SS3G: An Integrated Risk Analysis Program Using Engineering Principles for Building Damage
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We announce the development, with the support of an industrial consortium, of an extensive new integrated modeling system named SS3G (Safe-Site 3rd Generation). This system is the first such risk analysis program to provide a component-by-component analysis of building damage to explosions. It also employs our new and extensively verified correlation for occupant injuries as a function of building damage level. The SS3G system provides a modem interface based on a plot plan of a plant. Using a mouse, a user traces out diked areas (potential pool fire sites), congested areas (potential explosion sites), and target buildings. With a mouse click he defines the location of release points. Pop-up screens complete the definition of all sources, buildings, etc. SS3G has modules to model discharge rates, aerosol formation and rainout, pool spread and evaporation, and dispersion, both outdoors and indoors. Several innovative features are introduced. At the Mary Kay O'Connor symposium in 2000, we described the indoor dispersion module within SS3G, WELMIX, and the indoor explosion module, INVENT. WELMIX models concentration changes within a room from a pool evaporation module that develops time-varying sources. It can treat gas sensors in the room connected to automatic controls of the fresh air/recycle ratio and ventilation rate. The INVENT module calculates how a fireball grows and builds pressure until the pressure opens explosion vents (or breaks windows). A general treatment of air or fuel-limited combustion, pressure build up, and venting rates is included. Additional innovations are documented in this paper. They include coupling a pool fire model with a dispersion model of the plume and allowing hydrolysis reactions in the plume. A productivity feature for outdoor releases is the calculation of flammable mass within each congested region encountered by the plume as the plume is rotated with wind direction. The flammable mass calculation is used as the basis for predicting explosion impulse and overpressure contours. Building damage is predicted by accounting for the angle of each building surface to the blast waves. Standard building damage levels (1 to 4) are predicted for each part of a building, and used, along with building occupancy, to predict the fraction of occupants injured and the severity of their injuries. These innovations improve the ease and accuracy of risk analyses for fire and explosion events. Toxic releases are also treated.
Woodward, John; Pierorazio, Adrian (2001). SS3G: An Integrated Risk Analysis Program Using Engineering Principles for Building Damage. Mary Kay O'Connor Process Safety Center; Texas &M University. Libraries. Available electronically from