Aerodynamic Considerations in Open Shelters.
LAWRENCE LIVERMORE NATIONAL LAB CA
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Aerodynamic factors are addressed bearing on the suitability of open structures as blast shelters for people during a nuclear attack. The designs and performances of blast attenuators and closures are important because they determine the extent to which a structure is open. Modes of structure filling shock-driven or pressure-gradient-driven are described in terms of theoretical calculations and experimental investigations on full- and fractional-scale models of structures. Potential lethality mechanisms resulting from these structure-filling modes are discussed. This report concludes that small, open structures in an as is condition will be filled rapidly by the shock that enters the structure. For sufficiently weak shocks, there may exist some safe zones from the structure-filling modes, depending on the number, location, and size of openings, as well as on the number of rooms, and the proximity of objects that might be hurled at people during the blast. Large, open structures, on the other hand, will probably fill more slowly by pressure-gradient-driven flow. The fill times for small and large shelters can vary by more than a factor of 10, and can be as great as hundreds of milliseconds for a large shelter. The winds associated with pressure-gradient-driven structure filling can be lethal. Therefore, determining safe zones is a difficult, though probably not impossible, task. It is recommended that open structures not be used as blast shelters, except as an interim measure, if alternatives are available.
- Structural Engineering and Building Technology