Spreadsheets for Circular Culvert Design

Where to get circular culvert design spreadsheets

For Excel spreadsheets to make culvert design calculations in either U.S. or S.I. units, click here to visit our spreadsheet store. Obtain convenient, easy to use spreadsheets for culvert design calculations at reasonable prices. Read on for information about the use of Excel spreadsheets for this application.

Inlet Control and Outlet Control for Culvert Design

One of the general conditions for culvert design calculations is inlet control, in which the flow rate through the culvert is controlled at the inlet end of the culvert by the culvert diameter and other inlet conditions. The other general condition is outlet control, in which the flow rate is controlled by the outlet conditions and the entire length of the culvert.

Culvert Inlet Control Design Calculations

An equation that relates culvert parameters for inlet control conditions is:

where:

HW = headwater depth above inlet invert (ft - U.S. or m - S.I.)
D = inside height of the culvert (ft - U.S. or m - S.I.)
Q = discharge (cfs - U.S. or m³/s - S.I.)
A = cross-sectional area of culvert (ft² - U.S. or m² - S.I.)
S = culvert slope (dimensionless)
K1 = 1.0 for U.S. units or 1.811 for S.I. units
Ks = slope constant = -0.5 for a non-mitered or + 0.7 for a mitered inlet
Y and c are constants dependent on the type of culvert and type of inlet.

Culvert Outlet Control Design Calculations

An equation that relates culvert parameters for outlet control conditions is:

Where:

h_L = the head loss in the culvert barrel for full pipe flow (ft - U.S. or m - S.I.)
K_u = 29 for U.S. units or 19.63 for S.I. units
n = Manning roughness coefficient for the culvert material
L = length of the culvert barrel (ft - U.S. or m - S.I.)
R = hydraulic radius of the full culvert barrel = A/P (ft - U.S. or m - S.I.)
A = cross-sectional area of the culvert barrel (ft² - U.S. or m² - S.I.)
P = perimeter of the culvert barrel, ft or m
V = velocity in the culvert barrel, ft/sec or m/s
Ke = loss coefficient for pipe entrance

Spreadsheets for Circular Culvert Design Calculations

A spreadsheet screenshot for circular culvert design calculations

The Excel spreadsheet screenshot below shows part of a spreadsheet for circular culvert design calculations based on inlet control. Based on the indicated input values, the spreadsheet will calculate the minimum required culvert diameter and the headwater depth for the next larger standard culvert diameter.

For low cost, easy to use spreadsheets to make these calculations in S.I. or U.S. units, click here to visit our spreadsheet store.

References

1. Hydraulic Design of Highway Culverts,Third Edition, Publication No. FHWA-HIF-12-026, U.S. DOT/Federal Highway Administration, April, 2012.

2. Bengtson, Harlan H., "Pipe Culvert Design Spreadsheet Calculations", an online article