Research On Dynamic Response Of Steel Pipe Beam And Column Under The Action Of Fire And Shock

The steel structure has the advantages of uniform material,high reliability,high strength,light quality,good plasticity and toughness,convenient for mechanized manufacturing and construction and installation.With the wide application of steel structure in the field of building engineering,its stability and safety have been paid more and more attention.From the beginning of construction,the building structure should not only bear the normal design load,such as by impact,explosion and other accidental or deliberate human factors,steel pipe beams,columns will suffer the impact load,sometimes also bear the fire load.Under the influence of natural disasters and man-made factors,the steel tube construction usually there is a potential safety hazard and the impact load,fire load even under coupling action of impact load and fire load,bearing capacity of steel tube components will decline,local deformation and the overall bending deformation,while the upper weight fall can cause secondary damage of the structure,because of component failure,even cause the collapse of the structure.Therefore,it is of great significance to study the response mode of steel tube structures under the action of impact and temperature coupling,which can not only provide a reference for the fire-resistant and shock resistant design of structures,but also provide guidance for the reinforcement and prevention of existing structures.The mechanical response of steel tube beams and columns under the coupling action of fire and impact is studied by means of experiment and finite element analysis.Its main contents include:(1)The experimental study of steel tube beams and columns in the coupling environment was carried out respectively by the fire and impact coupling test device.Firstly,the fabrication process of steel tube beam and column is introduced.A high-speed camera was used to record the complete dynamic response process of steel tube beams and columns during the coupling test of fire and impact,and instantaneous photos of steel tube beams and columns were obtained.The experimental results show that the plastic deformation mode of steel tube is affected by two factors:temperature and input kinetic energy,and the plastic deformation mode of steel tube is affected by three factors:temperature,input kinetic energy and axial pressure ratio.1)for steel tube beams,when the temperature is relatively low,local deformation occurs in the impact area at the initial stage of the impact.In the middle and later stages of the impact,the specimen appears overall bending deformation with the increase of local deformation;When the temperature is high,the steel tube beam will flatten under the impact load,and the upper and lower surfaces of the impact area will collide.2)for the steel pipe,the deformation stage is similar to that of the steel pipe beam,but due to the axial force,the entire deformation process is faster and the mid-span deflection of the steel pipe is larger.Under the combined action of axial force,temperature and impact load,the steel pipe will collapse.Under the action of axial force,the steel tube will buckle when the temperature rises to a higher level.(2)The coupling effect of fire and impact is analyzed under two conditions of uniform temperature and non-uniform temperature by using general finite element software ABAQUS and shell element model.The numerical results show that:1)the energy dissipation of steel tube beam under the impact load is mainly concentrated at the mid-span impact area and the supports at both ends;2)when the temperature is low,the time history curve of the impact force is close.When the temperature is high,due to the degradation of material properties,the maximum impact force decreases obviously but decreases slowly;3)when the impact load is constant,the deflection of the upper and lower part of the mid-span increases with the rise of temperature:when the temperature is low,the deflection between different temperatures changes little,and when it reaches a certain temperature,the mid-span deflection will increase sharply.(3)By using ABAQUS and shell element model,the coupling effect of fire and impact was analyzed for the steel tube under two conditions of uniform temperature and non-uniform temperature.The numerical results show that:1)the energy dissipation area of the steel pipe column under the impact load is mainly concentrated at the fixed end of the span and the neutralization;2)when the axial force and temperature are fixed,the larger the impact load is,the greater the displacement of the mid-upper and lower surface is,that is,the larger the overall deformation and local deformation are,and the displacement of the end is also increased,but it will converge to a certain value.When the impact load reaches a certain value,the steel pipe column will collapse.At this time,the upper and lower surface displacement and the end displacement of the span will not converge to a certain value.3)when the temperature T is constant,the energy ratio R decreases with the increase of the axial pressure ratio.When the axial pressure ratio μN is constant,the energy ratio R decreases as the temperature T increases.4)column members will not collapse in the safety zone;Outside the safe area,column members collapse;The curve is the critical value.With the increase of temperature T and axial pressure ratio μN,the safe area gradually decreases.This study deepens the understanding of the dynamic response behavior of steel pipe beams and columns in the coupling environment of fire and impact,which is of great significance to the future theoretical research and engineering design.