Performance of different seismic retrofitting techniques in case of blastinduced progressive collapse

Extreme loading conditions such as man-made malicious actions, fires or natural events could induce local failure mechanisms (e.g., a loss of a member) which may trigger progressive collapse. The design or the assessment of a critical infrastructure needs to address the possibility of such an extreme circumstance taking place during its effective life-time. It is observed that blast-induced progressive collapse mechanisms involve non-linear structural behavior similar to that due to earthquakes. This work focuses on probabilistic analysis of progressive collapse of a typical RC structure, induced by a blast event. The objective is to verify the effectiveness of seismic retrofitting schemes against explosions and the eventual progressive collapse. The probabilistic analysis is performed by taking into account the uncertainties in loading such as planar configuration and amplitude of the blast loading. A standard Monte Carlo simulation method is employed to generate various realizations of the uncertain parameters within the problem. For a given realization, various component-level dynamic analyses are preformed within a certain range of distance, in order to quantify and locate the damage induced by shock wave on structural elements. As a case study, a 5-storey reinforced concrete frame structure designed for gravity loading only is considered. As possible retrofitting schemes, steel bracing, FRP wrapping and RC jacketing are compared. The probability of collapse considering both blast and earthquake for the structure before and after retrofit are compared.