| The reinforced concrete structure is widely used,the layout is flexible and the overall performance is good,and the fire resistance is better than the steel structure.The performance of the joints is relatively important compared with beam,plate and column components.Frame joints are the key performance points to connect the frame,which transmit and distribute the internal force and maintain the overall stability.The "strong column weak beam","strong shear weak bending" and "strong joint and weak component","strong joint" shows the importance of the mechanical properties of the joint according to the seismic code.It can be divided into: the top of the middle column joint,the top of the edge column joint,the middle of the column joint and the middle frame side column joint according to the position of the frame.Now the building fire has been the object of structural disaster prevention and control,so the study of high temperature frame joints of the fire resistance and deformation of the frame joint has practical significance.In recent years,the fire resistance research of reinforced concrete frame is relatively more important,but the fire component is bound by adjacent components and internal force constraint can not be simply expressed as a single component combination in the actual fire.In order to study the frame structure under fire further,the fire resistance of frame joints and the deformation of frame joints under high temperature are researched.The load of other components will be transferred to the other members by internal force redistribution,and the force will be transmitted to the frame joints in fire.So the joints resistance have some differences compare to other components in fire.There are relatively few researches on the temperature field analysis and joint deformation calculation of reinforced concrete frame joints under high temperature at home and abroad at this stage,which has great development space and significance.In this paper,a large number of references are put forward to derive the derivation of the deformation theory formula of the RC frame joint under fire.The finite element software ABAQUS is used to analyze the joint temperature field.The numerical results are compared with the experimental results of the literature[50] to verify the theoretical results,and the numerical calculation results is fit better to the experimental results.In this paper,the specific research work is as follows:(1)The relevant literature of domestic and foreign scholars about the internal force,deformation and temperature field calculation of the frame joints under high temperature have been summarized in this paper.(2)The force mechanism of the joint is explained and the internal force diagram of the joint under load-temperature coupling is drawn.In this paper,the ISO-834 standard heating curve,thermal parameters,mechanical properties and constitutive relation of steel and concrete under high temperature are obtained,the deformation calculation expression of beam-column joints under high temperature is derived through internal force analysis of the joint.(3)The joint theoretical model and boundary conditions,reinforcement of the joints and beam-column cross-section dimensions are introduced and the joint deformation verification formula is verified compared with the experimental results in the literature[50].(4)The numerical analysis of the temperature field of experimental frame in the literature[50] is carried out by numerical simulation software ABAQUS,and the analysis of the section and the deformation of the joint at different fire time are made.The comparison and analysis were conducted between theoretical results,simulation results and experimental results.(5)Combined with numerical simulation and experimental study,the temperature field distribution law and node deformation calculation method of reinforced concrete frame joints under high temperature are summarized. |
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