Pile Eccentricity Analysis for 2 Columns Combined Pilecap

1. PREPARED BY: FARDHAH MANIRAH BINTI AZMAN
SUPERVISED BY: IR AZHAR AHMAD
SKAA 4034 FINAL YEAR PROJECT
Piles Eccentricity Analysis For Two
Columns Combined Pile Cap

2. INTRODUCTION
– One type of failure for piled foundation is eccentricity.
– Pile eccentricity happens when there is short comings of
driving pre-designated piles at exactly correct position
on the ground.
– The deviation of these piles may jeopardize the integrity
of pile cap.

3. PROBLEM STATEMENT
The short comings of driving pre-designated piles at
exactly correct position has introduced the ‘pile
eccentricity’. The issues addressed are:
– Does the pile eccentricity influences the overall pile
group centroid and reliability of load carrying
capacity?
– What is the allowable maximum eccentricity for the
pile cap to be safe and reliable?
– What happens when there is an excessive eccentricities
occur?

4. OBJECTIVES
The objectives of this study are:
1. To develop Microsoft Excel Spreadsheet for
analyzing two columns combined pile cap with zero
and non-zero pile eccentricity.
2. To establish Net Pile Group Eccentricity Limit
Chart that can be used on site for immediate checking.
3. To establish an Optimum Add-On Pile Location
Chart for cases where excessive eccentricities occur.

5. SCOPE OF STUDY
In order to ensure the results obtained can help achieve
the objectives of this study, the scope has been limited
to:
– Two columns combined pile cap.
– Spacing between column: 1.75 m.
– Type of pile: Pre-cast Square RC Pile.
– Working load is 300 kN for 300 × 300 mm pile.
– Range of pile group: 4-9 piles.
– Type of failure: Eccentricity.

6. METHODOLOGY
Piles Eccentricity Analysis for Two Columns Combined Pile Cap
Analysis
Zero Eccentricity Non-Zero Eccentricity
Load Balance Check
Establish Net Pile Group
Eccentricity Limit Chart
Establish Optimum Add-
On Pile Location
Load on column 1 & 2, k, conversion factor, eccentricity value
User input
verified
outside safe zone
Centroid Loading, Pile Arrangement & Load Distribution
Location Add-On Pile
to determine
to obtain
checking, < 300 kN
OBJECTIVE 1
OBJECTIVE 2
OBJECTIVE 3

7. RESULTS & ANALYSIS
1. Microsoft Excel Spreadsheet Program
User Key-In Value:
Results Obtained from Program:
1000 kN 1100 kN
1750 mm
Fixed Parameters
Spacing between pile cap = 1.75 m
Ø RC Pile = 300 × 300 mm
Pile Working Load = 300 kN
Number of Pile = 6
Size of Pile Cap = 1800 × 3000 × 1100 mm
Total Service Load + Self-weight Pile Cap = 1648.50 kN
Position of each piles
Value of Net Eccentricity
Centroid point for loading and pile group
k = 4
Conversion factor = 1.4

8. RESULTS & ANALYSIS
Pile group with zero eccentricity:
P1 P2 P3
P4 P5 P6
C1 C2
Centroid line for loading and pile group align on the same line at
(0.00, 0.00) indicates that there is no eccentricity occur.
Legend
Centroid line (PG)
Centroid line (Loading)
P1 P2 P3 P4 P5 P6 C1 C2
X-Coordinate -1200.00 0.00 1200.00 -1200.00 0.00 1200.00 -916.67 833.33
Y-Coordinate 600.00 600.00 600.00 -600.00 -600.00 -600.00 0.00 0.00

9. RESULTS & ANALYSIS
Pile group with eccentricity:
Centroid line for pile group has been deviated from its original position.
The new centroid point of pile group is (-39.67, 14.00) while the
centroid point for loading remains the same (0.00, 0.00).
Legend
Centroid line (PG)
Centroid line (Loading)
25.00
75.00
98.00
75.00
15.00
100.00
45.00
150.00
34.00
125.00
Net
Eccentricity
(-238.00, 84.00)
P1 P2 P3 P4 P5 P6 C1 C2
X-Coordinate -1125.00 -98.00 1215.00 -1155.00 -150.00 1075.00 -916.67 833.33
Y-Coordinate 625.00 525.00 600.00 -500.00 -566.00 -600.00 0.00 0.00
My
Mx

10. RESULTS & ANALYSIS
Loading distribution for zero and non-zero eccentricity:
Pile Service Load+Sw/n Mxy/Ix Myx/Iy Load per Pile (kN) Checking (< 300kN, OK!)
P1 274.75 7.21 13.51 254.03 OK!
P2 275.75 6.03 0.73 267.99 OK!
P3 274.75 6.92 15.61 283.45 OK!
P4 274.75 6.07 13.88 266.94 OK!
P5 274.75 6.85 1.37 280.22 OK!
P6 274.75 7.25 13.87 295.87 OK!
Total Load 1648.50 BALANCED
Pile Service Load+Sw/n Mxy/Ix Myx/Iy Load per Pile (kN) Checking (< 300kN, OK!)
P1 274.75 0.00 0.00 274.75 OK!
P2 275.75 0.00 0.00 275.75 OK!
P3 274.75 0.00 0.00 274.75 OK!
P4 274.75 0.00 0.00 274.75 OK!
P5 274.75 0.00 0.00 274.75 OK!
P6 274.75 0.00 0.00 274.75 OK!
Total Load 1648.50 BALANCED
Zero eccentricity:
Non-zero eccentricity:
Total Service Load + Self-weight of Pile Cap = Total Load per Pile subjected to Moment

11. RESULTS & ANALYSIS
2. Net Pile Group Eccentricity Limit Chart

12. RESULTS & ANALYSIS
The highlighted zone is called safe zone which means any points located inside the
safe zone, the structure is considered safe and reliable to use.
Safe zone
Nultimate = 2100 kN
Ratio = 5.5
Net Pile Group
Eccentricity
X = -238.00 mm
Y= 84.00 mm

13. RESULTS & ANALYSIS
3. Additional Pile Procedure
The ultimate load is changed from 2100 kN to 2205 kN while other parameters
remains. The area of safe zone became smaller due to increase in loading.
Safe zone
Nultimate = 2205 kN
Ratio = 5.75
Net Pile Group
Eccentricity
X = -238.00 mm
Y= 84.00 mm

14. RESULTS & ANALYSIS
– Since the net pile group eccentricity is located outside the safe zone, some pile
may subjected to failure. Table below shows the distribution of loading for
ultimate load 2205 kN with same value set of eccentricity.
Pile Service Load+Sw/n Mxy/Ix Myx/Iy Load per Pile (kN) Checking (< 300kN, OK!)
P1 287.25 7.54 14.12 265.59 OK!
P2 287.25 6.31 0.76 280.19 OK!
P3 287.25 7.23 16.33 296.34 OK!
P4 287.25 6.34 14.51 279.08 OK!
P5 287.75 7.16 1.44 292.97 OK!
P6 287.75 7.58 14.50 309.33 FAILED!
Total Load 1723.50 BALANCED
Total Service Load + Self-weight Pile Cap = 1723.50 kN

15. RESULTS & ANALYSIS
– Since Pile 6 exceeds pile working load, a new pile is added to the structure.
– The location of pile is determined from Optimum Position of Add-On Single
Pile chart below.
238.00
-84.00
14.00
-39.67
P1
P2
P3
P4
P5 P6
C1 C2
Add-On
Pile
(238.00, -84.00)
Failed Pile

16. RESULTS & ANALYSIS
– Pile capacity checking is performed as shown in the table below after
additional pile. Pile working load is reduced about 15% from 300 kN to 255
kN.
Pile Service Load+Sw/n Mxy/Ix Myx/Iy Load per Pile (kN) Checking (< 255 kN, OK!)
P1 246.21 0.00 0.00 246.21 OK!
P2 246.21 0.00 0.00 246.21 OK!
P3 246.21 0.00 0.00 246.21 OK!
P4 246.21 0.00 0.00 246.21 OK!
P5 246.21 0.00 0.00 246.21 OK!
P6 246.21 0.00 0.00 246.21 OK!
Add-On Pile 246.21 0.00 0.00 246.21 OK!
Total Load 1723.50 BALANCED

17. CONCLUSION
This program serves to reduce time and save cost to solve problem
regarding pile eccentricity for engineers. Findings conforming to the
objectives of this study can be summarized as below:
1. A program for analyzing two columns combined pile cap with zero
and non-zero eccentricity using Microsoft Excel Spreadsheet was
developed.
2. A Net Pile Group Eccentricity Limit Chart to determine the
maximum allowable net eccentricity was established. The chart can be
used on site for immediate checking.
3. An Optimum Add-On Pile Location Chart was established. Load
balance check was conducted for verification.

18. FUTURE STUDY
Include design stage for two column
combined pile cap.
Multiple number of additional pile for
excessive eccentricity.
1
2

19. Thank You!