Differential pressures on building walls during tornadoes

In the United States, containment structures and some auxiliary structures (control buildings, auxiliary buildings, spent fuel buildings, etc.) in nuclear power plants are required to be designed to withstand the effects of the design basis tornado. In addition to velocity pressures and missile impact a tornado also causes a rapid change in atmospheric pressure, which can, in cases of closed or partially vented structures, produce direct differential pressure loading. In this paper a digital computer program is described which applies a tornado-induced, time-dependent atmospheric pressure change to a building and calculates the differential pressure histories across the interior and exterior walls of the building. Laws for quasi-steady, one-dimensional motion of an ideal compressible gas are used to calculate the pressures due to the flow of air through ports, doors and windows in the building. Numerical examples show that for each assumed atmospheric pressure change history a vent area to compartment volume ratio may be specified as the criterion for a building to be considered fully vented. (Auth.)