The isolated footing is used to support the load on a single column. It is usually either square or rectangular in plan. It represents the simplest, most economical type, and most widely used footing. Whenever possible, square footings are provided so as to lessen the bending moments and shearing forces at their critical sections.
Isolated footings are used in case of light column loads, when columns are not closely spaced, and in case of good homogeneous soil. Under the effect of upward soil pressure, the footing bends in a dish-shaped figure. An isolated footing must, for that reason, be provided by two sets of reinforcement bars situated on top of the other near the bottom of the footing. In the case of property line restrictions, footings may be designed for eccentric loading or combined footing is used as a substitute for the isolated footing.
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