47.5 MB - The Whole Building Design Guide

2.1.2.5 Hydrodynamic LoadsWater flowing around a building or a structural element that extendsbelow the flood level imposes hydrodynamic loads. Theloads, which are a function of flow velocity and structure geometry,include frontal impact on the upstream face, drag along thesides, and suction on the downstream side (see Figure 2-9). Waysto determine or estimate flood velocities are described in Section2.1.2.2 and Section 2.1.2.3.Figure 2-9: Hydrodynamic loads on a building or building elementThe most common computation methods for hydrodynamicloads are outlined in the design standard Minimum Design Loadsfor Buildings and Other Structures, produced by the AmericanSociety of Civil Engineers’ Structural Engineers Institute (ASCE/SEI, 2005). Those methods assume that the flood velocity is constant(i.e., steady state flow) and that the dynamic load imposedby floodwaters moving at less than 10 feet per second can beconverted to an equivalent hydrostatic load. This conversion is accomplishedby adding an equivalent surcharge depth to the depthof water on the upstream side. The equivalent surcharge depth isa function of the velocity. Loads imposed by floodwaters with ve-MAKING CRITICAL FACILITIES SAFE FROM Flooding2-23