The HExDAM damage algorithm is correlated against the Southwest Research Institute pressure-impulse diagrams. The VExDAM model employs Van den Berg’s TNO multi-energy method, which uses dimensionless curves of overpressure and pulse duration versus range to predict the resultant overpressure and impulse at each structure. The results were validated in a number of technical papers, written by the developer of the HExDAM and VExDAM models and has been used and validated extensively in other industry products and applications.
Blast Wave Pressure and Impulse with Shielding Effects
Conventional blast profiles are first computed and then BREEZE ExDAM’s shielding algorithm, utilizing finite line doublets from potential theory, reduces the spatial distribution of pressure/impulse behind shielding structures. Blast direction, structure orientation, and structure vulnerability are then taken into account by the shielding algorithm to simulate blast waves passing through and around structures. For example, a blast wave may destroy a glass window allowing persons standing behind the window to receive the full effect of the blast, but leave a concrete wall intact shielding people behind the wall. ExDAM models these complex geometric effects, which allows for the evaluation of existing structures as well as possible mitigation measures such as blast hardening or the addition of protective barriers.
Damage to Structures and Injury to People
BREEZE ExDAM calculates complex blast wave pressure distributions and consequent incident damage/injury levels, allowing the user to develop, analyze, and document detailed results utilizing advanced 3D graphical input/output in a fraction of the time. Damage effects are calculated based on the material type (e.g. glass, wood-frame, masonry, concrete construction) and incident pressure/impulse. Injuries are determined based on the ExDAM human body model, which is composed of 28 total body components and 19 different body component types (e.g. various bones, organs, etc). The model accounts for the fact that different structure/body components are sensitive to different aspects of a blast wave. For example, telephone poles are blown over by dynamic pressure and impulse while buildings are crushed by overpressure. Ear drums are sensitive to peak overpressure, while long bone and neck injuries are caused by the sudden push exerted by dynamic pressure and impulse.
If the magnitude of the blast and exposure to structural and human body components is unknown, then explosion modelers can make use of BREEZE VASDIP to generate the vulnerability parameters. These parameters can be exported for characterizing a distinct structure or human body component in BREEZE ExDAM HExDAM or VExDAM modules.
Secondary Explosions and Fragmentation
BREEZE ExDAM can trigger secondary (sympathetic) explosions based on damage levels produced by prior explosions. Injury due to fragmentation can also be predicted using HExFRAG. Sympathetic explosion scenarios can be analyzed by associating secondary explosions with structures components and setting trigger damage thresholds. Injuries due to secondary fragmentation (e.g., flying glass from a broken window) can be computed from the results of an individual explosion (i.e. incident pressures/impulses and structure damage levels) using the HExFRAG secondary fragmentation model. Fragmentation scenarios can be repeatedly analyzed after performing explosion model runs by assigning frangibility factors to structure components and placing people in various locations.