Research On Behavior Of Core Steel-tube Reinforced Concrete Column Under Three-surface Fire Loading In Axial Compression

Because of its high bearing capacity, fire resistance and good anti-seismicperformance, simple construction, convenient nodes, and many other good advantages,core steel-tube reinforced concrete column has been widely used in large span, highbuildings and all kinds of other major engineering. Currently with the structure form ofcomplication and the increase of induced factors of fire. Fire disasters caused casualtiesand economic loss is increasing. Therefore, research the mechanical properties of the coresteel-tube reinforced concrete column under the fire action is very important. Before themain research contents of core column under fire action is about columns being exposed tofire uniformly. But in practice, because of the barrier effect of adjacent walls, columnsmaybe suffer from three-surface fire.In this paper, using finite element analysis software ABAQUS sets up correspondinganalysis models. The main researches on core steel-tube reinforced concrete column are asfollows：(1) First of all, we should Select the actual fire temperature curve，reasonablethermal parameters, accurate boundary conditions and the actual temperature fieldcalculation equation. Analysis of cross-section temperature field of the core concrete filledsteel tube columns.(2) The second step we Select suitable constitutive relation and failure criterion. Thenseparate to do two types of simulation as follows: one way load on the core concrete filledsteel tube column to failure in normal temperature situation, on the other way load it tofailure in three surface temperature situation Then compare with them, analysis the corecolumn by room temperature loading to fire destruction, in order to get the change of theperformance of the mechanical components of the column. At last we come to theconclusion that loading the core column to failure at normal temperature with the stirruphas yield, lead to peripheral concrete crush. However, loading the core column to failure atthree surface heating processes because of its lateral bar had to yield; finally the column’sdamage is due to steel pipe near concrete crush. (3) Finally analyze the influence parameters related to core steel-tube reinforcedconcrete column’s mechanical property under three-surface fire loading in axialcompression. Including the initial axial compression ratio, the influence of exposure time,steel ratio, coefficient of position, the longitudinal reinforcement ratio and stirrupreinforcement ratio.Come to the conclusion that the initial axial compression ratio, theinfluence of exposure time, steel ratio and coefficient of position has large effect on theoverall performance of core steel-tube reinforced concrete column. The change oflongitudinal reinforcement ratio and stirrup reinforcement ratio has little effect on theultimate bearing capacity and the vertical displacement and lateral deflection.