Experimental Study On Mechanical Behavior Of Reinforced Concrete Stub Columns After Exposed To The Entire Period Of ISO-834 Standard Fire Under Axial Compression

Fire resistance of structures is an important and difficult research topic in structural engineering.There are relatively fewer researches on mechanical behaviors of fire-damaged reinforced concrete(RC)by far.Moreover,the influence of the initial load on the tested specimens was not considered when they were exposed in high temperature.Though in some researches the effect of the initial load was considered,their specimen size and axial compression ratio was relatively smaller.The paper does experiments to investigate the mechanical behaviors of reinforced concrete stub columns with large size,high axial compression ratio and different of stirrup ratio after exposed to the entire period of ISO-834 standard fire.And also the paper evaluates their residual loading capacity,rigidity and ductility.It will be expected to provide a reference for assessments and repair schemes of fire-damaged reinforced concrete.The main works are summarized as follows:(1)ABAQUS,a finite element analysis software,is adopted to simulate distribution of the sectional temperature field of RC stub columns which go through the entire period of ISO-834 standard fire.The reliability of finite element analysis model is validated with temperature field test of three RC stub columns.(2)Experimental study on the axial mechanical behavior of 21 RC stub columns,including three specimens at room temperature and eighteen specimens after entire period of ISO-834 standard fire heating and cooling process,was carried out.The effect of standard heating time,the axial load ratio and stirrup ratio on residual bearing capacity,axial stiffness and ductility of RC stub columns after exposure to high temperatures were experimentally studied.(3)Damage model of strength and elastic modulus of concrete and steel bar and stress-strain relationship of concrete and steel bar after exposure to high temperature was used to calculate residual bearing capacity,axial stiffness and ductility of RC stub columns.The paper gives an analysis of the effect of standard heating time,the axial load ratio on residual bearing capacity,axial stiffness and load-axial strain relationship of RC stub columns after exposure to high temperatures,by comparing the results of experiments with results of some related theories and experiments.