Fire Performance Indicator Research Of SRC Column Subjected To The ISO-834 Standard Fire Including A Cooling Phase

Because the steel reinforced concrete(SRC)structure has high bearing capacity,good deformation resistance,earthquake resistance,fire resistance,corrosion resistance and high performance advantages of technical and economic benefit etc.,so in the multi-layer,high-rise buildings and industrial buildings are widely used.At present,research on mechanical properties at room temperature of SRC column are more concentrated in the bearing capacity,seismic performance,structural design,and research on the mechanical properties under fire are more focused on fire resistance and mechanical properties after fire.In actual fire condition,SRC column would experience heating and cooling phase of a natural fire.Due to obvious temperature lag on cross section of SRC column under fire,temperature of inner material of SRC column keeps increasing when environment temperature begins to decrease.With material damaging,the load-bearing capacity of SRC column continues decreasing after the maximum environment temperature is attained which may reach a minimum value in cooling phase.So the SRC column may have delayed failure during the cooling phase.In order to prove the possibility of delayed failure and better evaluating fire performance,and research on the fire performance indicator DHP based on the analysis of both heating and cooling phase of SRC column,the following work has carried out:(1)The three-dimensional SRC column models for temperature field calculation and the whole process mechanics performance calculation were established based on the finite element software ABAQUS and rationality was verified by the existing experimental data.(2)The calculation subroutine USDFLD which can automatically identify and convert the constitutive relations of materials at different heating stages is developed and adopted in this paper.(3)Related fire examples and literature research show that the SRC column will have delayed failure during cooling phase,and this paper has verified the possibility through calculation.The mechanical properties of SRC columns were analyzed in different fire phases,in which the failure criterion SRC column was adopted same to fire resistance.With the analogy of fire resistance,the duration of heating Phase(DHP)which can cause the destruction of the SRC column in the cooling phrase,is defined as the indicator of fire resistance of the column in full-range fire.(4)To analyze the effect of some main parameters including fire load ratio,section size,slenderness ratio,eccentricity ratio,section size of profile steel,concrete strength produced on fire perfoemance of SRC column under full-range fire.The comparative analysis shows that the load ratio,column section size and slenderness ratio have great influence on the fire performance of SRC column under full-range fire.(5)On the basis of the above models,simplified formulas are established by regression analysis for calculating the fire resistance and DHP value of the SRC column.The function relation of DHP about R is also established based on the above simplified formulas.