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Flashcards in Chapter 3: Foundation Systems Deck (31)
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0
Q

Settlement

A

is a gradual subsiding of a structure as the soil beneath its foundation consolidates under loading.
On coarse sand and gravel soils, consolidation is usually slight and occurs rather quickly.
On moist, cohesive clay soils with relatively large percentage of voids, consolidation can be quite large and occur slowly over a long period of time.

1
Q

Principal loads on a foundation and forces acting on it:

A
  • dead and live loads acting vertically on the superstructure.

Foundation systems must anchor superstructure against wind-induced sliding, overturning, and uplift, withstand the sudden ground movements of an earthquake, and resist the pressure imposed by surrounding soil mass and groundwater on basement walls.

2
Q

Differential settlement

A

is the relative movement of different parts of a structure caused by uneven consolidation of the foundation soil.

3
Q

Foundation systems can be classified into two broad categories:

A
  • shallow foundations: employed when stable soil of adequate bearing capacity occurs relatively near to the ground surface.
  • deep foundations: employed when the soil underlying a foundation is unstable or of inadequate bearing capacity.
4
Q

Underpinning

A

refers to the process of rebuilding or strengthening the foundation of an existing building, or extending it when a new excavation in adjoining property is deeper than the existing foundation.

5
Q

Slurry wall

A

is a concrete wall cast in a trench to serve as sheeting and often as a permanent foundation.

6
Q

Dewatering

A

refers to the process of lowering a water table or preventing an excavation from filling with groundwater.

7
Q

Most common forms of spread footings

A
  • strip footings: continuous spread footings of foundations walls.
  • isolated footings: are the individual spread footings supporting freestanding columns and piers.
8
Q

Other types of spread footings include:

A
  • stepped footings
  • cantilever or strap footings
  • combined footing
9
Q

Foundation walls

A

provide support for the superstructure above and enclose a basement or crawl space partly or wholly below grade.

10
Q

Footings should be placed…

A

on undisturbed soil below frostline.

11
Q

Concrete foundation walls are…

A

cast-in-place and require formwork and access to place the concrete.

12
Q

Masonry foundation walls do not require…

A

formwork and utilize easily-handled small units.

13
Q

Wood joists on top of foundation walls include:

A
  • sill plate
  • anchor bolts
  • sill plate anchors or holddowns
  • header or rim joist
  • wood joist framing
14
Q

Wood beams on top of foundation walls

A

need a minimum 13mm air space on tops, sides and ends entering concrete or masonry wall unless pressure-treated wood is used. The minimum bearing for wood beams on concrete or masonry is 75mm, if area is not enough, then wall should be thickened with pilaster.

15
Q

Open-web steel joists

A

Minimum bearing for regular joists is 100 to 150mm. On concrete wall, they are anchored to steel base plates. On masonry walls, they are anchored to a continuous bond beam.

16
Q

A subsoil drainage system is required to…

A

collect and divert water away from a foundation to a storm sewer, dry well or natural outfall at a lower elevation on the site.

17
Q

Drainage mat or a gravel backfill allows…

A

water to flow down to the footing drains. Aprox 20mm thick.

18
Q

Cant strip

A

Chamber piece.

19
Q

Hydrostatic pressure

A

Pressure exerted by water.

20
Q

Dampproofing and waterproofing

A

Dampproofing is applied to a foundation wall when hydrostatic pressure from the groundwater table will not occur.

When subject to hydrostatic pressure, foundation walls should be waterproofed.

21
Q

Composite footing consists of…

A

a footing plate and a layer of gravel, sand or crushed stone.

22
Q

Types of Column Footings:

A
  • reinforced concrete column
  • wood post
  • steel column
23
Q

Concrete slabs on grade require…

A

the support of a level, stable, uniformly dense or properly compacted soil base containing no organic matter. Minimum slab thickness is 100mm.

24
Q

Three types of joints used on concrete slabs on grade:

A
  1. ISOLATION JOINTS (or expansion joints): allow movement to occur between concrete slab and adjoining columns and walls.
  2. CONSTRUCTION JOINTS: prevent vertical differential movement of adjoining slab sections.
  3. CONTROL JOINTS: create lines of weaknesses so the cracking that may result from tensile stresses occurs along predetermined spaces.
25
Q

Minimum depth of a footing is

A

305mm

26
Q

Pole foundations

A

elevate timber structures above ground plane, require minimal excavation and preserve the natural features and existing patterns of a site. They are particularly useful when building on steep slopes and in areas subject to periodic flooding.

27
Q

Two main types of deep foundations are:

A
  1. pile foundations

2. caisson foundations

28
Q

A pile foundation

A

is a system of end-bearing or friction piles, pile caps, and tie beams for transferring building loads down to a suitable bearing stratum.

29
Q

Types of pile foundations:

A
  • timber piles
  • composite piles
  • H-piles
  • pipe piles
  • precast concrete piles
  • cast-in-place piles (cased or uncased)
  • pedestal pile
  • micropiles
30
Q

Caissons are…

A

cast-in-place, plain or reinforced concrete piers formed by boring with a large auger or excavating by hand a shaft in the earth to a suitable bearing stratum and filling the shaft with concrete. They are also referred to as drilled piles or piers.