Research On Mechanical Behavior Of Hollow Steel Tubular Stub Columns After High Temperature

Steel has the advantages of high strength,light weight,convenient construction,good plasticity and toughness,so the steel structure is widely used in the construction industry.However,steel is not fire-resistant,it will bring immeasurable economic losses and casualties once the steel structure encounters fire.At present,a series of studies on the fire resistance of steel have been carried out at home and abroad,and experiments and finite element analysis have been carried out to investigate the mechanical properties of the concrete filled steel tube structure.However,the research on the mechanical properties of steel columns is not perfect.With the wide application of steel structures in civil engineering structures,the research on the mechanical properties of steel columns after high temperature has profound theoretical significance and significant engineering application value.In view of the fact that this paper uses the most widely used circular and square steel tubes in steel structures.In this paper,the experimental study method was used to study the axial compression behavior of 102 circular and square steel tube stub columns.The failure mode,load-displacement curves and load-strain curves of the specimens are mainly analyzed,and the calculation formula of the ultimate bearing capacity of the specimens is derived.The main conclusions are as follows: 1.High temperature causes a new failure mode of circular steel tube stub columns,and the high temperature has no effect on the failure mode of square steel tube stub columns.2.The initial stiffness of the circular steel tube with a wall thickness of 2mm is higher than the initial stiffness of the circular steel tube at room temperature after high temperature.The initial stiffness of the circular steel tube with a wall thickness of 3mm and 4mm is lower than the initial stiffness of the circular steel tube at room temperature;the initial stiffness of the square steel tube at high temperature is basically same to the initial stiffness of the square steel tube at room temperature.3.The ultimate bearing capacity of the specimen decreases with the increase of temperature and duration,the ultimate bearing capacity of the specimen increases with the increase of wall thickness.As the wall thickness increases,the influence of temperature and duration on the ultimate bearing capacity of the circular steel tube becomes smaller.The ductility of circular steel tube and square steel tube increases with the increase of wall thickness.The influence of wall thickness on the ductility of circular steel tube is greater than the ductility of square steel tube.Based on the experimental data,SPSS analysis is used to calculate the axial ultimate capacity of the circular steel tube stub columns and square steel tube stub column after high temperature,and the calibration is verified to have certain accuracy and safety.