ABSTRACT
Grates are often used to collect storm runoff into an outflow structure installed in a storage basin or on a highway median. A grate is installed at an inclined angle because an inclined grate surface may act as a regulator to the flow release and an inclined grate is not as vulnerable as the flat grate to debris clogging. The hydraulic performance of a grate depends on the water depth on top of the grate. A rack is simply a bar-screen that intercepts tree stumps, twigs, and floating debris in stormwater flows. The force analysis on a partially blocked trash rack is complicated because of the flare-end section (FES) geometry at the culvert entrance. The major external forces acting on the water flow include the reaction force from the wing walls, the contraction force through the trash rack, and the pinning force on the blocking object.
