WELCOME TO MY PRESENTATION

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MANDALAY TECHNOLOGICAL UNIVERSITYDEPARTMENT OF CIVIL ENGINEERING

Study on Performance of Pile Foundation in Horizontal and Sloping Ground

3rd Seminar(21.6.2016)

Supervised byDr. Kay Thwe TunAssociate ProfessorDepartment of Civil Engineering

Presented byMg Zin Ko LinnME.CSE-18

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Outline of Presentation

o Introductiono Objectiveso Scope of the studyo Case Study and Analysis resultso Future Plan

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Introduction

o A foundation is the most important part of the engineering

system.

o The foundation is that transmits the loads to the underlying

soil.

o The design of foundation must be considered depending upon

the superstructure of loads, geological conditions of soil, the

behaviors of earthquake and wind loadings and other

considerations.

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o If the building is rested on a weak soil formation which cannot

resist the loads coming from the proposed building, it is

needed to be choosen pile foundation.

o The soil-pile interaction mechanism in a sloping ground is

different from that in a horizontal ground.

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Objectives

o To compare the lateral deflection and moment of pile in

horizontal and sloping ground

o To find the effect of pile diameter on lateral deflection and

moment of pile in horizontal and sloping ground

o To study the effect of pile length on lateral deflection and

moment of pile in horizontal and sloping ground

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Scope of the Study

o A twelve-storyed reinforced concrete building is considered

in seismic zone 4.

o Dynamic analysis of superstructure is designed with the

application of ETABS computer software.

o For the building design, UBC-97 for loading and ACI (318-

99) for design is used.

o Soil parameters for substructure system are taken from soil

report.

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o The foundation design is studied at 1V:2H,1V:3H sloping

ground and horizontal ground.

o Parametric study is done by varying diameter and length.

o The pile foundation design is carried out by using ALLPILE

Software.

o Pile cap design is calculated by hand calculation.

o The behavior of pile foundation under seismic load are

considered by the help of PLAXIS Software.

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Profile of the Proposed Building

• Type of Structure :12-storeyed R.C Building

• Location :Seismic Zone (4)

• Type of Occupancy :Hotel

• Shape of Building :Rectangular shape

• Size of Building :Length = 130 ft

:Width = 60 ft

• Height of Building :Typical story height = 10 ft

:Bottom story height = 12 ft

:Total height = 134 ft9

3D View of Proposed Building10

Stability Checking for Proposed Building

Checking X-direction Y-direction Limit Remark

Sliding 3.11 3.11 1.5 Satisfied

Overturning Moment 10.75 5.26 1.5 Satisfied

Story Drift 1.59579 1.78814 2.4 Satisfied

P-∆ Effect 0.002235 0.002087 0.002353 Satisfied

Torsional Irregularity 1.01 1.04 1.2 Satisfied

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Allowable Bearing Capacity of the Soil

The bearing capacity of soil is the maximum average contact pressure between the foundation and the soil. Ultimate bearing capacity is the maximum pressure which can be supported without failure. Allowable bearing capacity is the ultimate bearing capacity divided by a factor of safety.

The allowable bearing capacity is calculated by the following three Equations:

1. Meyerhof's Equation,2. Hansen's Equation and3. Vesic's Equation

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Results of Allowable Bearing Capacity

Arthur q all: (ton / ft2)

Meyerhof 1.42

Hansen 1.14

Vesic 1.01

The average allowable bearing capacity = 1.19 ton/ft2

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The average allowable bearing capacity = 1.19 ton/ft2

The unfactored column load of superstructure = 25622.1 kips

Available foundation area of proposed building = 64x134

= 8576 ft2

Required bearing capacity =

= 25622.1 / 8576

= 2.99 k/ft2

Required bearing capacity of superstructure > Allowable bearing capacity of soil

Therefore, pile foundation is used.

Determination of Foundation Type

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Column Load Type

Type Column Load Range

Maximum Column Load(kip)

1 400 - 600 591.48

2 150 - 400 357.48

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Type 1 2Pile Diameter (ft) 2 2Pile Length (ft) 60 50

Applied Load (kips) 591.68 357.48

Allowable Compression Capacity (kips) 611.86 469.51

Tensile Strength (kips) 226 226Allowable Uplift Capacity (kips) 166.94 137.13

Settlement (in) 0.47304 0.20890

Design Result of Single Pile

Applied Load < Allowable Compression CapacityTensile Strength > Allowable Uplift CapacitySettlement < 1 in

So, the design of single pile foundation is acceptable for both type.

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For piles, a minimum amount of vertical steel reinforcement is 1 % of the cross sectional area of pile.

As = 0.01 x Ags

= 0.01 x π/4 x 22 x144 = 4.52 in2

Number of bars = As / Area of no.7 bar = 4.52 / 0.6 = 7.57 ( Say 8 numbers )

Perimeter with 3" clear cover = πD = π x (2 x12 – 6) = 56.55 in

Spacing between bars = Perimeter with 3" clear cover / number of bars = 56.55 / 8 = 6.48 in ( Say 6 in )

Use 8#7 longitudinal bar with 6" spacing in piles.

Pile Reinforcement

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Detailed of Pile Reinforcement

Type Diameter(ft) Main Steel Reinforcement

Tie Steel Reinforcement Cover(in)

1 2 8#7 #3 spiral @ 3" c/c 3

2 2 8#7 #3 spiral @ 3" c/c 3

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Results of Pile Cap Design by Hand Calculation

Type Length(ft)

Width(ft)

Thickness(ft)

Flexural design X-direction

Flexural design Y-direction

Temperature and

Shrinkage Steel

1 6 6 2.5 8#8@7"c/c 8#8@7"c/c #5@4"c/c

2 5 5 2 9#6@5"c/c 9#6@5"c/c #5@4"c/c

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TypePunching

Shear (kips)

Punching Shear

Strength (kips)

One-way Shear (kips)

One-way Shear

Strength (kips)

1 530.01 < 703.93 39.24 < 140.79

2 377.04 < 435 32.56 < 83.8

Shear Checking for Pile Cap

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Compression and Uplift Capacity

The compression and uplift capacity of group pile is varied along the length of pile and the results are shown in Figure.

0 10 20 30 40 50 60 700

100

200

300

400

500

600

700

0 13 28 45 6283

105127 147 167

8 2546

6993

129169

390

528

612

Vertical Capacity vs Pile Length

Compression Uplift

Pile Length, L (ft)

Pile

Cap

acity

, Q (k

ip)

Type-1

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0 10 20 30 40 50 600

50

100

150

200

250

300

350

400

450

500

0 10 2336

5166

83101

120137

822

3857

7798

129

161

261

470

Vertical Capacity vs Pile Length

Compression Uplift

Pile Length, L (ft)

Pile

Cap

acity

, Q (k

ip)

Type-2

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Vertical Load and Settlement

Type-1Settlement = 0.47304 in < Allowable settlement = 1 in

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Type-2Settlement = 0.20890 in < Allowable settlement = 1 in

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-3.00E-02-2.50E-02-2.00E-02-1.50E-02-1.00E-02-5.00E-030.00E+00

-1.11E-02 -9.56E-03-6.66E-03

-2.88E-02-2.49E-02

-1.75E-02

Deflection(in)

Series1

Type-1 Type-2

Effect of Slope Ratio on Pile head Deflection

Pile head deflection increase with increase in slope ratio.

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0.00E+005.00E+041.00E+051.50E+052.00E+052.50E+053.00E+053.50E+054.00E+05

1.84E+051.74E+051.53E+05

3.62E+053.44E+053.04E+05Moment(lb-In)

Series1

Type-2

Effect of Slope Ratio on Top Moment

Pile top moment also increase with increase in slope ratio.

Type-1

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-3.00E-02-2.50E-02-2.00E-02-1.50E-02-1.00E-02-5.00E-030.00E+00

-1.11E-02-5.79E-03-3.38E-03

-2.88E-02

-1.50E-02

Deflection(in)

Series1

Type-1 Type-2

1V:2H Sloping Ground

Effect of Pile Diameter on Pile Head Deflection

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1V:3H Sloping Ground

-2.50E-02-2.00E-02-1.50E-02-1.00E-02-5.00E-030.00E+00

-9.56E-03-5.00E-03 -2.93E-03

-2.49E-02

-1.30E-02

Deflection(in)

Series1

Type-1 Type-2

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Horizontal Ground Pile head deflection is found as decrease with increase in pile

diameter for all ground conditions.

-1.80E-02-1.60E-02-1.40E-02-1.20E-02-1.00E-02-8.00E-03-6.00E-03-4.00E-03-2.00E-030.00E+00

-6.66E-03-3.50E-03-2.07E-03

-1.75E-02

-9.18E-03

Deflection(in)

Series1

Type-1 Type-2

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Effect of Pile Diameter on Pile Top Moment

1V:2H Sloping Ground

0.00E+005.00E+041.00E+051.50E+052.00E+052.50E+053.00E+053.50E+054.00E+05

1.84E+051.99E+052.13E+05

3.62E+053.93E+05Moment(lb-in)

Series1

Type-1 Type-2

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1V:3H Sloping Ground

0.00E+005.00E+041.00E+051.50E+052.00E+052.50E+053.00E+053.50E+054.00E+05

1.74E+051.89E+05 2.02E+05

3.44E+05 3.73E+05Moment(lb-in)

Series1

Type-1 Type-2

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Horizontal Ground

Pile top moment increase with increase in pile diameter for all ground conditions.

0.00E+005.00E+041.00E+051.50E+052.00E+052.50E+053.00E+053.50E+05

1.53E+05 1.67E+051.79E+053.04E+05 3.30E+05Moment(lb-in)

Series1

Type-1 Type-2

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Effect of Pile Length on Pile Head Deflection

1V:2H Sloping Ground

-1.60E-02-1.40E-02-1.20E-02-1.00E-02-8.00E-03-6.00E-03-4.00E-03-2.00E-030.00E+00

-5.78E-03-5.79E-03-5.80E-03

-1.50E-02 -1.50E-02-1.51E-02Deflection(in)

Series1

Type-1 Type-2

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1V:3H Sloping Ground

-1.40E-02-1.20E-02-1.00E-02-8.00E-03-6.00E-03-4.00E-03-2.00E-030.00E+00

-4.99E-03 -5.00E-03 -5.01E-03

-1.30E-02 -1.30E-02 -1.30E-02

Deflection(in)

Series1

Type-1 Type-2

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Horizontal Ground

There is no considerable change in pile head deflection with increase in pile length.

-1.40E-02-1.20E-02-1.00E-02-8.00E-03-6.00E-03-4.00E-03-2.00E-030.00E+00

-4.99E-03-5.00E-03 -5.01E-03

-1.30E-02 -1.30E-02 -1.30E-02Deflection(in)

Series1

Type-1 Type-2

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Effect of Pile Length on Pile Top Moment

1V:2H Sloping Ground

0.00E+005.00E+041.00E+051.50E+052.00E+052.50E+053.00E+053.50E+054.00E+051.99E+051.99E+051.99E+05

3.93E+053.93E+053.93E+05Moment(lb-in)

Series1

Type-1 Type-2

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1V:3H Sloping Ground

Type-1 Type-20.00E+005.00E+041.00E+051.50E+052.00E+052.50E+053.00E+053.50E+054.00E+05

1.89E+05 1.89E+05 1.89E+05

3.73E+05 3.73E+05 3.73E+05Moment(lb-in)

Series1

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Horizontal Ground There is also no change in pile top moment with increase in pile

length.

0.00E+005.00E+041.00E+051.50E+052.00E+052.50E+053.00E+053.50E+05

1.67E+05 1.67E+05 1.67E+05

3.30E+05 3.30E+05 3.30E+05

Moment(lb-in)

Series1

Type-1 Type-2

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Conclusion

1. Lateral deflection and moment increase with increase in slope ratio. When 1V:2H slope decrease to 1V:3H slope, pile head deflection decrease to 14% and top moment decrease to 5%. When 1V:2H slope decrease to horizontal ground, pile head deflection decrease to 40% and top moment decrease to 16.5%.

2. The effect of pile diameter is studied and it is concluded that lateral deflection decrease with increase in diameter of pile for same length. This is due to the increase in surface area, pile stiffness and moment of inertia. But, pile lateral moment increase because moment is directly proportional with pile stiffness by Subgrade Reaction Approach.

3. The increase in length of pile is not significant affects on lateral deflection and moment of pile. The increase of pile length only affects the vertical capacity of pile depending upon the underlying soil conditions.

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Future Plan

o Behavior of pile foundation in horizontal and sloping ground

considering seismic effect will be evaluated by the help of

PLAXIS Software.

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THANK YOU FOR YOUR ATTENTION