.The occurrence of pinch phenomenon shows that the model has the ability of plastic deformation and can absorb seismic energy well.The difference between mechanical and displacement indexes analyzed by geometric mapping method and test indexes is within10%,which meets the control requirements of limit values.Therefore,the difference between the finite element simulation curve and the test curve is small,and the results are basically consistent,which fully proves the practicability and accuracy of ABAQUS finite element software in the numerical simulation analysis of fabricated frame joints.In engineering practice,most of the frame joints are subjected to shear failure under "strong beam and weak column","strong column and weak beam" and "strong member and weak node".In this paper,the design principle of "strong members and weak joints" with the most serious damage to frame joints is adopted to design the frame size,and a reinforced sleeve grouting connected frame finite element model and a cast-in-place frame finite element model are established to carry out mechanical analysis under monotonic load respectively,and the difference of mechanical properties between the assembled frame connected by sleeve grouting after shear damage and the cast-in-place frame is compared and analyzed.The results show that the expected failure modes have been realized.After the shear failure of the assembled frame joints,the frames connected by grouting sleeves have higher bearing capacity and ductility,and will not be disabled due to continuous collapse.The ultimate bearing capacity of the assembled frame is about 5% higher than that of the cast-in-situ frame.The ductility coefficient of the two frames is above 5.0.The assembled frame also shows good plastic deformation capability.In addition to tensile cracking damage of concrete in the gap between column footing and ground beam,the damage is mainly concentrated above the sleeve height,resulting in tensile cracking damage and compressive damage of concrete.Therefore,it is suggested to adopt tapered sleeve at column footing or increase column section.Five groups of different frame specimens were designed by changing five parameters,including sleeve size and length,sleeve position at beam end,axial compression ratio,beam end contact surface,and strength grade of post-cast concrete at joints.ABAQUS finite element simulation software was used to simulate the stress process under monotonic displacement.Compared with 290 mm sleeve,the bearing capacity of 340 mm sleeve such as yield strength and peak load is increased by 3%,ductility coefficient is increased by 9.1%,and initial stiffness is increased by 10.9%.Therefore,340 mm sleeve is adopted.For the shear failure of frame joints,the bearing capacity,ductility coefficient and initial stiffness decrease with the increase of the distance between the sleeve and the joint,and the variation range is within 5%.The position of the sleeve is not an important influence index on the mechanical properties of the specimens.The axial compression ratio is from 0.25/0.5 to 0.3/0.6 and0.35/0.7.The yield strength,peak load and other bearing capacity of the members are all increased by less than 7%,but the ductility coefficient is reduced by 14.2% and 24.6%respectively.When the load exceeds the peak load,with the increase of axial compression ratio,the bearing capacity and ductility decrease significantly,and the assembled frame connected by sleeve grouting will be limited in high-rise and super high-rise buildings.Compared with the plane contact,the bearing capacity under the groove surface contact is increased by less than 5%,the initial stiffness is increased by 10%,and the setting of shear groove can better transfer shear force.From C45 to C50 and C55,the ductility coefficient decreased by 5.3% and 11.1%,respectively.The bearing capacity mainly showed that the concrete strength grade of the early joint had no great influence on the specimen.When the peak load was loaded,the bearing capacity decreased significantly with the increase of the concrete compressive strength grade.According to the analysis of the seismic performance of the specimens,the ultimate bearing capacity of the fabricated frame is about 6% higher than that of the cast-in-place frame.In terms of ductility,the ductility coefficient of the two frames is above 4.0,and the vertex displacement angle is 1/36 and 1/31.The fabricated frame also shows good plastic deformation capability.Under the same displacement,the equivalent viscous damping coefficient of the fabricated frame is 0.124 and that of the cast-in-place frame is 0.118,which obviously shows that the fabricated frame has stronger energy dissipation capacity.The stiffness of the prefabricated frame is relatively large at the early stage,and the two tend to be consistent gradually with the reciprocating loading of displacement.Assembly frame can be used for analysis and calculation of cast-in-place frame in terms of failure mode,internal force,deformation and bearing capacity. |
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