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Thread: Plywood and Porches

  1. #1
    engineerx
    Guest

    Plywood and Porches

    This is silly. But circumstances have me calculating something that I for some reason cannot grasp.

    A dolly has about 700lbs on it (350 per wheel). It's on a platform made with 2x8 joists, with 30" spans. the actual platform is a little worn and weathered, so they've got a new piece of 3/4" plywood on it. Then they're going to take the dolly down the ramp to a concrete sidwalk.

    For the life of me, I can't calculate the load to prove the plywood won't break. I don't know if I'm not grabbing the right equation because I'm too detached from this kinda of problem, or if I need more coffee or what.

    But basically, I need the shear strength, and the shear stress of said plywood with 30" spans. As long as my stress is lower than the strength I'm fine right?

  2. #2
    Technical Fellow Kelly_Bramble's Avatar
    Join Date
    Feb 2011
    Location
    Bold Springs, GA
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    2,611

    Welcome

    Welcome to EE!

    First I would start here ---> http://www.engineersedge.com/beam-deflection-menu.htm

    Then, take a look at ---> http://www.engineersedge.com/mechani...ial_menu.shtml

    You assmue to a degree that the plywood distributes the load evenly.

    Also, proof loading the platform is as simple as getting a couple of well fed men to stand on the platform.

  3. #3
    Technical Fellow
    Join Date
    Feb 2011
    Posts
    1,043
    Unless I am misunderstanding something, but if the worn platform was OK, then surely a new piece of plywood would still be OK? Put the calculator away?

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