1. 1 2015 Midwest Geotechnical Conference Implementation of the AASHTO LRFD Geotechnical Strength Limit State for Bearing Resistance of a Single Driven Pile Naser Abu-Hejleh, Ph.D., P.E., FHWA Resource Center William Kramer, P.E., Illinois State DOT Mir A. Zaheer, P.E., Indiana State DOT Prof. James H. Long, University of Illinois Khalid Mohamed, P.E., FHWA Headquarter.

2. 2 Presentation Outline  Introduction  Geotechnical Strength Limit State for Bearing Resistance of a Single Driven Pile  Design Example  Static Analysis Methods  Field Analysis Methods  Summary

3. 3 Recent FHWA LRFD Implementation Resources

4. 4

5. 5 Report’s Goals  Help highway engineering agencies:  Develop more accurate and economical LRFD design guidance for driven piles  Implement AASHTO LRFD Design Specifications for driven piles

6. 6 Report’s 6 Chapters 1.Introduction 2.LRFD Design Limit States and Design Process for Driven Piles 3.Nominal Bearing Resistance of a Single Pile 4.Structural and Drivability Strength Limit States 5.Geotechnical Strength Limit States and Design charts 6.Construction of Driven Piles

7. 7 AASHTO Limit States for Driven Piles  Strength Limit States for Axial Compression Resistance of a Single Pile  Geotechnical, drivability, and structural  Geotechnical: covered in this presentation  Extreme Event Limit States for Axial Compression Resistance of a Single Pile.  Other Limit States (AASHTO LRFD Article 10.7.6)  Minimum penetration pile length.

8. 8 Driven Piles Issues Covered in the FHWA Report  Clarification of the AASHTO LRFD limit states for driven piles and the design process to address them.  Determination of the pile contract and order lengths  Procedure to determine the maximum factored compression load a pile can support, Q fmax.  Clarification and improvement of drivability analysis in the design Phase  Addressing the LRFD design limit states during construction

9. 9 Driven Piles Issues Covered in the FHWA Report and in this Presentation For the LRFD geotechnical strength limit state:  Improve the agreement between the pile lengths estimated in the design and finalized in the field.  Consideration and advantages of  Using static analysis methods to finalize pile length  Setup  Static load test  Development/Use of Design Charts

10. 10 Geotechnical Strength Limit States for Bearing Resistance of a Single Pile

11. 11  Effects. Added axial compression load and lost side geotechnical resistance  DD loads = DD lost side resistance  Total factored axial compression load = Q f + DD  p Factored Axial Compressive Loads Per a Pile at the Strength Limit 2014 AASHTO LRFD Downdrag (DD) Effects Downdrag (DD) Loads

12. 12 Pile Bearing Resistance Determination Methods 1. Static Analysis Methods (e.g.,β-method).  Soil/rock properties,  Performed during design 2. Field Analysis Methods. Two types:  Dynamic analysis methods: wave equation, dynamic testing with signal matching, formulas  Hammer and soil information, driving records  Full-scale Load Test. Most accurate

13. 13 Types of Pile Bearing Resistances  Driving Resistance, R ndr, mobilized during and at end of driving (EOD) condtions  Short-term Resistance, R nre, developed shortly after driving (e.g., due to setup) at BOR conditions  Long-Term Resistance, R n (ultimate in ASD)  R n = R nre - GL  GL= Geotechnical resistance losses (scour, DD)

14. 14 Geotechnical Strength Limit State for Bearing Resistance of a Single Pile  Equation: Q f +  p DD ≤  R n  R n = R nsta &  =  sta for static analysis methods; Or  R n = R nfield &  =  dyn for field analysis methods  Field analysis methods. Design Outputs:  Required bearing resistance to verify bearing resistance and finalize pile length in the field  Estimate of pile length, L, could be different than length finalized in the field  Static analysis methods. Finalize pile length, L, in design. No field verification of bearing resistance

15. 15 Geotechnical Strength Limit State for Bearing Resistance of a Single Pile  Equation: Q f +  p DD ≤  R n  Meet the limit state at the pile depth,L, where  R n = Required R n = (Q f +  p DD)/  ; or  Q f = Supported Q f =  R n -  p DD Design Charts: curves of supported Q f and bearing resistances at various depths

16. 16 Design Chart

17. 17 LRFD Design Example Details

18. 18 LRFD Design Example Problem  Develop design charts using   -method (static analysis method),  = 0.25  Wave equation analysis at end of driving (EOD) conditions,  =0.5  Wave equation analysis at beginning of redrive (BOR) conditions,  =0.5  Axial compression static load test,  = 0.75.  Use design charts to determine  Design pile length and required field bearing

19. 19 Static Analysis Methods Bearing Resistances for the β-Method

20. 20 Design Chart for the β-Method

21. 21 Bearing Resistances from Field Analysis Methods Two Options  EOD Conditions: Measure only R ndr at EOD  R nfield = R ndr -GL (no direct benefits from setup)  Required R ndr = (Q f +  p DD)/  dyn + GL  BOR Conditions: Measure both R ndr and R nre  R nfield = R nre -GL (benefit from setup)  Required R nre = (Q f +  p DD)/  dyn +GL

22. 22 ASD Platform- Required Resistance  Problem: Bearing resistances from field analysis methods (R nfield ) are not available in the design  Differences between design and field pile lengths  Solution: use resistance median bias factor, , to R nfield =  R nstat  BOR = R nre (field analysis method)/R nre (static analysis method)  EOD = R ndr (field analysis method)/R nre (static analysis method) Problem and Solution!!

23. 23 ASD Platform- Required Resistance Estimation of Local Median Resistance Bias (  ) and Setup Factors

24. 24 ASD Platform- Required Resistance Estimation of Field Bearing Resistances, R nfield Bearing Resistances for a Static Analysis Method β-method Multiply by Bearing Resistances for A Field Analysis Method Wave equation analysis BOR Conditions R nre, R ndr, R nstat, GL  BOR R nre, R ndr, R nfield, GL GL = 6 kips 0.58 GL = 0.58 x 6 = 3.5 kips EOD Conditions R nre, R nstat, GL  EOD R ndr, R nfield, GL GL = 6 kips sand = 0.58 clay= 0.39 GL = 3.5 kips

25. 25 Bearing Resistances for Wave Equation Analysis

26. 26 Design Chart for Wave Equation Analysis at EOD

27. 27 Design Chart for Wave Equation Analysis at BOR

28. 28 Design Curves for Various Design Methods

29. 29 ASD Platform- Required Resistance Advantages of Static Analysis Methods Setup, and Load Tests Method Length (ft) Required Bearing Resistance (Kips) EODBOR Wave Equation EOD 67220N/A Β-Method56N/A Wave Equation BOR 57145220 Static Load Test48103N/A

30. 30 Summary For the LRFD geotechnical strength limit state for bearing resistance of a single pile  Improve the agreement between the pile lengths estimated in the design and finalized in the field.  Consideration and advantages of  Using static analysis methods to finalize pile length  Setup and  Static load test  Development/Use of Design Charts

31. 31 Questions? Dr. Naser Abu-Hejleh, P.E. FHWA Resource Center naser.abu-hejleh@dot.govnaser.abu-hejleh@dot.gov; (708) 283-3550