AASHTO LRFD Section 10 7 and 10 8

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. 1. 1 10. 7. 1. 2 10. 7. 1. 3 10. 7. 1. 4 10. 7. 1. 5. 1 10. 7. 1. 5. 2 10. 7. 1. 5. 3 10. 7. 2. 1 10. 7. 2. 2 10. 7. 2. 3. 1 10. 7. 2. 3. 2 10. 7. 2. 4 10. 7. 2. 5 10. 7. 2. 6 10. 7. 3. 1. 2 10. 7. 3. 3. 1 10. 7. 3. 3. 2 10. 7. 3. 4 DRIVEN PILES General MINIMUM PILE SPACING, CLEARANCE AND EMBEDMENT INTO CAP PILES THROUGH EMBANKMENT FILL BATTER PILES PILE DESIGN REQUIREMENTS Determination of Pile Loads Downdrag Uplift Due to Expansive Soils Nearby Structures Service Limit State Design GENERAL TOLERABLE MOVEMENTS settlement Pile Groups in Cohesive Soil Pile Groups in Cohesionless Soil HORIZONTAL PILE FOUNDATION MOVEMENT SETTLEMENT DUE TO DOWNDRAG lateral squeeze Strength Limit State Design POINT BEARING PILES ON ROCK Piles Driven to Soft Rock Piles Driven to Hard Rock pile length estimates for contract documents nominal axial RESISTANCE CHANGE AFTER PILE DRIVING Relaxation Setup groundwater effects and BUOYANCY

Deep Foundations Overview n 10. 7 Driven Piles n Total re-write n 10. 8 Drilled Shafts n Re-organized + new & updated content

Service Limit State (10. 7. 2) Vertical Displacement n Additional equivalent footing diagrams added n Horizontal Displacement n P-y method for analysis of horizontal displacement now specifically called out n P multipliers for group effects updated and specified n Overall stability n

Vertical Displacement

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

S D P e P v r u c l a n i e v ir g r u c O d e Pm * P i f i d o M y P-multiplier (Pm) Spacing (S) Row 1 Row 2 3 D 0. 7 0. 5 5 D 1. 0 0. 85 Row 3 0. 35 0. 7 From Table 10. 7. 2. 4 -1

Overall Stability

Strength Limit State (10. 7. 3) Geotechnical Resistance n Emphasis of pile resistance verification during construction n De-emphasis on use of static analysis methods except for estimation of pile length for contract drawings n Structural Resistance n Axial n Combined bending and axial n Shear n Driven Resistance (10. 7. 7) n

Axial Geotechnical Resistance

Static Load Test

Settlement Load Elasti c pile c ompr essio n Pile top settlement Davidson Method Specified

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

Driving Formulas

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

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

Geotechnical Safety Factors for Piles Design Basis & Const. Control Subsurface Expl. Static Calculation Dynamic Formula Wave Equation CAPWAP Static Load Test FS Increasing Design/Const. Control X X X X X 3. 50 2. 75 2. 25 2. 00 1. 90

Static Analysis Methods Existing Methods Retained n FHWA Nordland/Thurman Method Added n 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)

Geotechnical Resistance Factors Pile Static Analysis Method Comp Ten - Method 0. 4 0. 3 - Method 0. 35 0. 25 - Method 0. 4 0. 3 Nordlund-Thurman 0. 45 SPT 0. 3 0. 25 CPT 0. 45 0. 35 Group 0. 6 0. 5 From Table 10. 5. 5. 2. 2 -1

Table 10. 5. 5. 2. 2 -1 Resistance Factors for Driven Piles CONDITION/RESISTANCE DETERMINATION METHOD Driving criteria established by static load test(s); quality control by dynamic testing and/or calibrated wave equation, or minimum driving resistance combined with minimum delivered hammer energy from the load test(s). For the last case, the hammer used for the test pile(s) shall be used for the production piles. Nominal Resistance of Single Pile in Axial Compression – Dynamic Analysis and Static Load Test Methods, dyn RESISTANCE FACTOR Values in Table 2 Driving criteria established by dynamic test with signal matching at beginning of redrive conditions only of at least one production pile per pier, but no less than the number of tests per site provided in Table 3. Quality control of remaining piles by calibrated wave equation and/or dynamic testing. 0. 65 Wave equation analysis, without pile dynamic measurements or load test, at end of drive conditions only 0. 40 FHWA-modified Gates dynamic pile formula (End Of Drive condition only) 0. 40 Engineering News Record (as defined in Article 10. 7. 3. 7. 4) dynamic pile formula (End Of Drive condition only) 0. 10

Table 10. 5. 5. 2. 2 -2 Relationship between Number of Static Load Tests Conducted per Site and (after Paikowsky, et al. , 2004) Resistance Factor, Number of Static Load Tests per Site Low* Medium* High* 1 0. 80 0. 70 0. 55 2 0. 90 0. 75 0. 65 3 0. 90 0. 85 0. 75 >4 0. 90 0. 80 Site Variability*

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) Low* Medium* High* Site Variability* Number of Piles Located within Site Number of Piles with Dynamic Tests and Signal Matching Analysis Required (BOR) < 15 3 4 6 16 -25 3 5 8 26 -50 4 6 9 51 -100 4 7 10 101 -500 4 7 12 > 500 4 7 12

Structural Axial Failure Mode

Structural Flexure Failure Mode

Structural Shear Failure Mode

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

Driven Performance Limit

Drivability Analysis (10. 7. 7) Specifically required n Purpose is to verify that the specified pile can be driven: n To the required minimum penetration n To the required ultimate resistance n Using a commonly available hammer n Without exceeding the permissible driving stress n At a reasonable penetration rate n

37. 5 ksi 550 kip 120 bpf

Driven Performance Limit

Extreme Event Limit State (10. 7. 4 ) n New section with limited guidance regarding extreme events (no guidance previously provided)

Piles - Other Considerations 10. 7. 5 Corrosion and Deterioration n Moved from section 10. 7. 1 with no major changes n 10. 7. 6 Determination of Minimum Pile Penetration n New section combining some of the existing material from section 10. 7. 1 with additional guidance. n Downdrag provisions extensively modified n

Downdrag New provisions in article 3. 11. 8 regarding determination of downdrag as a load n Revisions to load factors pending additional analysis/research n Prediction Method Piles, -Tomlinson Piles, -Method Drilled shafts, O’Neill and Reese (1999) Maximum Minimum 1. 4 1. 05 - 1. 25 -

10. 8 DRILLED SHAFTS Article re-organized to follow section 10. 7 n Most provisions refer back to section 10. 7 n Service limit state provisions removed from strength limit state resistance determination n Provisions for resistance determination updated n Detailed procedures for evaluation of combined side friction and end bearing in rock added to commentary n

10. 8 DRILLED SHAFTS 10. 8. 1. 1 10. 8. 1. 2 10. 8. 1. 3 10. 8. 1. 4 10. 8. 1. 5 10. 8. 1. 6. 1 10. 8. 1. 6. 2 10. 8. 1. 6. 3 10. 8. 2. 1 10. 8. 2. 2. 2 10. 8. 2. 2. 3 10. 8. 2. 2. 4 10. 8. 2. 3 10. 8. 2. 4 10. 8. 2. 5 10. 8. 3. 1 10. 8. 3. 2 10. 8. 3. 3 10. 8. 3. 4 General scope shaft spacing, clearance and embedment into cap shaft diameter and enlarged bases batter. ED shafts drilled SHAFT resistance DETERMINATION OF Shaft Loads General Downdrag Uplift Service Limit State Design tolerable movements settlement General Settlement of Single-Drilled Shaft Intermediate Geo Materials (IGM’s) Group Settlement HORIZONTAL MOVEMENT OF SHAFTS AND SHAFT GROUPS settlement due to downdrag lateral squeeze Strength Limit State Design general ground water table and bouyancy Scour downdrag 10. 8. 3. 5. 1 a 10. 8. 3. 5. 1 b 10. 8. 3. 5. 2 NOMINAL axial COMPRESSION resistance of single drilled shafts Estimation of Drilled Shaft Resistance in Cohesive Soils Side Resistance Tip Resistance Estimation of Drilled Shaft Resistance in Cohesionless Soils

Drilled Shaft Resistance in Rock Resistance Total Resistance QS QP A Side Resistance D Tip Resistance Displacement QR = f. Qn = fqp. Qp + fqs. Qs B C

Geotechnical Resistance Factors Drilled Shafts Method - Method (side) Clay or Sand (tip) Rock (side) Rock (tip) Group (sand or clay) Load Test Comp 0. 55 0. 7 Ten 0. 45 AASHTO Table 10. 5. 5. 2. 3 -1