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Figure 2: Continuous strip footing beneath a circular wall ring footing [Modeled in AutoCAD 2013

by J. Takchandra]

2.0

Spread/Isolated footing:

Spread/isolated footings, as the name suggests, are mass concrete bases. The

foundation is generally constructed to support and individual column or structural

element. It may take the form of rectangular or circular shapes, of uniform

thickness. In further cases, the slab may be stepped or hunched to spread and

distribute the load over a larger area. The following are some basic common spread

footing foundation base (cross-section):

2.1 Square isolated footing

Figure 3:Square isolated footing for a single R. C column [Modeled in AutoCAD 2013 by J.

Takchandra]

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footing may be rectangular or trapezoidal.

Figure 5: This figure illustrates a combined footing for two concrete columns. The distance

separating them is small enough facilitate joining of two isolated footings [Modeled in AutoCAD

2013 by J. Takchandra]

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Strap or cantilever footing

This foundation comprises of two isolated footing that are connected with a

structural strap or a lever. The strap is featured to connect the two footing in order

that they operate as a single unit under structural loads. It is important to note that

the strap is primarily a connection beam and does not resist any soil reaction (i.e.

the strap is designed as a rigid beam).

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Figure 6: This figure illustrates how a cantilever foundation is different from a combined footing. A

rigid foundation beam, as in this example, connects two isolated footing. Additionally, an

application of cantilever footings is where there is a difference in levels of footings [Modeled in

AutoCAD 2013 by J. Takchandra]

5.0

Mat or raft foundation

When a common foundation is provided for columns in two or more rows, the

footing is called a mat or raft foundation, as the name suggest. It is a large concrete

slab supporting a number of columns and walls. They are efficient in eliminating

differential settlement and in case where there are large discrepancies in uneven

load distribution, and in non-homogeneous soils. Individual pedestals may then be

constructed for columns.

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Figure 7: In this example, a mat/raft is employed as a rigid foundation. As seen, the entire column

layout of the building is enabled [Modeled in AutoCAD 2013 by J. Takchandra]

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