FRP Bridge Drain Pipe Systems

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Basic Design Characteristics for

Successful Installations

Points of Concern

• Expansion and Contraction

Free Floating Connection

Bridges are dynamic structures where slight shifts and vibrations are expected. The dynamic forces of both the bridge and drainage system don’t always agree. Leaving a free floating connection between deck outlets and

the subsequent pipe is one way to account for these anticipated movements.

Expansion JointsFor Approximately 200’ of Horizontal Pipe 1 Expansion Joint is Required

The Thermal Expansion Coefficient Value for FRP is 0.000014 in/in/FSo the Typical Expansion Formula isΔL (in) = L (in) x ΔT (F) x 0.000014

Anticipated Expansion of Pipe @ ΔT=100° & L=2400” ==> ΔL=3.36”

The Total Length of Movement for the Expansion Joint Fitting in Most Pipe

Diameters is Approximately 7”

Points of Concern

• System Slope

Slope Requirement of >2%

It is essential for conveyance systems being installed to meet these minimum slope requirements. While fiberglass pipe does have an excellent Hazen-Williams coefficient of 150, without the proper slope, systems will become more likely to collect debris and clog.

Slope in Respect to AngleSlope (%) = (Rise/Run) * 100

Angle = Arctan(Rise/Run)

Example: Slope = 2%

(Rise/Run) = .02 unit/unit

Angle = Arctan(.02) = 1.15°

Example: Slope = 3.5%

(Rise/Run) = .035 unit/unit

Angle = Arctan(.035) = 2°

Custom Fittings to Match Any Slope You May Need

Points of Concern

• System Slope

• Clean Outs

Clean Out Considerations

By placing clean out plugs at the end of long runs of pipe

maintenance crews will have the ability to service any

potential system clogs. With clean outs its not always the

quantity that matters. Strategic placement of the

clean outs is just as important. By placing a clean

out in a hard to reach area crews may not have the

required access to preform the needed work.

Points of Concern

• System Slope

• Clean Outs

• Horizontal Curves

Horizontal Curve PerformanceOur Product Exceeds a Stiffness Factor value of 200 in^3·lbf/in^2 @ 5% Deflection

This Means that Approximately 1’ of Deflection is Allowed Per 21’ Run of Pipe

If 1’ Deflection is Insufficient, Small Angled Elbows in the Range of 1°- 5°can be Added to Match the Horizontal Curves

Points of Concern

• System Slope

• Clean Outs

• System Outlets

System Outlets

A bent system outlet and a high class riprap will help minimize erosion at the base of the structure

Points of Concern

• System Slope

• Clean Outs

• System Outlets

• Hanger System

System SupportsDesign Engineers Should Locate Pipe Supports Near

Directional Changes and Socket Connections to Ensure All Joints Will Stay Secure Throughout the Systems Lifecycle

For Most Pipe Diameters Be Sure to Include a Hanger at Least Once Every 20 Feet of Horizontal Pipe That Runs

Parallel With the Bridge Deck

Recommended Maximum Support Spacing

Pipe Size (in.)

Support Spacing

Minimum Support

Width (in.)

Hanger Load Pipe Only (lbs.)

Hanger Load Pipe & Water

(lbs.)

4 16.5 1 ¼ 21.5 145

6 18.3 1 ½ 36.6 288

8 20.2 1 ¾ 52.6 518

10 21.3 1 ¾ 70.3 829

12 22.4 2 87.4 1221

14 23.2 2 104.1 1708

16 24.0 2 ½ 124.8 2268

18 24.8 3 143.9 2932

20 25.7 3 ¾ 218.5 3634

24 26.7 4 ½ 272.4 5586

Do you have specific questions about the system you are currently designing that we did not already answer?Please give us a call and we would be more than happy to further discuss your unique situation and help find a solution!Call Nathan Peters at (636) 938-6313

FRP Bridge Drain Pipe Systems

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