Chap. 4 & 5-Foundations

CMgt3350

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