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<br />5 <br /> <br />e <br /> <br />Improved Culvert Inlets <br /> <br />Three degrees of inlet refinement are discussed in a new <br />publication, "Hydraulic Design of Improved Inlets for Culverts" 0): <br /> <br />1- <br />2. <br />and 3. <br /> <br />Bevel-edged inlets <br />Side-tapered inlets <br />Slope-tapered inlets <br /> <br />Bevel-Edged Inlets <br /> <br />The first logical entrance improvement to a conventional <br />culvert is beveling the inlet edges. The bevels are sized in <br />proportion to the barrel dimensions, and various bevel angles may <br />be used (Figure 10). Design procedures are presented in REC No. 13 <br />for 1:1 and 1'1/2:1 bevels. Rounded edges which approximate the <br />bevels could also be used. <br /> <br />. <br /> <br />Beveled edges improve the entrance flow conditions and reduce <br />the contraction downstream of the culvert face, thereby utilizing <br />more of the available barrel area for the conveyance of water. <br />The control section remains near the culvert face and the available <br />headwater is effectively the same as for a conventional culvert. <br />Generally, little or no enlargement of the culvert inlet is required; <br />thus, structural problems are minor. <br /> <br />As a minimum, bevels should be used on all culverts operating <br />in inlet control. Also, if little additional cost is involved, <br />beveled edges can be used to increase the efficiency of culverts <br />operating in outlet control. Neither side- nor slope-tapered inlets <br />should be used on culverts operating in outlet control. <br /> <br />. <br /> <br />Beveled edges may easily be adapted to either pipe (Figures 11, <br />12, and 13) or box culverts (Figure 14). The socket end of concrete <br />pipes, if retained, performs similarly to a beveled edge. <br /> <br />Side-Tapered Inle ts <br /> <br />f' <br /> <br />The second degree of improvement, side-tapered inlets, involve <br />a structural modification to enlarge the face area of the culvert. <br />Research studies (4,5) indicated that the larger face area was most <br />efficiently obtained by tapering the sidewalls rather than the <br />culvert roof. Thus, the enlarged face area is transitioned to the <br />culvert barrel by tapered sidewalls. The floor and roof of this <br />inlet are straight line extensions of the barrel floor and roof. <br /> <br />. <br />