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<br />must be fitted into the roadway cross <br />section. The culvert barrel must have <br />adequate cover, the length should be <br />close to the approximate length, and the <br />head walls and wingwalls must be dimen- <br />sioned. <br /> <br />If outlet control governs and the headwater <br />depth (referenced to the inlet in vert) <br />is less than 1.2D, it is possible that <br />the barrel flows partly full though its <br />entire length. In this case, caution <br />should be used in applying the approximate <br />method of setting the downstream elevation <br />based on the greater of tail water or <br />(de + D)/2. If an accurate hcadwater is <br />necessary, backwater calculations snould <br />be used to check the result from the <br />approximate method. If the headwater <br />depth falls below 0.7SD, the approximate <br />method should not be used. <br /> <br />If the selected culvert will not fit the <br />site, return to the culvert design pro- <br />cess and select another culvert. If <br />neither tapered inlets nor flow routing <br />are to be applied, document the design, <br />An acceptable design should always be <br />accompanied by a performance curve which <br />displays culvert behavior over a range <br />of discharges. If tapered inlcts are to <br />be investigated, proceed to chapter IV. <br /> <br />, <br /> <br />, <br /> <br />If storage routing will be utilized, <br />proceed to chapter V. <br /> <br />, <br /> <br />Special culvert installations, such as <br />culverts with safety grates, junctions, <br />or bends are discussed in chapter VI. <br />Unusual culvert configurations such as <br />"broken-back" culverts, siphons, and low <br />head installations are also discussed. <br /> <br />, <br /> <br />S. Example Problems. The following <br />example problems illustrate the use of <br />the design methods and charts for selected <br />culvert configurations and hydraulic <br />conditions. The problems cover the fol- <br />lowing situations: <br /> <br />Problem No.1: Circular pipe cul- <br />vert, standard 2-2/3 by 1/2 in (6.8 by <br />1.3 cm) CMP with beveled edge and rein- <br />forced concrete pipe with groove end. <br />No FALL. <br /> <br />Problem No.2: Reinforced <br />in-place concrete box culvert with <br />edges and with bevels. No FALL. <br /> <br />cast- <br />square <br /> <br />Problem No.3: Elliptical pipe <br />culvert with groove end and a FALL. <br /> <br />Problem No.4: Analysis of an <br />existing reinforced ,concrete box culvert <br />with square edges. <br /> <br />so <br />