Study On Mechanical Behavior Of Prefabricated SRC Column Steel Beam Joints Considering Floor Composite Effect

At present,in order to solve the problems of low production efficiency,environmental protection and construction quality in the construction industry,China has issued a number of policies to encourage development of prefabricated buildings,so as to promote the process of building industrialization.Because the prefabricated building is assembled by prefabricated components,the seismic performance of prefabricated building joints has become an important research point in order to put the prefabricated building into use.In the actual use process,in addition to connecting beam and column members,the existence of floor will also have an impact on the mechanical performance and seismic performance of the joints.That’s means that in the study of the seismic performance of the new joints,the composite action of the floor should be considered.Therefore,based on the existing research results of our group,this paper studies the seismic performance of the middle joints of the new prefabricated SRC column-steel beam frame structure considering the floor composite effect,which provides a theoretical basis for the application and development of the new joints.The main contents of this paper are as follows:(1)Three specimens with different beam to column linear stiffness ratio and bending capacity of steel beam were set up.MTS actuator was used to apply quasi-static load on the joint.And the failure phenomenon and performance degradation of the joint were analyzed.The test results show that the specimen with the smallest beam to column linear stiffness ratio tends to be flexural failure at the beam end.With the increase of beam to column linear stiffness ratio,the ultimate failure mode of the specimen changes to compression bending failure at the column end.The hysteretic curves of the three specimens are full and have good energy dissipation performance.(2)Three refined finite element models corresponding to the test nodes were established by ABAQUS.On the one hand,the stress distribution of the joint is further clarified.On the other hand,the reliability and accuracy of the model are verified by comparing the numerical simulation results with the experimental results,which lays a foundation for further research.The results show that the failure mode,hysteretic curve and skeleton curve of the test and numerical simulation are basically consistent,and the average error of yield load and failure load is 8.51%,less than 10%.It can be considered that the finite element models of the three specimens are effective and reliable.(3)According to the comparison of numerical simulation and experimental results,the joint model with good fitting degree is selected.Then,the influence of "floor composite action" on the failure mode,hysteretic curve and skeleton curve of the joint is studied by numerical simulation.And the results show that the joints with composite floor action are more inclined to column end failure,and the energy dissipation capacity of the joints are decreased.(4)In order to investigate the static behavior of the joint under the combined action of floor slab,the monotonic loading process of 12 joint specimens with different parameters was simulated.The simulation results show that with the increase of axial compression ratio,the bearing capacity of the structure increases,but the plastic deformation capacity and ductility of the joint decrease significantly;the bearing capacity of the joint can be improved by appropriately increasing the width of the floor;the concrete thickness or the reinforcement ratio of the floor have little effect on the joint.(5)The low cycle cyclic loading process of the middle node model considering the composite action of the floor is simulated,and 12 nodes are set up.The failure mode,hysteretic curve,skeleton curve,ductility coefficient,energy consumption and stiffness degradation of the joint specimens under different axial compression ratio,floor width,floor thickness and floor reinforcement ratio are discussed in detail,and the influence of various parameters on the new type of fabricated SRC is obtained The influence law of column steel beam joint can provide reference for further optimization design.