What is the sectional modulus for SHS square hollow section in cm3 and mm3?

Question

The steel size is 100mm x 100mm x 5mm thick

Answer 1

I = 10^4/12 - 9^4/12 = 286.583 cm^4

Section Modulus = I/(d/2) = 286.583/5 = 57.317 cm^3

= 57316.67 mm^3

Answer 2

Use a standard table if you are allowed to .

Inertia modulus  I = [(b * h^3) / 12]

for your Hollow square = [ (100 * 100 ^3) / 12] - [ (90 * 90^3) / 12]

                                 = 2,865,833 mm^4

                                 = 2.9 (10^6) mm^4

maximum distance from centre = root(50^2+50^2) = 70.7 mm

Section modulus = I / max distance

                              = 2.9 (10^6) mm^4 / 70.7 mm

                              = 40.5 (10^3) mm ^3