Study On Fire Resistance Of Steel Frame Under Earthquake Fire Condition

After the earthquake,there is a series of chain reactions,which leads to a series of secondary slope failures.The damage is much greater than the earthquake itself,both in space and in time.With the rapid development of our country,gas,a variety of high-power electrical equipment has been widely used in the city,when the earthquake,electrical leakage,gas leakage is likely to cause a large area of fire.According to the previous data,the loss caused by the earthquake alone is often not caused by the secondary fire.In order to study the amplification effect of secondary fire,the finite element model of2 D and 3D steel frame is established by using ABAQUS finite element analysis software.The deformation of steel frame under three different conditions of single fire,single earthquake and post-earthquake fire is simulated,and the results are compared.Then draw the similarities and differences between plane and three-dimensional space frame.The main conclusions are as follows:(1)The fire response of steel frame with initial earthquake damage and no initial earthquake damage is similar,and the response of the room at the bottom of the structure is stronger than that of the upper room.For space steel frames,when the rooms in the same layer are compared with each other,the fire resistance of the corner room is the longest,followed by the side of the room,and finally the central room.(2)With the increasing of the seismic damage degree of the steel structure,the failure time of each room decreases gradually.The failure time of the room at the bottom is much lower than that in the middle and upper room.The order of the decrease of the failure time is the bottom,middle and top.The main reason for this phenomenon is due to the earthquake damage induced increase was decreased with the increase of the floor,at the bottom of each column of the room damage increase,the middle of the room,at the top of the minimum.(3)Compared with the single fire,the failure time of all the rooms will be reduced with the increase of residual horizontal displacement under different damage degree.When the residual deformation in a certain extent,the structure failure time decreases rapidly,once more than a certain range,the effect of residual deformation is not so obvious,the failure time decline gradually decreased.(4)The residual deformation under the same load with a different frame in the fire room is different,with the increase of load level,the failure time of each room and the failure temperature gradually decreased,and the decreased velocity increase.(5)Comparison of earthquake fire and fire alone can be found at the bottom of the room is on fire,the extent of damage is the most serious,especially in the middle span of the room,we can determine the underlying room for the weakness of the structure should be first column as the key consideration in the fire resistant design.The top two room fire fire damage relative to other layers of relatively light structure,the fire resistant design can be reduced than other appropriate level of protection,save cost,achieve the key protection.(6)If the steel frame under earthquake action alone,although the extent of structural damage increases with the increase of earthquake intensity,but the structure is still in a stable state of normal,and the relative damage degree of post-earthquake fire destroy the structure of the structure or a very small.Compared with the conventional fire,the structure of the earthquake will be faster to reach the failure state because of the post-earthquake damage.Thus,once the earthquake occurs after the fire,it is easy to form a disaster chain,resulting in greater damage than a single disaster.