Comparative response of multistory reinforced concrete frame buildings to subsurface blast and earthquake loading based on ES EN 1998–1:2015

This study presents a comparative analysis of reinforced concrete frame buildings under subsurface blast and earthquake loads. Four configurations (6- and 12-story with 3×3 and 3×4 bays) are analyzed. Blast loads use a 3 kg TNT subsurface explosion at 4 m, 7 m, and 10 m standoff in sandy soil. Earthquake loads use ES EN1998-1:2015 response spectra (PGA 0.05 g–2 g, 5% damping). Linear direct integration time-history is used for blast,response spectrum analysis for seismic. Results show that increasing standoff from 4 to 10 m reduces displacements by 85–90%. For the specific scenario studied (3 kg TNT, linear elastic response, sandy soil), displacements at 4 m standoff are comparable to 0.2 g–0.3 g PGA earthquakes (Ground Type A/B, Spectrum Type 1). At 7 m, blast effects are comparable to ~0.1 g PGA; at 10 m, displacements fall below 0.05 g PGA. Additional response parameters (base shear, acceleration, and modal periods) show that this displacement-based comparison does not extend to other design metrics. These findings are limited to linear elastic global displacement comparison and do not constitute a general equivalence for blast-resistant design. Nonlinear material response, larger charge weights, and soil–structure interaction require further investigation.