Analysis Of Fire Resistance Of Steel-concrete T-shaped Columns Under Fir

Section concrete(SRC)columns are structural members with section steel as the skeleton,and an appropriate amount of longitudinal stress reinforcement and transverse stirrup.Finally,concrete is poured out.Compared with reinforced concrete structure,steel reinforced concrete structure has better ductility,bearing capacity,stiffness and seismic performance,and the construction period is shorter.Compared with steel structure,steel concrete structure has better corrosion resistance,fire resistance and better economic benefits.With the rapid development of Chinese society and economy,the application of steel concrete structure in large and highrise buildings has gradually increased.Nowadays,with frequent building fires,SRC structures are more and more likely to suffer from fire.SRC structures play a key role in the overall stability of buildings under fire.Therefore,it is of great practical significance to study the fire resistance of SRC column and its fire resistance calculation model.Based on the development and research of steel reinforced concrete columns at home and abroad,this thesis uses ABAQUS software to conduct numerical simulation and parameter analysis of the fire resistance limit of T-shaped SRC columns.The specific research is as follows:(1)The research on the fire resistance of steel-concrete structure and the calculation model of temperature field are systematically summarized.(2)Based on the experimental and theoretical studies on the fire resistance of steel reinforced concrete structures by domestic and foreign scholars,the finite element software ABAQUS was adopted in this study,and appropriate thermal parameters were selected to conduct numerical simulation on the temperature field of T-shaped SRC columns mentioned in literature [59].The temperature curves of different fire time column and different measuring points are obtained.The numerical results are compared with the experimental data to verify the validity of the model,and the error analysis is carried out.(3)Based on the temperature field model,the mechanical analysis model under the temperature rise curve of the test was established by using ABAQUS software,and compared with the relevant test results.The feasibility of the model is verified by analyzing the displacement-time curve and failure pattern,and the possible causes of error are analyzed.(4)Based on the verification of the effectiveness of the fire resistance analysis model,the fire resistance model under the standard temperature rise curve(ISO834)was established,and the influencing factors on the fire resistance limit of T-shaped SRC column were analyzed.The analysis parameters include axial compression ratio,eccentricity,concrete strength,protective layer thickness,section steel yield strength,steel content and steel yield strength.(5)For the temperature field model,compared with the standard temperature rise curve(ISO-834),the temperature-time curve of each measuring point presents a hysteresis phenomenon,and the farther the distance from the surface of the concrete column,the more obvious the hysteresis phenomenon.This indicates that it plays a better protective role for the internal section steel.The temperature difference of each measuring point decreases gradually with time,and the temperature rise of each measuring point is faster in the early stage,and gradually gentle and tends to a constant temperature in the late stage.At the same time,the closer to the surface of the concrete column,the higher the constant temperature value.(6)Under the coupling action of temperature and external load caused by open flame test,the vertical deformation trend of axial compression column will undergo four stages: basically unchanged,expansion deformation,compression deformation and final failure.In the fire test,the bending failure occurs when the axial column or the bias column reaches the fire resistance limit state.For T shaped SRC column,the fire resistance limit is mainly affected by axial compression ratio and eccentricity.With the increase of axial compression ratio,the fire resistance limit of specimens decreases by 32.3%-39.4%.The fire resistance limit of component column decreases by 26.3%～33.3% with the increase of eccentricity.With the increase of yield strength,the fire resistance of section steel increases by 6.2% to 23.2%.With the increase of concrete strength,the fire resistance limit decreases by 6.1% to 14.1%.With the increase of the thickness of the protective layer of concrete,the fire resistance limit has almost no change.With the increase of steel content,the refractory limit increases by 10% to 29.3%.(7)After comprehensive numerical simulation analysis,a simplified calculation method for the fire resistance limit of T-shaped SRC columns was derived by using linear regression research method,which provides a reference for the fire resistance design of special-shaped columns.