Definition of isolated footing & its reinforcement detailing
Different types of foundations are found in a building which range from isolated footing, combined footing, strip footing, raft footing, pile foundations etc. To select which foundation will be perfect for your building, focus should be given on the structural requirement and soil conditions.
Reinforcement detailing of footing as well as site analysis for the type of footing and structural design of footing are equally vital for the structure. If the detailing is perfect, it reveals the design need of the footing for structural strength. A perfect detailing of reinforcement involves various factors like cover to reinforcement on the basis of ecological considerations for stability, least possible reinforcement and bar diameters, exact dimensioning of footing etc.
DETAILING OF ISOLATED FOOTING:
The least density to primary reinforcement in footing should not be under 50mm if footing touches with earth surface directly, and 40mm for exterior uncovered face like surface leveling PCC. If surface leveling is unutilized, then it is necessary to indicate a cover of 75mm to cover rough surface of excavation. For raft foundation, the least cover to reinforcement should be 75mm whether build on PCC or directly on earth surface.
Reinforcement Distribution in Footing:
The reinforcement is allotted evenly across the complete width of footing in one-way RCC footing.
The reinforcement that is expanded in both directions is allotted evenly across the full width of the footing in two-way square footings. But for two-way rectangular footings, reinforcement is allotted across the full width of footing in long direction. But for short direction, the reinforcement is circulated in the central band based on the calculations given under.The remainder reinforcement in short direction is circulated evenly on both sides of the central band.
Where y denotes the long side and x is the short side of the footing
To get the sample drawing, go through the following link.