Study On Mechanical Behavior Of Axially Restrained Reinforced Concrete Short Columns At Elevated Temperatures

Fire resistance of structures is an important research topic in the field of structural engineering.At present,the experimental study is paid more attention to the mechanical properties of reinforced concrete under fire,but less to consider the influence of initial load.Although some studies have considered the influence of per-load,the specimen size is small.The dimensional effect will result in the obvious non-uniform temperature field of the component at elevated temperature,which will directly affect the mechanical properties of reinforced concrete members under fire.And at present,the research of concrete fire resistance at home and abroad is based on a single component.However,the mutual restraint on adjacent components exists objectively in the actual fire.When the components of the structure are affected by fire,the fire resistance is different from that of single component due to the constraint of surrounding components.Therefore,the experimental study on the behavior of the reinforced concrete short columns with large size,large axial compression ratio,and the effect of different constraints on the mechanical properties of axial compression to the ISO-834 standard temperature in heating and cooling phase,the specific contents are as follows:(1)ABAQUS finite element analysis software is used to analyze the section temperature field distribution of reinforced concrete short columns experienced ISO834 standard fire.At the same time,the practicability of the finite element analysis model is proved by experimental data of 3 reinforced concrete short columns.(2)The experimental study on the axial compressive behavior of 21 reinforced concrete short columns when experienced ISO-834 standard fire temperature in heating and cooling phase,the influence of restraint mode,standard heating time and axial compression ratio on deformation,residual bearing capacity,axial compression stiffness of concrete short columns under fire were mainly studied.(3)In this paper,the variation low of strength,elastic modulus and the stress-strain relation on steel bars and concrete were used at elevated temperature.And the residual bearing capacity,axial compression stiffness and load axial deformation relation of reinforced concrete short columns are calculated after the specimen being exposed to high temperatures.Besides,the effects of axial compression ratio,standard heating time and axial compression stiffness and load axial deformation of reinforced concrete short columns under fire were analyzed,compared with theoretical analysis and relevant experimental results.