Module of simulation, analysis, evaluation and graphical representation of possible effects on buildings and people under blast in the urban space
- Software application for defining the threat: Allows the user to define the threat by entering / selecting / calculating the following parameters:
- Type of bomb vehicle: Different categories of bomb vehicles are predefined. There is the possibility of defining a new one. The amounts of explosive were introduced according to ATF – Department of the Treasury Bureau of Alcohol, Tobacco and Firearms.
Figure 1. The architecture of the innovative 9SOL system
2. Software application for environmental blast characterization: performs the determination of parameters in the shock wave front and the reflected pressure and impulse depending on the threat set by the application 1 and the stand-off The mathematical models used are based on the Rankine-Hugoniot and Kingery Bulmash equations as well as complex algorithms to determine the visibility of the structures and building elements by the direct shock wave. In engineering calculations, the blast loadings on a building are simulated using pressure-time variation. This pressure time history is characterized by the peak of overpressure, the positive phase duration and the shock wave parameter. To define peak overpressure and impulse it has to determine first the parameters of shock wave. Parameters needed to fully define the shock wave are:
- peak positive overpressure, Δp f
- impulse for positive phase Ip and positive phase duration, tp;
- arrival time, ts and wave form parameter, b. For this software application the effect of negative pressure phase of the blast wave was negligible.
The most commonly used relation to describe pressure–time variation is modified Friedlander equation:
where: P0 is the atmospheric pressure.
The equation used to determine the overpressure is the Kingery and Bulmash equation:
where A, B, C, D and E are constants.
Also, for a blast wave the positive impulse represent the area under the positive phase of pressure-time curve and can be expressed using the following equation:
The graphical representation of the overpressure on different buildings for the same bomb vehicle can be shown in the following figure.
3. Software application for the estimation of the level of buildings damage under blast: estimates the levels of destruction of buildings based on the destruction thresholds according to national and international standards. Obstacles are not taken into account. The levels of damage are calculated in according with AASTP-1 equation:
where K is a coefficient that depends on the level of the damage and WTNT is the TNT equivalent of the explosive charge, in kg.
The graphical representation of the levels of damages for the detonation of a bomb vehicle (cargo van) is presented in the following figure.
4. Software application for structure characterization: performs the database with the characteristics of the analyzed structures. Depending on the data contained in the national regulations, the user has the possibility to select the characteristics of the buildings for which the behaviour under blast loadings will be determined. There are predefined some features as followings: the type of building; year of construction; destination; class of importance; the geometry of the building; type of building materials used, etc. The application provides the user with the ability to modify / define new data / features. Output data will be used by other applications to estimate the buildings level of damage and to assess the potential for the occurrence and propagation of the progressive collapse.
5. Software application for the assessment of the level of destruction of buildings and the occurrence of progressive collapse: performs a precise estimation of the effect of the blast on buildings and evaluates the potential for the occurrence and propagation of the progressive collapse. The application uses models with a single degree of freedom and P-I diagram to estimate the strength of the building elements under blast. Estimation is done on three levels of damage: 30%, 60% and 100%. The level of 100% damage corresponds to the moment of element collapse.