Study On Seismic Behavior Of Prefabricated Frame Joints After High Temperature

Prefabricated buildings has the advantages of high industrialization,fast construction,saving resources and labor costs,reducing construction waste pollution and so on,which has been vigorously promoted by the state and the government.The joint is the key part of the prefabricated structure which connects the prefabricated components as a whole and transmits the load.Under the action of fire,the composite surface of the prefabricated components and the grouting sleeve of the reinforcement connection in the prefabricated joint are inevitably affected by high temperature,which is quite different from the traditional full cast-in-place construction joint.The performance of assembled joints after high temperature is the basis for the performance evaluation and reinforcement of joints after fire.It is of theoretical significance and practical value to carry out the research on the seismic performance of prefabricated column composite beam joints after high temperature.In this paper,the pseudo-static tests of four precast column composite beam joints under the condition of load during the whole process of fire temperature rise and fall are carried out,and the finite element model is established to carry out the analysis of key influence parameters.The main research contents and conclusions are as follows:1.Taking the fire time,load ratio of beam end and stirrup ratio as the main parameters,four prefabricated column composite beam assembly joints are designed,and the whole process of fire temperature rise and fall test is carried out for each joint specimen under the state of load.The results show that: with the increase of load ratio and heating time,the peak displacement and residual displacement of the joint beam end will increase;after the fire,the surface of the joint concrete will become light pink,some concrete will burst and fall off;part of the grouting material in the grouting sleeve will turn black into powder and be pushed out;transverse cracks will appear at the interface between the laminated beam and the core area and the upper and lower columns Sewing.2.The quasi-static test is carried out on the joints after the fire temperature rise and fall,and the load displacement hysteretic curve,ductility,energy dissipation coefficient and failure mode of each joint are obtained.The results show that the interface between the prefabricated beam and the core area will be partially separated and the interface between the core area and the upper and lower columns will be staggered at the later stage of loading;the connection between the post cast strip and the sleeve in the joint area is safe and reliable under the reciprocating load after fire;the extension of the fire time and the increase of the load ratio at the end of the beam have adverse effects on the seismic performance of the joint after fire,which are shown as the reduction of the ultimate load and the initial stiffness The decrease of stirrup ratio has an adverse effect on the continuous loading after the beam ends yield.3.ABAQUS software is used to establish the calculation model of the whole process of node temperature rise and fall and the hysteretic performance after high temperature.The difference of temperature field,hysteretic curve and test results is compared to verify the rationality of the model.The effects of temperature rise time,reinforcement ratio,load ratio of beam end on the process of joint temperature rise and fall and seismic performance after high temperature are studied.The results show that: with the increase of the heating time and the load ratio of the beam end,the residual deformation of the beam end increases after high temperature;the extension of the heating time,the increase of the load ratio of the beam end and the decrease of the reinforcement ratio of the beam end all have adverse effects on the earthquake resistance of the joint after disaster.