There are many important formula in IS:456 and yes it is very difficult to remember each and every formula in IS 456:2000. As a civil engineer, you must know that useful formula when you work at the site. In this article, I will share some useful formula from IS:456 civil engineer must remember. I also advise you to go through the entire code for once and focus more on these areas.

Nominal cover to meet durability requirements

Not less than

20 mm for mild exposure.

30 mm for moderate exposure.

45 mm for severe exposure.

50 mm for very severe exposure.

75 mm for extreme exposure.

Reference: Table 16 of IS 456:2000

Go through Table 16 A of IS 456:2000 also. (For fire resistance).

When you start working at the site, the cover that needs to be provided will be the main concern.

Know some properties of materials as per the code

The nominal maximum size of course aggregates should not be greater than 1/4th of the thickness of the member. (Refer to the clause 5.3.3 of IS 456:2000 for more details.)

Modulus of elasticity of steel Es can be taken as 200 Kn/m2. (Refer to the clause 5.6.3 of IS 456:2000 for more details).

Modulus of elasticity of concrete Ec = 5000 √fck

where fck is Characteristic compressive strength of concrete in 28 days.

(Refer to the clause 6.2.1 of IS 456:2000 for more details.)

Unless more accurate calculations are warranted, the unit weights of plain concrete and reinforced concrete made with sand and gravel or crushed natural stone aggregate may be taken as 24 kN/m3 and 25 kN/m3 respectively. (Refer to clause 19.2 of IS 456:2000 for more details.)

Span to Depth ratio of beams are very important. (Refer to the clause 23.2.1 of IS 456:2000 for more details.)

Basics of working stress design and Limit stress design are also very important. Just go through those clauses once in a while. You’ll at least know where to find the information required.

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