Blast and impact loading on reinforced concrete elements: from vapour cloud explosion assessment to energy absorption capacity of restrained members

Doktorsavhandling, 2026

Extreme dynamic loads (such as blasts and impacts), though infrequent, pose a serious threat to public safety and critical infrastructure. Moreover, the risk associated with such loads is connected to modern society’s demands, including transport of dangerous goods and densification of urban environments. Properly addressing this risk requires understanding both the development and propagation of blast loads and associated effects, as well as the response of reinforced concrete (RC) structures under impulsive actions. This research integrated these aspects by examining blast generation from vapour cloud explosions (VCEs) in traffic environments and the behaviour of RC elements subjected to blast and impact loading.

The first part examined VCEs in scenarios involving groups of vehicles. Computational fluid dynamics was employed to investigate how parameters related to the traffic configuration and the premixed fuel-air cloud influence the severity of the explosion. Based on these results, practical recommendations for applying a simplified approach—the Multi‑Energy Method—in such environments were developed, providing a reliable and consistent basis for blast load estimation in vehicle-populated environments.

The second part of the thesis focused on the behaviour of RC structures under impulsive loading, with a general focus on ductile failure modes that enable higher energy absorption capacity. Initially, the risk of shear failure (brittle) occurring prior to bending failure (ductile) in slender RC one-way slabs subjected to blast loading was examined. Although flexural failure was found to be the more probable response mode for the studied slabs, a reliability-based overstrength factor was proposed to further increase the probability of achieving a flexure-dominated response. Thereafter, the impact response of RC one-way elements under different boundary conditions was investigated, including the effects of membrane action and repeated loading. The results showed that the energy dissipated under impact and subsequent static loading exceeded the energy absorption capacity under static loading only, indicating potential for more optimal structural designs regarding impulsive actions. In addition, membrane action was observed to enhance both the load-carrying capacity and deformation limit of restrained RC elements under static and impact loading. Finally, different simplified methods for predicting key aspects of the dynamic response were developed and validated, thereby supporting the analysis and assessment of impact-loaded RC structures.