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Practical Implementation of LRFD for Geotechnical Engineering Features Design and Construction of Driven Pile Foundations Wednesday, June 22, 2011 PDCA.

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Presentation on theme: "Practical Implementation of LRFD for Geotechnical Engineering Features Design and Construction of Driven Pile Foundations Wednesday, June 22, 2011 PDCA."— Presentation transcript:

1 Practical Implementation of LRFD for Geotechnical Engineering Features Design and Construction of Driven Pile Foundations Wednesday, June 22, 2011 PDCA Professors Workshop By Jerry A. DiMaggio, PE, D. GE, M. ASCE E-Mail: jdimaggio2@verizon.netjdimaggio2@verizon.net 1

2 ASCE LRFD Webinar Series 2 * Check ASCE website for latest information #Topic2009201020112012 1Fundamentals of LRFD – Part 11/16, 8/76/301/18, 10/13 2Fundamentals of LRFD – Part 21/30, 9/87/152/4, 10/21 3Subsurface Explorations6/30, 11/54/152/17, 8/182/3 4Shallow Foundations7/241/6, 5/7, 11/85/20, 12/12 5Deep Foundations – Piles1/25, 6/1, 12/146/21, 11/7 6Deep Foundations – Shafts2/8, 6/111/7, 7/81/23 7Deep Foundations – Micropiles9/103/3, 7/291/12 8Earth Retaining Structures – Fill8/203/11, 9/123/9 9Earth Retaining Structures – Cut10/219/302/28 10MSE Walls4/4, 12/2 11Ground Anchors5/23/29

3 Presnetation Assumptions/References Basic knowledge of: – LRFD (previous webinars) – Basic Deep Foundation Design and Construction Primary References: – Section 10 of AASHTO (2010, 5 th Edition) – List of other references provided at end 3

4 Driven Pile Foundations TopicSlides General (Section 3, Section 10.4, 10.7.1) 4 – 18 10.5 Limit States and Resistance Factors 19 – 22 10.7.2 Service Limit State 23 – 31 10.7.3 Strength Limit State 32 – 58 10.7.4 Extreme Event Limit State 59 – 65 10.7.5 Corrosion and Deterioration 66 – 69 10.7.8 Drivability Analysis 70 – 73 4

5 Section 10 Contents ArticleTopic 10.1Scope 10.2Definitions 10.3Notation 10.4Soil and Rock Properties 10.5Limit States and Resistance Factors 10.6Spread Footings 10.7Driven Piles 10.8Drilled Shafts 10.9Micropiles Refer to Section 3 for Loads and Load Factors 5

6 Deep Foundation Types Material Driven Piles Drilled Shafts/ Micropiles Jacked/ Special Prestressed concreteXX Post-tensioned concreteXX Pre-cast concreteX Cast-in-place concreteXXX SteelXXX WoodX Specialty/CompositesXXX 6

7 Section 10.7 Driven Piles ArticleTopic 10.7.1General 10.7.2Service Limit State Design 10.7.3Strength Limit State Design 10.7.4Extreme Event Limit State Design 10.7.5Corrosion and Deterioration 10.7.6Minimum Pile Penetration 10.7.7Driving Criteria for Bearing 10.7.8Drivability Analysis 10.7.9Test Piles 7

8 Professional Discipline Communication Geotechnical, Structural, Hydraulic, and Construction specialists all play an important role and have different responsibilities on deep foundation projects. Project specific loads, extreme events, performance requirements, scour, pile cap details, specifications, plans construction, pile damage are ALL KEY issues for a successful project! The Geotechnical Design Report is a key communication tool. 8

9 10.7.1 GENERAL Consider spread footings first. Basic guidelines for driven pile configurations – Minimum spacing 2.5 pile diameters or 30 inches. – Minimum of 9 inches pile cap edge and be embedded 12 inches into the pile cap or if with strands or bars then the pile embedment should be 6 inches. – Piles through embankments should extend 10 ft into original ground or refusal on rock. Maximum of 6 inch fill size. – Batter Piles: stiffness, don’t use in downdrag situations, concern in seismic situations. 9

10 Comparison of LRFD and ASD approaches for Deep Foundations SameDifferent Determining resistance Comparison of load and resistance Determining deflection Separation of resistance and deflection 10

11 AASHTO Table 3.4.1-1 11

12 DC DW EH EV ES LL WA EQ CT DD 12

13 Load Factors for Permanent Loads,  p AASHTO Table 3.4.1-2 13

14 Load Type and Direction StructuralGeotechnical Vertical or horizontal Permanent/Transient Vertical/Horizontal Downdrag/Setup/Relaxation 14

15 Downdrag 15 Design Method Load Factors MaximumMinimum Piles  -method 1.400.25 -method 1.050.30 ShaftsReese & O’Neill (1999)1.250.35 “Geotechnical” load Can be significant particularly given the max load factors Articles 3.4.1 and 3.11.8 15

16 AASHTO Section 10.4 Soil and Rock Properties DISCUSSED IN PREVIOUS WEBINAR ON SUBSURFACE INVESTIGATIONS – Next Offering on August 18, 2011 ArticleTopic 10.4.1Informational Needs 10.4.2Subsurface Exploration 10.4.3Laboratory Tests 10.4.4In Situ Tests 10.4.5Geophysical Tests 10.4.6Selection of Design Properties 16

17 Deep Foundation Selection Method of support Bearing material depth Load type, direction and magnitude Constructability Cost  Expressed in $/kip capacity  Include all possible costs 17

18 Pile Types Based on Soil Displacement During Driving Low DisplacementHigh Displacement 18

19 Driven Pile Foundations TopicSlides General (Section 3, Section 10.4, 10.7.1) 4 – 18 10.5 Limit States and Resistance Factors 19 – 22 10.7.2 Service Limit State 23 – 31 10.7.3 Strength Limit State 32 – 58 10.7.4 Extreme Event Limit State 59 – 65 10.7.5 Corrosion and Deterioration 66 – 69 10.7.8 Drivability Analysis 70 – 73 19

20 Strength Limit State Driven Piles ARTICLE 10.5.3.3 Axial compression resistance for single piles Pile group compression resistance Uplift resistance of single piles Uplift resistance of pile groups Pile punching failure in weaker stratum Single pile and pile group lateral resistance Constructability, including pile drivability 20

21 SPECIAL DESIGN CONSIDERATIONS Negative shaft resistance (downdrag) Lateral squeeze Scour Pile and soil heave Seismic considerations 21

22 10.5LIMIT STATES AND RESISTANCE Strength Limit State (will be discussed later) – Structural Resistance – Geotechnical Resistance – Driven Resistance Service Limit State – Resistance Factor = 1.0 (except for global stability) Extreme Event Limit State – Seismic, superflood, vessel, vehicle – Use nominal resistance 22

23 Driven Pile Foundations TopicSlides General (Section 3, Section 10.4, 10.7.1) 4 – 18 10.5 Limit States and Resistance Factors 19 – 22 10.7.2 Service Limit State 23 – 31 10.7.3 Strength Limit State 32 – 61 10.7.4 Extreme Event Limit State 62 – 65 10.7.5 Corrosion and Deterioration 66 – 69 10.7.8 Drivability Analysis 70 – 73 23

24 Service Limit State Checks Global StabilityVertical and Horizontal Displacements 24

25 Settlement of Pile Groups Article 10.7.2.3.1 [Hannigan (2006)] Treat as equivalent footings Categorize as one of the 4 cases shown here 25

26 FxFxFxFx H1H1H1H1 H2H2H2H2 DxDxDxDx DxDxDxDx M1M1M1M1 M2M2M2M2 10.7.2.4 Horizontal Loads and Pile Moments 26

27 Horizontal Response Assumes nominal resistance is adequate No consideration of possible brittle response of geomaterial LPILE type p-y model or Strain Wedge Method IsolatedGroup 27

28 P-y Results for Single Element 28

29 P-y Results for Pile Groups Spacing (S) P-multiplier (P m ) Row 1Row 2Row 3 3B0.80.40.3 5B1.000.850.7 AASHTO Figure 10.7.2.4-1 29

30 DxDxDxDx DxDxDxDx Moment Pile Head Fixity 30

31 Tolerable Movements and Movement Criteria 10.5.2.2 Service loads for settlements, horizontal movements and rotations. Omit transient loads for cohesive soils Reference movements to the top of the substructure unit. Angular Distortion (C10.5.2.2) 31

32 Driven Pile Foundations TopicSlides General (Section 3, Section 10.4, 10.7.1) 4 – 18 10.5 Limit States and Resistance Factors 19 – 22 10.7.2 Service Limit State 23 – 31 10.7.3 Strength Limit State 32 – 58 10.7.4 Extreme Event Limit State 59 – 65 10.7.5 Corrosion and Deterioration 66 – 69 10.7.8 Drivability Analysis 70 – 73 32

33 33 STRENGTH LIMIT STATES Structural Axial Driven (Assess Drivability) Flexure Shear GeotechnicalAxial 33

34 Axial compression Combined axial and flexure Shear LRFD Specifications Concrete – Section 5 Steel – Section 6 Wood – Section 8 Methods for Determining Structural Resistance 34

35 Factors Affecting Allowable Structural Pile Stresses Average section strength (F y, f c ’, wood crushing strength) Defects (knots in timber) Section treatment (preservation for timber) Variation in materials Load factor (overloads or pile damage) 35

36 Concrete (5.5.4.2) Axial Comp. = 0.75 Flexure = 0.9 (strain dependent) Shear = 0.9 Steel (6.5.4.2) Axial = 0.5-0.7 Combined Axial= 0.7-0.8 Flexure = 1.0 Shear = 1.0 Timber (8.5.2.2 and.3) Compression = 0.9 Tension = 0.8 Flexure = 0.85 Shear = 0.75 LRFD Specifications Structural Resistance Factors 10.7.3.13 Pile Structural Resistance 36

37 Field methods  Static load test  Dynamic load test (PDA)  Driving Formulae  Wave Equation Analysis Static analysis methods Determining Nominal Axial Geotechnical Resistance of Piles 37

38 Geotechnical Safety Factors for Piles (ASD) Basis for Design and Type of Construction Control Increasing Design/Construction Control Subsurface explorationXXXXX Static analysisXXXXX Dynamic formulaX Wave equationXXXX CAPWAP analysisXX Static load testXX Factor of Safety (FS)3.502.752.252.001.90 38

39 Pile Testing Methods Analysis Method Resistance Factor (  ) (AASHTO 2010) Factor of Safety (FS) EstimatedMeasured Capacity Stress Energy Capacity Stress Energy Dynamic formula 0.10 or 0.40 3.50X Wave equation 0.502.75XXX Dynamic testing 0.65 or 0.75 2.25XXX Static load test 0.75 to 0.80 2.00X 39

40 Geotechnical Nominal Resistance of Piles: Static Load Tests ASTM D1143 (10.7.8.2) Test Setup Results and Definition of Failure 40

41 Dynamic Load Test (PDA) ASTM D4945 10.7.3.8.3 41

42 Wave Equation Driven Resistance 10.7.3.8.4 42

43 Wave Equation Applications ItemUse Develop driving criterion Blow count for a required nominal resistance Blow count for nominal resistance as a function of energy/stroke Check drivability Blow count vs penetration depth Driving stresses vs penetration depth Determine optimal driving equipment Driving time Refined matching analysis Adjust input values based on dynamic measurements 43

44 68 blows / 0.25 m 195 MPa 1480 kN 2.6 m Wave Equation Results 44

45 Driving Formulas (Article 10.7.3.8.5) 45

46 Pile Testing Methods Analysis Method Resistance Factor (  ) (AASHTO 2010) EstimatedMeasured Capacity Stress Energy Capacity Stress Energy Dynamic formula 0.10 or 0.40X Wave equation 0.50XXX Dynamic testing 0.65 or 0.75XXX Static load test 0.75 to 0.80X 46

47 ● Calculate pile length for loads ● Determine number of piles ● Determine most cost effective pile type ● Calculate foundation settlement ● Calculate performance under uplift and lateral loads Static analysis methods and computer solutions are used to: 47

48 Static Analysis Methods Primary use is for pile length estimation for contract drawings and feasibility. Secondary use for estimation of downdrag, uplift resistance and scour effects Should rarely be used as sole means of determining pile resistance. ONLY IN SPECIAL SITUATIONS! 48

49 Side Resistance Tip Resistance Total Resistance A B C D RPRPRPRP RSRSRSRS R R =  R n  qp R p +  qs R s R R =  R n =  qp R p +  qs R s Displacement Vertical Displacement Resistance Large Pile Diameter Resistance 49

50 Computation of Static Geotechnical Resistance AASHTO 10.7.3.7.5-2 RPRPRPRP RSRSRSRS R R =  R n  R n  qp R p +  qs R s  R n =  qp R p +  qs R s R P = A P q P R S = A S q s 50

51 Nominal Resistance: R n = R s1 + R s2 + R s3 +R t Factored Resistance: R R =  R n =  (R s3 + R t ) Soil Resistance to Driving (SRD): SRD = R s1 + R s2 + R s3 +R t EXAMPLE SOIL PROFILE SRD = R s1 + R s2 / 2 + R s3 +R t (with clay soil strength change) ((with no soil strength changes ) 51

52 Static Analysis Methods  method b method method method Nordlund -Thurman method SPT-methodCPT-method Driven Piles 52

53 Resistance Factors Static Analysis Methods AASHTO Table 10.5.5.2.3-1 Method Resistance Factor,  CompressionTension  - method 0.350.25  - method 0.250.20 - method 0.400.30 Nordlund- Thurman0.450.35 SPT0.300.25 CPT0.500.40 Group0.600.50 53

54 Combining Geotechnical Resistance Factors C10.7.3.3  dyn x R n =  stat x R nstat The length predicted by this method may be overly conservative and need to be adjusted to reflect experience. Local experience replaces this suggested relationship. 54

55 Driven Pile Time Dependent Effects (Article 10.7.3.4) Setup Relaxation RPRPRPRP RSRSRSRS RPRPRPRP RSRSRSRS RPRPRPRP RSRSRSRS RPRPRPRP RSRSRSRS 55

56 SOIL SETUP Soil setup is a time dependent increase in the static pile resistance Large excess positive pore pressures are often generated during pile driving Soil setup frequently occurs for piles driven in saturated clays as well as loose to medium dense silts and fine sands as the excess pore pressure dissipate Magnitude of setup depends on soil characteristics and pile material and type 56

57 Point Bearing on Rock (Article 10.7.3.2) Soft rock that can be penetrated by pile driving may be treated similar to soils. Steel piles driven into soft rock may not require tip reinforcement. On hard rock the nominal resistance is controlled by the structural capacity. See Article 6.9.4.1 and the driving resistances in 6.5.4.2 and 6.15 for severe driving. PDA should be used when the nominal resistance exceeds 600 kips. C10.7.3.2.3 Provides qualitative guidance to minimize pile damage when driving piles on hard rock. 57

58 Pile Group Resistance 10.7.3.9 & 11 Static Geotechnical Resistance Figures 10.7.3.11-1 and -2 for group uplift resistance for cohesionless and cohesive soils respectively. Take lesser of 58

59 Driven Pile Foundations TopicSlides General (Section 3, Section 10.4, 10.7.1) 4 – 16 10.5 Limit States and Resistance Factors 17 – 20 10.7.2 Service Limit State 21 – 29 10.7.3 Strength Limit State 30 – 58 10.7.4 Extreme Event Limit State 59 – 65 10.7.5 Corrosion and Deterioration 66 – 69 10.7.8 Drivability Analysis 70 – 73 59

60 EXTREME EVENT LIMIT STATES 10.5.5.3 Scour Vessel and Vehicle collision Seismic loading and site specific situations. (Uplift Resistance should be 0.80 rather than 1.00 for all extreme checks.) 60

61 Piles Subject to Scour 10.5.5.3.2 61

62 Seismic – Articles 10.7.4, 10.5.5.3.3 Liquefaction: Neglect axial resistance in liquefiable zone Lateral Spreading: Either consider forces due to lateral spreading or improve ground; reduce P-y curve based on duration of strong shaking and ability of the ground to fully liquefy during strong shaking Downdrag: Do not combine “seismic” downdrag with “static” downdrag 62

63 Driven Pile Foundations TopicSlides General (Section 3, Section 10.4, 10.7.1) 4 – 18 10.5 Limit States and Resistance Factors 19 – 22 10.7.2 Service Limit State 23 – 31 10.7.3 Strength Limit State 32 – 58 10.7.4 Extreme Event Limit State 59 – 62 10.7.5 Corrosion and Deterioration 63 – 66 10.7.8 Drivability Analysis 67 – 73 63

64 10.7.5 Corrosion and Deterioration Identified by soil resistivity & pH testing If pH < 4.5, design should be based on an aggressive environment Corrosion of steel pile foundations, particularly in fill soils, low pH soils and marine environments Sulfate, chloride, and acid attack of concrete pile foundations Decay of timber piles from wetting and drying cycles from insects and marine borers 64

65 Aggressive Subsurface Environments Resistivity < 2000 ohms-cm pH < 5.5 pH between 5.5 and 8.5 in soils with high organic content Sulfates > 1,000 ppm Landfills and cinder fills Soils subject to mine or industrial drainage Areas of mixed resistivity (high and low) Insects (wood piles) 65

66 Pile Driving Induced Vibrations See Hannigan (2006) Vibration induced damage Vibration induced soil densification 66

67 Driven Pile Foundations TopicSlides General (Section 3, Section 10.4, 10.7.1) 4 – 18 10.5 Limit States and Resistance Factors 19 – 22 10.7.2 Service Limit State 23 – 31 10.7.3 Strength Limit State 32 – 58 10.7.4 Extreme Event Limit State 59 – 62 10.7.5 Corrosion and Deterioration 63 – 66 10.7.8 Drivability Analysis 67 – 73 67

68 Section 10.7.8 Driven Piles Requirements for drivability analysis have been added and clarified 68

69 Pile TypeLoading TypeLimiting Driving Stress SteelCompression/Tension Concrete Compression Tension Prestressed Compression Tension Tension (in severe corrosion) TimberCompression/Tension 69

70 Concrete piles, = 1.00  AASHTO Article 5.5.4.2.1 Steel piles, = 1.00  AASHTO Article 6.5.4.2 Timber piles, = 1.15  AASHTO Article 8.5.2.2 Driven Resistance Factors 70

71 Driven Pile Foundations TopicSlides General (Section 3, Section 10.4, 10.7.1) 4 – 18 10.5 Limit States and Resistance Factors 19 – 22 10.7.2 Service Limit State 23 – 31 10.7.3 Strength Limit State 32 – 58 10.7.4 Extreme Event Limit State 59 – 62 10.7.5 Corrosion and Deterioration 63 – 66 10.7.8 Drivability Analysis 67 – 71 71

72 5 th Edition 2010 Changes Sec 10.5 Specification references to changes in resistance factors based on pile group size moved to the commentary. The definition of foundation redundancy (in commentary) was simplified. Tables relating resistance factor to site variability were removed from the specifications and decisions were deferred to the engineer. The site variability method was retained as an acceptable option to aid in engineering judgment. Precaution for static analysis predictions for piles greater than 24“ was added. The resulting changes based on the above was a modest increase for several resistance factors. 72

73 5 th Edition 2010 Changes Sec 10.7 Use of dynamic tests with signal matching to estimate side friction were added as a reasonable alternative to static analysis methods or load testing. Table 10.7.2.4-1, small adjustments in the p-multipliers for group lateral load analysis. Provisions for piles driven to hard rock (Article 10.7.3.2) were made more complete. Article 10.7.3.3 changed to clarify the use and potential pitfalls of the approaches provided to estimate the pile length required. Article C10.7.3.4.3, guidance added regarding the length of time needed for various soil conditions before a restrike should be attempted. 73

74 Table 10.5.5.2.3-1 Resistance Factors for Driven Piles Static Load Test with Dynamic Tests – 0.80 (minimum test number 2 and minimum percentage 2% of tests) Static Load Test without Dynamic Tests – 0.75 Dynamic Testing 100% production piles – 0.75 Dynamic Tests – 0.65 (minimum test number 2 and minimum percentage 2% of tests) Wave Equation – 0.50 74

75 For More Information on Driven Piles 75

76 REFERENCES Allen, T. M. 2005. “Development of Geotechnical Resistance Factors and Downdrag Load Factors for LRFD Foundation Strength Limit State Design”, FHWA-NHI-05- 052, FHWA, Wash. DC. Barker, R. M. et al 1991. “Manuals for the Design of Bridge Foundations” NCHRP Report 343. Transportation Research Board, NRC, Wash., DC. Hannigan P.J. et al, 2005. “Design and Construction of Driven Pile Foundations”, FHWA-HI-05, FHWA, Wash. DC Paikowsky S. G. et al, 2004. “Load and Resistance Factor Design (LRFD) for Deep Foundations”, NCHRP Report 507. Transportation Research Board, NRC, Wash. DC. 76

77 Practical Implementation of LRFD for Geotechnical Engineering Features Design and Construction of Driven Pile Foundations Wednesday, June 22, 2011 PDCA Professors Workshop By Jerry A. DiMaggio, PE, D.GE, M. ASCE E-Mail: jdimaggio2@verizon.netjdimaggio2@verizon.net 77


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