Hi,

This is probably aimed at the Structural Engineers out there.

I have a plate that is 10,000mm long by 3,000mm wide and 30mm thick steel is mild steel grade S355.

I want to know if I picked this plate up in the center how much it would sag on the ends (deflection) under its own weight. No applied load

I get

Length 5000mm (half 10meters). L

6.93 Kn / per meter (706.5 Kg /m x 9.81 / 1000) W

Moment of Inertia 6750000 (3000 x 30^3 / 12) I

Elastic modulus 210000 E

I am now a bit confused as to what is the correct formula to use to find the deflection.

Should I use (W x L^4) / (384 x E x I) or (W x L^3) / (3 E x I) or another formula?

The sag using these calc seem very small.

Also I assume that if I welded one of the 3 meter ends to a plate the sag under its own weight over the 10meter length would be double the above.

Thanks

Mark