Estimating Reinforcements for a Concrete Footing
Independent footing, also known as isolated footing, is a type of foundation attached to a single column and is the simplest and most common type of foundation. According to the plan and design of the footing, reinforcement for this footing can either be plain or have bends and hooks.
HOW TO CALCULATE FOR QUANTITY OF STEEL BARS FOR A CONCRETE INDEPENDENT FOOTING:
- Determine the length, width and underground protective covering of your concrete footing:
- Determine the cut length of one reinforcement bar:
- Determine the steel bar commercial length to be used and the number of cuts that can be made per steel bar:
- Determine the specified bar spacing or, if already provided, the number of bar cuts of your footing:
- Get the number of steel bars to be ordered:
Determine the following information based on the design of the your concrete footing.
From the information gathered, get the cut length of footing reinforcement bar. If the dimensions of the footing's length and width are different, get both cut lengths.
Steel bars are usually commercialy available in five(5) lengths: 6m, 7.5m, 9m, 10.5m and 12m. In order to calculate the quantity of steel bars to be ordered, we need to determine how many cuts can be made in a piece of steel bar.
If the quotient is not a whole number, it means the commercial length selected is not divisible with the cut length. This will result in extra cuts. In order to avoid excess cuts, select a commercial length that is divisible by the cut length.
For example, if your cut length is 2.5 meters, a 6 meter long steel bar will produce an excess cut of 1 meter.
However, if you select a 7 meter long steel bar, no excess cuts will be produced.
Unless specified in the drawings, the total number of bar cuts you will need for the footing will depend on the specified spacing of the footing.
SAMPLE PROBLEM 1
Compute for the quantity of steel bars needed for an independent footing that is 1500mm long and 1000mm wide, with the following given specification:
Bar Spacing = 200mm O.C.
SOLUTION
- Determine the length, width and underground protective covering of your concrete footing:
- Determine the cut length of one reinforcement bar:
- Determine the steel bar commercial length to be used and the number of cuts that can be made per steel bar:
- Determine the specified bar spacing or, if already provided, the number of bar cuts of your footing:
- Get the number of steel bars to be ordered:
Footing Width = 1000mm
Protective Cover = 75mm
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