precast concrete pipe
TRANSCRIPT
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PRECAST
CONCRETE PIPE
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WHY PROVIDE
GUIDELINES?
• Past problems.
• Was tedious to keep track of variables.
• Was easy to make mistakes.
• Wanted a design tool to reduce
problems.
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TOPICS
• Minimum Structure Size.
• Maximum Angle into Rectangular
Structures.
• Minimum Angle between Pipes entering
Round Structures.
• Minimum Pipe Depth.
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MINIMUM
STRUCTURE SIZE
• The precast opening is typically 6 inches
larger than the pipe’s outside diameter.
Opening
Pipe
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Table 4-2
of
Storm Drain Handbook
August 2000
Values based on
Openings for Concrete Pipe
MINIMUM
STRUCTURE SIZE
Minimum Dimensions
For Structures
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Maximum Angle (Skew) into a
Rectangular Structure
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MAXIMUM ANGLE (SKEW)
INTO A RECTANGULAR STRUCTURE12
”
Pre
cast O
penin
g
6” OD Pipe
60
”
Pre
cast O
penin
g
54” OD Pipe
6”
Structure
Wall
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Structure Wall
Good practice to allow 2" ofcontruction tolerance.
Skew
Pip
e
Tolerance
TanxThckWally .=
.ThckWall
yTan = y
R
ODPipeCos =
Cos
ODPipeR = R
Tolerance = Precast Opening – R – y
MAXIMUM ANGLE (SKEW)
INTO A RECTANGULAR STRUCTURE
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Example:
Given: 24” Concrete Pipe at 17 degree skew
Structure Wall Thickness = 8”
A 24” concrete pipe has a 30” outside
diameter and a 36” precast opening.
Tolerance = Precast Opening – R – y
= 36” – (30”/Cos 17o) – 8” x Tan 17o
= 2.2”
MAXIMUM ANGLE (SKEW)
INTO A RECTANGULAR STRUCTURE
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Table 4-3 of
Storm Drain Handbook – August 2000
Values are based on 2 inches of construction tolerance,
structures with 8-inch walls and concrete pipe dimensions.
Use Round Structure or Rearrange Pipes
if these Angles are Exceeded.
MAXIMUM ANGLE (SKEW)
INTO A RECTANGULAR STRUCTURE
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Minimum Angle Between Pipes
Entering Round Structures
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Plan View
Structure
Pipe #1
Pip
e #
2
MINIMUM ANGLE BETWEEN PIPES
ENTERING ROUND STRUCTURE
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MINIMUM ANGLE BETWEEN PIPES
ENTERING ROUND STRUCTURE
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Pipe #1 Precast Opening
Pipe #2 Precast Opening
Plan ViewPipe #1 Half angle
Pipe #1 Half angle
..
/)(
RadStruct
Opening21AngleHalfSin =
Separation Angle
Yields 2” Inside
HALF ANGLE DIAGRAM
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Table 4-6
of
Storm Drain
Handbook
Partial View
Read Notes!
MINIMUM ANGLE BETWEEN PIPES
ENTERING ROUND STRUCTURE
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• Minimum Cover Requirements of Index
205.
• Strive to maintain a 6-inch precast
section above the pipe opening while
avoiding Grates, Inlet Tops and Top
Slabs.
MINIMUM DEPTH
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MINIMUM DEPTH
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MINIMUM DEPTH
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MINIMUM DEPTH
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MINIMUM DEPTH
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MINIMUM DEPTH
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MINIMUM DEPTH
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MINIMUM DEPTH
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Inlet Types B & G were not included due to
planned design changes.
Table 4-4 of Storm Drain Handbook (partial view)
*** Read Notes ***
MINIMUM DEPTH
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• Index 220: Inlet Type S; Recommended Max pipe
in long wall should be 30”, not 36”
• Index 221: Inlet Type V; Recommended Max pipe
in long wall should be 30”, not 36”
• Index 230: Inlet Type A; Recommended Max pipe
in long wall should be 18”, not 24”
FUTURE CHANGES TO THE ROADWAY
& TRAFFIC DESIGN STANDARDS
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• Index 232: Inlet Type C; Recommended Max pipe
in long wall should be 18”, not 24”
• Index 232: Inlet Type E; Recommended Max pipe
in long wall should be 36”, not 42”
• Index 234: Inlet Type J; Recommended Max pipe
in long wall should be 30”, not 36”
FUTURE CHANGES TO THE ROADWAY
& TRAFFIC DESIGN STANDARDS