Dynamic Responses Of Steel Structures Under Blast And Fire Loading

Steel structure has been quite widely applied at home and abroad, and these steel structure buildings have an important political and economic significance. The will be a serious threat to the safety of human life and property once the catastrophic events such as explosions and fires happen. Consequently, it is necessary to do some research on fire and blast resistance capability of steel structures. There is a lot of studies about the response behavior of steel structures under separate explosion and fire loading. However, the research on properties of steel structures is relatively less. The performance studies and response analysis of steel structures under the both explosion and fire loads have become more and more important after the "911" event in the United States.Numerical simulation and analysis on responses of steel beam and gabled frame under fire and blast loading are performed by using ABAQUS general finite element program. Research work of this article mainly includes following respects:(1)Two situations of applying fire and blast load in a different order are considered. The failure criterions of steel beam and gabled frame are determined by research and analysis. The established criterions are:The steel beam’s failure criterions is its maximum deflections equaling to span/10, under the two situations of applying fire and blast load in a different order; when gabled steel frame first be heated by fire then be impacted by blast loading, The damage accumulation of the gabled steel frame’s beam is serious under indoor explosion, and we make the gabled steel frame’s suddenly collapsing as its failure criterion. The gabled steel frame’s failure criterion is its column’s maximum deflections equaling to column height/60under outdoor explosion; When gabled steel frame first be impacted by blast loading then be attacked by fire, if the gabled steel frame can continue to bear the load after the blast loading, we make its beam’s maximum deflections equaling to span/10as its failure criterion, under both indoor explosion and outdoor explosion conditions. (2) The pulse amplitude-impulse (P-l) diagrams of the situation that steel beam and gabled frame and first be heated by fire then be impacted by blast loading and the critical temperature-impulse (Tcr-I) diagrams of the situation that steel beam, and gabled frame first be impacted by blast loading then be attacked by fire are obtained according to the established failure criterion. The influence of temperature on pulse amplitude-impulse (P-I) diagrams, and the influence of pulse amplitude on critical temperature-impulse (Tcr-I) diagrams are discussed. The analysis results show that:the higher the temperature, the lower the impact resistance of steel beam and gabled frame is. The blast loading can reduce the fire resistance capability of steel beam and gabled frame under indoor explosion loading obviously. The influence of blast loading on the fire resistance capability of gabled steel frame can be ignored, when the gabled steel frame can continue to bear the load after the blast loading.(3) The influence of blast loading types on the fire and impact resistance capability of steel beam is studied. These research findings show that:the impact resistance capability of steel beam under rectangular pulse loading, triangular pulse loading and exponential pulse loading reduced in turn, when steel beam first be heated by fire then be impacted by blast loading and the static load ratio and temperature are the same. When steel beam first be impacted by blast loading then be attacked by fire and the static load ratio and dynamic load ratio are the same, the fire resistance capability of steel beam under rectangular pulse loading, triangular pulse loading and exponential pulse loading reduced in turn;With the increase of dynamic load ratio, the influence of blast loading types on the fire resistance capability of steel beam decreases.