Corneliu Cismasiu

In densely built urban areas, explosive events produce blast waves that interact strongly with surrounding structures, resulting in amplified pressures and highly variable injury patterns. These complex interactions challenge conventional blast models and emphasize the need for improved, rapid injury estimation methods to support effective emergency response and mitigation. To address this need, the present study develops predictive equations for the rapid estimation of TNT blast-induced human injuries in urban environments, with particular emphasis on densely built areas characterized by complex street geometries. These equations were derived through regression analysis of an extensive dataset of simulated blast events with varying charge sizes, placed in three representative urban scenarios characterized by distinct street layouts and topographic conditions. The numerical simulations were performed using validated finite-volume Computational Fluid Dynamics models implemented in the GPU-accelerated commercial software Viper::Blast. The proposed equations allow the delineation of primary and secondary injury zones. Primary injuries are associated with overpressure effects on air-filled organs, while secondary injuries result from debris and projectiles and are directly correlated with predicted damage to masonry elements and glazing. Tertiary and quaternary injuries, which are respectively related to body displacement and impact, burns, inhalation hazards, and psychological effects, are not addressed in the present research. Results show that the urban fabric strongly influences both the extent and the shape of the injury zones. In contrast, terrain topography, provided that slopes remain relatively moderate, has only a minimal effect. Overall, the predictive equations offer a rapid yet reliable tool for quantifying blast-related injuries in urban environments. They support risk assessment, mitigation planning, and emergency response strategies for both accidental and deliberate explosions.

Accurate blast models are essential for disaster management and emergency preparedness. Semi-empirical methods, which rely on free-field assumptions, struggle to provide precise data for complex building shapes because they ignore shock wave reflections. This research numerically investigates the effects of an explosion on a large building of complex geometrical configuration using blastFoam, estimating the façade damage and assessing risks to occupants. To evaluate the importance of accurately modelling the building’s geometry, four levels of detail were considered. Additionally, simulations were also performed using the Load Blast Enhanced (LBE) method from LS-DYNA to compare the estimates of this faster semi-empirical approach with those obtained through CFD analyses. The findings reveal that simpler CFD models are adequate for façade analysis and injury assessment around the building but fall short for predicting injury distribution within interior spaces or between buildings. The LBE underestimates both structural damage and human injury levels, while detailed CFD highlights the importance of accounting for interior walls and windows to enhance blast pressure predictions.

Shock absorbers have been widely used in the automotive and aeronautical industries for many years. Inspired on these devices, the paper presents an analytical and numerical assessment of a high performance protective system for building structures against blast loads, which is composed of a shielding element connected to the main structure, at the floor levels, through ductile Energy Absorbing Connectors (EACs). The EACs exploit the external tube inversion mechanism to absorb a significant part of the imparted kinetic energy from the blast wave. While the system prototype has been developed in laboratory, it was characterized and tested in a full-scale blast testing campaign. A validated finite element model was used next to analyze its performance in a more demanding design scenario. The introduction of EACs notably reduces the peak horizontal loads and the kinetic energy transferred to the protected structure, being expected a significant reduction of the stresses in the supporting vertical elements, in addition to the protection of structural and non-structural members. These results encourage further studies of the presented protective system that can be potentially employed for a large variety of blast threat scenarios, especially when increasing the stand-off is not a possible/viable option and sensitive facilities have to be protected.

Being able to efficiently mitigate the effects of blast loads on structures, sacrificial cladding solutions are increasingly used to protect structural elements from the effects of accidental explosions and/or terrorist attacks. The present study analyses the loss of effectiveness of a deterministically designed sacrificial cladding when variability in the material properties and uncertainties in the mechanical model are considered. The results of an experimental campaign are used to validate the numerical models that allow the deterministic design of a sacrificial cladding which successfully improves the blast resistant capabilities of a given structural element. Nonetheless, it is shown that, taking into account the probabilistic variability of key parameters is of vital importance when designing sacrificial cladding solutions, since, when not properly designed for the structural element it intends to protect, adding a sacrificial cladding might negatively impact its blast resistant capabilities. Additionally, it is concluded that the deterministic approach might be against safety. In the reported case study, when comparing the admissible charge weight yielding from the deterministic and probabilistic approaches, one verifies that the former allows a higher charge weight.

This work studies the low-velocity impact response of 3D-printed layered structures made of thermoplastic materials (PLA and PETg), which form sacrificial claddings for impact protection. The analyzed structures are composed of crushable cellular cores placed in between terminal stiffening plates. The cores tessellate either honeycomb hexagonal unit cells, or hexagonal cells with re-entrant corners, with the latter exhibiting auxetic response. The given results highlight that the examined PETg protectors exhibit higher energy dissipation ratios and lower restitution coefficients, as compared to PLA structures that have the same geometry. It is concluded that PETg qualifies as an useful material for the fabrication of effective impact protection gear through ordinary, low-cost 3D printers.