Behavior Of Concrete-Filled Steel Tube Reinforced Concrete Column Subjected To Non-uniform Fires Based On The Overall Stage Fire

For the high bearing capacity,good seismic performance and excellent resistance to fire,concrete filled steel tube reinforced concrete(CFSTRC)has been gradually used in high and super-high buildings.In recent years,however,building fire is more and more frequent.To the safety of people s life and property,it is urgent to resolve the issue of its fire performance.Currently,the mechanical properties of CFSTRC have been researched widely,and achieved fruitful research outputs,but the study of its fire resistance is still limited,especially its non-uniform fire performance has not been reported.For this,the paper has mainly carried on the following aspects of the work:(1)To lay the foundations for the subsequent research work,experimental data of CFSTRC under normal temperature and fire at home and broad has been collected firstly,and then,a preliminary analysis of its axial compression,bias,pure bending performance has been done.(2)Start with the temperature research of reinforced concrete,concrete filled steel tube and steel reinforced concrete,distinguish between uniform and non-uniform under fire,the temperature field of CFSTRC has been studied meticulously,which,provide the temperature data for the follow-up study.(3)Based on reasonable thermodynamic properties of tube and concrete,finite element model of CFSTRC under the condition of non-uniform fires,such as single-sided,two and three surfaces have been created respectively to research its mechanical properties.Then,the temperature distributions,failure modes,variation of internal force and the interaction between tube and concrete are analyzed meticulously,and also,the parameters of fire load ratio,cross-sectional dimensions,slenderness ratio,steel and concrete strength inside and outside are analyzed.(4)On account of experiencing the ambient load,heating,coolingand post-fire phases,a reasonable elevated temperature and cooling sections of the constitutive model of steel and concrete has been selected,we analyzed the mechanical performance of CFSTRC after ISO-834 standard fire and the whole period of fire which conbined loads with fire.