1. FRP Bridge Drain Pipe
Systems
Basic Design
Characteristics for
Successful Installations

2. Points of Concern
• Expansion and Contraction

3. 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.

4. Expansion Joints
For Approximately 200’ of Horizontal
Pipe 1 Expansion Joint is Required
The Thermal Expansion Coefficient
Value for FRP is 0.000014 in/in/F
So the Typical Expansion Formula is
ΔL (in) = L (in) x ΔT (F) x 0.000014
Anticipated Expansion of Pipe @
ΔT=100° & L=2400” ==> ΔL=3.36”

5. The Total Length of Movement for the
Expansion Joint Fitting in Most Pipe
Diameters is Approximately 7”

6. Points of Concern
• Expansion and Contraction
• System Slope

7. Slope Requirement of >2%

8. 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.

9. Slope in Respect to Angle
Slope (%) = (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°

10. Custom Fittings to Match
Any Slope You May Need

11. Points of Concern
• Expansion and Contraction
• System Slope
• Clean Outs

12. Clean Out Considerations

13. 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.

14. Points of Concern
• Expansion and Contraction
• System Slope
• Clean Outs
• Horizontal Curves

15. Horizontal Curve Performance
Our 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

16. Points of Concern
• Expansion and Contraction
• System Slope
• Clean Outs
• Horizontal Curves
• System Outlets

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

18. Points of Concern
• Expansion and Contraction
• System Slope
• Clean Outs
• Horizontal Curves
• System Outlets
• Hanger System

19. System Supports
Design 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

20. Recommended Maximum
Support Spacing
Pipe Support Minimum Hanger Hanger
Size Spacing Support Load Pipe Load Pipe
(in.) (ft.) Width (in.) Only (lbs.) & Water
(lbs.)
4 16.5 1¼ 21.5 145
6 18.3 1½ 36.6 288
8 20.2 1¾ 52.6 518
10 21.3 1¾ 70.3 829
12 22.4 2 87.4 1221
14 23.2 2 104.1 1708
16 24.0 2½ 124.8 2268
18 24.8 3 143.9 2932
20 25.7 3¾ 218.5 3634
24 26.7 4½ 272.4 5586

21. 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