WHRP Year in Review

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Evaluation of Constructed, Cast-in-Place (CIP)
Piling Properties Project 0092-09-04 Closeout
Presentation/Webinar Presenter Name(s) Devin K.
Harris, Ph.D. Assistant Professor Department of
Civil and Environmental Engineering Michigan
Technological University Co-PI Tess Ahlborn,
Ph.D., P.E. November 3, 2011
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Presentation Outline

• Project Overview and Objectives
• Specimen Fabrication
• Experimental Studies
• Results
• Conclusions/Findings
• Questions and Discussion

3
Project Schedule and Budget

• Project Awarded November 11, 2009
• Draft Final Report Submitted June 30, 2011
• 1 Project Extension (PI due to injury)
• 1 Administrative Extension (WHRP)
• Award Amount 90,000

4
Project Objective

• CIP tubular piles used by WisDOT in bridge and
  retaining wall structures
• Characterize the axial capacity of typical
  (composite, non-composite, and core)
• Investigate the level of composite action between
  the steel shell and concrete core
• Assess the quality of the concrete core resulting
  from the placement method (free-fall)

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Proposed Investigation

• Phase I Literature review
• Phase II Installation site survey
• Phase III Refinement of research plan
• Phase IV Pile fabrication
• Phase V Experimental testing program
• Phase VI Finite element analyses
• Phase VII Report/Presentation

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Literature Review Phase I

• Existing literature yield limited result for CIP
  tubular piles
• Results primarily related to bearing capacity
• Literature primarily centered on tubular sections
  for buildings
• Typically smaller with longer unbraced lengths
• Review of current design methods (State Agencies,
  Design Codes, International)
• Resistance vs. structural capacity based

?
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Pertinent Design Methods

• Axial Compression (Squash Load)
• Elastic/Inelastic buckling
• Tables/Historical Practices

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Design Methods

• Resistance Based
• Not investigated
• Structural Capacity
• Piling
• AASHTO LRFD
• Non-Composite
• Composite

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AASHTO Structural Capacity

• Non-composite design

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AASHTO Structural Capacity, cont.

• Non-composite Design, cont.
• 10 ¾ in. with 3/8 in. wall
• 240 kip
• 10 ¾ in. with ½ in. wall
• 228 kip
• 12 ¾ in. with 3/8 in. wall
• 346 kip

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AASHTO Structural Capacity, cont.

• Composite Design

Filled Tubes Encased Tubes
C1 1.00 0.70
C2 0.85 0.60
C3 0.40 0.20
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WisDOT Approach

• WisDOT LRFD Bridge Design Manual
• 11.3.1.12.2.1 Driven Cast-in-Place Concrete
  Piles
• Designed as reinforced concrete beam-columns, as
  described in LRFD 5.7.4.4 and 6.9.5.2
• For consistency with WisDOT design practice, the
  steel shell is ignored when computing the axial
  structural resistance

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WisDOT Approach contd

• WisDOT LRFD Bridge Design Manual

• Current design
• 75 tons (150k) on 10-3/4 (0.219 wall)
• 105 tons (210k) on 12-3/4 (0.25 wall)
• 125 tons (250k) on 14 (0.25 wall)
• fc limited to 3.5 ksi (F0.75) with no long.
  reinforcement

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Design Methods used by Transportation Agencies
Design Method States
Composite Indiana, Maine, Massachusetts, Nebraska, Nevada, and South Carolina
Non-Composite Florida, Idaho, Missouri, Montana, New Jersey, Pennsylvania and Wisconsin
Tables Alabama, Connecticut, Delaware, Minnesota, North Carolina, Texas, Virginia
Resistance Based Michigan, Ohio, Oregon, Rhode Island, Washington D.C.
Other California (allowable stress), Iowa (pipe piles not allowed)
Not Listed Alaska, Arkansas, Arizona, Colorado, Georgia, Hawaii, Illinois, Kentucky, Maryland, New Hampshire, New Mexico, New York, South Dakota, Tennessee, Vermont, Washington, West Virginia, Wyoming
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AASHTO Structural Capacity contd

• Composite Design, cont.
• 10 ¾ in. with 3/8 in. wall
• 972 kip
• 10 ¾ in. with ½ in. wall
• 1170 kip
• 12 ¾ in. with 3/8 in. wall
• 1234 kip

• Non-composite Design
• 10 ¾ in. with 3/8 in. wall
• 240 kip
• 10 ¾ in. with ½ in. wall
• 228 kip
• 12 ¾ in. with 3/8 in. wall
• 346 kip

Note Wall dimensions based on actual piles used
in the study
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Installation Site Survey Phase II

• Phase eliminated early on due to the challenge
  finding a participating contractor
• WisDOT aligned the project team with a contract
  willing to assist (Pheifer Bros. Construction
  Co.)
• Site selected based on existing project schedule
  (tasks were off the critical path)

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Refinement of Research Plan Phase III

• Research plan finalized in collaboration with
  WHRP TOC Chair
• Focus study on 10-3/4 and 12-3/4 diameter
  tubulars (at least 30 feet long)
• Ensure piles selected satisfied WisDOT
  construction specifications (e.g. minimize welded
  sections)

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Pile Fabrication Phase IV

• Piles driven in parallel with an ongoing new
  bridge construction site near Waupaca, WI.
• 2 nominal pile sizes
• 10-3/4 diameter
• Wall thickness (0.375 and 0.5) seam welded
• 12-3/4 diameter
• Wall thickness (0.375) spiral welded
• Appropriate pile diameters - thicker than
  expected
• Note Contractors allowed to use increased wall
  thickness for ease of driveability

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Pile Driving and Concrete Placement

• On site installation
• Driven 15 ft.
• Caissons for curing
• Companion Cylinders cast
• On-site concrete testing
• 2-3/4 slump
• 5 air content
• 7-day concrete strength
• 4,349 psi

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Pile Driving and Concrete Placement
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Pile Driving and Concrete Placement
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Pile Removal and Transportation

• Piles removed after 8 days of in place curing
  (6-4-10)
• Transported to Michigan Tech Benedict Laboratory
  for Testing
• Specimens stored outside (covered) for 1 month
  (laboratory modifications and pile cutting
  coordination)

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Pile Cutting and Preparation

• Cutting performed by Cutting Edge Services Inc.
• Diamond Wire Saw typical for subsea pipe cutting
• 82 Cuts
• 1-11ft. section
• 2-12in. sections
• 15 to 18-18in. sections
• About 30 min a cut

Hard Drive Video
Weblink to Video
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Final Pile Sections and Intended Use

• 11 ft. Section
• Future flexure testing on 10 ft. clear span
• 12 in. Sections
• Core samples
• 18 in. Sections
• Core Samples
• Whole Section Loading
• Core Loading
• Push-through
• Determined post-cutting

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Final Pile Section/Nomenclature
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Experimental Testing Program Phase V

• Compression Testing
• Testing of the composite section (loading entire
  x-section)
• Testing of core region (loading only core of
  entire x-section)
• Testing of cored sections
• Flexural testing
• Push-through testing

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Compression Testing

• Objective Evaluate the axial capacity of stub
  pile sections. The stub sections were deemed
  representative of the short unbraced lengths of
  embedded piles.

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Experimental Set-ups (Compression)
Coring internal specimens for cored compression
testing
Core centered plates
Full section loading
Core-only section loading
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Compression Testing Results (Whole section)
10-3/4 (1/2 wall)
12-3/4 (3/8 wall)
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Compression Testing Results (Core section)
10-3/4 (1/2 wall)
12-3/4 (3/8 wall)
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Compression Testing Results - Cores
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Flexural Testing

• Objective Evaluate the composite action between
  the steel shell and concrete core.
• Bond difficult to assess from an external
  perspective, but a change in linearity of strain
  distribution and slip would indicate loss of bond.

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Experimental Set-ups (Flexure)
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Flexural Testing - Results
Strain vs. load (all gauges) for (10-3/4
0.375 wall) Pile 1
Strain vs. load through cross-section depth
(10-3/4 0.375 wall) Pile 1

• Results did not provide a direct measure of bond
  strength, but demonstrated that the bond
  integrity is greater than the cracking strength
  of the composite section, as no slip was observed
  throughout the testing

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Push-through Testing

• Objective Evaluate the bond capacity in direct
  shear. Stub sections intended for compression
  testing were used for the push-through tests.

Push-through loading
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Experimental Set-ups (Push-through)
Failure mechanism
Test configuration
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Push-through testing
Seam welded
Spiral welded
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Push-through testing

• Measured bond stress (0.29 0.53 ksi)
• Literature 0.2 2.0 ksi (concrete to rebar)

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Finite Element Modeling Phase VI

• Specimen models
• Compression specimens (Loading entire
  cross-section and Loading core only)
• Embedded pile model
• Variations in soil constraint conditions
• Limited to validation range of experimental
  program
• Models developed using ANSYS Commercial FEA
  software
• Solid element models with full composite behavior

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Finite Element Model Specimen Comparison

• L/D expected to yield fully plastic response
  rather than elastic buckling
• Models limited to linear elastic region
• Loading applied proportional to stiffness for
  uniform stress distribution (displacement-controll
  ed)
• Boundary conditions selected to ensure pure
  compression

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Finite Element Model Specimen Comparison
10-3/4 (1/2 wall)
12-3/4 (3/8 wall)
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Finite Element Model In-Service Behavior
(Embedded in Soil)

• End of pile assumed fixed due to bedrock
• Contributions from vertical compaction, shear
  distortion, and lateral compaction
• Soil response model as a series of discrete
  springs with equivalent stiffnesses
• Loose sandy soil, compact sandy soil, loose
  gravel soil, and compact gravel soil
• Loading limited to 1,000 kips based on testing

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Finite Element Model In-Service Behavior
(Embedded in Soil)
10-3/4 (1/2 wall)
12-3/4 (3/8 wall)

• Soil contribution matched stub section response

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Findings and Recommendations

• No compression failures were observed in the
  compression test specimens (no buckling,
  squashing)
• True measure of axial capacity was not determined
  (limited to 1,000k frame capacity)
• Specimens all exhibited capacities above 1,000 k
  (lower bound) gt WisDOT design capacities
  (189-317)
• Non-linear response was observed in small
  specimens, but not failure
• Previous studies indicated that typical failure
  mode should be squash failure

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Findings and Recommendations

• Loading mechanism has an influence on the
  behavior of the pile
• Loading the entire x-section, as would be
  expected in-service yielded larger axial strain
  in the shell (more stiff than core-only loading
  scenario)
• Loading only the core section of the x-section
  resulted in a delay in load sharing between the
  section components
• Geometric non-linearities in cut sections
  resulted in inconsistencies between experimental
  and finite element model results
• Finite element mode demonstrated that in-service
  conditions similar to stub section

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Findings and Recommendations

• All of the core concrete appear to be well
  consolidated and relatively uniform and free of
  voids
• Assessment based on visual observation of cored
  specimens and cut ends of sections
• Core compressive strength ranged from 6,000-9,400
  psi vs. in-situ strength of companion cylinders
  of 7,600 psi.
• Failure of some specimens during coring observed,
  but attributed to typical core extraction failure
  (based on successful removal of surrounding core
  samples).
• Flexural testing results did not provide a direct
  measure of bond strength, but demonstrated that
  the bond integrity gt cracking strength of the
  composite section

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Findings and Recommendations

• Current WisDOT practices is overly conservative
  with respect to the axial capacity
• Uncertainty still remains with respect to
  long-term durability of steel shell (function of
  down-hole conditions )
• Bond is comparable to other steel/concrete
  composite systems
• Core concrete is well consolidated using current
  placement methods.

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Questions and Discussion

• Contact Information
• Devin K. Harris, Ph.D.
• Assistant Professor
• Department of Civil and Environmental Engineering
• Michigan Technological University
• dharris_at_mtu.edu

Thank you for your attention