Research On The Mechanical Behavior Of Steel Columns Under Fire And Explosion

Fire softens steel components, while the strain rate effect caused byexplosion increases the strength of steel. The influence of fire and that ofexplosion are reverse, thus, the combined action of fire and explosionmakes the stability analysis of steel columns more difficult.In the paper, finite element analysis software was used to analyzestability of steel structure under combined effect of fire and explosion. Theapplicability of material models used in conditions of high temperature andexplosion were discussed before analysis. The applicability study shows:(1) Cowper-Symonds and Johnson-Cook model are applicable to analyzeexplosion at ambient temperature;(2) The combination ofCowper-Symonds model and high-temperature material models can beused to analyze explosion at high temperature. Then, a comparisonbetween numerical simulation results of different material models andother scholars’ experimental results was conducted. The comparisonverifies reliability of finite element analysis and reasonable parameterselection of material models. On the aforementioned basis, studies mainlyabout three aspects were conducted.First, the influence of high temperature on stability of steel columns.The high-temperature influence on the instability ultimate load wasdiscussed after analyses of temperature distribution of component underdifferent fire conditions. A curve was fitted that describes the load-capacitydeclines with the rise of temperature.Second, the influence of explosion on stability of steel columns.Analysis shows that impact resistance of steel columns is under axialimpact ratio control. Impact resistance varies when explosion break out from different directions, and destruction mechanism and morphology alsodiffers. In addition, when steel columns are under axial impact, theload-capacity, compared with static load, improves a lot.Third, impact resistance of steel columns under combined action offire and explosion. Under the condition of explosion at high temperaturemainly, dynamic response of steel columns was analyzed. The study showsultimate impact resistance decreases with the increase of temperature andaxial force. When using the spring to simulate the actual boundaryconditions, the change of axial force caused by temperature will have ahuge effect on impact resistance of steel columns.