GSA 8'4 Piled Raft Analysis

1
GSA 8.4 Piled Raft Analysis
2
Piled-raft analysis

• The view of piled-raft plus soil model

3
Piled-raft analysis

• The view of piled-raft model plus loadings

4
How the pile-soil interaction works

• Schematic view of how piled-raft analysis works

5
How the pile-soil interaction works

• Basic idea of GSA pile-soil interaction
• The plasticity of the soil immediately around the
  pile are modelled by nonlinear springs. The
  forces in the nonlinear springs are dependent on
  the relative displacements of the pile and soil
  at the same points (pile locations)
• This approach is also used by other pile-soil
  interaction programs such as SPLINTER
• This approach is being considered as industry
  standard for this type of analysis

6
How the pile-soil interaction works

• Every nodes on the piles are connected by 3
  nonlinear springs to represent the soil
  non-linear behaviour immediately around the piles
  in the 3 directions.
• The non-linear springs are then attached to the
  ground (soil) that is still considered as elastic
  media and the settlements are calculated using
  Mindlin method

Non-linear springs
A node on pile
Representing soil and they all coincide with the
pile node
7
How the pile-soil interaction works

• The forces in the non-linear springs (the
  pile-soil interaction force) are

Ax, Ay Az are the interaction area for the
nodes cx, cy cz are the interaction
coefficients (see next slide) fx fy are the
soil contact strengths in x y directions fz is
the soil shear strength between pile and soil
8
How the pile-soil interaction works

• A section of pile represented by a pile node

tz
Ax ByH Ay BxH Az pH 2H(BxBy)
sx
tz
H
sy
By
Bx
9
How the pile-soil interaction works
c
1.0
dx/By etc
dx, dy dz are the differences of displacements
between pile and soil in x, y z directions at
the same points
-1.0
10

• oasys.intranet.arup.com
• www.oasys-software.com