Finite Element Analysis On Fire Resistance Performance Of The Joint Of Square CFST Column And I-beam

With the modern buildings are tending to higher,larger-scale and complex,building hazards caused by fire is more serious.The concrete-filled steel tubular(CFST)composite structure has the advantages of high strength,good plasticity and toughness,simple construction,good economic effect and fire resistance,so that its application in modern architecture is more extensive.In the different structural design,the form of beam-column joint will be different,as the key part of the overall frame bearing force,the study of joint performance is an important part of structural engineering.In this paper,the finite element analysis on fire resistance performance of the joint of square CFST column and I-beam is introduced,which mainly includes the following three aspects:(1)Based on the determined mechanical parameters and constitutive relations of steel and concrete at room temperature,ANSYS finite element software was used to calculate the bearing capacity of CFST columns and I-beam joint,analyzed the stress state of the joint bearing process,and parameterized analysis of the factors affecting the bearing capacity of the joint.It is shown that the effect of steel strength on the bearing capacity of the joint is the most obvious.Secondly,in the geometrical parameters of the beam,the maximum amount of steel is increased by increasing the height of the beam.The influence of the width of the external plate on the bearing capacity of the joint is not obvious(2)Based on the determined thermal parameters of steel and concrete under high temperature and fire model,ANSYS finite element software was used to analyze the temperature field of the square CFST column and I-beam joint with external plate that tested in ISO-834 standard fire under the condition of temperature increase,and the distribution of the temperature field in the column length direction and the cross section.Through the parametric analysis,it can be seen that the coating of the fireproof coating can effectively reduce the temperature of the components under the fire;the concrete floor can slow down the temperature rise rate of the fire surface to achieve the effect of fire;the existence of core concrete can absorb the heat of the steel pipe Steel pipe temperature.(3)The finite element analysis of the temperature of the composite structure joint in room temperature and the temperature field under ISO-834 standard fire is carried out.The finite element software of ANSYS is used to calculate the heat-structure coupling of the joint under constant load,which analysis the fire resistance performance and stress distribution of the joint under ISO-834 standard fire.Through the analysis of parameters,the protective effect of coating fire protection layer is most obvious for improving the fire resistance performance of the joint.The effect of reducing the load ratio of the beam-end is obvious than that of the node.When the axial compression ratio is not higher than 0.6,Which has little effect on the fire resistance of the joints.Changing the geometry size of steel beam has little effect on the fire resistance performance of joint.Finally,based on the previous research,this paper provides the direction suggestion for the fire resistance design of the square CFST column and I-beam joint with external plate.