John C. Ryan, Ph.D., P.E.

Ryan Structural Engineers

Mt. Pleasant, SC

Design, Testing, and Use of an Innovative Prestress Concrete Pile Joint

• Handling equipment relatively large• Special permit loads• Escort requirements

Long Pile Handling

Driving Long Piles

Pile Installation

-2 Cranes-Power Pak /Air Compressor-Hammer and Leads-5 or 6-man crew

-Difficult Handling-Fuel for 3-Large Engines-Maintenance of 3 Machines

& Hammer

Up to 65 ft-long pile segments:

(4

Fork-truck and spreaderfor unloading & staging

Spliced-Pile Alternative

Spliced-Pile Alternative

110-ft Spliced Pre-stress Pile:

-Purpose-built driving rig-2-man crew

-Reduced Fuel Cost-Reduced Transportation Cost-Reduced Maintenance-High Production Rate-Increased Job Site Safety

Emeca Pile Joint

Male Stud

Female Socket

Locking pin hole

Cover Plate

Reinforcing

Emeca Pile Joint

Automated Robotic Fabrication

Tension

Limit States 3. & 7.: Weld rupture at reinforcing/locking mechanism interface

Note: Welds are designed to develop reinforcing

Butt-Joint at female socket

Lap-Joint at Male Stud

Structural Analysis

1. Develop loads to be transferred across splice

- L-pile analysis (bending, shear)- Driving stresses (compression, tension)- Structural uplift requirements (tension)

2. Provide splice that adequately transfers:

- Compression

- Shear

- Tension

- Bending

Compression

Compression is transferred directly through bearing of

faying surfaces

Assembly Diagram of Emeca Joint

Shear

• Shear capacity is typically controlled by the shear capacity of the reinforced concrete section

• Shear capacity at the splice is based on shear yield mechanical fixture:

Shear failure plane

Tension

Tensile Limit States

1.&9. Transfer tensile force from prestress to mild reinforcing

2.&8. Tensile yield of mild reinforcing

3. Weld rupture at female socket

4. Tensile rupture of female socket

5. Shear rupture of pin

6. Tensile rupture male stud

7. Weld rupture at male stud

Tension

Limit States 1 & 2:

CASE 2: Lembed. < Ld for strand:

* Bond Limit (Strand)

OR

Mild Reinforcing Steel Limit * Ref: ACI 12.9.1

CASE 1: Lembed. ≥ Ld for strand:

Rupture Limit (Strand)

OR

Mild Reinforcing Steel Limit

Tension

In General:

When mechanical joining mechanism are designed to develop reinforcing:

(1) strand slip,

(2) strand rupture OR

(3) yield of reinforcing will control over all tensile limit states

Auxiliary Reinforcing

Auxiliary Reinforcing

Auxiliary Reinforcing

Tension

Summary:

• Welds and locking mechanisms develop reinforcing

• Controlling Limit States:

(1) Strand slip (2) Strand Rupture, or (3) Yield of Reinforcing

• With Auxiliary Reinforcing, (1) Strand Slip will NOT control

• The limits states of the tension component of the bending couple are analogous

Bending Analysis at Joint

Critical Sections:

S2-Prestress Section

S1-Section at Joint

Bending Analysis at Joint

S1- Reinforced Section (12-in. pile)

Bending Analysis at Joint

S1- Reinforced Section (12-in. pile)

Mn = 41.7 ft-k

Bending Analysis at Joint

max. stress in strand = fps = 173 ksi

S2- Prestress Section (12-in. pile)

Bending Analysis at Joint

S2- Prestress Section (12-in. pile)

PCI Figure 4.12.4 (p. 4-122)

30 in.

173 ksi

Bending Analysis at Joint

fps = 173 ksi Mn = 33.5 ft-k

S2- Prestress Section (12-in. pile)

Analysis at Joint

Summary:

12-in. Pile Splice

14-in. Pile Splice

Limit

Tension - Tn 95.6 kips 150 kips Yield of Mild Reinforcing

Bending - Mn 33.5 ft-kips 55.2 ft-kips Strand Slip

reinforcing added - Mn

41.5 ft-kips 73.7 ft-kips Yield of Mild Reinforcing

Shear - Vn 19.0 kips 26.4 kips Shear Capacity of Pile

Unreduced Capacities of Pile at Joint

Interaction of 12-inch Piles vs. Emeca Joint

Cross Section

Interaction of 14-inch Piles vs. Emeca Joint

Cross Section

Bending Tests – University of South Carolina

Test Set-up:

Recorded Data:- Load- Displacement at ¼ points- Rotation at Joint

Loading Protocol:- Quasi-static loading

Bending Tests – University of South Carolina

Test Specimens (12 Total):

I. Splice only

(6) 28-ft. long piles, spliced at midpoint

(3) 14-in. Specimens (6 strand) (3) 12-in. Specimens (4 strand)

II. Splices with “Auxiliary Reinforcing”

(6) 28-ft. long piles, spliced at midpoint

(3) 14-in. Specimens (6 strand) (3) 12-in. Specimens (4 strand)

Auxiliary reinforcing – (4) #5’s x 60”

Bending Tests

Results:

Failure Mode 1:

-Exhibited by all Type I Specimens

-Characterized by strand slip at critical bending section (S2)

Failure Mode 2:

-Exhibited by all Type II Specimens

-Characterized by rupture of mild reinforcing at critical section (S1)

Bending Tests

Moment Strength Results (ft-kips):

Theoretical Test Results Mean Low

Mn Mn′ Mean Low Mn′ Mn′

Splice Only12 in. 37 47 53.6 52.7 114% 111%

14 in. 61 79 85.4 77 108% 97%

Auxiliary Reinforcing

Added

12 in. 37 53 63 59.7 119% 112%

14 in. 67 93 99.3 90.5 107% 97%

Mn′ –Calculated theoretical moment using tested material strength:

Fy = 73 ksi fc′ = 7,000 psi

Recommendations for Use

1. SDC C: Pile joints must be located > 20 ft below pile cap

2. SDC D, E, and F: Pile joints must be located outside of the “ductile-zone” in defined in IBC 1809.2.3 (35 ft below pile cap, minimum)

3. Mn (joint) > 50% Mn (pile)

4. Minimum 28-day compressive strength of concrete = 6,000 psi

5. Design strength of pile at the splice can be determined using:

- Strain compatibility, and- Standard ACI development length formulation (for prestress & mild reinforcing)

General:

Vitol Oil - Port Canaveral, FL• 6,300 - 100-ft spliced piles• Spliced pile solution saved $10M+• 30%-35% cost savings to project

Emeca Pile Joint PDCA National Project of the Year, 2008

Casting Splices

Casting the Emeca Pile Joint:

• Casting guides used to square and center joints in piles• Proper production fit-up between any two piles is facilitated with use of casting guides

Casting Splices

Piles removal from forms:• Pile handling efficiency greatly improved• Removal can be done with small machines

Casting Splices

Piles stored after casting:• No match-casting• Any two piles can be spliced

Casting Splices

Preparation after casting:•Strands ground flush •Square end verified

Installation

Production:• 30 – 100 ft. long spliced piles / rig / day• 2 men per rig

Installation

Pile Splicing in the Field:• Precision fabrication facilitates proper fit-up• Splicing piles takes 3-5 minutes

Projects

Owner: Vitol Oil CompanyContractor: Sun MarineProject Status: CompleteEmeca Product: 12-in. Pile JointsNotes: 6300, 100-ft-long piles installed

Vitol Oil Tank Farm, Seaport Canaveral, FL

Projects

Owner: Northrup GrummanContractor: Ford Pile FoundationsProject Status: ActiveEmeca Product: 12-in. Pile JointsNotes: Piles and splices designed to resist hydrostatic tension

Northrup Grumman Naval Shipyard - Dry Dock Facility, Newport News, VA

Projects

Contractor: Junttapojat OyEmeca Product: 14-in. Pile JointsNotes: - 8000 Emeca Pile Joints used on project - 656,000 total pile length - Up to 105 foot long piles driven in 3 sections - Battered piles driven at 4V:1H

Vousaari Harbor Project for the Port of Helsinki, Helsinki, Finland

Projects

Contractor: Aarsleff PilingStatus: CompleteEmeca Product: 16-in. Pile JointsNotes: 50 wind turbine foundations constructed using 85-ft-long,16-in. spliced piles

Wind Farm, Ransonmoor, Finland

Projects

Contractor: Kiewit ConstructionProject Status: ActiveEmeca Product: 14-in. Rock Points customized for 30-in.-square concrete piles Notes: Piles driven through concrete mooring anchors at approximately 30-ft.

Brayton Point Cooling Tower, Summerset, MA

Projects

Anacostia Naval Station Drainage Phase IV, Washington, DC

Owner: NAVFACProject Status: Completed August 2008General Contractor: Corinthian ContractorsPile Contractor: Coastal Pile Driving, Inc.Property Manager: Whiting-Turner ContractingProduct: 12-in. Pile JointsNotes: Up to 83-ft-long spliced piles