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
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