Chap. 4 & 5-Foundations

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Building Structures

Chapters 4 and 5

Foundations

Foundation Plan


Shows the position of piles,
footings, column bases,
thickened slabs, and all
necessary elevations and
details

Shallow Foundations


Cast
-
in
-
place reinforced concrete


Usually a continuous strip footing


Sometimes called spread footings

Typical Spread Footing

Shallow Foundations

Deep Foundations


Used for large buildings


Piles


Caissons


Deep wall foundations (slurry walls)


Mats

Parts of a Pile

Classification of Piles


Material


Wood


Steel


Concrete


Composition


Classification of Piles (cont.)


Method of placement


Driving


Drop


Mechanical


Steam


Compressed air


Internal combustion


Vibratory


Pouring into predrilled shafts


Classification of Piles (cont.)


Method of Bearing



Bearing piles


Friction piles


Friction
-
plus
-
bearing piles


Sheet piles

Bearing Capacity


Look at the example on page 111

Pile Cap


If two or more piles are located at the same bearing area
they MUST be connected by a pile cap.

Pile Cap

Pile Cap With Isolator Pad

Wood Piles


80’ lengths are not uncommon


Tip diameter 6”


Head diameter 20”


Indefinite life expectancy below
groundwater level


They are light


They have greater friction


Concrete Piles


Cast
-
in
-
place


Shell type


Shell
-
less type


Precast


Round


Square


Hexagon


Octagon


Simple Shell
-
less Pile


Drill a hole, reinforce, and pour in concrete

Shell
-
less Pile

Button
-
bottom Pile


Steel shelled pile, has increased bearing, used
in high compression soils

Swaged Pile


Steel shell with precast concrete plug used when
driving into difficult soil conditions

Precast Reinforced Piles


Usually 16’ sections


Very expensive in lengths over 55’


Hollow in center to allow water jet
assistance


Precast Pile

Precast Pile

Steel Piles


Primarily used for loads under friction
resistance


Driven in clusters with a pile cap on
top


Range in diameters from 8” to 72”

Steel Piles

Steel Piles

Composite Piles


Wood and concrete are the most common


Wood pile is driven down to ground level


Top fitted with steel casing


Driven down to desired depth


Concrete is poured in the shell

Composite Pile

Caissons


Complete bearing unit


Up to 10’ diameter hole borings


Depths of over 150’


Drilled caissons can be 24” to 42” in diameter
with depths of over 200’


Metal shell, box, or casing is placed in hole,
reinforcing, and cast
-
in
-
place concrete




Belling of Piles and Caissons

Belling a Pile

Driving a Pile

Vibrating a Pile


A pile that would take an hour to drive, can be
placed in 2
-
3 minutes with a vibratory hammer.

Mat Foundation

Cofferdams


Temporary boxlike structure used to hold
back water or earth while work is being
done inside.


It is later removed for reuse.

Mat Foundation


Huge monolithic pad that is poured in
conjunction with the footing


Thickness ranges from 3’ to 8’


Layers of reinforcing are installed
throughout the mat

Soil Compaction


Vibrate the soil during saturation to move,
shake, and float particles to the desired
density


Holes are backfilled with gravel or crushed
stone and compacted until they are
consolidated to structural bearing capacity

Soil Compaction

Soil Compaction

Assignment


Go to http://www.walinco.org.uk/


Look up:


Tubular steel piles


Sectional driven high
-
strength piles


Screw spliced concrete piles


Jacked solid concrete piles


When are they used


How are they installed


Advantages or disadvantages of each system