How to calculate section modulus of channel section

[Mech King]

Hi guys,

I am trying to calculate the section modulus of some channel section. I was going to use the value provided on the data sheet but its confusing me because it has values of section modulus in the X and Y axis. Am i right in assuming that i use section mod value where the load is perpendicular to its axis?

Also how would you calculate this value from scratch. I am familiar with calculating the section modulus of a sections that are symetrical in two axis, but not with those in one.

Any help would be much appreciated.

Cheers,

Amir

 

[elterrible]

You are doing bending calculations right?

Yes you would be interested in the section modulus of the axis perpendicular to the load.

Also the section modulus of the top and bottom of the channel (on the same axis) will be different if the cross-section isn't symmetrical about that axis (the neutral axis won't be in the center of the cross section). If you are putting a load on the top and creating bending moments, then you would use the bottom section modulus to check tension and the top section modulus to check compression stresses.

Theres some info there (though its a bit short) explaining it:

http://en.wikipedia.org/wiki/Section_modulus

 

[Mech King]

Thanks very much for the clarification elterrible, much appreciated.

Yes its for a bending moment, i haven't really worked with beams that are symetrical in one plane only so was a bit unsure. Thanks for your help,

Cheers

Amir