Advanced Construction Technology
By Professor Chris Gorse & Ian Dickinson – licensed under the Creative Commons Attribution – NonCommercial – Share Alike License
http://creativecommons.org/licenses/by-nc-sa/2.5/
Pad Foundations
Chris Gorse and Ian Dickinson
These slides should be read in conjunction with Emmitt, S. and Gorse,
C. (2010) Barry’s Advanced Construction of Buildings. Oxford, Blackwell
Publishing
Pad foundations
Pads
Ground
beams
Pad foundations.
More commonly used under point loads such as columns, but
can be used under ground beams to transfer continuous loads.
The width and depth of each pad foundation will depend on the
soil conditions and building loads.
Pad foundation
Loads transferred
through column to
base-plate then to
concrete pad
foundation
Pad foundations are
often rectangular or
square and are placed
to receive point loads
at a central position
Base plate
Pad foundation
Excavation for pad foundation
Bolt boxes for steel columns ready to be positioned in the concrete
Excavation of pad foundation
Pad foundations neatly excavated
Pad foundations – ground beams
Point loads from
columns transferred to
pad foundation
Any continuous loads
applied through walls are
transferred along
reinforced concrete
beams to the pad
foundation
Ground beam
Pad foundation
Stable load bearing strata
Pad foundation and ring beam excavation. String lines mark out the
centre lines for the holding down bolts. The holding down bolt box will
be positioned when the concrete is poured.
Pad foundation and ground beam excavation. Ready to receive steel
reinforcement cages and concrete
Pad foundation, with holding-down bolts for column. Reinforcement starter
bars are evident, these will be used to tie the ground beam into the
foundation.
Reinforced pad foundation
Point loads from columns
transferred to pad foundation
Load from column
distributed across the
full area of the
foundation
Reinforcement runs in
both directions
Reinforced Pad
foundation
Exploded view showing
reinforcement
Distributing the load
Large point load
The reinforcement in the pad
foundation adds tensile strength
allowing the loads to be
distributed over a larger area.
As the load is distributed
over a larger area the load
per unit area is reduced
Mass fill pad foundation
Point loads from columns
transferred to pad foundation
By excavating deeper into the
ground and filling with concrete the
loads of the building can be
transferred to lower strata.
Where the surface soil and strata is
week it may be possible to excavate
deeper to good load-bearing strata.
Pad foundation and column base (prior
to filling with grout)
Base of column fastened to the pad foundation by holding down bolts. Wedges hold
the column in position until the bolts and column base is grouted. Expanding grout
will be poured under and around the base plate filling all the voids and making sure
the column and pad foundation make proper contact with each other.
Steel wedge holds the steel column in
the correct position
Sand position around the column ready to receive expanding grout. The
group secures the base plate in its final position.
Discussion
• Identify and discuss the situations where pad
foundations are most likely to be used.
• What is the most common type of structure
that would be founded on a pad foundation.