Theoretical Framework for Structural Robustness Assessment of Reinforced Concrete Buildings Subject to Blast Loading from Improvised Explosive Devices in North-East Nigeria

Public buildings, markets, and institutional facilities in North-East Nigeria have been subjected to improvised explosive device attacks that have caused catastrophic structural collapses with mass casualty consequences, yet no structural robustness assessment framework calibrated to the explosive threat environment and building typologies of the region exists. This study develops a theoretical framework for structural robustness assessment of reinforced concrete buildings subject to blast loading from improvised explosive devices in North-East Nigeria, addressing the gap between generic international counter-terrorism structural guidelines and the specific threat-building-context combination of the region. The framework integrates an improvised explosive device threat characterisation model derived from a database of documented attacks in Borno, Yobe, and Adamawa States with simplified blast load prediction models calibrated for the charge configurations and structural standoff distances characteristic of the regional threat environment. Structural response is assessed using a consequence-based robustness index that quantifies the residual structural capacity following the loss of primary load-bearing elements under blast impulse loading, calibrated through dynamic finite element analyses of reference building configurations. Four reinforced concrete frame building typologies representing market buildings, educational facilities, healthcare centres, and administrative offices were modelled in LS-DYNA and subjected to near-field and far-field blast scenarios. The framework identifies intervention typologies including blast-resistant glazing, sacrificial facade elements, column section enhancement, and tie force augmentation that achieve cost-effective robustness improvements within the resource constraints of North-Eastern Nigerian institutional construction. The original theoretical contribution lies in the integration of regional threat characterisation with probabilistic consequence assessment and the derivation of a context-specific robustness metric. Keywords: structural robustness, blast loading, improvised explosive devices, North-East Nigeria, progressive collapse.