The Fire Resistance Of Reinforced Concrete Beam-Column Joints During Heating And Cooling Phases

In the past,most of the researches on the fire resistance of reinforced concrete structures focused on the stage of fire heating and post-fire,but in the actual fire,the structure only heated up in a limited time.They will then be in the cooling phase because of the depletion of combustible materials.In order to understand the effect of the whole fire process on the structure,it is necessary to study the performance of the structure in the cooling stage.As an important part of the structure,there still not have the research on the fire resistance of the whole fire process for the reinforced concrete beam-column joints.And the fire experiment has the problems of long time consuming and high test cost.Therefore,ABAQUS software is used in this paper.The working mechanism of reinforced concrete beam-column joints under the heating and cooling of fire is studied and analyzed.The main tasks are as follows:(1)The thermal performance and thermodynamics performance of steel bar and concrete in heating and cooling stage are determined.The ABAQUS was used to analyze the temperature field changes of reinforced concrete girder-column joints under fire heating and cooling,and it also analyzes the different fire time and fire scenery on the distribution of temperature field.(2)Using a calculation program that can automatically identify and convert the constitutive relations of materials,a finite element analysis model of reinforced concrete beam-column joints under the combined loads and fire including heating and cooling phase,and the analysis results are verified by the tests.Through the finite element analysis model,deformations,stress and strain of reinforced concrete beam-column joints under the combined loads and fire including heating and cooling phase are analyzed.(3)The parameters such as column load ratio,beam load ratio,beam-column linear stiffness ratio,longitudinal reinforcement ratio of beam and column,concrete cover of beam and column are studied on failure modes and fire resistance of reinforced concrete beam-columnu joint.The main influence parameters are determined and the influence rules are given.(4)Based on the whole process of fire heating and cooling,the parameters such as column load ratio,beam load ratio,beam-column linear stiffness ratio,longitudinal reinforcement ratio of beam and column,concrete cover of beam and column,affecting the deformation of reinforced concrete beam-column joints are studied.The main influence parameters are determined and the influence rules are given.