Influence of masonry infills on blast response of earthquake-resistant reinforced concrete buildings

The present study investigates the influence of masonry infill strength on the blast performance of earthquake-resistant reinforced concrete (RC) buildings under surface burst. These buildings, having three-dimensional RC moment resisting frames, are designed to withstand different levels of seismic demand. The masonry infills are modelled as an equivalent diagonal strut using a macro-modelling approach to account for its in-plane strength and stiffness. The blast-induced loads are directly applied as nodal loads on the exposed beam-column joints, and nonlinear time history analyses are then performed to obtain the various response quantities such as top floor displacement, interstory drift ratio, and base shear. The comparative matrices of various response quantities are developed to examine the effect of infill's nonlinearity. Further, the influence of the infill strength and seismic design level of the considered buildings is probabilistically assessed by developing the blast fragility curves using an uncoupled approach. It is observed that the consideration of infill's nonlinearity influences the blast response up to a certain scaled distance only. Moreover, increasing the infill strength does not necessarily enhance the blast performance; however, designing the building to higher seismic demand results in improved blast per-formance. In addition, proper insight into seismic design level and infill strength of any RC building is required prior to plan and design them with suitable blast-mitigation measures.