How to calculate section property?

Question

what is the step to calculate section modulus for steel section for example for zed or top hat section

Answer 1

1. Split the section up into rectangles

2. Calculate the area of each rectangle (Call this A).

3. Calculate the distance from a baseline to the Centre of Gravity (C of G) for each area) (call this distance g)

4. Multiply each area by its g. This is the First Moment of Area (FMOA)

5. Add all the  FMOAs together and divide by the total area of all rectangles. This will give you the distance of the overall C of G from the baseline. Call this G

6. Calculate the Second Moment of Area (Moment of Inertia) for each of  the rectangles .

7. Calculate A x (G-g)^2 for each Area.

8. Add all results from step 7 and 8. This gives you the total I (Moment of Inertia) mm^4

9. Divide I by the greatest distance from the overall C of G to the extreme fibre. This gives you zed mm^3