Study On Fire Resistance Of Recycled Concrete Filled Steel Tubular Columns Under Fire

Recycled concrete is a new type of environmental protection material,and with the development of the times,it is more and more widely used in various high-rise buildings and large bridges.Recycled concrete column with square steel tube gives full play to the advantages of steel tube and recycled concrete.Firstly,this paper introduces the background of the project,and summarizes the research progress and current situation of recycled concrete,concrete filled steel tubular columns and fires by domestic and foreign scholars.Secondly,the thermal and thermal properties of steel and concrete are introduced in detail,and the appropriate thermal and thermodynamic parameters are selected to provide the basis for subsequent finite element analysis.Then,on the basis of the finite element analysis software ABAQUS.a model of recycled concrete filled steel tubular column under fire is established for theoretical analysis.Because the sequential coupling method is used to study the fire resistance of recycled concrete filled steel tubular columns under fire,the analysis process includes two parts:the first part is the analysis of temperature field,which is the basis of the fire resistance performance analysis of recycled concrete filled square steel tubular columns,reflecting the temperature of each node at a certain time;the second part is the analysis of mechanical field,using the method of constant load temperature rise to study.Finally,the parameters of the recycled concrete filled steel tube column under the fire are analyzed.In the temperature field analysis,the replacement rate of recycled aggregate,the section steel content and the duration of fire are taken as parameters to analyze the influence of the temperature field on the recycled concrete filled steel tube column.In the mechanical field analysis,the influence of recycled aggregate replacement rate,steel-containing rate,axial compression ratio and load eccentricity rate on the fire resistance performance of recycled concrete-filled steel tubular columns is analyzed.Temperature field analysis:the replacement rate of recycled aggregate and the fire time are the important influencing factors of the temperature field distribution of the recycled concrete filled steel tube column under the fire.The influence of steel content on the temperature distribution of recycled concrete filled steel tube column under fire is not obvious.Mechanical field analysis:axial pressure ratio and load eccentricity are important factors affecting the fire resistance of recycled concrete filled steel tube column under fire.The fire resistance of the recycled concrete filled steel tube column below the fire will increase and then decrease the replacement rate of recycled aggregate(from 0 to 0.5 and then to 1),but the effect is not significant.The fire resistance of the recycled concrete column decreases with the increase of steel content,but the influence is not obvious.