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BRIDGE FOUNDATION DESIGN. Local Agency Workshop February, 2009 Jan Six, P.E. Sr. Geotechnical Engineer ODOT Bridge Engineering Section. ODOT FOUNDATION DESIGN. Standards Foundation Design Process Foundation Reports Plans & Specifications Construction Assistance. Standards. - PowerPoint PPT Presentation

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Local Agency Workshop

February, 2009

Jan Six, P.E.

Sr. Geotechnical Engineer

ODOT Bridge Engineering Section

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Standards Foundation Design ProcessFoundation ReportsPlans & SpecificationsConstruction Assistance

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ODOT Geotechnical Design Manual (GDM) (available from ODOT Geo-Environmental web site)AASHTO LRFD Bridge Design SpecificationsODOT Bridge Design & Drafting ManualODOT Standard SpecificationsFHWA Design Manuals (Geotechnical Circulars)

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Foundation Design Process

To determine the bridge foundation system that will result in the most cost effective bridge design, taking into account all the appropriate foundation design and construction considerations.

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Foundation Design Process

Scoping & Field ReconnaissanceField ExplorationsLaboratory TestingFoundation Design Foundation ReportsSpecificationsConstruction Support

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Foundation Design Process

Scoping and Field Reconnaissance

Identify Foundation Design Elements of ProjectNew Bridge FoundationsBridge WideningRetaining WallsCulvertsConduct Office Data ResearchOld Foundation Data on Existing StructurePile Record BooksMaintenance Records

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Foundation Design Process

Field Reconnaissance

Observe Site Conditions affecting Exploration, Design and/or ConstructionSurface Conditions/ Obstructions (logs, riprap)Wetland Areas, R/W or other access restrictionsBridge Condition (settlement, corrosion) Scour or stream bank erosionUtilities (buried & overhead)Slope instabilities (slides, settlement, water problems)Locate Exploration Holes (test pits)

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Foundation Design Process

Field Explorations

Typically done by contract drillers under contract to ODOTObtain Preliminary Bent LocationsTypically Locate Drill Holes at all Bridge Bents (per AASHTO)Identify Permits of Entry and Environmental ClearancesUtility Locations & Notifications

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Foundation Design Process

Field Explorations

Standard Penetration Resistance Test (SPT ‘N’ value)Undisturbed Samples (Laboratory Testing)Rock Core Drilling (Rock hardness, RQD)Special In-Situ Tests (Cone Penetrometer, Pressuremeter)

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Foundation Design Process

Field Explorations

Standard Penetration Resistance Test 140lb. hammer, 30” drop#blows/6” incrementSPT ‘N’ value = #blows/last 12”

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Foundation Design Process

Field Explorations

Undisturbed Sample (Shelby Tube)

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Field Explorations

Exploration Log

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Foundation Design Process

Laboratory Testing

Amount depends on the soils and project designPurpose of obtaining engineering properties of soils and rock materials for use in designTypical Lab Tests:Shear Strength of SoilsUnconfined Compressive Strength (rock)Consolidation Tests (settlement)Unit Weight & Index Tests

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Foundation Design Process

Construct Subsurface ProfileStratigraphy & Geologic ModelGroundwater ConditionsEngineering Design Parameters Foundation TypeSeismic Analysis

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Foundation Design Process

Subsurface Geologic Profile

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Foundation Design Process

Seismic Analysis (Earthquake Design)Two Level DesignSeismic design is evaluated in terms of the overall bridge performance using the 500 yr. & 1000 yr. mean return period earthquakes. Bridge performance must meet “Serviceability” criteria for 500 year event and Life Safety criteria (no collapse) for 1000 yr event.

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Foundation Design Process

Seismic Analysis (cont.)Ground Acceleration (PGA)2002 USGS MapsSite Specific Analysis (optional)Liquefaction AnalysisLateral Spread, Slope InstabilityApproach Fill SettlementBridge Damage PotentialMitigation Measures

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Foundation Reports

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Foundation Design Process

Foundation type depends on combinations of:Foundation Materials & ConditionsStructure Type & Loads Performance CriteriaSite Conditions/Construction Constraints Extreme Event EffectsSeismic Loads (Liquefaction Potential) Scour DepthsCosts & Construction Time

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Foundation Design Process

Other Project Considerations:In-Water Work PeriodsEnvironmental RestrictionsNoise or Vibration ConstraintsConstruction Access/Traffic Control

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Foundation Design Process

Shallow FoundationsSpread Footings (on engineered fill)MSE Abutment Wall w/ Spread FootingDeep FoundationsDriven PilesDrilled ShaftsMicropiles

Types of Foundations

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Foundation Design Process

Spread Footing DesignSettlementBearing Resistance Sliding ResistanceOverturning (eccentricity)Overall Stability (slope stability)

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Foundation Design Process

Pile DesignMost CommonSteel Pipe Piles (open or closed end)H-PilesLess CommonPrestressed ConcreteTimber

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Foundation Design Process

Pile DesignBearing Resistance (compression and tension)Lateral ResistanceSettlement and Downdrag AnalysisCorrosion Potential/ProtectionTip Protection Pile Drivability (construction)Group Settlement, Group Effects

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Foundation Design Process

Drilled Shafts High bearing resistanceHigh lateral resistanceCost-effective in river environmentsCan be socketed into bedrockPotential construction issuesHole stability (caving, groundwater)Difficulty with drilling obstructionsNeed very good subsurface dataNeed good experienced contractors

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Foundation Design Process

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Foundation Design Process

Micropiles Small diameter, drilled-in-place pilesRarely usedRelatively expensiveApplicable for:low overhead clearanceboulders in foundation soilsunderpinning projects

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Foundation Reports

Project description (scope & purpose)Office research & summary of pertinent records relating to foundation design and construction. Description of the geologic settingSummary of hydraulics information affecting foundation recommendationsSubsurface explorations and conditionsBoring logsGroundwater conditionsSpecial field testingLaboratory test results

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Foundation Reports

Seismic Analysis & Recommendations500 yr. and 1000 yr. event analysis Peak Ground Acceleration (PGA), Sa & S1AASHTO soil site class and response spectraLiquefaction AssessmentExtent of Liquefaction & Potential ImpactsLateral Spread PotentialReduced Foundation CapacitiesSettlement, Downdrag PotentialLiquefied Soil Parameters for Bridge AnalysisMitigation Recommendations Site Specific Analysis & Response Spectra (optional)

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Foundation Reports

Foundation RecommendationsSpread Footings (on engineered fill)PilesDrilled ShaftsMicropiles

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Foundation Reports

Spread FootingsRecommended Footing Elevation(s) Nominal Bearing ResistanceFactored Bearing Resistance (Allowable Bearing Capacity)Nominal bearing resistance for service limit state (settlement)Description and properties of the anticipated foundation material

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Foundation Reports

Pile FoundationsType (Pipe Pile, H-pile, Concrete or Timber)Size or Dimensions (O.D., wall thickness, etc.) Material Specification (e.g., ASTM spec & grade of steel), Tip Treatment (PP open or closed-end, reinforcement)Nominal Bearing Resistances, estimated tip elevation for bearing estimated cutoff elevation, “estimated” or “order” lengths Minimum Required Tip Elevation (reason for req’d. tip elev.)Resistance Factors (f factor) and Factored ResistancesNominal (Ultimate) Uplift CapacitiesSoil Parameters for Lateral Load AnalysisPile Group Settlement

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Foundation Reports

Pile Foundations (continued)Downdrag Effects (reduced capacities or mitigation) Liquefaction Effects: reduced pile capacities (axial, uplift, lateral, etc)Pile Drivability AnalysisWave Equation Parameters (for special provisions/contractors)

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Foundation Reports

Pile Driving Stress Problems

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Foundation Reports

Drilled ShaftsShaft Type (i.e., end-bearing, friction or both)Nominal Resistance for various diameters and lengthsEstimated Shaft Settlement vs. Shaft Diameter and LoadFactored Resistance and Resistance FactorsSoil Parameters for Lateral Load AnalysisLiquefaction Effects: reduced shaft capacities (axial, uplift, lateral, etc) Load Test recommendations (if appropriate)

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Foundation Reports

Construction & Specification RecommendationsPile FoundationsPile Driving CriteriaWave Equation Input Criteria (if applicable)Number of Pile SplicesIs Set Period (freeze) acceptable?Is Preboring or Jetting acceptable?Effects of driving on adjacent structuresPotential Driving Obstructions (e.g., boulders, existing piles, utilities) been identified?

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Foundation Reports

Construction & Specification RecommendationsDrilled ShaftsEnd bearing or friction shaft designationTemporary or Permanent casing recommendationsGroundwater conditionsBoulders and/or obstructions expected to be encountered Cross Hole Sonic Logging (CSL) Quality Control

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Foundation Reports

Structural Defect Produced by Interruption in Concreting and Low Slump Concrete

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Foundation Reports

Construction & Specification RecommendationsOther Foundation RecommendationsDetour Bridge RecommendationsFalsework SupportFalsework foundation type recommendationsFoundation ExcavationsGroundwater conditions & possible mitigationShoring and BracingCofferdamsUnique Special ProvisionsSpecific Geotechnical/Geologic information

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Foundation Reports

Foundation Data Sheet (part of bridge plans)Locations all explorations (borings, test pits, hand augers, etc.)Explorations plotted in elevation viewSubsurface conditions depicted with soil and rock unit descriptions SPT (“N” values), Undisturbed SamplesHighest measured groundwater levels and the date measuredPercent rock core recovery and rock hardness.

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Foundation Reports

Distributed To:Structural Designer(s)Specification WriterProject Manager’s Office (inspector)Project Team LeaderRegion Geo-OfficeHQ Bridge Engineering OfficeFHWA (for large projects)

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Plans & Specifications

Plans ReviewPile type, size and gradeDrilled Shaft size, tip elevations, min. rock socket depthNominal ResistancesResistance FactorsPile Driving Criteria Required Pile Tip ElevationPile Tip treatmentSplicing DetailFootings: Nominal Resistance Maximum Footing Elevation

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Plans & Specifications

SpecificationsPiling (Section 520)Estimated Pile Lengths (steel piles)Number of Pile SplicesTip Treatment (open or closed end, reinforcement)Driving CriteriaWave Equation Input (if applicable)Pile freeze, preboring or jetting allowed

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Plans & Specifications

SpecificationsShafts (Section 512)Designated Friction or End BearingPermanent Casing RequirementsCrosshole Sonic Log (CSL) testing required

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Construction Assistance

Pile Hammer & Equipment Review & ApprovalPile Driving Criteria (inspectors graph)Pile Driving Problem SolvingPile Record BooksDrilled Shaft Installation PlanDrilled Shaft Construction FormsReview of CSL test resultsMaterials SubstitutionsFoundation Inspection AssistanceClaims Resolution

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Thank You!

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