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 ProfessorDepartment of Civil and Environmental Engineering Michigan Technological University

Co-PI: Tess Ahlborn, Ph.D., P.E.

November 3, 2011

Presentation OutlineProject Overview and ObjectivesSpecimen FabricationExperimental StudiesResultsConclusions/FindingsQuestions and Discussion

Project Schedule and BudgetProject Awarded: November 11, 2009Draft Final Report Submitted: June 30, 20111 Project Extension (PI due to injury)1 Administrative Extension (WHRP)Award Amount: $90,000

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

Proposed InvestigationPhase I Literature reviewPhase II Installation site surveyPhase III Refinement of research planPhase IV Pile fabricationPhase V Experimental testing programPhase VI Finite element analysesPhase VII Report/Presentation

Literature Review Phase IExisting literature yield limited result for CIP tubular pilesResults primarily related to bearing capacityLiterature primarily centered on tubular sections for buildingsTypically smaller with longer unbraced lengthsReview of current design methods (State Agencies, Design Codes, International)Resistance vs. structural capacity based

Pertinent Design MethodsAxial Compression (Squash Load)Elastic/Inelastic bucklingTables/Historical Practices

Design MethodsResistance BasedNot investigatedStructural CapacityPilingAASHTO LRFDNon-CompositeComposite

AASHTO Structural CapacityNon-composite design

AASHTO Structural Capacity, cont.Non-composite Design, cont.10 in. with 3/8 in. wall240 kip10 in. with in. wall228 kip12 in. with 3/8 in. wall346 kip

AASHTO Structural Capacity, cont.Composite Design

Filled TubesEncased TubesC11.000.70C20.850.60C30.400.20

WisDOT ApproachWisDOT LRFD Bridge Design Manual11.3.1.12.2.1 Driven Cast-in-Place Concrete PilesDesigned 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

WisDOT Approach contdWisDOT LRFD Bridge Design ManualCurrent design75 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 (=0.75) with no long. reinforcement

Design Methods used by Transportation Agencies

Design Method States CompositeIndiana, Maine, Massachusetts, Nebraska, Nevada, and South CarolinaNon-CompositeFlorida, Idaho, Missouri, Montana, New Jersey, Pennsylvania and WisconsinTablesAlabama, Connecticut, Delaware, Minnesota, North Carolina, Texas, VirginiaResistance BasedMichigan, Ohio, Oregon, Rhode Island, Washington D.C.OtherCalifornia (allowable stress), Iowa (pipe piles not allowed)Not ListedAlaska, Arkansas, Arizona, Colorado, Georgia, Hawaii, Illinois, Kentucky, Maryland, New Hampshire, New Mexico, New York, South Dakota, Tennessee, Vermont, Washington, West Virginia, Wyoming

AASHTO Structural Capacity* contdComposite Design, cont.10 in. with 3/8 in. wall972 kip10 in. with in. wall1170 kip12 in. with 3/8 in. wall1234 kip

Non-composite Design10 in. with 3/8 in. wall240 kip10 in. with in. wall228 kip12 in. with 3/8 in. wall346 kip

Note: Wall dimensions based on actual piles used in the study

Installation Site Survey Phase IIPhase eliminated early on due to the challenge finding a participating contractorWisDOT 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)

Refinement of Research Plan Phase IIIResearch plan finalized in collaboration with WHRP TOC ChairFocus 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)

Pile Fabrication Phase IVPiles driven in parallel with an ongoing new bridge construction site near Waupaca, WI.2 nominal pile sizes10-3/4 diameterWall thickness (0.375 and 0.5) seam welded12-3/4 diameterWall thickness (0.375) spiral weldedAppropriate pile diameters - thicker than expected**Note: Contractors allowed to use increased wall thickness for ease of driveability

Pile Driving and Concrete PlacementOn site installationDriven ~15 ft.Caissons for curingCompanion Cylinders castOn-site concrete testing2-3/4 slump5% air content7-day concrete strength4,349 psi

Pile Driving and Concrete Placement

Pile Driving and Concrete Placement

Pile Removal and TransportationPiles removed after 8 days of in place curing (6-4-10)Transported to Michigan Tech Benedict Laboratory for TestingSpecimens stored outside (covered) for ~1 month (laboratory modifications and pile cutting coordination)

Pile Cutting and PreparationCutting performed by Cutting Edge Services Inc.Diamond Wire Saw typical for subsea pipe cutting 82 Cuts1-11ft. section2-12in. sections15 to 18-18in. sectionsAbout 30 min a cut

Weblink to VideoHard Drive Video

Final Pile Sections and Intended Use11 ft. SectionFuture flexure testing on 10 ft. clear span12 in. SectionsCore samples18 in. SectionsCore SamplesWhole Section LoadingCore LoadingPush-through*

* Determined post-cutting

Final Pile Section/Nomenclature

Experimental Testing Program Phase VCompression TestingTesting of the composite section (loading entire x-section)Testing of core region (loading only core of entire x-section)Testing of cored sectionsFlexural testingPush-through testing

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

Experimental Set-ups (Compression)Core centered platesFull section loadingCore-only section loadingCoring internal specimens for cored compression testing

Compression Testing Results (Whole section)10-3/4 (1/2 wall)12-3/4 (3/8 wall)

Compression Testing Results (Core section)10-3/4 (1/2 wall)12-3/4 (3/8 wall)

Compression Testing Results - Cores

Flexural TestingObjective 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.

Experimental Set-ups (Flexure)

Flexural Testing - ResultsResults 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 testingStrain vs. load through cross-section depth (10-3/4 0.375 wall) Pile 1 Strain vs. load (all gauges) for (10-3/4 0.375 wall) Pile 1

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

Experimental Set-ups (Push-through)Test configurationFailure mechanism

Push-through testingSeam weldedSpiral welded

Push-through testingMeasured bond stress (0.29 0.53 ksi)Literature: 0.2 2.0 ksi (concrete to rebar)

Finite Element Modeling Phase VISpecimen modelsCompression specimens (Loading entire cross-section and Loading core only)Embedded pile modelVariations in soil constraint conditionsLimited to validation range of experimental programModels developed using ANSYS Commercial FEA softwareSolid element models with full composite behavior

Finite Element Model Specimen ComparisonL/D expected to yield fully plastic response rather than elastic bucklingModels limited to linear elastic regionLoading applied proportional to stiffness for uniform stress distribution (displacement-controlled)Boundary conditions selected to ensure pure compression

Finite Element Model Specimen Comparison10-3/4 (1/2 wall)12-3/4 (3/8 wall)

Finite Element Model In-Service Behavior (Embedded in Soil)End of pile assumed fixed due to bedrockContributions from vertical compaction, shear distortion, and lateral compactionSoil response model as a series of discrete springs with equivalent stiffnessesLoose sandy soil, compact sandy soil, loose gravel soil, and compact gravel soilLoading limited to 1,000 kips based on testing

Finite Element Model In-Service Behavior (Embedded in Soil)Soil contribution matched stub section response10-3/4 (1/2 wall)12-3/4 (3/8 wall)

Findings and RecommendationsNo 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) > WisDOT design capacities (189-317%)Non-linear response was observed in small specimens, but not failurePrevious studies indicated that typical failure mode should be squash failure

Findings and RecommendationsLoading mechanism has an influence on the behavior of the pileLoading 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 componentsGeometric non-linearities in cut sections resulted in inconsistencies between experimental and finite element model resultsFinite element mode demonstrated that in-service conditions similar to stub section

Findings and RecommendationsAll of the core concrete appear to be well consolidated and relatively uniform and free of voidsAssessment based on visual observation of cored specimens and cut ends of sectionsCore 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 > cracking strength of the composite section

Findings and RecommendationsCurrent WisDOT practices is overly conservative with respect to the axial capacityUncertainty still remains with respect to long-term durability of steel shell (function of down-hole conditions )Bond is comparable to other steel/concrete composite systemsCore concrete is well consolidated using current placement methods.

Questions and DiscussionContact InformationDevin K. Harris, Ph.D.Assistant ProfessorDepartment of Civil and Environmental EngineeringMichigan Technological Universitydharris@mtu.edu Thank you for your attention

***Same as WisDOTMost states do not use additional reinforcementSimplifies to only contribution from concrete core*Three sizes we tested with their non-composite nominal capacities*To use composite AASHTO requires >4% Area total to be steelEuler bucklingbased on unbraced lengthChoose 18 in as would be similar to some soils and fit in test framebased on effective modulus and yield*Composite vs. Non-composite capacities*Pile Drive on site in Wisconsin, Just outside of Waupaca (southeast of Stevens Point)(west of Appleton)Drove pile section 15ftCaissons placed aroundCast the coreDid on site testingSlump 2-3/4Air 5%Cylinders for determining strength7-day strength was found to be enough to pull the sections 7 day is also when contractors begin using pile members*Pile Drive on site in Wisconsin, Just outside of Waupaca (southeast of Stevens Point)(west of Appleton)Drove pile section 15ftCaissons placed aroundCast the coreDid on site testingSlump 2-3/4Air 5%Cylinders for determining strength7-day strength was found to be enough to pull the sections 7 day is also when contractors begin using pile members*Diamond wire sawusually used to cut pipe underwaterclamps onto member to cutdiamond wire blade can go through almost any materialwater cooled82 cuts totalsections varied slightly in total length1 11ft section15-18 18 in section2 12 in sections to utilize the most possible**Pile Sections used for whateach test was done on varied depths throughouttypically 4 sections of each size for each testPiles numbered based on size and then also a corresponding letterLettered from a to z at the top z at the bottom*