Study On The Fire-Resistance Performance Of The Precast Column And Composite Beam Assembled Monolithic Joints

The assembled concrete structure can not only reduce a large number of field construction operations,but also ensure the seismic performance of the structure.It is the preferred way to transform concrete structure from traditional construction to modern factory manufacture,and it conforms to the direction of green industrialization advocated by the state.At present,the research on assembled joints mainly focuses on static and seismic performance,while the research on the fire resistance of fabricated reinforced concrete frame joints is relatively less,and there is a lack of relevant knowledge about the fire resistance and safety of assembled joints under fire.It is not only unsafe,but also lack of relevant scientific basis to design and fire-resistant protection according to concrete frame joints.The fire resistance limit of the joints in the assembled reinforced concrete frame is tested,and the influence of various parameters on the fire resistance limit of the joints in the assembled reinforced concrete frame is analyzed by using the finite element software ABAQUS.The research contents and results are as follows:(1)Fire resistance tests were carried out on three prefabricated concrete joints and one concrete frame joint of the same size.The influence of beam-column stiffness ratio and load ratio on the fire resistance limit of assembled joints is analyzed.The results show that the failure of the joint is caused by the fire resistance of the beam.The displacement of the beam increases slowly.When the fire resistance limit is reached,the displacement of the beam increases sharply.When the joint is damaged,the column is in the stage of thermal expansion.Compared with cast-in-place joints,the fire resistance limit of assembled joints is slightly lower than that of cast-in-place joints.(2)The thermal-mechanical coupling model of the above-mentioned joints is established by using the finite element software ABAQUS.The rationality of the model is verified by comparing with the experimental temperature field and the displacement curve of beam and column.(3)Based on the above model,the parameters of linear stiffness ratio,load ratio and reinforcement ratio are selected to study the effects of these parameters on temperature field distribution,mechanical properties and fire resistance limit of joints in assembled concrete.