Transcript Slide 1

Small Structure Design 101
Purdue University Road School 2011
Small Structure Design 101
Presenters:
Mark Williams, PE
INDOT Design, Vincennes District
Richard Thomas, PE
INDOT Design, Vincennes District
Site Criteria
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A culvert should be used
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Where a bridge is not hydraulically required.
Where debris and ice are tolerable.
Where it is more economical than a bridge.
Site Criteria (Cont.)
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Length and Slope
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Approximate existing topography.
Invert should be aligned with channel
bottom and skew angle of stream.
Clear-zone and embankment geometry
may dictate length.
Site Criteria (Cont.)
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Location in Plan
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Place normal to roadway if no defined
channel.
Minimize channel relocation and erosion.
Locate utilities before final location is
chosen.
Location in Profile
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Approximate natural stream profile.
Hydraulic Design Criteria
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Allowable Headwater (AHW)
Roadway Serviceability
Maximum Velocity
Minimum Velocity
Allowable Headwater (AHW)
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New Alignment
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1.5 in. Maximum Backwater.
Exceptions
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Backwater Dissipates to 1.5 in. or less at
R/W.
Backwater is Contained in the Channel.
Allowable Headwater (Cont.)
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Existing Conditions
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Proposed Surcharge ≤ Existing Surcharge.
If Existing Surcharge > 1 ft., Proposed
must not be > 1 ft. above the Natural
Channel Flood Profile.
Allowable Headwater (Cont.)
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Right of Way
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The Ponding Limit Cannot Exceed the R/W
for New Alignment.
Upstream Channel
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The Ponding Limit Cannot Exceed the
Banks of Upstream Channel for New
Alignment.
Allowable Headwater (Cont.)
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Other Constraints
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Grades of Adjacent Drives.
Finished Floor Elevations of Buildings.
Elevation of Existing Cropland or Other
Property.
Design Storm Frequency
Roadway Serviceability
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For Q100 Design Storm
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Headwater must be at least 2 ft below
edge of pavement
For Design Storm less than Q100
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Headwater cannot exceed edge of
pavement
Maximum Velocity
Vo ≤ 6.5 ft/s
Revetment Riprap
6.5 ft/s ≤ Vo < 10 ft/s
Class 1 Riprap
10 ft/s ≤ Vo < 13 ft/s
Class 2 Riprap
Vo ≥ 13 ft/s
Energy Dissipator
Vo = Outlet Velocity
Minimum Velocity
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Typical Minimum Outlet Velocity is
3 ft/s.
Culvert Sizing Process
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Priority System
Interior Designation
Minimum Culvert Size
Cover
Priority System
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Trial
Trial
Trial
Trial
Trial
Trial
1.
2.
3.
4.
5.
6.
Single Circular Pipe.
Single Deformed Pipe.
Single Specialty Structure.
Multiple Circular Pipes.
Multiple Deformed Pipes.
Multiple Specialty Structures.
Interior Designation
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Run Hydraulic Design for both Smooth
Interior and Corrugated Interior.
Four Possible Situations.
Interior Designation (Cont.)
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Situation 1. Required Smooth and
Corrugated Sizes are Identical.
Situation 2. Required Smooth and
Corrugated Sizes are Different.
Situation 3. Acceptable Size for one but
not the other.
Situation 4. No Acceptable Size.
Minimum Culvert Size
Pipe Cover
Circular Pipe
Deformed Corrugated
Pipe
Minimum Cover
Maximum Cover
1 Ft
100 Ft
1.5 Ft
13 Ft
Pipe Material Selection
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Computer Program (INDOT Website)
Information Required
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Pipe Classification
Pipe Interior Designation (Smooth/Corrugated)
Pipe Criteria (Size, Cover, Slope)
Pipe Service Life
Abrasive or Non-Abrasive Site
Structure pH
Pipe Classification
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Type 1. Under Mainline or Public Road.
Type 2. Storm Drain.
Type 3. Under Drive or Field Entrance.
Type 4. Underdrain or Drain Tile.
Type 5. Broken Back or other which
requires coupled pipe.
Pipe Service Life
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Based on Functional Classification of
Mainline Roadway
75 Years- Freeway, Expressway, Arterial
50 Years- Collector or Local Road
Abrasive or Non-Abrasive
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Abrasive
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Mainline Culvert
Public Road or Drive Culvert Installed in a
Natural Channel.
Non-Abrasive
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Storm-Drain, Public Road, or Drive Culvert
on a Constructed Side Ditch Line.
Structure pH
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Maximum pH. Cannot Exceed the Map
pH (Fig. 28-6A IDM).
Lack of Sample. Use pH From Nearest
Structure. If Not Available Within
Project Limits Use pH Map Value.
Side Ditch Culvert. Use pH for the Most
Downstream Culvert for Each Culvert in
Ditch Line.
Plans
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Plan & Profile Sheet. Appropriate
Location for Drainage Structure
Identification.
Detail Sheet. Detail Drainage Structures
and Features that are not included in
the Standard Drawings.
Plans (Cont.)
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Structure Data Sheet.
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Backfill Method, Structure Backfill (CYS), Type.
Flowable Backfill (CYS), Type.
Scour Protection Information
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Sump Depth (IN), Geotextile (SYS),
Riprap (Type & Tons)
Video Inspection Length.
Pipe Material Sheet. List Acceptable Pipe
Materials for each Pipe Structure.
Structure Backfill
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Type 1
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Longitudinal or Transverse Structure Within
5 ft. of the back of paved Shoulder or back
of Sidewalk of a New Facility.
Structure for an Existing Facility Where all
Existing Pavement is to be Replaced.
Structure Backfill (Cont.)
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Type 2
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Longitudinal or Transverse Structure Within
5 ft. of the back of paved Shoulder or back
of Sidewalk Where Undisturbed Existing
Pavement is to Remain.
Precast Concrete 3 Sided or 4 Sided
Structure with Cover of 2 ft or Greater.
Structure Backfill (Cont.)
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Type 3
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Behind Mechanically Stabilized Earth
Retaining Walls.
Type 4
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Trench Where Utility Line is Present.
Behind Reinforced Concrete Slab Bridge
End Bent.
Structure Backfill (Cont.)
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Type 5
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Precast Concrete 3 Sided or 4 Sided
Structure with Cover Less than 2 ft.
Filling Voids in an Underground Facility.
Filling an Abandoned Pipe or Structure.
Other Application that does not Require
Excavation.
Backfill Methods
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Method 1
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Under New or Replacement Mainline or
Public Road.
Under Median Embankment.
New Structure Under Existing Mainline or
Public Road.
Backfill Methods (Cont.)
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Method 2
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Placed Under a Drive in New or
Replacement Work.
Method 3
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Under New or Replacement Median
Trench.
Backfill Quantities
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Measured by CYD Computed from Neat
Line Limits.
Hand Calculation
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IDM Chapter 17
Standard Drawings Section 715-BKFL
Computer Program
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www.in.gov/dot/div/contracts/standards/0
7Bkfl-qt.xls
Pavement Replacement
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Longitudinal Pay Limits
Pipe Under Existing Roadway
Culvert Modifications
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Culvert Slip Lining
Culvert Extension
Culvert End Treatment
Headwalls and Anchors
Culvert Slip Lining
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Two Common Types
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High Density Polyethylene Pipe (HDPE)
Cured in Place (CIPP)
Culvert Slip Lining (Cont.)
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Review Pipe Inspection Report
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Structures with an overall rating of 2 to 5
should be considered for lining.
Overall ratings of 0 or 1 are normally
structures that need to be replaced.
Field Review
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Pictures
Measurements
Culvert Slip Lining (Cont.)
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Factors to Consider
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Structure barrel should be relatively
straight and not significantly deformed.
Existing backfill free from large voids.
Should be sufficient room to work from at
least one end of the existing structure.
In a location where road closure is
undesirable or impractical.
Hydraulic capacity of liner.
Liner cost vs. replacement cost
Lining Design Criteria
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Time of Concentration < 1 Hour
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May increase backwater over existing if:
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Time of Concentration > 1 Hour
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Headwater maintains road serviceability.
Headwater does not reach fixed private
property structures.
May not increase backwater, unless
contained within channel banks or R/W.
Check Outlet Velocity
Lining Design Procedure
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HDPE Liners
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Manning’s n=0.012.
Use maximum pipe liner size from tables in
Standard Specification Section 725.
Use largest possible liner, even if smaller
liner is hydraulically adequate.
Lining Design Procedure (Cont.)
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CIPP Liners
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Only considered if HDPE will not work (cost).
Manning’s n=0.012.
Structures < 96” diameter or equivalent.
Will reduce existing structure size as follows:
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Dia.
Dia.
Dia.
Dia.
≤ 24”, reduce by 1”
from 27” to 48”, reduce by 2”
from 54” to 72”, reduce by 3”
from 78” to 96”, reduce by 4”
Culvert Extensions
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Match Existing Pipe Size and Interior
Designation.
Perform Appropriate Hydraulic Analysis.
Culvert End Treatment
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Projecting
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Extends beyond the roadway embankment.
Can be damaged during maintenance.
Low construction cost.
Poor hydraulic efficiency.
Anchor should be used for 42” or larger
diameter.
Clear zone requirements.
Culvert End Treatment (Cont.)
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Mitered
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Hydraulically more efficient than projecting.
Mitered to match fill slope.
Pipe End Section
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For corrugated metal or concrete pipe.
Retards embankment erosion.
May improve hydraulic efficiency.
Culvert End Treatment (Cont.)
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Wingwall
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Retain roadway embankment
Used where side slopes of channel are
unstable.
Best hydraulic efficiency if flare angle is
between 30° and 60°.
Should be used on precast concrete
drainage structures.
Culvert End Treatment (Cont.)
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Apron
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Reduce scour
Should extend at least one pipe diameter.
Should not protrude above normal
streambed elevation.
May be constructed of riprap and
geotextile or concrete.
Culvert End Treatment (Cont.)
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Cutoff Wall
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Prevent piping along culvert barrel.
Should be used for culverts with headwalls.
Should be minimum of 20” depth.
Specialty Structures
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Precast Concrete Box Culvert
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Maximum span is 12 ft.
The recommended layout is to extend the
box to the point where the roadway
sideslope intercepts stream flowline.
End of box culvert should be protected
with guardrail or located beyond the clear
zone.
Specialty Structures
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Precast Concrete Oversize Box Structure
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12’ < Clear Span ≤ 20’
Three-sided structure with base slab may
be an acceptable alternate. Consult with
Hydraulics Team for guidance. Run cost
comparison.
If distance from top of structure to top of
pavement is less than 2’, then all top slab
reinforcement should be epoxy coated.
Wingwalls and headwalls required.
Wingwalls and Headwalls
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Information on Plans
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Plan view showing total length of structure,
skew angle, distance from roadway centerline
to each end, and flare angle of wingwalls.
Elevation view of structure including
wingwalls and headwalls. Dimension span,
rise, and height of headwalls.
Wingwalls and Headwalls (Cont.)
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Information on Plans
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Label wingwalls A to D and include a table
with dimensions, elevations, areas for each
wingwall.
Show approximate footing configuration with
typical section through each wingwall. Footing
dimensions should not be shown. Contractor
is responsible for footing design.
Wingwalls and Headwalls (Cont.)
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Information on Plans
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Include a table with soil parameters
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Allowable soil bearing pressure.
Angle of friction between wingwall footings and
foundation soil.
Angle of internal friction of the foundation soil.
Ultimate cohesion of foundation soil.
Ultimate adhesion between foundation soil and
concrete.
Wingwalls and Headwalls (Cont.)
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Information on Plans
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Show conceptual layout for precast concrete
structures or precast wingwalls and headwalls.
Fabricator will design and detail structure after
work is under contract.
For structures > 12’ span, fabricator will
provide design computations and shop
drawings for approval.
Culvert Sumping
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Structure invert elevation and scour
protection placed below the stream
flowline to satisfy IDEM 401 Permit.
Show scour protection limits on plans.
Identify geotextile and riprap quantities
for scour protection in Structure Data
Table. These quantities are not pay
quantities.
Culvert Sumping
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Three-Sided Structure
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18” sump for sand stream bed.
12” sump for other soil type stream bed.
3” sump for rock stream bed.
Pipe or Box Structure
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Refer to Standard Drawings and IDM Figure
31-3B(1).
Structure diameter or rise may need to be
increased if sump exceeds 3”.
Geotechnical Requirements
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Pipe structure replacements require a
geotechnical investigation.
Pipe structures < 36 in. diameter or
pipe extensions < 5 ft may qualify for
geotechnical waiver.
Check with INDOT’s Office of
Geotechnical Engineering.
References
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Standard Specifications
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211.
213.
714.
715.
716.
717.
Structural Backfill
Flowable Backfill
Concrete Box Structures
Pipe Culverts
Trenchless Pipe
Structural Plate Pipe
References (Cont.)
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Indiana Design Manual (IDM)
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Chap.
Chap.
Chap.
Chap.
17.
28.
31.
34.
Quantity Estimating
General Information (Hydraulics)
Culverts
Energy Dissipators
External Dissipator (Example)
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Existing
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66” x 260’ CMP
Ample R/W at Outlet.
Proposed
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HDPE Liner
Vo = 17.15 fps
HY8 to design External Dissipator.
External Dissipator (Example)
External Dissipator (Example)
External Dissipator (Example)
Internal Dissipator (Example)
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Existing
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42” x 295’ CMP
Distance from Outlet to R/W = 6 ft.
Proposed
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HDPE Pipe Liner
Vo = 18.6 fps
No room for External Dissipator
HY8 to design Internal Dissipator
Vo = 9.0 fps (w/Internal Dissipator)
Internal Dissipator (Example)
Internal Dissipator (Example)
Internal Dissipator (Example)
Box Culvert Plans (Example)
Box Culvert Plans (Example)
Box Culvert Plans (Example)
Box Culvert Plans (Example)
Box Culvert Plans (Example)
Box Culvert Plans (Example)
Box Culvert Plans (Example)
Box Culvert Plans (Example)