Comprehensive Guide on Steel Quantity Calculation for Slab, Footing, and Column

Constructing sturdy and durable structures entails meticulous planning and accurate estimation of materials, particularly steel reinforcement. This guide focuses on the step-by-step process of determining the steel quantity required for concrete slabs, footings, and columns, based on design drawings and structural specifications.

Calculating Steel Quantity for Slab

To commence the calculation for a concrete slab, you need to:

1. Obtain Design Details

Refer to the design drawings to acquire slab dimensions and reinforcement specifications.

2. Determine Number of Steel Bars

Utilize the following equations to calculate the number of steel bars:

• Main Steel Bars:
  • No. of bars = (Slab length (L) / spacing) + 1 (Equation 1)
• Shrinkage and Temperature Steel Bars:
  • No. of bars = (Slab length (S) / spacing) + 1 (Equation 2)

3. Calculate Cutting Length

Compute the cutting length for both main and shrinkage steel bars using equations:

• Main Steel Bars:
  • Cutting length = clear span (S) + Ld + inclined length + 2 x 45 degree bend (Equation 3)
• Shrinkage and Temperature Steel Bars:
  • Cutting length = clear span (S) + Ld + inclined length + 2 x 45 degree bend (Equation 4)

Where:

• Ld: development length
• Inclined length = 0.45D
• D = slab thickness – 2 * concrete cover – bar diameter

Example: Calculating Steel for One-Way Slab

Consider the following illustration:

• Main Steel Bars:
  • No. of bars = (10m / 0.15m) + 1 = 67
  • Cutting length = 10m + 1.2m + 2.25m + 2 x 45 degree bend
• Shrinkage and Temperature Steel Bars:
  • No. of bars = (10m / 0.2m) + 1 = 51
  • Cutting length = 10m + 1.2m + 2.25m + 2 x 45 degree bend

After obtaining cutting lengths, convert them into kilograms or tons, as steel is ordered by weight.

Calculating Steel for Footing

For determining steel quantity in footings, adhere to the following steps:

1. Acquire Footing Details

Gather information about footing size and reinforcement specifics from the design drawings.

2. Compute Number of Bars

Use Equation 8 to calculate the required number of bars for both directions.

3. Determine Length of Bars

Apply Equation 9 to find the length of one bar.

4. Calculate Total Length

Multiply the number of required bars by the length of one bar to obtain the total length of bars.

Example: Steel Calculation for Footing

Suppose we have a footing with a length (L) of 2 meters and a width (W) of 1.5 meters. Concrete cover for both sides is 0.05 meters.

• Number of bars in longitudinal direction:
  • No. of bars = ((2m – 0.05m – 0.05m) / 0.2m) + 1
• Length of one bar:
  • Length of bar = 2m – 0.05m – 0.05m + 2 x bend length

Calculating Steel Quantity for Columns

Determining steel quantity in columns involves the following steps:

1. Obtain Column Details

Refer to design drawings to acquire column size and reinforcement details.

2. Compute Longitudinal Steels

Calculate the total length of longitudinal bars considering column height and laps for footing.

3. Calculate Stirrups

• Compute the cutting length of stirrups using Equation 10.
• Calculate the number of stirrups and estimate the total length.

After calculating lengths, convert them into kilograms or tons. Total steel quantity of the column equals the sum of both main and stirrup steels.

By following these detailed steps, accurate estimation of steel quantity for slabs, footings, and columns can be achieved, ensuring structural integrity and cost-effectiveness in construction projects.