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<br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />II <br />I <br />I <br />I <br />I <br />I <br />I I <br />I <br />I <br />I <br />I <br />I <br /> <br />Lesson 3 <br /> <br />Culvert Design - Participant Workbook <br /> <br />3.9 CULVERT DESIGN METHOD <br /> <br />CULVERT DESIGN METHOD <br /> <br />CULVERT DESIGN METHOD (cont) <br /> <br />. DESIGN IS BASED ON LOCATION OF CONTROL <br />(INLET OR OUTLET) <br />. CONCEPT OF "MINIMUM PERFORMANCE" IS <br />APPLIED <br />. FOR A GIVEN Q, A CULVERT SIZE AND <br />MATERIAL ARE ASSUMED AND THE HW <br />CALCULATED (INLET AND OUTLET CONTROL) <br />. THE HIGHER HW IS THE CONTROLLING <br />HEADWATER ELEVATION <br /> <br />. CONTROLLING HW COMPARED TO DESIRED <br />DESIGN HW TO EVALUATE PERFORMANCE <br />. OUTLET VELOCITY EVALUATED TO DEFINE <br />NEED FOR OUTLET PROTECTION <br />. EVALUATION OF HEADWATER AND OUTLET <br />VELOCITY CONTINUES UNTIL AN <br />ACCEPTABLE CULVERT CONFIGURATION IS <br />DEFINED <br />. SELECTED CULVERT MUST THEN FIT <br />ROADWAY CROSS SECTION <br /> <br />3.28 Culvert Design Method <br /> <br />3.29 Culvert Design Method (cont) <br /> <br />A. The basic design method is based on the location of the control (inlet or <br />outlet). <br /> <br />B. Although control may oscillate from inlet to outlet, the concept of <br />"minimum performance" is applied meaning that while the culvert may <br />operate more efficiently at times, it will never operate at a lower <br />performance than calculated. <br /> <br />B. The design procedure then is to assume a pipe size and material and <br />calculate the headwater elevation for both inlet and outlet control (using <br />the HDS-5 nomographs or HYDRAIN, HY-8). The inlet and outlet control <br />results are compared and the higher of the two is designated as the <br />controlling headwater elevation. <br /> <br />3-13 <br />