0
$\begingroup$

I'm building a frame that will receive a point load mid span (likely it won't be but want to design for worse case).

The frame is 1.5 x 0.095 square tubing, and it will be skinned with 14ga on one side. Span is 21" and frame is welded.

My question is how do you determine deflection when a beam is skinned with metal? Shouldn't this increase its strength?

I want to make it stronger than needed, but not unnecessarily heavy. I was originally debating between 0.095 and 0.065 wall tubing and 12 vs 14 GA sheeting.

I'm using 2250# for my point loading figure at center of 21" span.

enter image description here

$\endgroup$
3
  • 1
    $\begingroup$ Clarify your dimensions, as numbers only are not clear. $\endgroup$
    – Solar Mike
    Nov 5, 2023 at 18:00
  • $\begingroup$ You can estimate a new moment of inertia for the skinned beam using the parallel axis theorem which is in any structures textbook, or wiki, no doubt. $\endgroup$ Nov 5, 2023 at 20:54
  • $\begingroup$ The sheet metal buckles easily, and given the way it is attached, it usually does not contribute much in stiffness. You won't regret by ignoring it. $\endgroup$
    – r13
    Dec 5, 2023 at 23:32

1 Answer 1

0
$\begingroup$

This a very rough calculation not considering the dynamic load factor of the application of the random load which could be up to three,

$$\sigma = \frac{M}{s}= \frac{2250*21}{4 *0.12953}=91,569lbs >>36000lbs$$

  • $\sigma = stress<3600 \text{ A35 steel yield}$

  • M = moment inch.lbs

  • S = 1.5x1.5 square tube section modulus Because the member is significantly under-designed we do not need to investigate the effect of galvanization. It is not going to be adding enogh strength to make the member 2.8 times mor strong.

$\endgroup$

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge you have read our privacy policy.

Not the answer you're looking for? Browse other questions tagged or ask your own question.