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10.7 DRIVEN PILES 10.7.1 General 10.7.1.1 MINIMUM PILE SPACING, CLEARANCE AND EMBEDMENT INTO CAP 10.7.1.2 PILES THROUGH

AASHTO LRFD Section 10.7 and 10.8 Deep Foundations “ BY FAR THIS SECTION HAS BEEN IDENTIFIED AS THE MOST PROBLEMATIC SECTION OF THE AASHTO LRFD SPECS. BY THE STATE DOTS”. 10.7 DRIVEN PILES 10.7.1 General 10.7.1.1 MINIMUM PILE SPACING, CLEARANCE AND EMBEDMENT INTO CAP

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10.7 DRIVEN PILES 10.7.1 General 10.7.1.1 MINIMUM PILE SPACING, CLEARANCE AND EMBEDMENT INTO CAP 10.7.1.2 PILES THROUGH

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  1. AASHTO LRFD Section 10.7 and 10.8 Deep Foundations“BY FAR THIS SECTION HAS BEEN IDENTIFIED AS THE MOST PROBLEMATIC SECTION OF THE AASHTO LRFD SPECS. BY THE STATE DOTS”

  2. 10.7DRIVEN PILES 10.7.1 General 10.7.1.1MINIMUM PILE SPACING, CLEARANCE AND EMBEDMENT INTO CAP 10.7.1.2PILES THROUGH EMBANKMENT FILL 10.7.1.3BATTER PILES 10.7.1.4PILE DESIGN REQUIREMENTS 10.7.1.5Determination of Pile Loads 10.7.1.5.1 Downdrag 10.7.1.5.2 Uplift Due to Expansive Soils 10.7.1.5.3 Nearby Structures 10.7.2 Service Limit State Design 10.7.2.1GENERAL 10.7.2.2TOLERABLE MOVEMENTS 10.7.2.3settlement 10.7.2.3.1 Pile Groups in Cohesive Soil 10.7.2.3.2 Pile Groups in Cohesionless Soil 10.7.2.4HORIZONTAL PILE FOUNDATION MOVEMENT 10.7.2.5SETTLEMENT DUE TO DOWNDRAG 10.7.2.6lateral squeeze 10.7.3 Strength Limit State Design 10.7.3.1POINT BEARING PILES ON ROCK 10.7.3.1.1 Piles Driven to Soft Rock 10.7.3.1.2 Piles Driven to Hard Rock 10.7.3.2pile length estimates for contract documents 10.7.3.3nominal axial RESISTANCE CHANGE AFTER PILE DRIVING 10.7.3.3.1 Relaxation 10.7.3.3.2 Setup 10.7.3.4groundwater effects and BUOYANCY

  3. Deep Foundations Overview • 10.7 Driven Piles • Total re-write • 10.8 Drilled Shafts • Re-organized + new & updated content

  4. Service Limit State (10.7.2) • Vertical Displacement • Additional equivalent footing diagrams added • Horizontal Displacement • P-y method for analysis of horizontal displacement now specifically called out • P multipliers for group effects updated and specified • Overall stability

  5. Vertical Displacement

  6. Horizontal Displacement (P-y method) Properties A, E, I Qt P Ht Mt y y y

  7. S P P Original curve Modified curve Pm * P y D P-multiplier (Pm) From Table 10.7.2.4-1

  8. Overall Stability

  9. Strength Limit State (10.7.3) • Geotechnical Resistance • Emphasisof pile resistance verification during construction • De-emphasis on use of static analysis methods except for estimation of pile length for contract drawings • Structural Resistance • Axial • Combined bending and axial • Shear • Driven Resistance (10.7.7)

  10. Axial Geotechnical Resistance

  11. Static Load Test

  12. Load Elastic pile compression Settlement Pile top settlement Davidson Method Specified

  13. Dynamic Load Test (PDA) Method & equations are now prescribed

  14. Driving Formulas

  15. Driving Formulas • FHWA Gates Method • Method & Equation Prescribed • Engineering News Method • Equation Modified to Produce Ultimate Resistance by Removing the Built-in Factor of Safety = 6

  16. Driving Formula Limitations • Design “stresses” must be limited if a driveability analysis is not performed • limiting stresses prescribed • Limited to nominal resistances below 300 tons

  17. Geotechnical Safety Factors for Piles

  18. Static Analysis Methods • Existing Methods Retained • FHWA Nordland/Thurman Method Added Applicability limited to: - Prediction of pile penetration (used without resistance factors) - Rare case of driving to prescribed penetration or depth (no field determination of pile axial resistance)

  19. Geotechnical Resistance FactorsPile Static Analysis Methods From Table 10.5.5.2.2-1

  20. Table 10.5.5.2.2-1 Resistance Factors for Driven Piles

  21. Table 10.5.5.2.2-2 Relationship between Number of Static Load Tests Conducted per Site and  (after Paikowsky, et al., 2004)

  22. Table 10.5.5.2.2-3 Number of Dynamic Tests with Signal Matching Analysis per Site to Be Conducted During Production Pile Driving (after Paikowsky, et al., 2004)

  23. Structural Axial Failure Mode

  24. Structural Flexure Failure Mode

  25. Structural Shear Failure Mode

  26. Methods for determining structural resistance • Axial compression • Combined axial and flexure • Shear LRFD Specifications Concrete – Section 5 Steel – Section 6 Wood – Section 8

  27. Driven Performance Limit

  28. Drivability Analysis (10.7.7) • Specifically required • Purpose is to verify that the specified pile can be driven: • To the required minimum penetration • To the required ultimate resistance • Using a commonly available hammer • Without exceeding the permissible driving stress • At a reasonable penetration rate

  29. 37.5 ksi 550 kip 120 bpf

  30. Driven Performance Limit

  31. Extreme Event Limit State (10.7.4 ) • New section with limited guidance regarding extreme events (no guidance previously provided)

  32. Piles - Other Considerations • 10.7.5 Corrosion and Deterioration • Moved from section 10.7.1 with no major changes • 10.7.6 Determination of Minimum Pile Penetration • New section combining some of the existing material from section 10.7.1 with additional guidance. • Downdrag provisions extensively modified

  33. Downdrag • New provisions in article 3.11.8 regarding determination of downdrag as a load • Revisions to load factors pending additional analysis/research

  34. 10.8 DRILLED SHAFTS • Article re-organized to follow section 10.7 • Most provisions refer back to section 10.7 • Service limit state provisions removed from strength limit state resistance determination • Provisions for resistance determination updated • Detailed procedures for evaluation of combined side friction and end bearing in rock added to commentary

  35. 10.8DRILLED SHAFTS 10.8.1General 10.8.1.1scope 10.8.1.2shaft spacing, clearance and embedment into cap 10.8.1.3shaft diameter and enlarged bases 10.8.1.4batterED shafts 10.8.1.5drilled SHAFT resistance 10.8.1.6DETERMINATION OF Shaft Loads 10.8.1.6.1General 10.8.1.6.2Downdrag 10.8.1.6.3Uplift 10.8.2Service Limit State Design 10.8.2.1tolerable movements 10.8.2.2settlement 10.8.2.2.1General 10.8.2.2.2Settlement of Single-Drilled Shaft 10.8.2.2.3Intermediate Geo Materials (IGM’s) 10.8.2.2.4Group Settlement 10.8.2.3HORIZONTAL MOVEMENT OF SHAFTS AND SHAFT GROUPS 10.8.2.4settlement due to downdrag 10.8.2.5lateral squeeze 10.8.3Strength Limit State Design 10.8.3.1general 10.8.3.2ground water table and bouyancy 10.8.3.3Scour 10.8.3.4downdrag 10.8.3.5NOMINAL axial COMPRESSION resistance of singledrilled shafts 10.8.3.5.1Estimation of Drilled Shaft Resistance in Cohesive Soils 10.8.3.5.1aSide Resistance 10.8.3.5.1bTip Resistance 10.8.3.5.2Estimation of Drilled Shaft Resistance in Cohesionless Soils

  36. Drilled Shaft Resistance in Rock Total Resistance A Side Resistance B Resistance C D Tip Resistance QS Displacement QR = fQn = fqpQp + fqsQs QP

  37. Geotechnical Resistance Factors Drilled Shafts AASHTO Table 10.5.5.2.3-1

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