Scaffold pad allowable bearing on concrete 1

[novembertango88]

Hi all,

I am verifying a scaffold design and can't find any guidance for allowable bearing on concrete.

The pads are 12" by 18" and result in a bearing pressure of 69kN/m2.

For base plate design I would usually limit to 0.4* fcu = 0.4* 40kN/m2 = 16kN/m2.

Does this apply in the same way or am I missing something?

Thanks,Steve

 

[HTURKAK]

0.4 *fcu is OK for bearing stress but there is a small problem regarding the units.. fcu could be 40 Mpa so the unit of all. bearing stress will be 16 MPa ( 16 000 000 Pa or N/m2 ) and that makes 16000 kN/m2


16kN/m2, could be allowable bearing pressure for soil ..Check your units ..

 

[novembertango88]

Crikey, thanks HTYRKAK! Only 10^3 out!

 

[jayrod12]

So the total leg load is around 9.5 kN, or 2000 lbs? Yeah that's pretty well bugger all on a baseplate of that size. You'd need roughly 3,500 27 PSI concrete for that, which if you're saying the concrete is 40 MPa, it is far in excess of 27 PSI, closer to 5,500.

Edit:Math error.

 

[Guest090822]

AASHTO uses an allowable bearing stress on concrete of 0.30 f'c and AISC uses 0.35 f'c

Not sure why the mixing of units, but if the 2,000 pound load is disturbed to an 18"x12" plate then the stress is only 9 psi, which is very low.

I think you need to double check your units and/or clarify the problem.