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Any Mechanical Engineers willing to a solve a math problem?

Discussion in 'General Technical Questions and Answers' started by WA7F, Jul 12, 2019.

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  1. WR2E

    WR2E Ham Member QRZ Page

    I'm not a structural engineer, but I play one on the internet.

    Seriously Dave, ask (and pay) a real engineer.
    WN1MB likes this.
  2. WA7F

    WA7F Premium Subscriber QRZ Page

    It’s a wooden pole barn built to code. The wooden trusses are adequate to support the roof and snow loading. I intend to add rectangular steel tubing supports at the ends of the I-beams and gussets between the two. Other than excluding side support which the structure can easily provide the pole barn can be removed from the equation. My only concern at the moment is what the I-beam span will support.
  3. WA7F

    WA7F Premium Subscriber QRZ Page

    Thanks for the good intentions but, if you aren’t educated in this area or haven’t at least picked up a welder and fabricated steel structures then you are not really helping. I’d rather have no reply’s then a bunch of worry worts.
    W6KCS likes this.
  4. K8MHZ

    K8MHZ Ham Member QRZ Page

    Depending on where you live, snow load may be a huge determining factor.
  5. WR2E

    WR2E Ham Member QRZ Page

    You're welcome, I am, and I have.

    Suit yourself, if you find some fool that's willing to work for you for free and accept the liability, then have at it. Good luck to you AND them.
  6. KA0HCP

    KA0HCP XML Subscriber QRZ Page

    Your list of equipment to be supported goes beyond a casual or light use. Pay a few hundred dollars to a local engineer to design this for you. It will save you worry, and the costs of inappropriate materials orders or rebuilding after a collapse. b.
  7. SM0AOM

    SM0AOM Ham Member QRZ Page

    Not being an ME, but an EE which is supposed to know the basics of structural engineering, I dug out an old compendium and used the formulas for beam deflection as functions of point and distributed loads.

    In your case, the assumptions are that the 24 ft beam is flexibly supported at each end, with any vertical members sufficiently dimensioned not to buckle for the vertical loads.

    From published data for the S 8x23 I-beam:

    Weight per ft = 23 lbs
    Moment of inertia = 64.9 in^4
    Young's Modulus for structural steel= 2 900 000 psi

    Maximum permitted deflection under load = span/500 = 0.6 in (taken from the Structural Norms for lifts and cranes here)

    Distributed load from own weight = 552 lb
    Resulting deflection = 0.09 in

    Point load at centre = 2000 lb
    Resulting deflection = 0.5 in

    Adding up deflections = 0.5+0.09 = 0.59 in,
    assuming that the deformations are within their linear range,
    which is less than permitted in the structural norms.

    So, an additional load of 2000 lb at the centre could be allowed.

    My education and compendium uses SI units, so a quite awkward exercise of converting back and forth from SI to Imperial units resulted.

    Hope this helps.

    Last edited: Jul 12, 2019
    W6KCS, WB5THT and NN4RH like this.
  8. WA7F

    WA7F Premium Subscriber QRZ Page

    I meant it when I said thanks for the concern. I just don’t see this as that crictical and I was just looking for ballpark numbers to make sure the I-beam is large enough for the task.

    When not in use the big cat has been hanging from a large pallet rack in storage for a few years now but, I don’t want to use that structure in the shop. I’ll figure this out from the online tools. Thanks again.
  9. WA7F

    WA7F Premium Subscriber QRZ Page

    Thank you, Karl-Arne. This is exactly the type of information that I needed.
  10. N0TZU

    N0TZU Platinum Subscriber Platinum Subscriber QRZ Page

    Snow load is accounted for where?
    WN1MB likes this.

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