nonlinear modeling of piles using sap2000

7/25/2019 Nonlinear Modeling of Piles Using SAP2000

1/7

Nonlinear Modelling of Pile using SAP 2000

Indo-Norwegian Training Programme on

Nonlinear Modelling and Seismic Response Evaluation of StructuresDecember 14-16, 2014Continuing Education Center, IIT Roorkee

Non-Linear Modelling/Analysis of Pile using SAP 2000

Shrabony Adhikary

Research Scholar, Department of Earthquake Engineering, IIT RoorkeeFor Queries please mail to:[email protected]

Step-1 Obtain the p-y,t-z and q-z curves at different depths along the pile

for the given soil profile

Soil Profile

Depth (m) Soil Type Undrained shear strength(kN/m

2)

Unit weight(kN/m

3)

0-2 Stiff Clay 80 17

2-8 Stiff Clay 100 188-12 Stiff Clay 120 19.5

12-16 Stiff Clay 150 20

16-22 Stiff Clay 180 20

22-40 Stiff Clay 200 21

Laterally loaded Piles in Stiff Clay

As per API (2005) the lateral soil resistance deflection relationship for stiff clay above water

table is nonlinear and in the absence of experimental data the following expression can be used

25.0

50

5.0

y

y

p

p

ltu

(1)

where the value of premains constant beyond y=16y50in case of stiff clay and y50=2.550D, is

the deflection at one-half the ultimate soil resistance and 50 =strain at one-half the maximum

difference in principal stresses of undisturbed soil sample.
mailto:[email protected]:[email protected]:[email protected]:[email protected]


2/7




ltup

p

50y

y

0 0

0.5 10.84 8

1 16

1

pult can be obtained asdescribed in the following section.

D

ZcJZcp uuult 3 (2)

uult cp 9 (3)

Z= depth under consideration, cuis the shear strength at depthZ, andDis the width of the pile.J

is taken as 0.5. ultp is calculated at each depth wherep-ycurve is desired.

Table 1Representative values of50

and cufor normally consolidated clay

Consistency of clay cu(kPa) 50 Soft < 48 0.020

Medium 48-96 0.010

Stiff 96-192 0.005

Derivation of p=y curve parameters

pult(Eq.2) 283.67 327.33 454.00 505.33 556.67 608.00 659.33 710.67 895.50 9

pult(Eq.3) 720.00 720.00 900.00 900.00 900.00 900.00 900.00 900.00 1080.00 10

y50 0.02 0.02 0.02 0.02 0.02 0.02 0.02 0.02 0.02

17.00 17.00 18.00 18.00 18.00 18.00 18.00 18.00 19.50

z 1.00 2.00 3.00 4.00 5.00 6.00 7.00 8.00 9.00

cu 80.00 80.00 100.00 100.00 100.00 100.00 100.00 100.00 120.00 1

D 1.50 1.50 1.50 1.50 1.50 1.50 1.50 1.50 1.50

J 0.50 0.50 0.50 0.50 0.50 0.50 0.50 0.50 0.50

e50 0.01 0.01 0.01 0.01 0.01 0.01 0.01 0.01 0.01


3/7




Axially loaded Pilesin Stiff Clay

As per API (2005) piles should be designed for static and cyclic axial loads. The total ultimate

axial load carrying capacity of the pile is provided through soil-pile skin friction and end bearing

resistance of the pile tip, i.e.

pspufuAu AqAfQQQ (4)

where,fuQ is the skin frictional resistance in kN; puQ is the total end bearing capacity of the pile

in kN; f is thethe unit skin friction in kN/m2

,Asis the side surface area of the pile in m2

,q is

the end bearing capacity in kN/m2

,Apis the gross end area of the pile in m2.

For clay

ucf (5)

ucq 9 (6)

and = a dimensionless factor, uc is the undrained shear strength of the soil, and the factor is

computed as per the following equations, 0.15.0 5.0 and 0.15.0 25.0 , and 1.0,

where0

/pcu and 0p is the effective overburden pressure

As per API (2005) the analytical expression to find the skin friction capacity of piles is given by

cc z

z

z

z

t

t 2

max

(7)

where, z is the local pile deflection in m, zc is the relative displacement required and is taken as

0.005 m in case of clay. tmax is the maximum shear stress in kN/m2

and t is the shear stress at

nodal point in kN/m2. The t-zcurves as defined in API (2005) are the function ofz/D and t/ tmax .


4/7




D

z

maxt

t

0 0

0.0016 0.3

0.0031 0.5

0.0057 0.750.0080 0.9

0.01 1.0

0.02 0.7-0.9

0.7-0.9

Derivation of t=z curve parameters

17.00 17.00 18.00 18.00 18.00 18.00 18.00 18.00 19.50 1

z 1.00 2.00 3.00 4.00 5.00 6.00 7.00 8.00 9.00 1

cu 80.00 80.00 100.00 100.00 100.00 100.00 100.00 100.00 120.00 12

po' 17.00 34.00 52.00 70.00 88.00 106.00 124.00 142.00 161.50 18

4.71 2.35 1.92 1.43 1.14 0.94 0.81 0.70 0.74

0.34 0.40 0.42 0.46 0.48 0.51 0.56 0.60 0.58

f 27.16 32.30 42.46 45.73 48.43 51.48 55.68 59.58 69.61 7

As per API (2005) the analytical expression to find pile tip settlement curves is given by

3/1

max

cbz

z

q

q (8)

where, qmaxis the maximum bearing stress in kN/m2;zis the axial tip deflection of the pile in m

, and zcb is the maximum displacement required to develop qmax. The q-zcurves as defined in

API (2005) are the function ofz/D and q/ qmax .

D

z

max

q

q

0.002 0.25

0.013 0.5

0.042 0.75

0.073 0.9

0.1 1


5/7




Step-2 Define section properties>Link support properties>Add new

properties

Define Multilinear Force-Deformation Parameters in terms of force-displacement curves as

obtained. It is to be noted that the p-y and t-z curves are to be defined in both tension and

compression however, the q-z curves should be defined only for compression.


6/7





7/7




References

American Petroleum Institute (API), 2005.Recommended Practice for Planning, Designing and

Constructing Fixed Offshore Platforms. API-RP2A-WSD, Washington, D.C.

Erhan, S., and Dicleli, M. 2014. Effect of dynamic soilbridge interaction modeling assumptions

on the calculated seismic response of integral bridges. Soil Dynamics and Earthquake

Engineering, 66(0):42-55.

Shirato M, Koseki J, and Fukui J. 2006. A new nonlinear hysteretic rule for winkler type soil-pile

interaction spring that consider loading pattern dependency. Soil Found Jpn Geotech

Soc,46(2):17388.

nonlinear modeling of piles using sap2000

Documents