Culvert Hydraulics - Hydraulics - Lecture Slides, Slides of Pneumatics

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Culvert Hydraulics using the

Culvert Design Form

Objectives

• Know how to use the culvert design form to evaluate and size simple culverts (page 344 of HDS 5)

Step 1

• Summarize all known data and select a

preliminary culvert size, shape and entrance

type

Step 2

• Choose a culvert type and size

Step 4-Outlet Control Calculations

• Outlet control calculations
  • Determine TW depth
  • Determine critical depth
  • Find the average of critical depth and diameter
  • Determine depth from culvert outlet invert to HGL
  • Determine all head losses
  • Calc the Elev of the HW for outlet control

Step 5-Evaluate Results

• Higher of the two elevations designates

control

• Choose larger culvert if the highest elevation

is unacceptable

Step 2

Inlet Control

Calculations

• HW/D from Design Chart 3B = 0.
• HW=0.96*6’=5.8’
• A =45 deg bevel, pg 27
• B =33.7 deg bevel

Step 3-Inlet Control Calculations Calculate HW Elev for inlet control

• ELhi =HW (^) i +ELi
• 5.8 ft + 100 ft = 105.8 feet

Step 4-Outlet Control Calculations TW Depth

• Determine TW depth
• backwater or normal depth calculations
• Given as 3.5’

Step 4-Outlet Control Calculations Find average of dc + D

16

(3.8+6)/2 = 4.9’

Step 4-Outlet Control Calculations Determine ho

• ho is the depth from the culvert outlet invert to the hydraulic grade line
• Larger of:
  • TW (3.5’) or
  • Avg. of (dc & D-4.9’) ---See Figure III-9 (D)

Outlet Control

Head Losses

• Can use Chart 6
• Line D/Ke
• Line Q/Turning Pt
• H=2.6’

Step 4-Outlet Control Calculations Calculate HW Elevation

• Outlet Invert Elev + Head Losses + ho
• 98+2.6+4.
• HW elevation based on outlet control = 105.5’