1. Innovation
Extending Cast-In-Place Box Culverts
With
Precast Box Culverts
ADOT Tucson District
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2. WHY PRECAST ?
Anticipated future improvements of transportation
system
• Upgrades
• Widening current roadways
Increased capacity
Safety improvements
Less impact to traveling public during construction
Improvements of internal costs for construction through
work zone efficiency
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3. Innovative
Construction Methods
Precast concrete pipes
Implemented use of precast items
• AASHTO Girders
• Concrete Barrier
• MSE Wall Panels
• Cattle Guards
• Catch Basins
• Manholes
Precast box culverts
• Accelerates construction schedule
• Reduces work zone exposure to traveling public and workers
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4. Recent Projects with
Precast CBCs
SR 79, MP 124.1 to 127.4 (Constructed)
• First Tucson District Project with Precast Box Culverts
SR 86, Brawley Wash to MP 141 (Constructed)
SR 86, MP 141 to Reservation Boundary (Constructed)
I-10, Val Vista Road to Earley Road (Parsons Brinckerhoff)
(Under Construction)
SR 86, San Pedro Segment (Under Construction)
SR 86, Kitt Peak (Kimley-Horn) (Stage IV)
SR 86, Santa Rosa Segment (Stage IV)
SR 86, Fresnal to Sells (Stage II)
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5. Projects
SR 79, MP 124.1 to 125.7
James Gomes, ADOT R.E.
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6. SR 79, MP 124.1 to 125.7
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7. SR 79, MP 124.1 to 125.7
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8. SR 79, MP 124.1 to 125.7
Contract Documents
• Special Provisions
• Project specific requirements
• Project Plans
• Locations
• Details
• Standard Drawings
• B-Standards
• C-Standards
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9. SR 79, MP 124.1 to 125.7
Pre-Cast RCBC Submittal
• Manufacturer through Contractor
• ADOT Bridge Group
• ADOT Review & Approval
Production
• Prepare formwork
• Fabrication
• Materials Group – Oversight and Inspection
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10. SR 79, MP 124.1 to 125.7
Project Site Preparation
• Traffic Control
• RCBC Wingwall and Headwall Removal
• Structural Excavation
• Bedding Material
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11. SR 79, MP 124.1 to 125.7
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12. SR 79, MP 124.1 to 125.7
Installation
• Delivery and Inspection
• Survey
• Crane Location
• Alignment and Installation
• Finish Work
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13. SR 79, MP 124.1 to 125.7
Installation
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14. SR 79, MP 124.1 to 125.7
Installation
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15. SR 79, MP 124.1 to 125.7
Installation
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16. SR 79, MP 124.1 to 125.7
Installation
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17. SR 79, MP 124.1 to 125.7
Installation
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18. SR 79, MP 124.1 to 125.7
Closure Pour
• Approved Concrete Mix
• Reinforcement
• Formwork
• Constructability Issues
o Rebar Clearances
o Formwork
o Concrete Clearances
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19. Reinforcement
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20. Constructability
“Formwork”
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21. Constructability
“Concrete Placement”
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22. SR 79, MP 124.1 to 125.7
Backfill and Clean-up
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23. Lessons Learned
Benefits Drawbacks
Reduced Durations Closure Pour
• Work Zone Hazard Constructability
• Traffic Control Costs Need for Standardization
• QA Inspection Time
Less Impacts to Public
Higher Strength Material
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24. Next Project
I-10, Val Vista Road to Earley Road
Greg Bambauer, Parsons Brinckerhoff
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25. I-10, Val Vista Road to
Earley Road
Nine-mile interim widening project
A total of 44 cross-drainage structures
• 24 box culvert extensions
o 6-Single Cells
o 6-Double Cells
o 8-Triple Cells
o 1-Four Cell
o 1-Five Cell
o 1-Six Cell
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26. I-10, Val Vista Road to
Earley Road
Discussions with District identified design criteria
• Limit precast extensions to 3-cells or less
• Minimize closure pour
o Preference to 1-foot
• PB structural engineers designed the closure pour
and the cast-in-place end section
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27. I-10, Val Vista Road to
Earley Road
3-Cell Closure
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28. I-10, Val Vista Road to
Earley Road
3-Cell Closure
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29. I-10, Val Vista Road to
Earley Road
CIP closure and end Section
• No standard available
• Many precast options: choice is difficult
o Need to design a generic closure and end section
• District provided previous design for closure pour
• PB reviewed and revised slightly to achieve
enhanced strength
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30. I-10, Val Vista Road to
Earley Road
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31. I-10, Val Vista Road to
Earley Road
Construction Award
• Manufacturer Submitted Shop Drawings for Review
• Identified Large Bevels at Base of Precast Section
o Concerns
 Hydraulics
 Transition to CIP is Abrupt
 Potential Debris Collection
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32. Hydraulics
Haunches Abrupt Transition
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33. I-10, Val Vista Road to
Earley Road
Concerns
• Hydraulics
o Conducted a simplified HECRAS analysis
for low flows through Structure
o Found minor increases in headwater
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34. I-10, Val Vista Road to Earley
Road Change In Headloss
Hydraulics ∆hL=0.10'
12.0% ∆hL=0.10'
• Single 10’x4’ CBC
• Varied discharge 10.0% ∆hL=0.07'
∆hL=0.04'
• Compared 8.0%
∆hL=0.03'
Increase (%)
∆hL=0.02'
o Standard CIP 6.0% ∆hL=0.04'
∆hL=0.01'
o Precast with abrupt
4.0%
and smooth
transition 2.0%
0.0%
50 100 150 200
Flow Rates (cfs)
Standard Coefficients
Smooth: 0.1 Contraction and 0.3 Expansion
Abrupt: 0.3 Contraction and 0.5 Expansion
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35. I-10, Val Vista Road to
Earley Road
Concerns, con’t
• Potential Debris Collection
o Transition to CIP End section to precast section is abrupt
o Revised detail to provide smoothing within the closure and CIP
end section to mitigate clogging & enhance performance
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36. I-10, Val Vista Road to
Earley Road
Revised Detail for Smoothing
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37. I-10, Val Vista Road to
Earley Road
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38. Next Project
SR 86, Kitt Peak Segment
Rick Solis, Kimley-Horn
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39. SR 86, Kitt Peak Segment
PROJECT BACKGROUND
4.3 Mile Roadway Widening Project
Purpose to improve Safety and Operational
Characteristics
Rural Roadway Located Approx. 30 miles Southwest of
Tucson and within the Tohono O'odham Nation
44 Total Cross Drainage Structures
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40. SR 86, Kitt Peak Segment
General Considerations
• Number of barrels
• Existing skew vs. extension skew
o Design the extension to the flow-line path
o Hydraulic limitation
• Field measure existing CBC wall thickness
• Utilize AASHTO guidelines for precast unit dimensions
• Design extension to clear zone with 1-foot holdback
• Determine the required closure pour width (2-foot minimum)
• Duration of closure
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41. SR 86, Kitt Peak Segment
Closure-pour and end section design considerations
• Minimum closure length: 2-foot
o Allows for a transition between existing CBC and precast CBC
o Allows for development of edge beam
o Constructability is driving the minimum closure length
• Closure-pour transition rate
o 2:1 maximum
• Precast extensions are designed with 1-foot holdback
o Allows for development of edge beam incorporated into CIP
headwalls and wing walls
o Allows for construction of haunch transitions and wedge transition
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42. SR 86, Kitt Peak Segment
Closure pour and end section
design considerations, cont’d
• AASHTO standards include
haunches at all four corners
• Haunches require transitions at the
bottom of the corners within the
closure and end section
• Some precast companies in Arizona
do not have forms for the AASHTO
standard
• Review shop drawings for
concurrence with AASHTO
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43. SR 86 Kitt Peak Segment
Moving Beyond the Old 3-Cell Limit for Extensions
• Consultation with Local Contractors
• 4-Cell Box Culvert Extension Using Precast Box Culverts
o Resulting 3-foot Closure Pour
• 8-Cell Extension Using Precast Box Culverts
o Resulting 6-ft Closure Pour
• Project is expected to Bid April 2012
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44. 8-Cell Box Extension
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45. Further Evaluation
Cost / Benefit
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46. Cost - Benefit Analysis
Acceleration of construction
• Reduced Work Zone Exposure
• Reduced Impact to Traffic
• Reduced Inspection Time
Higher Strength Material
Reduced Material Waste (Concrete, Forms, etc…)
Partnering Between ADOT, Contractors and material suppliers
improves construction efficiency and reduces Public Expenditures
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47. Precast verses Cast-In-Place
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48. Maintenance and Protection
of Traffic (MPT)
MPT costs include traffic control devices
Cost can vary
Shorter schedules reduce MPT costs
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49. User Costs
User costs through the traffic control factor
• Travel delays as a result of speed limit reductions
• Queues as a result of lane capacity reductions
• Travel time for use of detours
• Delays from flagging operations
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50. Compare MPT and User Costs
Precast verses Cast-In-Place
Determine MPT Costs:
• Determine a traffic control plan
• Quantify traffic control items
• Estimate duration for Precast and for Cast-In-Place
• Summarize MPT costs for Precast and Cast-In-Place
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51. Compare MPT and User Costs
Precast verses Cast-In-Place
Determine User Cost Approach
• FHWA has outline of user cost and considerations
• NJDOT has developed Road User Cost Manual
with worksheets for quantifying costs
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52. Compare MPT and User Costs
Precast verses Cast-In-Place
Compare Costs
• Total MPT, User Costs, Construction Costs
o Precast
o Cast-In-Place
• Compare cost differential
• Evaluate the overall benefits/costs
o Are costs worth the savings?
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53. Compare MPT and User Costs
Precast verses Cast-In-Place
Example – SR 79 Culvert Extension
• MPT Costs - Typical flagging MPT plan
o Includes: Vertical Panels, Portable Sign Stands,
Type A and C Warning Lights, Signs, and Flagging Services
o Duration Estimated: 250 Days for Precast
330 Days for Cast-In-Place
o MPT costs estimated: $76,000 – Precast
$104,000 – Cast-In-Place
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54. Compare MPT and User Costs
Precast verses Cast-In-Place
Example – SR 79 Culvert Extension
• User Costs – Using NJDOT Spreadsheets
o SR 79, 2-lane roadway, 3000 ADT
o No anticipated queues from MPT plan
o No detour delays
o Travel delay in reducing speed from 65 to 35 mph
through work zone
o Calculated Road User Costs factoring CPI: $800/day
o Estimated User Cost: $200,000 – Precast
$264,000 – Cast-In-Place
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55. Compare MPT and User Costs
Precast verses Cast-In-Place
Example – SR 79 Culvert Extension
Cost Comparison
MPT User Construction Total
Precast $76,000 $200,000 $483,000 $759,000
Cast-In-Place $104,000 $264,000 $480,000 $848,000
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56. Other Costs
Work Zone Exposure
Client Internal Costs
• Inspector Time
• Certificate Processing
Contractor Overhead
• Move to next project sooner
Efficiency Leads to Cost Saving
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57. FUTURE
Todd Emery, ADOT Tucson District Engineer
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58. FUTURE
Precast Transition/Connection
• Alternative Connection Options
Precast Wingwalls
Standardization of Precast Box Culverts
• ADOT Bridge Group
Other Precast Elements
• Bridge Substructure
• Bridge Decks
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59. QUESTIONS
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