| Compared with cast-in-place concrete,precast concrete components have various advantages in terms of use and quality.Compared with cast-in-place concrete,precast structures can better control quality,ensure higher quality aggregate supply,and ensure professional labor under factory conditions.At present,the joints of precast beams and columns designed to resist seismic loads have been studied at home and abroad.Various studies show that the key to ensure the good performance of the structure is related to the energy dissipation capacity of the precast members and the strength requirement of the connection,that is,the ability of the structure to withstand large inelastic deformation without strength loss.At present,the research and application show that it is necessary to further improve the joint stability,structural tolerance,installation speed and reduce the construction tolerance of precast members.In order to further improve the seam between prefabricated parts used in low-rise buildings in some problems,improve the most vulnerable and the most critical of the precast concrete structure parts,advancing the precast concrete frame structure in most countries the use of high earthquake area,in combination with the connection method of steel structure in current national prefabricated construction standard "technical specification for concrete structures of prefabricated JGJ1 and the prefabricated concrete construction technology standard"(GB/T 51231,such as a number of provisions,on the basis of comparing the advantages and disadvantages of domestic and foreign prefabricated node,put forward a new type of beam to column node connection.Nodes connected by steel dark bracket bolts,early through the stress analysis was carried out on the different assembly boundary nodes,bearing capacity of bearing capacity calculation and the numerical simulation of quasi assembly plan,numerical simulation and parameter optimization,get ideal assembly scheme,again through the assembly and equally cast-in-situ cross node numerical simulation on low cycle reciprocating displacement loading on the node of the hysteresis curves,skeleton curves,etc.In order to further compare with the actual cast-in-place structure,the parameters of reinforced concrete and the size of components in this paper refer to the structural parameters selected in the study on the seismic performance of cast-in-place frame structure.On this basis,in order to verify the bearing capacity of the assembly joints of the new type of steel,and the impact of different types of steel on the seismic resistance of the structure,this paper made two full-size t-shaped joints,one with l-shaped Angle steel embedded in the beam and the other with channel steel embedded in the beam.The experimental results show that the anti-seismicperformance of the new joints can reach more than 80% of that of the traditional cast-in-place structure,and the anti-seismic performance of the same type of assembly structure is greatly improved.In order to further compare and study node parameters,the results of numerical simulation and experiment are compared.The results of parameter analysis are as follows:(1)Through finite element simulation analysis,it can be concluded that the length of embedded steel beam,exposed dark bracket of column and embedded section steel in beam have a great impact on the bearing capacity of the joints.In the end,the length of dark bracket should be 200 mm and the length of beam internal section steel should be 600 mm.In this connection form,4 bolts with diameter of 20 mm shall be adopted in combination with structural dimensions.The length of h-shaped steel as dark leg part shall not be less than150 mm.In consideration of convenient practical construction,the section of dark leg of shaped steel shall be 250 250 mm.(2)It can be seen from the failure pattern and crack distribution of the structure during the experiment that with the increase of displacement,the load of pc-2 increases faster than that of pc-1,the crack appears earlier and the failure is uniform.As can be seen from the experimental results,the prefabricated joints of this type show sufficient bearing capacity,relatively good stiffness,ductility and energy dissipation capacity,and the change of the type of steel in the beam has a great impact on the structural performance,while the pc-2 shows higher bearing capacity but greater stiffness and faster concrete crushing.The performance of the two new assembly experimental nodes is slightly lower than that of the simulated assembly results in all aspects,but it can reach 80% of the same kind of cast-in-place structure,which is optimized compared with the performance of other dry assembly structure test results.(3)The comparison of comprehensive experimental results and simulation results shows that the structure meets the requirements of structural design of strong column and weak beam,and the numerical calculation results are basically consistent with the experimental results.The research results of this paper provide some reference for the application of prefabricated concrete-shaped steel dry joints in engineering. |
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