Laterally Loaded Piles

1. ‫الرحيم‬‫الرمحن‬‫اهلل‬‫بسم‬
Report on
made by
Structural engineering Department
‫إنشاءات‬ ‫قسم‬
Under the supervision of
Dr/Waseim Azzam
Faculty of. Engineering, Tanta University, Tanta, Civil Engineering Department
Laterally Loaded Piles
Ahmed Khalil Ebrahim Saif El Den
Sec:1

2. Introduction
Piles are commonly used to transfer vertical (axial) forces,
Examples of structures where piles are commonly used as
foundations are tall buildings, bridges, offshore platforms,
defense structures, dams and lock structures, transmission
towers, earth retaining structures, wharfs and jetties.
However, in all these structures, it is not only the axial force
that the piles carry; often the piles are subjected to lateral
(horizontal) forces and moments. In fact, there are some
structures (oil production platforms, earth retaining
structures, wharfs and jetties) where the primary function of
piles is to
transfer lateral loads to the groundWind gusts are the most
common cause of lateral force (and/or moment) that a pile
has to support. The other major cause of lateral force is
seismic activity. The horizontal shaking of the ground
during earthquakes generates lateral forces that the piles
have to withstand. Certain buildings are also acted upon by
lateral earth pressures, which transmit lateral forces to the
foundations.

3. Causes of lateral forces.
 For tall buildings and transmission towers, wind action is the
primary cause.
 For offshore oil production platforms, quays, harbors, wharfs
and jetties, wave action gives rise to lateral forces.
 In the case of bridge abutments and piers, horizontal forces
are caused due to traffic and wind movement.
 Dams and lock structures have to withstand water.pressures
which transfer as horizontal forces on the supporting piles.
 Defense structures often have to withstand blasts that cause
lateral forces.
 In the case of earth retaining structures, the primary role of
piles is to resist lateral forces caused due to the
lateral.pressures exerted by the soil mass behind the
retaining wall.
 Sometimes, piles are installed into slopes, where slow
ground movements are taking place, in order to arrest the
movement. In such cases, the piles are
subjected to lateral forces
 The horizontal shaking of the ground during earthquakes
generates lateral forces that the piles
 Impact Loads from Ships
 Eccentric Loads on Columns
Analysis of laterally loaded piles
is very important to the geotechnical and civil
engineering profession.

4. Load Transfer Mechanisms
understanding of the load transfer mechanisms for piles is
necessary for analysis and design. Piles transfer axial and lateral
loads through different mechanisms.
In the case of axial (vertical) loads, piles may be looked
upon as axially loaded columns; they transfer loads to the
ground by shaft friction and base resistance.. This mechanism is
called base resistance or end-bearing resistance.
The total resistance (shaft friction plus end-bearing resistance)
keeps a pile in equilibrium with the applied load. Piles that
transfer most of the axial load through the base are called
end-bearing piles, while those that transfer most of the load
through shaft friction are called friction piles.
For end-bearing piles, it is necessary to have the pile base
inserted into a strong layer of soil (dense sand, stiff clay or
rock). Typically, engineers would prefer to design end-bearing
piles because the base resistance
is more reliable than shaft friction. However, if no such strong
layer is available at a site, then engineers have to rely only on
shaft friction

5. In the case of lateral loads, piles behave as transversely
loaded beams. They transfer lateral load to the surrounding soil
mass by using the lateral resistance of soil
When a pile is loaded laterally, a part or whole of the pile tries
to shift horizontally in the direction of the applied load, causing
bending, rotation or translation of the pile.The pile presses
against the soil in front of it (the soil mass lying in
the direction of the applied load), generating compressive and
shear stresses and strains in the soil that offers resistance to the
pile movement

6. Often, the load acting on a superstructure is larger than the
capacity of a single pile.When that happened, piles are grouped
under each column to resist the total force acting at the column
base. The piles in a group no longer behave as isolated units
but interact with each other and resist the external load in an
integrated manner
Each pile in a group, whether loaded axially or laterally,
generates a displacement field of its own around itself. The
displacement field of each pile interferes and overlaps with
those of the adjacent piles; this results in the interaction between
piles.

7. Interaction between piles occurs in the case of laterally loaded
pile groups as well. In a laterally loaded pile group, each pile
pushes the soil in front of it (in the direction of the
applied force). Movement of the piles placed in the first
(leading) row in the direction of the applied force is resisted by
the soil in front of it. In contrast, the piles in the rows behind the
first row (the piles in the trailing rows) push on the soil which in
turn pushed on the piles in the rows in front of them. The
resistive forces acting on the trailing-row piles are in
general less than the resistive forces acting on the leading row

8. Solution
Batter Piles
 Very common solution to lateral loading
 Form a very stiff system than can
 pose problems in seismic situations Basically turn lateral
loads into axial loads
 Analytic Methods for LateralLoading
 Rigid Methods (Broms)
Used for light weight « short » foundations
Same limitations as rigid methods for mat foundations
 Depth to Fixity Methods (Davisson)
Only considers a certain depth as flexible
Structural engineers could analyse the foundation as a
structure once the depth of fixity was known Too
simplistic
 Finite Element Analysis
 p-y curves
 Horizontal Modules of Sub grade Reaction Method
 Soil as Elastic Continuum Method (Poulos & Hull)
p-y curves are the best way of determining lateral
capacity

9. determine lateral load capacity in field
Lateral Loading Test
ASTM D3966
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