IOWA STATE UNIVERSITY
Civil, Construction & Environmental Engineering
Bradley Fleming, Sri Sritharan, & JinWei Huang
Iowa State University
Kanthasamy Muraleetharan & Gerald Miller
Oklahoma University
Dream it, Design it, Build it.
www.ccee.engineering.iastate.edu
1. Finite Element (OpenSees)
– Detailed 3D analysis
– Used to understand complex interactions
between
•
•
pile and improved soil
improved soil and unimproved soil
2. p-y Analysis Method (LPILE)
– Simple 2D analysis
– Attractive for engineers in industry
– Account for improved soil of limited width by
applying modification factors to p-y relationships
Soil “Island” (OpenSeesPL soil mesh generation)
• 10.3 m long, 5.15 m wide, and 7.62 m high
• 3,450 nodes
• 2,492 soil elements
Pile (forceBeamColumn)
• 7.23 m total length
• 34 beam elements
• 5.3 m embedded length
• Non-linear fiber section
(half of pile)
P
Clay
Sand
Contact Elements (BeamContact3D)
Soil Elements (SSPbrick)
Clay
• PressureIndependMultiYield
• Gmax = 3250 kN/m2
• c = 30.5 kN/m2
• γsat =1.8 ton/m3
Sand
• PressureDependMultiYield
• Gmax = 1.0E+5 kN/m2
• φ = 37 deg.
• γsat =2.0 ton/m3
Soil
Pile
m1
slave
m2
r
Unimproved Pile
Improved Pile
P
moment
Mu
P
i=1
i=2
..…
..…
i=1
i=2
E pI p
curvature
p
y
..…
..…
i=n
i=n
• Attenuation of stresses in soil layer
1
0.9
0.9
0.7
0.6
𝜎𝑖𝑗 𝜎𝑖𝑗, 𝑚𝑎𝑥
𝐾0 (𝛽𝑟 𝑟𝑜 )
𝜙=
𝐾0 (𝛽)
0.8
𝜎𝑖𝑗 𝜎𝑖𝑗, 𝑚𝑎𝑥
or
𝑢 𝑢𝑚𝑎𝑥
1
Guo and Lee (2001)
0.5
0.4
0.3
0.2
0.6
0.5
0.4
𝜙𝑠𝑜𝑓𝑡 𝑐𝑙𝑎𝑦
0.3
0.1
0
0
𝜙𝐶𝐷𝑆𝑀
0.7
0.2
𝜙 =0.05
0.1
0.8
5
10
15
𝑟 𝑟𝑜
0
0
5
𝑙𝑒𝑓𝑓 𝑟𝑜
𝑙𝑒𝑓𝑓 𝑟𝑜
𝑏 2 ≥ 𝑙𝑒𝑓𝑓
𝑘𝐶𝐷𝑆𝑀
10
𝑏 < 2𝑙𝑒𝑓𝑓
𝑘𝑒𝑓𝑓
15
𝑟 𝑟𝑜
p
pult
ki
R  Leff ki
0.5pult
Improved Soil
Unimproved Soil
𝑅𝐼
𝑅𝑈
𝐿𝐼
𝐿𝑈
•
R – Equivalent rigidity (analogous to AE
for axially loaded member)
•
Leff - Length of uniform soil layer
•
ki – Equivalent stiffness of the p-y
curve
•
S - Stiffness of spring
1
y
y50
1
1
1


S eff S I SU
𝑆𝐼 = 𝑅𝐼 𝐿𝐼
𝑆𝑒𝑓𝑓
𝑆𝑈 = 𝑅𝑈 𝐿𝑈
𝐿𝑒𝑓𝑓,𝑈
𝐿𝑈 = 𝐿𝑒𝑓𝑓,𝑈 −
𝐿𝐼
𝐿𝑒𝑓𝑓,𝐼
1
0.9
0.8
𝜎𝑖𝑗 𝜎𝑖𝑗, 𝑚𝑎𝑥
0.7
𝜙𝑆𝑜𝑓𝑡 𝐶𝑙𝑎𝑦
0.6
0.5
𝑘𝑒𝑓𝑓 =
𝜙𝐶𝐷𝑆𝑀
0.4
0.3
𝑘𝑖,𝐶𝐷𝑆𝑀 𝑘𝑖,𝑠𝑜𝑓𝑡 𝑐𝑙𝑎𝑦 𝐿𝑒𝑓𝑓,𝐼
𝑘𝑖,𝐶𝐷𝑆𝑀 𝐿𝑒𝑓𝑓,𝐼 − 𝐿𝐼 + 𝑘𝑖,𝑠𝑜𝑓𝑡 𝑐𝑙𝑎𝑦 𝐿𝐼
𝜙𝐶𝑜𝑚𝑏𝑖𝑛𝑒𝑑
0.2
𝜙 = 0.05
0.1
0
0
5
𝐿𝐼
10
15
𝐿𝑈
𝐿𝑒𝑓𝑓,𝐼
𝐿𝑒𝑓𝑓,𝑈
20
25
30
𝑟 𝑟𝑜
keff
p
ki,CDSM
P3
CDSM
1
Modified
1
0.5pult,CDSM
Ωp (0.5pult,CDSM)
P1
P2
ki,soft clay
1
Soft Clay
0.5pult,soft clay
y50,CDSM
Ωy (y50,CDSM)
y50,soft clay
JinWei Huang (2011)
y
0
Deflection (in)
10
15
20
5
25
30
0
120
5
10
Deflection (in)
15
20
25
30
480
25
100
420
100
20
360
80
10
40
60
240
180
40
Pile 1-9DST
Pile 1-0DGH
120
20
LPILE
5
LPILE
20
60
0
0
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0
0
0
0.1
Deflection (m)
JinWei Huang (2011)
0.2
0.3
0.4
0.5
Deflection (m)
0.6
0.7
0.8
Force (kips)
60
300
Force (kN)
15
Force (kips)
Force (kN)
80
Displacement (in.)
0
5
10
15
20
0
25
Displacement (in.)
10
15
20
5
25
140
60
30
12
120
50
25
10
100
30
6
Pile 2-0DAB
80
15
60
Pile 2-6DEF
Pile 2-0DCD
20
4
LPILE
LPILE
10
0
0
0.1
0.2
0.3
0.4
0.5
Displacement (m)
10
Pile 2-6DGH
40
0.6
0.7
2
20
0
0
5
0
0
0.1
JinWei Huang (2011)
0.2
0.3
0.4
0.5
Displacement (m)
0.6
0.7
Force (kip)
8
Force (kN)
20
Force (kip)
Force (kN)
40
0
5
10
Displacement (in.)
15
20
25
30
0
200
2
4
Displacement (in.)
6
8
10
12
180
180
160
40
160
35
140
40
35
30
30
120
100
20
80
Force (kN)
25
100
20
80
15
15
Pile 2-9DKL (Pull)
60
60
Pile 2-12DMN
Pile 2-9DKL (Push)
10
40
40
LPILE
LPILE
20
0
0
0.1
0.2
0.3
0.4
0.5
Displacement (m)
0.6
10
0.7
0.8
5
20
0
0
5
0
0.05
JinWei Huang (2011)
0.1
0.15
0.2
0.25
Displacement (m)
0.3
0
0.35
Force (kip)
25
120
Force (kip)
Force (kN)
140
-13.6
-9.8
16.4
Displacement (in.)
-1.8
2.2
6.2
300
Sidewall Fracture near
ground surface
35
150
200
*
0
32.6
100
Force (kN)
5
Force (Kips)
15
50
52.6
*
25
100
Force (kN)
-5.8
12.6
0
-5
-7.4
-50
-15
-100
-27.4
-100
TPU
-25
-150
-45
-0.4
-0.2
0
0.2
0.4
-47.4
-35
-200
-0.6
TPI
-200
LPILE
0.6
LPILE
-300
-0.25 -0.2 -0.15 -0.1 -0.05
0
-67.4
0.05 0.1 0.15 0.2 0.25
Displacement (m)
Displacement (m)
Created byJinWei
JinWeiHuang
Huang,
2010 (ISU)
(2011)
Force (kip)
-23.6
200
Displacement (in.)
-3.6
6.4
-300
-200
Moment (kN-m)
-100
0
100
200
300
400
-400
0
0
1
-300
-200
Moment (kN-m)
-100
0
100
200
300
400
0
1
5
5
3
10
4
Depth (m)
2
Depth (ft)
Depth (m)
2
3
10
Improvement
Depth
4
15
5
15
5
6
20
7
-3,540 -2,540 -1,540
-540
460
1,460
Moment (kip-in.)
TPU +12" Disp.
LPILE +12" Disp.
2,460
TPU -12" Disp.
LPILE -12" Disp.
3,460
6
20
7
-3,540 -2,540 -1,540
-540
460
1,460
Moment (kip-in.)
2,460
TPI +6" Disp.
TPI -6" Disp.
LPILE +6" Disp.
LPILE -6" Disp.
Created byJinWei
JinWeiHuang
Huang,
2010 (ISU)
(2011)
3,460
Depth (ft)
-400
0
• Both LPILE and OpenSees closely resembles
centrifuge and field behavior
• OpenSees is an effective analysis tool but
requires specialized knowledge and involves
high computation costs
• LPILE is an attractive tool for engineers and
has flexibility to modify p-y curves
• The proposed method for modifying p-y
curves does well in characterizing the
behavior of piles in improved soil of limited
width