Study On Fire Resistance Behavior Of SRC Column-RC Beam Frame Under Column Failure Mode

The frame structure is one of the most widely used structural forms.Under the action of fire and high temperature,due to material performance degradation and additional temperature stress,the bearing capacity of the structure is significantly reduced.In severe cases,the structure may collapse,causing casualties and property losses.Therefore,the fire resistance of the frame structure has attracted increasing attention.Recently,domestic and foreign scholars have carried out research on the fire resistance of steel frames,reinforced concrete frames,concrete filled steel tube frames,and steel reinforced concrete frames.However,there are few researches on the fire resistance of the steel reinforced concrete column-reinforced concrete beam composite frames under high temperature.This paper studies the fire performance of the SRC column-RC beam portal frames with different parameters at high temperatures.Focusing on the analysis of the fire resistance,failure process,and failure mechanism of the frame under the column failure mode.In the process of in-depth analysis of the influence of different parameters on the fire resistance of the frame,it was found that the main factors affecting the critical failure state of the beam and column under high temperature are the beam load ratio and the column axial compression ratio.The main research work and conclusions are as follows:1.Using the ABAQUS software,the finite element analysis model of the steel reinforced concrete column-reinforced concrete beam composite frame under fire was established.The calculated temperature and frame displacement were compared with the experimental data in the literature to verify the rationality of the model.2.Analyzing the temperature distribution law inside the frame under the high temperature of the fire,the deformation of beams and columns,the fire resistance,the failure form,the failure mechanism of the frame through a typical example.It is concluded that there are three ultimate failure modes of the frame under high temperature,namely column failure,beam failure,and beam-column mixed failure.The focus is on the analysis of the failure process,failure mechanism,and fire resistance of the frame under the action of various parameters in the column failure mode.3.Through 288 calculation examples of different parameters,the parameters affecting the fire resistance of steel reinforced concrete column-reinforced concrete beam frames were studied in depth.Analyzed the influence of different column slenderness ratio λ,column steel ratio α,beam-to-column stiffness ratio κ,beam section size b × h,column section size B × D,concrete strength C,beam load ratio m,column axial compression ratio n on the fire resistance of the frame.The results show that the fire resistance of the frame decreases with the increase of column slenderness ratio λ,column axial compression ratio n,beam load ratio m,increases with the increase of column steel ratio α,column section size B × D,and concrete strength C.The beam-to-column stiffness ratio κ,the beam section size b×h mainly affects the ultimate failure mode of the frame under high temperature.4.Aiming at the frame calculation examples of three typical column sections,analyze the influence of different column axial compression ratio n and beam load ratio m on the fire resistance and failure mode of the frame.The range of beam load ratio m and column axial compression ratio n corresponding to the critical state of beam failure and column failure of different sizes of frames under high temperature is obtained.