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Water pressure inside the culvert barrel can reverse the wall moments and add to slab positive moments and may be checked. The program is able to use full or partial depth of water pressure and no water pressure as two loading cases. Water weight is taken as 62.4 pcf. The input is the height of the water table above the centerline of the top slab for exterior water pressure, and the elevation head above the bottom of the top slab for the interior water pressure. So, for example, an interior pressure head input of 0-ft indicates a triangular pressure load resulting from the culvert being filled with water, but no additional pressure.
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