Numerical damage evaluation of perforated steel columns subjected to blast loading

The structural performance of perforated steel columns(PSCs) is significantly more complex than the one of solid web I-shaped elements under the diversity of blast loading scenarios. The damage criterion of PSCs is not only related to initial deformation response during the blast but also the residual axial load capacity and it can be considered as a reliable index after the blast effects. Therefore, the PSCs damages will be studied in two stages; direct and post blast effects. In the present study, the dynamic response of PSCs was numerically evaluated under different levels of blast threats using LS-DYNA software. Extensive explicit finite element(FE) analyses are carried out to investigate the effect of various parameters, such as web opening shapes, boundary conditions and strengthening details on the damage index and toughness of the PSCs compared to the parent steel sections. The results of the comparative study show that the damage and toughness decrease when the support condition changes from pinned to fixed ends through the two stages of loadings. PSCs give high toughness compared to its parent sections during blast shock stage while, a remarkable decrease in toughness is observed during the application of axial gravity after blast shock. Furthermore, the web opening shapes have slight effects on the global dynamic behavior of PSCs, particularly in terms of residual capacity. On the contrary, the retrofitting strategy using both closed holes at end and vertical stiffeners have an effective enhancement to get higher toughness in case of the extreme blasts.