Effect of Blast-Induced Column Failure Pattern on Collapse Behavior of Steel Frames

Abstract

This paper proposes two reduced-order modeling approaches (Equivalent spring model and Single degree of freedom model) to simplify the traditional dynamic analysis of a whole structure by two steps: (1) local damage analysis of columns under blast on a member level, and (2) global analysis with an equivalent spring model considering the failure process of damaged columns. This avoids the global structural analysis in Step 1 and also avoids the simulation of blast loads in Step 2. The failure time and residual load-bearing capacity of damaged columns under blast are considered and their effect on the global collapse resistance is studied. The results show that they have significant effect on the collapse resistance. The longer the failure time, the larger the residual resistance, the smaller the structural displacement, and the greater the collapse resistance. It is found that the dynamic behavior of structures is sensitive to the ratio of column failure time to the structural vibration period t0/T. The larger the t0/T, the smaller the dynamic amplification effect. It is suggested to consider a smaller dynamic amplification factor rather than 2 for t0/T >0.3. For the selection of analysis methods for blast-induced collapse of structures, it is recommended to adopt the alternate path method for t0/T <0.2, and static analyses for t0/T >3. While for 0.2< t0/T <3, dynamic analyses considering the effect of failure time and residual resistance of damaged columns should be conducted.