Influence of seismic design criteria on blast resistance of RC framed buildings: A case study

In the last decades iconic and public buildings in urban habitat have been subjected to terrorist attacks and many of them are located in earthquake-prone regions. This study is aimed at assessing the influence of seismic design criteria on blast resistance of RC framed structures. Two 3D models were developed and analysed for a case-study building: one was designed for earthquake resistance according to Eurocode 8 (EC8); the other was designed only for gravity loads according to codes and practice going back to the 1970s. Several blast scenarios were considered and a two-step analysis procedure was used. Local analysis was carried out to identify columns directly failing under blast scenarios, whereas global pushdown analysis was performed on each 3D damaged model to assess robustness. Dynamic increase factors at both material and structural levels were assumed. Flexural–shear interaction and limited strength of beam–column joints were also addressed in the case of EC8-nonconforming building. Local pressure–impulse analysis was carried out in addition to simplified static and dynamic analyses; the same numbers of collapsed columns were found for the EC8-conforming building, while static analysis was too conservative for the EC8-nonconforming building. Pressure–impulse diagrams let to predict residual load-carrying capacity of adjacent columns. Seismic design criteria provided sufficient robustness only against some blast scenarios. In the case of EC8-nonconforming building, inclined beams in the staircase induced higher robustness against explosions occurring there and global ductility reduced under increasing load-bearing capacity. The latter can enhance by increasing longitudinal rebar in a way to avoid flexural–shear interaction, and/or reducing stirrup spacing.