BRIDGE FOUNDATION DESIGN
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BRIDGE FOUNDATION DESIGN







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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.
BRIDGE FOUNDATION DESIGN

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Slide 1

BRIDGE FOUNDATION DESIGN

Local Agency Workshop

February, 2009

Jan Six, P.E.

Sr. Geotechnical Engineer

ODOT Bridge Engineering Section

Slide 2

ODOT FOUNDATION DESIGN

Standards Foundation Design Process Foundation Reports Plans & Specifications Construction Assistance

Slide 3

Standards

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

Slide 4

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.

Slide 5

Foundation Design Process

Scoping & Field Reconnaissance Field Explorations Laboratory Testing Foundation Design Foundation Reports Specifications Construction Support

Slide 6

Foundation Design Process

Scoping and Field Reconnaissance

Identify Foundation Design Elements of Project New Bridge Foundations Bridge Widening Retaining Walls Culverts Conduct Office Data Research Old Foundation Data on Existing Structure Pile Record Books Maintenance Records

Slide 7

Foundation Design Process

Field Reconnaissance

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

Slide 8

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

Slide 9

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)

Slide 10

Foundation Design Process

Field Explorations

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

Slide 11

Foundation Design Process

Field Explorations

Undisturbed Sample (Shelby Tube)

Slide 12

Field Explorations

Exploration Log

Slide 13

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 Soils Unconfined Compressive Strength (rock) Consolidation Tests (settlement) Unit Weight & Index Tests

Slide 14

Foundation Design Process

Construct Subsurface Profile Stratigraphy & Geologic Model Groundwater Conditions Engineering Design Parameters Foundation TypeSeismic Analysis

Slide 15

Foundation Design Process

Subsurface Geologic Profile

Slide 16

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.

Slide 17

Foundation Design Process

Seismic Analysis (cont.) Ground Acceleration (PGA) 2002 USGS Maps Site Specific Analysis (optional) Liquefaction Analysis Lateral Spread, Slope Instability Approach Fill Settlement Bridge Damage Potential Mitigation Measures

Slide 18

Foundation Reports

Slide 19

Foundation Design Process

Foundation type depends on combinations of: Foundation Materials & Conditions Structure Type & Loads Performance Criteria Site Conditions/Construction Constraints Extreme Event Effects Seismic Loads (Liquefaction Potential) Scour Depths Costs & Construction Time

Slide 20

Foundation Design Process

Other Project Considerations: In-Water Work Periods Environmental Restrictions Noise or Vibration Constraints Construction Access/Traffic Control

Slide 21

Foundation Design Process

Shallow Foundations Spread Footings (on engineered fill) MSE Abutment Wall w/ Spread FootingDeep Foundations Driven Piles Drilled Shafts Micropiles

Types of Foundations

Slide 22

Foundation Design Process

Spread Footing Design Settlement Bearing Resistance Sliding Resistance Overturning (eccentricity) Overall Stability (slope stability)

Slide 23

Foundation Design Process

Pile Design Most Common Steel Pipe Piles (open or closed end) H-Piles Less Common Prestressed Concrete Timber

Slide 24

Foundation Design Process

Pile Design Bearing Resistance (compression and tension) Lateral Resistance Settlement and Downdrag Analysis Corrosion Potential/Protection Tip Protection Pile Drivability (construction) Group Settlement, Group Effects

Slide 25

Foundation Design Process

Drilled Shafts High bearing resistance High lateral resistance Cost-effective in river environments Can be socketed into bedrock Potential construction issues Hole stability (caving, groundwater) Difficulty with drilling obstructions Need very good subsurface data Need good experienced contractors

Slide 26

Foundation Design Process

Slide 27

Foundation Design Process

Micropiles Small diameter, drilled-in-place piles Rarely used Relatively expensive Applicable for: low overhead clearance boulders in foundation soils underpinning projects

Slide 28

Foundation Reports

Project description (scope & purpose) Office research & summary of pertinent records relating to foundation design and construction. Description of the geologic setting Summary of hydraulics information affecting foundation recommendations Subsurface explorations and conditions Boring logs Groundwater conditions Special field testing Laboratory test results

Slide 29

Foundation Reports

Seismic Analysis & Recommendations 500 yr. and 1000 yr. event analysis Peak Ground Acceleration (PGA), Sa & S1 AASHTO soil site class and response spectra Liquefaction Assessment Extent of Liquefaction & Potential Impacts Lateral Spread Potential Reduced Foundation Capacities Settlement, Downdrag Potential Liquefied Soil Parameters for Bridge Analysis Mitigation Recommendations Site Specific Analysis & Response Spectra (optional)

Slide 30

Foundation Reports

Foundation Recommendations Spread Footings (on engineered fill) Piles Drilled Shafts Micropiles

Slide 31

Foundation Reports

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

Slide 32

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 Resistances Nominal (Ultimate) Uplift Capacities Soil Parameters for Lateral Load Analysis Pile Group Settlement

Slide 33

Foundation Reports

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

Slide 34

Foundation Reports

Pile Driving Stress Problems

Slide 35

Foundation Reports

Drilled ShaftsShaft Type (i.e., end-bearing, friction or both) Nominal Resistance for various diameters and lengths Estimated Shaft Settlement vs. Shaft Diameter and Load Factored Resistance and Resistance Factors Soil Parameters for Lateral Load Analysis Liquefaction Effects: reduced shaft capacities (axial, uplift, lateral, etc) Load Test recommendations (if appropriate)

Slide 36

Foundation Reports

Construction & Specification Recommendations Pile Foundations Pile Driving Criteria Wave Equation Input Criteria (if applicable) Number of Pile Splices Is Set Period (freeze) acceptable? Is Preboring or Jetting acceptable? Effects of driving on adjacent structures Potential Driving Obstructions (e.g., boulders, existing piles, utilities) been identified?

Slide 37

Foundation Reports

Construction & Specification Recommendations Drilled Shafts End bearing or friction shaft designation Temporary or Permanent casing recommendations Groundwater conditions Boulders and/or obstructions expected to be encountered Cross Hole Sonic Logging (CSL) Quality Control

Slide 38

Foundation Reports

Structural Defect Produced by Interruption in Concreting and Low Slump Concrete

Slide 39

Foundation Reports

Construction & Specification RecommendationsOther Foundation Recommendations Detour Bridge Recommendations Falsework Support Falsework foundation type recommendations Foundation Excavations Groundwater conditions & possible mitigation Shoring and Bracing Cofferdams Unique Special Provisions Specific Geotechnical/Geologic information

Slide 40

Foundation Reports

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

Slide 42

Foundation Reports

Distributed To: Structural Designer(s) Specification Writer Project Manager’s Office (inspector) Project Team Leader Region Geo-Office HQ Bridge Engineering Office FHWA (for large projects)

Slide 43

Plans & Specifications

Plans ReviewPile type, size and grade Drilled Shaft size, tip elevations, min. rock socket depth Nominal Resistances Resistance Factors Pile Driving Criteria Required Pile Tip Elevation Pile Tip treatment Splicing Detail Footings: Nominal Resistance Maximum Footing Elevation

Slide 44

Plans & Specifications

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

Slide 45

Plans & Specifications

Specifications Shafts (Section 512)Designated Friction or End Bearing Permanent Casing Requirements Crosshole Sonic Log (CSL) testing required

Slide 46

Construction Assistance

Pile Hammer & Equipment Review & Approval Pile Driving Criteria (inspectors graph) Pile Driving Problem Solving Pile Record Books Drilled Shaft Installation Plan Drilled Shaft Construction Forms Review of CSL test results Materials Substitutions Foundation Inspection Assistance Claims Resolution

Slide 47

Thank You!


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