This document summarizes the predesign and construction phase load testing programs for the 5.2 mile Croatan Bridge project in North Carolina. Key points: - Predesign testing in 1997 obtained soil parameters and tested test piles to inform the bridge design. Dynamic and static load tests were performed on square and cylinder test piles. - Construction phase testing from 1998-2000 involved 25 dynamic load tests to determine pile order lengths for the 2,368 production piles based on a test pile. Static tests were also performed. - Load testing resulted in estimated savings of $1.4 million from reduced pile lengths and a more efficient design. Pile capacities and driving criteria were established to ensure design requirements were met.

1. CCROATANROATAN SSOUNDOUND BBRIDGERIDGE
Predesign and Construction
Phase Load Test Programs
Geotechnical Engineering Unit
NCDOT
By: John Fargher

2. 5.2 Mile Bridge
Water Depth is 10 Feet (typical)
Scour Ranges from 12 to 30 Feet
Bridge Types
Conventional (267 Interior Bents)
Segmental (174 Interior Bents)
Trestle Bents and Footing on Pile Bents
Pile Types
24 inch Square PPC Piles
30 inch Square PPC Piles
54 inch Diameter PPC Cylinder Piles
AASHTO and Vessel Impact Loadings
Project Details and
Design Parameters
Project Location
and Alignment

3. Predesign Load Test Program (1997)Predesign Load Test Program (1997)
StrategyStrategy
Obtain soil design parameters for modeling lateral stability,Obtain soil design parameters for modeling lateral stability,
bearing capacity, and pile driveability. During construction,bearing capacity, and pile driveability. During construction,
pile order lengths and driving criteria would be set bypile order lengths and driving criteria would be set by
performing dynamic load tests (PDA’s) on production piles.performing dynamic load tests (PDA’s) on production piles.
Load TestsLoad Tests
Pile Driving Analyzer (PDA)Pile Driving Analyzer (PDA)
Axial Static Load Test (Conventional)Axial Static Load Test (Conventional)
Lateral Load Test (Conventional)Lateral Load Test (Conventional)
Test PilesTest Piles
Pile #1 - 95 Feet - 30 inch Square PPC PilePile #1 - 95 Feet - 30 inch Square PPC Pile
Pile #2 - 125 Feet - 30 inch Square PPC PilePile #2 - 125 Feet - 30 inch Square PPC Pile
Pile #3 - 144 Feet - 54 inch Cylinder PPC PilePile #3 - 144 Feet - 54 inch Cylinder PPC Pile
Pile #4 - 144 Feet - 54 inch Cylinder PPC PilePile #4 - 144 Feet - 54 inch Cylinder PPC Pile
CostCost - $998,000 (Bid)- $998,000 (Bid)
SavingsSavings - $1,800,000 (Estimated)- $1,800,000 (Estimated)

4. Cylinder Pile Installation
Purpose - Evaluate Pile Driveability, Jetting, and
Set-up of Large Cylinder Piles at the Project Site
30 inch Square Pile Alternate was Selected by Bid 54 inch Square Pile

5. Pile Plunged at 250 tons (FS=1)…No Good
Virtually No Set-up or Pile “Freeze”
30 inch Square Pile
Axial Static Load Test
Unique Reaction Frame

6. Structurally Failed
54 Inch Cylinder Pile
Design Capacities
(Allowable)
24 inch Square Piles - 150 Tons
30 inch Square Piles - 250 Tons
54 inch Cylinder Piles - 500 Tons
Pile Broke at 1500 Tons…FS=3
WOW!!!

7. 30 inch Square Piles
Lateral Test Load - 19.5 Tons
Deflection - 13 inches
Purpose - Determine Lateral Soil Parameters of “Muck” Layer
Lateral Load Test

8. Florida Pier Model -Transverse Vessel
Impact Loading of 60 Pile Bent
Outcome of Lateral Load Test
 “Muck” Layer was an Order of Magnitude Stiffer Laterally than Predicted
 Reduction in Pile Embedment Required for Fixity
 Reduced the Number of Piles
Model Used to Determine:
Pile Group is Fixed
Minimum Tip Elevation
Inputs:
Loads
Structural Parameters
Soil Parameters
Check:
Stability
Moments, Shears, Deflections
Bearing and Pull-out

9. Construction Phase Load Test ProgramConstruction Phase Load Test Program
(1998 to 2000)(1998 to 2000)
25 - Dynamic Load Tests (PDA’s)25 - Dynamic Load Tests (PDA’s)
Tip Elevation Must Be Greater than Min. Tip El. Required For FixityTip Elevation Must Be Greater than Min. Tip El. Required For Fixity
No Pile Splicing of Concrete Piles AllowedNo Pile Splicing of Concrete Piles Allowed
3 foot Maximum Build-ups3 foot Maximum Build-ups
Cut-Offs Greater than 6 feet Require Drilling for DowelsCut-Offs Greater than 6 feet Require Drilling for Dowels
Fuel Setting and Stroke AdjustmentsFuel Setting and Stroke Adjustments
Tensile Stress Problems EncounteredTensile Stress Problems Encountered
1 - Axial Static Load Test (Conventional)1 - Axial Static Load Test (Conventional)
To insure that pile lengths are reduced in these regionsTo insure that pile lengths are reduced in these regions
To be performed prior to giving Order Lengths for 57 bentsTo be performed prior to giving Order Lengths for 57 bents
To Determine Pile Order Lengths for 2368 PilesTo Determine Pile Order Lengths for 2368 Piles
To Control Pile Driving (Quality Control)To Control Pile Driving (Quality Control)

10. For Each Blow it Records:
Compressive and Tensile Stresses
Energy in the Pile
Damage to the Pile
Computer that is
Attached to the Pile by
means of Strain Gages
and Accelerometers.
It Predicts:
Capacity (Skin and Total)
Hammer Stroke
Pile Driving Analyzer (PDA)
The PDA is Used to
Monitor and Control
Pile Driving

11. Determined Based on a PDA Test PileDetermined Based on a PDA Test Pile
To Reduce Pile Lengths andTo Reduce Pile Lengths and
Achieve Minimum Tip Elevation and BearingAchieve Minimum Tip Elevation and Bearing
PDA’s Performed Adjacent to BoringsPDA’s Performed Adjacent to Borings
Each PDA May Represent between 36 to 258 PilesEach PDA May Represent between 36 to 258 Piles
PDA Sequence is Contractors’ OptionPDA Sequence is Contractors’ Option
With Each Successive PDA there is a Learning CurveWith Each Successive PDA there is a Learning Curve
The 2 Curves have 3 feet of Super ElevationThe 2 Curves have 3 feet of Super Elevation
Trestle Bents have Battered Leading and Trailing PilesTrestle Bents have Battered Leading and Trailing Piles
PDA Test PilesPDA Test Piles
Pile Order Lengths
Considerations:Considerations:
Goal -Goal -

12. Axial Static Load Test
30 inch Square Pile
Purpose - Shorten 410 piles 10 meters each
Cost $170,000
Savings $643,864

13. Construction Load Test Savings
Estimated Savings = $1.4 Million (from Pile Length Reduction Only)
# Piles Order Lengths Reduction # Piles Order Lengths Reduction
PDA #1 66 32 to 35 m 0 m PDA #14 258 40 to 41 m 0 m
PDA #2 36 35 m 0 m PDA #15 52 36 m 4 m
PDA #3 42 41 m 6 m PDA #16 84 36 m 4 m
PDA #4 77 41 m 2 to 5 m PDA #17 130 34 to 32 m 10 m *
PDA #5 91 40 to 41 m 7 to 10 m PDA #18 84 31 to 32 m 10 m *
PDA #6 119 39 m 4 to 10 m PDA #19 119 32 to 34 m 10 m *
PDA #7 112 39 m 0 to 2 m PDA #20 77 34 m 10 m *
PDA #8 49 38 m 1 to 2 m PDA #21 77 43 m 0 to 3 m
PDA #9 63 42 to 44 m 0 m PDA #22 154 43 to 44 m 0 to 1 m
PDA #10 70 39 m 5 m PDA #23 91 39 to 41 m 0 to 3 m
PDA #11 108 35 m 4 to 6 m PDA #24 85 40 to 41 m 0 m
PDA #12 70 35 m 7 m PDA #25 42 36 m 1 m
PDA #13 216 41 to 42 m 0 m * Based on Static Load Test

14. Hammer
Adjustments
Delmag D100-13 (Diesel)
4 Fuel Settings
Conmaco 300E5 (Air)
2 Stroke Settings
Hammers Currently in Use
Proposed Hammers
Delmag D80-13 (Diesel)
4 Fuel Settings
ICE 205S (Diesel)
Variable Stroke Settings

15. NCDOT’s Experience with Predesign Load Testing
TR NEWS Sept/Oct 1999 Issue
Research Pays Off Article
Condensed Version
By: John Fargher, Nariman Abar, Jamey Batts, Brian Keaney, and Sean Byrne
Transportation Research
Record No. 1663

16. For additional information contact: jfargher@dot.state.nc.us