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<br />fice coefficient can be computed to account for friction; therefore, the <br />special bridge routine would be suitable for pressure flow through long <br />culverts. <br />3. Weir flow is computed in the special bridge routine; therefore, <br />dams and weirs can be modeled as well as bridges. When computing pres- <br />sure flow or weir flow, the program user might consider whether the <br />bridge deck could survive such conditions. <br />4. Combinations of low or pressure flow and weir flow can be com- <br />puted using the hydraulic formulas. An iterative procedure solves the <br />combination flow problem for a variety of conditions. For low flow and <br />weir flow solutions the bridge must have piers for the program to handle <br />the low flow part of the combination flow. Otherwise the program will <br />revert to the normal bridge routine. <br /> <br />Loss Coefficients <br /> <br />After the cross sections are located and the method of solution is <br />determined, the program user has to select coefficients associated with <br />the method chosen. For the normal bridge routine the Manning's "n" val- <br />ues are used to determine the friction loss. The contraction and ex- <br />pansion losses caused by the bridge are estimated using contraction and <br />expansion coefficients. <br />Contraction and Expansion Coefficients. These coefficients are <br />used to compute energy losses associated with changes in the shape of <br />river cross sections. The loss due to expansion of flow is usually <br /> <br />28 <br />