A Group B A A20405 Foundation by 0uS3Gy

VIEWS: 8 PAGES: 86

									Foundation
  Presented by:

  Lewis Ayan
Mond. Fakhruddin
   Zuhilman
   Ibrahim
      Fadli
                 Foundation
• The basis on which something is grounded
• A lower support of a structure
• The foundation of a building is the soil or rock on
  which it sits.
• The footing is that portion of its structure that
  serves to transfer the weight of the building
  into the ground itself.
• Most foundations extend underground, and the
  foundations of large buildings often penetrate to
  the bedrock.
        The design of foundations consists
            of 3 essential operations:

• calculating the loads that must be transferred
  from the structure to the strata supporting it;
• determining the exact character of subsurface
  conditions; groundwater conditions, to a depth
  of at least twice the width of the structure; and
• designing a foundation structure that will safely
  transfer the loads from the structure to the
  foundation beds that have been found at the
  site.
   Variations in Site Conditions
Subsurface conditions at any building site
can be grouped into three main types:

1. Solid rock - may exist either at ground surface or so
   close to it that buildings may be founded directly upon it;

2. Bedrock - may exist beneath the surface but at such a
   depth that building loads may, if necessary, be transferred
   indirectly to it;

3. Bedrock - may be so far beneath the ground surface
   that it is neither practicable nor economical to transfer
   building loads to it, the loads having to be carried by the
   superincumbent soil.
Material of Foundations


 Usually foundation is
 made from concrete
Foundation formwork
TYPES OF FOUNDATION
    Shallow foundation



  Spread        Mat/Raft
foundation     foundation
SHALLOW FOUNDATION
   SHALLOW FOUNDATION
1> Advantages
• Cost (affordable)
• Construction procedure (simple)
• Material used (mostly concrete)
• Workers (doesn‟t need experience)
2> Disadvantages
• Settlement
• Limit capacity „soil‟ structure
• Irregular ground surface (slope,
  retaining wall)
• Foundation subjected to pullout,
  tension, moment.
 SPREAD/PAD FOUNDATION
• As a foot of a column/bearing wall
  (footer/footing)
• Under the column and bearing wall
  located a layer of concrete slab.
• Only column and bearing wall have
  their own individual footing.
• Small area of footing
• Used when surface soils are
  sufficiently strong and stiff to support
  the imposed loads.
• For the good strength soil, pad
  foundation most suitable used to
  reduce cost & ease of construction.
• The system: structural load spread
  out over a broad area under the
  building.
Shape of spread/pad foundation
•   Square spread footing
•   Rectangular spread footing
•   Circular spread footing
•   Continuous spread footing
•   Combined footing
•   Ring spread footing
       Square spread footing
• Located a single column & support at
  the center.
• Concrete mix
• Used to support an individual point load
  such as that due to a structural column.
• Usually consist of a block or slab of
  uniform thickness.
• Usually shallow, but deep foundation
  also can be used.
   Rectangular Spread footing
• Footing with large area
• Especially design for column/bearing
  wall which present large load at a
  moment.
• Rectangle shape.
     Circular Spread footing
• Circle shape from plan view but most
  to a cylinder with low high.
• Used for light standard, flag poles,
  and power transmission lines.
     Continuous/Strip footing
• Especially used for bearing wall which
  support large load.
• Long area of footing
• Not for all bearing wall but only for
  certain wall according to avoid from
  misspend.
          Combine footing
• Shape:
  - rectangular
  - trapezoidal
  - cantilever
• Design for more than one column
• Column axis is located too close for
  each –other-need combine footing.
• Ease of construction.
         Ring spread footing
- continuous footings that have been wrapped into
   a circle
- commonly used to support the walls above-
   ground circular storage tanks.
- The contents of these tanks are spread evenly
  across the total base area and this weight is
   probably greater that the tank itself
         Mat/raft foundation
1) Definition:
   A foundation (usually on soft ground)
   consisting of an extended layer of
   reinforced concrete.
• 1 layer concrete slab that strengthen with
   steel reinforced.
• Used to spread the load from a structure
   over a large area.
• Normally consist of concrete slab
  which extend over the entire loaded
  area.
• Maybe stiffened by ribs or beams.
• Advantage: reduce differential
  settlements
• Often needed on soft/loose soil with
  low bearing capacity as they can
  spread the load over a larger area.
     To design mat foundation
1. Determine the capacity of the foundation
2. Determine the settlement of foundation
3. Determine the differential settlement
4. Determine the stress distribution beneath
   the foundation
5. Design the structural component of the
   mat foundation using the stress
   distribution obtain from 4.
Mat/raft foundation
          Deep foundation
• Deep foundations are those founding too
  deeply below the finished ground surface
  for their base bearing capacity to be
  affected by surface conditions, this is
  usually at depths >3 m below finished
  ground level.
          Caisson foundation
• Similar in form to pile foundations, but are
  installed using a different method.
• Caissons are created by auguring a deep hole
  into the ground, and then filing it with
  concrete.
• Drilled either to bedrock or deep into the
  under laying soil
• Special drilling bits are used to remove the soil
  for these “belled caissons”
       Diaphragm foundation

• Diaphragm walls are underground
  structural elements commonly used for
  retention systems and permanent
  foundation walls.
• Diaphragm walls are constructed using the
  slurry trench technique. The technique
  involves excavating a narrow trench.
• Slurry trench excavations can be
  constructed in all types of soil.
Diaphragm wall construction
begins with the trench being
excavated in discontinuous sections
or “panels”.
Panels are usually 8 to 20 feet
long with widths varying from 2 to
5 feet.
Diaphragm walls are commonly
used in congested areas
The picture above shows a Diaphragm wall excavation.
Diaphragm walls are constructed using the slurry trench
                      technique
A grab used
     for
excavation
                Once the excavation
  Diaphragm     of a panel is complete, a
     wall       steel reinforcement cage
reinforcement   is placed in the center of
 & concreting   the panel.

                Concrete is poured in
                one continuous
                operation through one or
                more tremie pipes that
                extend to the bottom of
                the trench.

                The tremie pipes are
                extracted as the
                concrete rises; however,
                the discharge end of the
                tremie pipe always
                remains embedded in
                the fresh concrete.
                The finished wall after
Reinforcement
                      excavation
               PILES
Long, slender members that transmit
foundation loads through soil strata of
low bearing capacity to deeper soil or rock
strata having a high bearing capacity.
       End bearing piles




End bearing piles are those which
terminate in hard, relatively impenetrable
material such as rock or very dense
sand and gravel.
            Friction piles




• Friction piles obtain a greater part of
  their carrying capacity by skin friction or
  adhesion. This tends to occur when
  piles do not reach an impenetrable
  stratum but are driven for some
  distance into a penetrable soil.
Settlement reducing piles
         Settlement reducing piles are
         usually incorporated beneath
         the central part of a raft
         foundation in order to reduce
         differential settlement to an
         acceptable level. Such piles
         act to reinforce the soil
         beneath the raft and help to
         prevent dishing of the raft
         in the centre.
             Tension piles
• Structures such as tall chimneys,
  transmission towers and jetties can be
  subject to large overturning moments
  and so piles are often used to resist the
  resulting uplift forces at the
  foundations. In such cases the resulting
  forces are transmitted to the soil along the
  embedded length of the pile.
                      Piles in fill




• Piles that pass through layers of moderately- to poorly-
  compacted fill will be affected by negative skin friction,
  which produces a downward drag along the pile shaft and
  therefore an additional load on the pile. This occurs as the
  fill consolidates under its own weight.
   TYPES OF PILES

       • Steel piles
     • Concrete piles
• Timber piles (wood piles)
                   Steel piles
• Steel piles withstand driving pressure well and
  very reliable end bearing members.

• Pipe piles are normally, not necessarily filled with
  concrete after driving.

• Strength, relative ease of splicing and economy
  are some of the advantages cited in the selection.

• Corrosion (salt, acid, moisture and oxygen) >
  restricted use for marine installations.
Steel piles
           Concrete piles
• Much more resistance against
  corrosive elements
• Concrete is available in most parts of
  the world than steel.
• Concrete piles may be pre-cast or
  cast-in place.
Pre-cast concrete piles
Formed, cast to specified lengths and shapes and cured at pre
casting stations before driven in to the ground.

Their shape and length are regulated at the prefab site.
Usually came in square, octagonal or circular cross-section.

The diameter and the length of the piles are mostly governed
by handling stresses.

Limited to less than 25 m in length and 0.5 m in diameter.

Some times it is required to cut off and splice to adjust for
different length. Where part of pile is above ground level, the
pile may serve as column.
Cast-In-Place Concrete Piles

• Made at the construction
• Steel shell is grounded to the soil to as container
  to allow the concrete filled in it
• Not contribute load capacity to the pile
     Timber piles (wood piles)
• Timber piles are frequently used as
  cohesion piles and for pilling under
  embankments.
• Made from tree trunks with the branches
  and bark removed.
• Normally wood piles are installed by
  driving. Typically the pile has a natural taper
  with top cross-section of twice or more than
  that of the bottom.
• To avoid splitting in the wood, wood piles are
  sometimes driven with steel bands tied at
  the top or at the bottom end
Can be form of >>>>>>>

       Shrinkage                     Expansion


        Cause                          Cause


        Settlement                     Heave
 When dry conditions prevail, soils consistently lose
 moisture and shrink. When moisture levels are high, the
 opposite is true, and soils swell

 It will most likely manifest itself in the form of visible
 cracks in the foundation walls, exterior brick walls, or
 interior sheetrock or plaster walls. Officially, any
 structure movement is known as differential settlement.
               Causes
•   Poor drainage
•   Moisture around the foundation
•   Transpiration
•   Plumbing leaks
•   Bad Design
•   Faulty Construction
•   Extraordinary Loads
     Poor drainage
Yard and gutter
downspouts
discharging at
the base of the
foundation are
among other
causes
           Moisture
Moisture around the foundation can
cause the soils to become over-
saturated and lose the strength to
support weight. When this happens,
structures “settle” or sink into the
ground
       Transpiration
During an active season, roots
extending beneath and around the
footings of the house can remove
moisture from the soil, causing it to
become desiccated. Again, where
expansive soils exist this removal of
moisture will cause soil shrinkage and
settlement.
Plumbing leaks


 Home‟s pipes
 Poor Construction
• Material used
• Construction workers
              Bad design
• Failure to take into account the loads the
  structure will be called upon to carry,
• erroneous theories,
• inaccurate data,
• ignorance of the effects of repeated or
  impulsive stresses
• improper choice of materials or
  misunderstanding of their properties.
     Faulty Construction
• The use of salty sand to make
  concrete,
• Bad riveting or even improper
  tightening torque of nuts,
• bad welds,
        Extraordinary loads

• Extraordinary loads are often natural,
  such as repeated heavy snowfalls, or
• the shaking of an earthquake, or
• the winds of a hurricane. A building
  that is intended to stand for some
  years should be able to meet these
  challenges.
              Earthquakes
The picture on the right
shows a building which
has lost the ground
floor.

This house will
probably have to be
demolished.
Do New Houses Have Foundation
Failure?

        Unfortunately, for many
homeowners, problems may develop
relatively soon after the house has been
completed. While older homes
experience some settling over time,
serious foundation failures occur more
frequently in homes less than ten years
old.
When the ground shakes,
lose particles (i.e. soil)
moves in a fashion similar
to a liquid (i.e. water).

When the soil (which is
lose) surrounding it is
shaken the foundation in
effect sinks. This is often
uneven and the building
may topple.
Bulging floors,

Cracked walls

Doors that won't close

  The problem occurs when only part of the
foundation heaves or settles, causing cracks and
other damage. This differential movement is
largely caused by differences in soil moisture.

 Settlement cracks are nearly always vertical.
Exterior Warning Signs :

   Wall Rotation
   Separation around garage door, windows and/or
  walls
   Cracked bricks
   Broken and/or cracked foundation
   Displaced Moldings

Interior Warning Signs

    Misaligned Doors and Windows
    Cracked sheetrock
    Cracks in Floor
Cracked walls
Cracked foundation
Misaligned Doors and Windows
Thanks!

								
To top