FEA On Fire Resistance Of CFST Columns With Fire Protection Layer Of Lightweight Aggregate Concrete

When the CFST columns widely used in engineering are exposed to fire,their fire resistance limit usually cannot meet the relevant requirements of the current fire resistance design codes due to the exposed steel tube.Lightweight aggregate concrete has the advantages of light weight,good thermal insulation performance,and low price.It can be used as a fire protection material for CFST columns,but currently there is no research report on the fire resistance of lightweight aggregate concrete as the fire protection coating for load-bearing components.In order to verify that the lightweight aggregate concrete fire protection layer can effectively improve the fire resistance of CFST columns,this paper is based on the fire resistance performance test results of CFST columns without fire protection,fireproof coating protection and cement mortar fire protection at home and abroad.The ABAQUS finite element method was used to analyze the temperature field and fire resistance limit of the lightweight aggregate concrete fire protection CFST columns under fire,and based on this,reference recommendations for fire resistance design were made.The specific contents are as follows:(1)Summarize domestic and foreign research results on material thermal parameters,and determine suitable material thermal parameters.Based on the theory of temperature field solution,ABAQUS was used to establish the temperature field analysis models of CFST columns that can consider the thermal resistance of the interface,and the comparison of the finite element calculation results is in good agreement with the experimental results collected at home and abroad.Analyze the influence of the parameters such as heating time,section size,steel ratio and thickness of the lightweight aggregate concrete fire protection layer on the temperature distribution of the cross-section temperature of the CFST columns when the lightweight aggregate concrete is used as the fire protection and determine the main influencing factors.(2)Summarize the domestic and foreign research results on the thermodynamic parameters of steel and concrete,select the appropriate material thermodynamic parameters,and determine their high temperature constitutive model.Based on the analysis of temperature field,the finite element analysis models of the fire resistance limit of the CFST columns are established,which are in good agreement with the test results of domestic and foreign.Analyze the influence of the parameters such as section size,material strength,steel ratio,load ratio,eccentricity,slenderness ratio and thickness of light aggregate concrete fire protection layer on the fire resistance when lightweight concrete is used as fire protection,and determine the main influencing factors.(3)Based on the analysis results of the fire resistance limit parameters,the simplified calculation formula for the ultimate bearing capacity of the commonly used CFST columns under fire in the project and the calculation formula of the thickness of the lightweight aggregate concrete fire protection layer under the given design load.The calculation results of the two formulas are in good agreement with the calculation results of the finite element.