47.5 MB - The Whole Building Design Guide

and columns, because the element is surrounded by water. If notoriented parallel to the flow of water, shearwalls may experiencehydrostatic loads due to a difference of water depth on eitherside of the wall. To reduce excessive pressure from standingwater, floodplain management requirements in A Zones call foropenings in walls that enclose areas below the flood elevation(see description of continuous perimeter wall foundation in Section2.3.1.2).Buoyant forces resulting from the displacement of water arealso of concern, especially for dry floodproofed buildings andaboveground and underground tanks. Buoyancy force is resistedby the dead load of the building or the weight of the tank.When determining buoyancy force, the weight of occupantsor other live loads (such as the contents of a tank) should notbe considered. If the building or tank does not weigh enough“empty,” then additional stabilizing measures need to be takento avoid flotation. This becomes a significant consideration fordesigns intended to dry floodproof a building. Buoyancy forceis slightly larger in saltwater, because saltwater weighs slightlymore than fresh water.Figure 2-8: Hydrostatic loads on buildings2-22 MAKING CRITICAL FACILITIES SAFE FROM Flooding