Thumb Rules on Rebars in Civil Engineering

               

                      As a civil engineer it is better to have knowledge about the thumb rules. These rules are quite useful in sites. However, the values obtained from these thumb rules might not be correct so calculation must be done for proper estimation. Thumb rule only helps to get an idea about the result. Below are some of the practised thumb rules in civil engineering: -

1)    Thumb rule for Steel quantity required for Slab, Beams, Footings & Columns: -

            Steel required in Residential buildings = 4.5 Kgs to 4.75 Kgs / Sq. Ft.

            Steel required For Commercial buildings = 5.0 Kgs to 5.50 Kgs/Sq. Ft.

2)    Percentage of Steel in Structural Members:

            a) Slab – 1% of the total volume of concrete

            b) Beam – 2% of the total volume of concrete

            c) Column – 2.5% of total volume of concrete

            d) Footings – 0.8% of the total volume of concrete

Example:

How to calculate the steel quantity of slab having the Length, width, and depth of the slab is 5m x 4m x 0.15m

Step 1: Calculate the Volume of Concrete

The Total Volume of Concrete for given Slab = 5 x 4 x 0.15 = 3m3

Step 2: Calculate the steel quantity using formula

As per the guidelines are given in the B N Dutta reference book the steel quantity of slab is 1% of the total volume of concrete utilized.

Thumb rule to estimate Steel quantity of above slab = (Volume of Concrete * Density of Steel * % of       Steel of Member)

Steel weight required for above slab = 3 x 7850 x 0.01 = 235Kgs

For accurate estimation, you can refer to Bar Bending Schedule.

3)    Thumb Rules For Civil Engineers for Brickwork: -

        Brickwork for 1m3         Cement Qty in m3         Cement Qty in Bags

        230 mm Brickwork              0.876m3                         25.4 Bags

        115 mm Brickwork               0.218m3                       6.32 Bags