Title: HYDRAULIC CHARACTERISTICS OF RECESSED CURB INLETS AND BRIDGE DRAINS. FINAL REPORT
Abstract: One of the many concerns about roadway safety is how to remove precipitation runoff from the roadway surface quickly and efficiently. On uncurbed roadways, water simply drains into adjacent ditches. On curbed roadways, water is removed by allowing it to flow down a gutter until it reaches an inlet structure, at which point it is diverted through a subsurface drainage system. The problem is that not all inlet structures are uniformly effective. This study analyzed the effectiveness of both grate and curb inlets; the efficiency of several types of bridge deck drains was also investigated. Overall, the study had three objectives: (1) to determine the hydraulic characteristics of recessed curb inlets for different flow conditions and curb inlet geometries; (2) to determine the hydraulic characteristics of three types of bridge deck drains with different flow conditions and geometries; and, finally, (3) to provide predictive equations for performance and capacity--so as to obtain new design guidelines for the construction of both recessed curb inlets and bridge drains. Concerning recessed curb inlets, three geometries of inlets and three inlet lengths were tested. For the experiments, the flow rate into the recessed curb inlet, the flow rate passing the inlet section (the carryover), and water depths on the roadway surface were measured. Based on an approach that categorizes curb inlets as either 100% efficient or less than 100% efficient, a new design equation (the captured flow divided by the gutter flow) was developed in which a facility's efficiency is expressed as a function of the effective length of the inlet divided by the effective length required to capture all of the flow. For all three bridge deck drains tested, regression analysis was used to determine the flow into the inlet as a function of the upstream uniform flow depth, the longitudinal roadway slope, and the cross slope. In this way, empirical equations for predicting the capacity for the flow conditions most likely to be encountered on bridges were obtained.
Publication Year: 1992
Publication Date: 1992-11-01
Language: en
Type: article
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