PILES TABLE OF CONTENTS - Virginia Department of ... · PDF file23.01-12 Steel H-Pile Design...

PILES TABLE OF CONTENTS

PART 2 DATE: 30Jan2018 SHEET 1 of 1

FILE NO. 23.TOC

CHAPTER 23 – PILES

TABLE OF CONTENTS

FILE NO. TITLE DATE

TABLE OF CONTENTS

23.TOC Table of Contents ........................................................................... 30Jan2018 23.00 Introduction .................................................................................... 30Jan2018

DESIGN GUIDE FOR LATERALLY UNSUPPORTED PILES

23.01-1 Notes and Definitions ..................................................................... 30Jan2018 23.01-2 Design Criteria ............................................................................... 30Jan2018 23.01-3 Design Criteria ............................................................................... 30Jan2018 23.01-4 Coarse Grain Soil Example ............................................................ 30Jan2018 23.01-5 Cohesive Soil Example .................................................................. 30Jan2018 23.01-6 Layered Soil Example .................................................................... 30Jan2018 23.01-7 Layered Soil Example .................................................................... 30Jan2018 23.01-8 Steel H-Pile Design Criteria ........................................................... 30Jan2018 23.01-9 Steel H-Pile Design Criteria ........................................................... 30Jan2018 23.01-10 Properties for Designing Steel H-Piles .......................................... 30Jan2018 23.01-11 Steel H-Pile Design Example ......................................................... 30Jan2018 23.01-12 Steel H-Pile Design Example ......................................................... 30Jan2018 23.01-13 Prestressed Concrete Pile Design Criteria .................................... 30Jan2018 23.01-14 Prestressed Concrete Pile Design Example .................................. 30Jan2018

LATERAL LOADED PILE ANALYSIS FOR POINT OF FIXITY

23.02-1 Design Procedure .......................................................................... 30Jan2018 23.02-2 Design Assumptions and Results .................................................. 30Jan2018 23.02-3 L-Pile Results for Scour Condition ................................................. 30Jan2018 23.02-4 L-Pile Results for Non-Scour Condition ......................................... 30Jan2018

PILES INTRODUCTION


FILE NO. 23.00

INTRODUCTION

It is the intent of this chapter to establish the guidelines and specific requirements of the Structure and Bridge Division for the design and analysis of laterally unsupported piles, specifically relating to the use of steel H-piles and prestressed concrete piles subjected to scour and biaxial bending. It provides design procedures and examples for determining the point of fixity, effective length factor, ‘K’, and the structural capacity of these piles. This chapter also provides a bridge specific example for determining the point of fixity for a laterally loaded pile for use in Elastic Frame Analysis using commercially available software for non-linear analysis of piles, L-Pile. Point of fixities for both the existing or final profile and the scoured condition may need to be determined. Shorter distances to points of fixities based on existing or final profile (non-scoured) can control design in exterior spans of large units and affect bridge behavior. Example calculations in this chapter show for scoured conditions, but non-scoured is similar. References to the AASHTO LRFD specifications in this chapter refer to the AASHTO LRFD Bridge Design Specifications, 7th Edition, 2014, and VDOT Modifications (current IIM-S&B-80). The practices and requirements set forth herein are intended to supplement or clarify the requirements of the AASHTO LRFD specifications, and to provide additional information to assist the designer. In the event of conflicts(s) between the practices and requirements set forth herein and those contained in the AASHTO LRFD specifications, the more stringent requirements shall govern. Standards for prestressed concrete piles are located in the Manual of the Structure and Bridge Division, Part 3.

Standard BPP-1 (Carbon Steel Strands) Standard BPP-2 (Stainless Steel Strands) Standard BPP-3 (Carbon Fiber Reinforced Polymer [CFRP] Strands)

It is expected that the users of this chapter will adhere to the guidelines and requirements stated herein. Major changes and/or additions to the past office practice (Part 2 of this manual) are as follows:

1. Updated calculations for design of steel H-piles to reflect AASHTO LFRD Specifications from previously referenced AASHTO Standard Specifications.

2. Added example including as-built bridge data for a laterally loaded pile analysis using L-

Pile for use in Elastic Frame Analysis. NOTE: Due to various restrictions on placing files in this manual onto the Internet, portions of the drawings shown do not necessarily reflect the correct line weights, line types, fonts, arrowheads, etc. Wherever discrepancies occur, the written text shall take precedence over any of the drawn views.

PILES DESIGN GUIDE FOR LATERALLY UNSUPPORTED PILES

GENERAL INFORMATION AND DEFINITIONS

PART 2

DATE: 30Jan2018

SHEET 1 of 14

FILE NO. 23.01-1

GENERAL INFORMATION: For the 100 year storm, the factored capacity is checked using the AASHTO Strength and Service Load Combinations and Load Factors. For the 500 year storm, the factored capacity is checked using the AASHTO Extreme Event Load Combinations and Load Factors. AASHTO Load Combinations and Load Factors shall be in accordance with Table 3.4.1-1.

This guide does not indicate how to determine the axial loads and moments to be used in the formulas for analysis of piles. Because the piles are not laterally restrained, sideway is not prevented; therefore, it is recommended that the designer utilize appropriate structural modeling software, such as RCPier, to determine the applied axial loads and moments.

DEFINITIONS:

b Pilewidthindirectionofbending ft

D Pileembedmentlengthintoground ft

D Depthofassumedpointoffixity ft

N StandardPenetrationTest STP Blowcount

c Cohesivestrength 0.125 ∙ N ksf

S undrainedshearstrengthofclays c ksf

n rateofincreaseofsoilmoduluswithdepthforsandsasspecifiedinTableC10.4.6.3 2

E Modulusofelasticityofconcrete AASHTOC5.4.2.4

586,029 ksf forf c 5,000psi

641,962 ksf forf c 6,000psi

E Modulusofelasticityofpile ksf

E soilmodulusforclays 0.465 ∙ S ksi (AASHTO C10.7.3.13.4)

A Grossareaofpile in

I MomentofInteriaofpile ft

S Elasticsectionmodulusofpile in

Z Plasticsectionmodulusofpile in

r radiusofgyrationofpile in

L Unsupportedlengthofpile ft

δ deflectionofpileincoarsegrainsoils; ifδ ∙ D 4, thenpinnedend; otherwisefixedend

β deflectionofpileincohesivesoils; ifβ ∙ D 2.25, thenpinnedends; otherwisefixedend


DESIGN CRITERIA

PART 2

DATE: 30Jan2018

SHEET 2 of 14

FILE NO. 23.01-2

DESIGN CRITERIA: POINT OF FIXITY FOR FREE STANDING PILE DESIGN CRITERIA: Point of fixity for both the existing or final profile and the scoured condition may need to be determined. EFFECTIVE LENGTH FACTOR – K: Top

Bottom

Top: R_free & T_free R_fixed & T_free R_free & T_fixed

Bottom: R_fixed & T_fixed R_fixed & T_fixed R_fixed & T_fixed

K = 2.1 K = 1.2 K = 0.8

Pier bent on single rowof piles with load appliedin longitudinal direction

Pier bent on piles with load applied in transverse direction

Integral abutment on piles with load applied in longitudinal direction

End Conditions: R = Rotation; T = Translation

D must be ≥ 3D for fixity to be assumed


DESIGN CRITERIA

PART 2

DATE: 30Jan2018

SHEET 3 of 14

FILE NO. 23.01-3

DESIGN CRITERIA (Cont’d): Table 1 – Rate of Increase of Soil Modulus with Depth, (ksi/ft)

for Sand (AASHTO Table C10.4.6.3-2)

Consistency Dry or Moist Submerged

Loose 0.417 0.208

Medium 1.11 0.556

Dense 2.78 1.39 Table 2 – Relationship between unconfined compressive strength, standard penetration

resistance, and unit weight for cohesive soils (Teng, 1962)

SHEAR STRENGTH OF COHESIVE SOILS

Consistency Very Soft

Soft Medium Stiff Very Stiff

Hard

qu = Unconfined compressive strength, lb/ft2

Standard penetration resistance N = No. of blows per ft. Unit weight, pcf (saturated)

110 - 130

130+

Cohesive (c) = ½ unconfined compression strength Table 3 – Relationship between relative density, standard penetration resistance, angle of

internal friction and unit weight for cohesive soils (Teng, 1962)

RELATIVE DENSITY OF GRANULAR SOILS

Compactness Very

Loose Loose Medium Dense

Very Dense

Relative density Standard penetration resistance, N = No. of blows per foot Angle of internal friction ∅ (degrees) * Unit weight, pcf Moist Submerged

<100 <60

95-125 55-65

110-130 60-70

110-140 65-85

>130 >75

*Highly dependent on gradation

0 500 1000 2000 4000 8000

0 2 4 8 16 32

100 - 120 120 - 140

28 30 36 41

0 4 10 30 50

0 15% 35% 65% 85% 100%


COARSE GRAIN SOIL EXAMPLE

PART 2

DATE: 30Jan2018

SHEET 4 of 14

FILE NO. 23.01-4

POINT OF FIXITY FOR FREE STANDING PILE – COARSE GRAIN SOIL EXAMPLE: Coarse grain soil, medium relative density (N = 27 blows/ft), above ground water. HP12x53 subject to biaxial bending.

Pile Length 60ft Scour Depth 10ft D 50ft

I 393in I 127in E 29,000ksi

r 5.03in r 2.86in Based on N = 27, a medium-dense soil is assumed. Use Tables 1 and 3 on File No. 23.01-3 to determine the value of nh by performing linear interpolation between a medium soil (N = 20, nh = 1.11), and a dense soil (N = 50, nh = 2.78); n 1.5ksi/ft

E I29,000 393

14479,146kip ∙ ft E I

29,000 127144

25,576kip ∙ ft

D 1.8E In

1.879,146

1.5x144inft

5.86 ft (AASHTO C10.7.3.13.4-2)

D 1.8E I

n1.8

25,576

1.5x144inft

4.68 ft (AASHTO C10.7.3.13.4-2)

δnE I

0.3071ft

δ ∙ D 15.35 4 ∴ fixed end

δnE I

0.3851ft δ ∙ D 19.24 4 ∴ fixed end

DD

505.86

8.53 3 ∴ fixed end

DD

504.68


ScourDepth D 10ft 5.86 ft 15.86 ft


Single row of piles with fixed ends in x-direction: Where: Unsupported length of pile

K Effective length factor

R Radius of gyration

K 2.1 Kr

2.1 15.86x 12inft

5.0379.47

Single row of piles with fixed ends in y-direction:

K 1.2 K

r

1.2 14.68x 12inft

2.8673.9


COHESIVE SOIL EXAMPLE

PART 2

DATE: 30Jan2018

SHEET 5 of 14

FILE NO. 23.01-5

POINT OF FIXITY FOR FREE STANDING PILE – COHESIVE SOIL EXAMPLE: Cohesive soil, blow count N 12blows/ft

Pile Length: 60ft Scour Depth 10ft D 50ft HP12x53 subject to biaxial bending.

I 393in I 127in b 12.045in E 29,000ksi r 5.03in r 2.86in b 11.78in

c 0.125Nksf 1.5ksf S c 1.5ksf E 0.465 ∙ S 0.698ksi Note: Soil modulus is reduced for pile spacing < 8 times the pile width, see Article C10.7.3.13.4. (For this example, since a specific pile spacing is not provided, no reduction is assumed.)

D 1.4E IE

1.429000 393

0.698x

1

12inft

7.42 ft (AASHTO C10.7.3.13.4-1)

D 1.4E I

E1.4

29000 1270.698

x1

12inft

5.59 ft (AASHTO C10.7.3.13.4-1)

βEE I

x12inft

0.1891ft

β ∙ D 9.44 2.25 ∴ fixed end

βEE I

x12inft

0.251ft

β ∙ D 12.52 2.25 ∴ fixed end

DD

507.42


DD

505.59




Single row of piles with fixed ends in x-direction: Where: Unsupported length of pile

K Effective length factor

R Radius of gyration

K 2.1 Kr

2.1 17.42 x 12inft

5.0387.26

Single row of piles with fixed ends in y-direction:

K 1.2 K

r

1.2 15.59 x 12inft

2.8678.51


LAYERED SOIL EXAMPLE

PART 2

DATE: 30Jan2018

SHEET 6 of 14

FILE NO. 23.01-6

POINT OF FIXITY FOR FREE STANDING PILE – LAYERED SOIL EXAMPLE: Soil Layer 1: Sand, N = 5 blows/ft nh1 = 0.417 ksi/ft Depth, d1 = 4 ft

Soil Layer 2: Sand, N = 10 blows/ft nh2 = 0.60 ksi/ft Depth, d2 = 4 ft

Soil Layer 3: Sand, N = 20 blows/ft nh3 = 1.11 ksi/ft Depth, d3 = 20 ft

Determination of the point of fixity for a layered soil condition is based on a trial and error approach, using an initial assumption of nh, selected based on the soil conditions observed. In this case, the values for nh were determined using linear interpolation based on the “compactness” description of the soil from the provided “N” values, and the nh values provided in Table 1 on File No. 23.01-3. Assume an initial average nh: n 0.50ksi/ft Pile EI 79,146kip ∙ ft

D 1.8EIn

1.879,146

0.50x144inft

7.303 ft d 3.303 ft

Due to rigidity of pile and soil profile, point of fixity does not extend into third soil layer; therefore, recalculate fixity based on two-layer soil profile. Calculate second moment of area for two-layer soil diagram taken about D:

n3D

n d3

n d y

3

7.3030.417 4

30.417 4 2 3.303

0.60 3.3033

0.60 3.303 1.652

0.527ksift

Use new nh to calculate new D:

D 1.879,146

0.527x144inft

7.226 ft d 3.226 ft


LAYERED SOIL EXAMPLE

PART 2

DATE: 30Jan2018

SHEET 7 of 14

FILE NO. 23.01-7

POINT OF FIXITY FOR FREE STANDING PILE – LAYERED SOIL EXAMPLE (Cont’d):

n3

7.2260.417 4

30.417 4 2 3.226

0.60 3.2263

0.60 3.226 1.613

0.526ksift

D 1.879,146

0.526x144inft

7.228 ft ∴ Use this value as convergence.

Where: di = depth of layer

yi = distance from assumed D to center of layer


STEEL H-PILE DESIGN CRITERIA

PART 2

DATE: 30Jan2018

SHEET 8 of 14

FILE NO. 23.01-8

STEEL H-PILE DESIGN CRITERIA: Compression members shall satisfy the following slenderness ratios:

Kr

120; For primary members

Determine axis for elastic critical buckling resistance:

If > , Use about the x-axis, otherwise use about the y-axis

If K < K , flexural buckling shall be applicable:

Pπ E

Kr

A (AASHTO 6.9.4.1.2-1)

If K > K , torsional buckling and flexural torsional buckling shall be applicable:

Pπ ECK z

GJA

I I (AASHTO 6.9.4.1.3-1)

Check compressive slenderness limits of member elements:

If 0.56 , then: Q 1.0 (AASHTO 6.9.4.2.1-1)

If 0.56 < 1.03 , then: Q 1.415 0.74 (AASHTO 6.9.4.2.2-1)

If 1.03 , then: Q .

(AASHTO 6.9.4.2.2-2)

Determine compressive resistance:

P Q F A

If 0. 44 , then: P = 0.658 P (AASHTO 6.9.4.1.1-1)

If 0. 44 , then: P = 0.877P (AASHTO 6.9.4.1.1-2)

P ∅ P (AASHTO 6.9.2.1-1)


STEEL H-PILE DESIGN CRITERIA

PART 2

DATE: 30Jan2018

SHEET 9 of 14

FILE NO. 23.01-9

STEEL H-PILE DESIGN CRITERIA (Cont’d):

Where: ∅ 0.7 for combined axial & flexural resistance of H-piles as specified in Article 6.5.4.2

Cw = warping torsional constant (See HP Shapes Properties Table on Sheet 9)

G = shear modulus for elasticity for steel determined as specified in Article 6.9.4.1.3

J = St. Venant torsional constant (See HP Shapes Properties Table on Sheet 9)

Qs = slender element reduction factor determined as specified in Article 6.9.4.2

Po = equivalent nominal yield resistance determined as specified in Article 6.9.4.1.1

b = half-flange width of rolled I- and tee sections as specified in Table 6.9.4.2.1-1

Check flexural slenderness limits of flanges:

λ = = slenderness ratio for flange (AASHTO 6.12.2.2.1-3)

λ = 0.38 = limiting slenderness ratio for compact flange (AASHTO 6.12.2.2.1-4)

λ = 0.83 = limiting slenderness ratio for non-compact flange (AASHTO 6.12.2.2.1-5)

If λ λ , then: M M 1.5F S (AASHTO 6.12.2.2.1-1)

M M 1.5F S

If λ λ λ , then: M 1 1SZ

λ λ

0.45EFyf

F Z

(AASHTO 6.12.2.2.1-2)

M 1 1S

Zλ λ

0.45EFyf

F Z

If λ λ , then: M F S (AASHTO C6.12.2.2.1)

M F S

M ∅ ∙ M (AASHTO 6.12.1.2.1-1)

M ∅ ∙ M

Where: ∅ 1.0 for combined axial & flexural resistance of H-piles as specified in Article 6.5.4.2 Check combined axial and flexure:

If 0.2 , then: P2.0P

MM

M

M1.0 (AASHTO 6.9.2.2-1)

If 0.2 , then: PP

89

MM

M

M1.0 (AASHTO 6.9.2.2-2)


PROPERTIES FOR DESIGNING STEEL H-PILES

PART 2

DATE: 30Jan2018

SHEET 10 of 14

FILE NO. 23.01-10

PROPERTIES FOR DESIGNING STEEL H-PILES:

HP Shapes Dimensions

Shape Area,

A Depth,

d

Web Flange

Thickness, tw

Width, bf

Thickness, tf

in. 2 in. in. in. in.

HP14x117 x102 x89 x73

34.4 30.0 26.1 21.4

14.2 14.0 13.8 13.6

0.805 0.705 0.615 0.505

14.9 14.8 14.7 14.6

0.805 0.705 0.615 0.505

HP12x84 x74 x63 x53

24.6 21.8 18.4 15.5

12.3 12.1 11.9 11.8

0.685 0.605 0.515 0.435

12.3 12.2 12.1 12.0

0.685 0.610 0.515 0.435

HP10x57 x42

16.8 12.4

9.99 9.70

0.565 0.415

10.2 10.1

0.565 0.420

Properties

Shape Nominal Weight

Axis X-X Axis Y-Y

l S r Z l S r Z

lb/ft in.4 in.3 in. in.3 in.4 in.3 in. in.3

HP14x117 x102 x89 x73

117 102 89 73

12201050 904 729

172 150 131 107

5.96 5.92 5.88 5.84

194 169 146 118

443 380 326 261

59.5 51.4 44.3 35.8

3.59 3.56 3.53 3.49

91.4 78.8 67.7 54.6

HP12x84 x74 x63 x53

84 74 63 53

650 569 472 393

106 93.8 79.1 66.7

5.14 5.11 5.06 5.03

120 105 88.3 74.0

213 186 153 127

34.6 30.4 25.3 21.1

2.94 2.92 2.88 2.86

53.2 46.6 38.7 32.2

HP10x57 x42

57 42

294 210

58.8 43.4

4.18 4.13

66.5 48.3

101 71.7

19.7 14.2

2.45 2.41

30.3 21.8


STEEL H-PILE DESIGN EXAMPLE

PART 2

DATE: 30Jan2018

SHEET 11 of 14

FILE NO. 23.01-11

STEEL H-PILE DESIGN EXAMPLE: Coarse grain soil, medium relative density, above ground water. HP 12x53 Fy = 50 ksi E = 29,000 ksi Strength I Loading 100 Year Storm Pile Length = 60 ft Scour Depth = 10 ft D = 50 ft

P 124kip M 250kip ∙ in M 50kip ∙ in

K K 2.1 K 1.2 15.86ft

Determine axis for critical buckling resistance:

Kr

79.47 K

r73.9 (See coarse grain soil example.)

Kl120, ∴ element satisfies limiting slenderness ratio requirement.

Since Kr

K

r critically bucking,

K , will be determined about the x-axis.

K 2.1 15.86 x12inft

399.67 in K 1.2 14.68 x 12inft

211.4in

Since K K , torsional buckling and flexural torsional buckling shall be applicable:

Pπ ECK

GJA

I I; where G 0.385 ∙ E 1.12x10 ksi

π 29000 4080

399.671.12x10 1.12

15.5393 127

590.57kip

Check compressive slenderness limits of member elements:

bt

60.435

13.79 0.56EF

13.49 ∴ By inspection, 0.56EF

bt

1.03EF

Q 1.415 0.74bt

F

E1.415 0.74

60.435

5029000

0.991


STEEL H-PILE DESIGN EXAMPLE

PART 2

DATE: 30Jan2018

SHEET 12 of 14

FILE NO. 23.01-12

STEEL H-PILE DESIGN EXAMPLE (Cont’d): Determine compressive resistance:

P Q F A 0.991 50 15.5 768.2kip

PP

590.6768.2

0.77 0.44

P 0.658 P 0.658.. ∙ 768.2 445.7 kip

P ∅ P 0.7 445.7 312kip

Check flexural slenderness limits of flanges:

λb2t

122 0.435

13.79

λ 0.38EF

0.382900050

9.15

λ 0.83EF

0.832900050

19.99 ∴ Section is non-compact.

λ λ λ , M 1 1SZ

λ λ

0.45EFyf

F Z 1 166.774

13.79 9.15

0.452900050

∙ 50 74

M 3.54x10 kip ∙ in

M 1 1S

Zλ λ

0.45EFyf

F Z 1 121.132.2

13.79 9.15

0.452900050

∙ 50 32.2

M 1.37x10 kip ∙ in

M ∅ M 1.0 3.54x10 3.54x10 kip ∙ in M ∅ M 1.0 1.37x10 1.37x10 kip ∙ in

Check combined axial and flexure:

PP

124312

0.40 0.2

PP

89

MM

M

M0.40

89

2503540

501370

0.49 1.0 ∴ Pile is adequate.

DESIPR

P P

Psh

T

C

W

IGN GUIDRESTRES

PRESTRES

er AASHTO 5

Klr

22

er AASHTO 5hall be such t

ension stress

fPA

Compression s

fPA

fPA

Where: P = ap

M = ap

Size in.

ArA

in

12 14

14 19

18 32

20 40

24 57

* Values fo

** With squa

DE FOR LSSED CON

SSED CONC

5.7.4.3, the ef

: For co

5.9.4.2, the athat:

ses:

M ∙ cI

0

0.1

0.0

stresses:

M ∙ cI

0.4

M ∙ cI

0.60

pplied axial loa

pplied momen

rea Ag

n.2

Mom of Iner

in.4

44 172

96 320

24 874

00 1333

76 2764

or fcpe taken froare strand pat

PILESLATERALNCRETE

CRETE PIL

ffects of slend

ompression m

llowable stres

k

19 ∙ f′ kssc

0948 ∙ f′ ks

5 ∙ f′ k

0 ∙ f′ k

ad

nt = Mx + My

ent rtia Ig

4

Sectio Modul

S

in.3

28 288

01 457

48 972

33 1333

48 2304

om VDOT Stattern

S LLY UNSU

PILE DE

LE DESIGN

derness may

members not b

sses at the se

ksi, for compo

si, for componsubjected to nconditions

ksi, for composubjected to s

ksi, compress

ksi, compress

Propertie

on us

Radius o Gyratio

r

in.

3.46

4.04

5.20

3 5.77

4 6.93

andard BPP P

UPPORTESIGN CR

N CRITERIA

be neglected

braced agains

erviceability li

onents with un

nents with bonot worse tha

onents with bosevere corros

sion due to pr

sion due to pr

es

of n

Compress effective allowance

Std. PS Strands

751

834

835

806

751

Plan sheets

ED PILESRITERIA

A:

d if:

st sidesway

mit state afte

nbonded pres

nded prestresn moderate c

onded prestresion condition

restress plus p

restress plus t

sive stress in prestress for

es for all prespsi

s

Stainles Steel Str

871

850

867

876

747

**

S PART 2

DATE: 30

SHEET 13

FILE NO.

r prestress lo

stressing tend

ssing tendonscorrosion

essing tendons

permanent lo

total load

concrete dueces only (afte

stess losses),

ss rands

CFRStran

1 78

0 85

7 86

6 83

7 78

**

Jan2018

3 of 14

23.01-13

osses

dons

s

ns

oads

e to er fcpe

RP nds

83

54

61

39

83


PRESTRESSED CONCRETE PILE DESIGN EXAMPLE

PART 2

DATE: 30Jan2018

SHEET 14 of 14

FILE NO. 23.01-14

PRESTRESSED CONCRETE PILE DESIGN EXAMPLE: 12” prestressed concrete pile using standard prestress strands (4), moderate corrosion conditions. f’c = 5 ksi Strength I Loading 100 Year Storm Pile Length = 60 ft Scour Depth = 10 ft D = 50 ft K = 1.2 P 72kip M 120kip ∙ in M 12kip ∙ in

Klr

1.2 60x12inft

3.464249 22 ∴ Slenderness effects shall be considered.

Check serviceability stresses:

fPA

M ∙ cI

0.19 ∙ f

fPA

M ∙ cI

0.75172144

132 61728

0.793 ksi 0.424 ksi ∴ Tension OK

fPA

M ∙ cI

0.45 ∙ f′

fPA

M ∙ cI

0.75172144

132 61728

1.71 ksi 2.25 ksi ∴ Compression OK

fPA

M ∙ cI

0.60 ∙ f′

fPA

M ∙ cI

0.75172144

132 61728

1.71 ksi 3.0 ksi ∴ Compression OK

For 12” prestressed concrete pile using standard prestess strands, fcpe is the same value for both square and circular strand patterns. For pile sizes with different values, check serviceability stresses for both patterns. Reference: Teng, W. C. 1962. Foundation Design. Prentice-HalI, Inc., Englewood Cliffs, New Jersey.

PILES LATERAL LOADED PILE ANALYSIS FOR POINT OF FIXITY

DESIGN PROCEDURE


FILE NO. 23.02-1

POINT OF FIXITY ANALYSIS FOR LATERALLY LOADED SINGLE PILE: Design Procedure for single pile analysis: The design of a pile foundation requires the designer to consider factors involving performance, costs and methods of construction. Two aspects of design are the computation of loading that will cause the pile to fail as a structural member and the level of loading that will cause an unacceptable lateral deflection. This step-by-step procedure describes the use of an acceptable software program that has the capacity to develop p-y curves to determine the pile length to establish fixity. The final pile length (structural length) can then be used to determine the structural capacity of the selected pile. 1. Collect all relevant data, including the soil profile, soil properties, magnitude and type of

loading, and performance requirements for the structure being analyzed. Since limiting deflection criteria is a service condition, the loads used will be service limit state (unfactored).

2. Select a pile type and size for analysis. If a prestressed concrete pile is chosen, reinforcing will also be needed to determine pile properties. The analysis program selected may then compute remaining pile information used for analysis.

3. Develop site specific p-y curves based on in-situ data. The designer can obtain the soil data required from the selected analysis software using boring logs in conjunction with Tables 1 through 3 on File No. 23.01-3. Alternatively, soil parameters can be obtained directly from a geotechnical engineer. Most analysis programs have the ability to select p-y curves for each soil layer based on the provided soil input information. Alternatively, the user may input developed p-y curves.

4. Run software analysis using an initial pile depth based on the limiting project specific deflection criteria. Plot deflection verse depth curves for each load case under study. Several trial sizes and depths may be required to achieve the established design criteria. After the deflection criteria has been satisfied, the determination of fixity can be determined from the plots of Pile Depth verse Deflection.

5. Select the point of fixity from the plotted curves. Point of fixity is where the deflection curve crosses the zero line when subjected to service lateral loads. There is no universal opinion as to whether fixity should occur at one or two crossings of the zero line. Choosing fixity at the second crossing would be a conservative assumption and will be used for this example.

The software used in this sample analysis is L-Pile 2016, Version 9. L-Pile is a multi-purpose program that can analyze a pile subjected to lateral loading. It computes deflection, shear, bending moment and soil response with respect to depth in nonlinear soils. The soil and rock is modeled using lateral load transfer curves (p-y) based on either published recommendations, or alternatively, user input p-y curves developed for each soil layer. Several types of pile head loading conditions may be selected along with the structural properties of the pile. The determination of point of fixity for a laterally loaded pile requires a pile deflection verse pile depth curve for all of the chosen load cases, as well as the soil profile along the length of pile. For this analysis, loads at the service limit state were chosen. Soils information from the boring logs was used in conjunction with the corresponding values for the soil properties provided in Tables 1 through 3 on File No. 23.01-3. The Coefficient of Horizontal Subgrade Reaction (k) was chosen by L-Pile using the user provided information.


DESIGN ASSUMPTIONS AND RESULTS


FILE NO. 23.02-2

DESIGN ASSUMPTIONS AND RESULTS: Loading: 1. The loads used for this example are per pile and unfactored. The loads used are 134 kips

vertical, 4.15 kips lateral longitudinal, 6.68 kips lateral transverse.

2. Moment at the top of pile was not used for this analysis. Both a fixed and free head (i.e., top of pile) condition is achievable without moment input, and therefore was not calculated for this example.

3. Since this analyses is for point of fixity, service limit state loads were used. Pile head deflection may have a limiting value depending on performance criteria that has been established. For this example, ½ inch at the top of pile is used.

4. Pile group effects were not considered.

5. In the longitudinal direction, the pile is assumed to be in a free head condition (i.e., rotation free and translation free). In the transverse direction, the pile is assumed to be in a fixed head condition (i.e., rotation fixed and translation free; slope equals zero).

Soils: 1. Soil properties used were determined using boring logs in conjunction with Tables 1 through

3 on File No. 23.01-3.

2. A 3.5 foot scour depth was assumed for this example. Results: 1. Plots of pile head deflection verse pile depth for scour and non-scour conditions are shown

on File Nos. 23.02-3 and -4, respectively.

2. The analysis considers the nonlinear properties of the soils. For this example, the effects of scour can be seen as negligible as shown by the top of pile deflections of the plots.

3. From both plots, the first inflection point is at a depth of approximately -18 ft. for the free head condition and approximately -23 ft. for the fixed head condition. The second inflection point occurs at approximately -36 ft. for both cases. The second inflection point is chosen for fixity and an unbraced length of 36 ft. below the pile head is assumed for determining the structural capacity of the pile.


L-PILE RESULTS FOR SCOUR CONDITION


FILE NO. 23.02-3


L-PILE RESULTS FOR NON-SCOUR CONDITION


FILE NO. 23.02-4

PILES TABLE OF CONTENTS - Virginia Department of ... · PDF file23.01-12 Steel H-Pile Design...

Documents

Transcript of PILES TABLE OF CONTENTS - Virginia Department of ... · PDF file23.01-12 Steel H-Pile Design...