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Thread: Beam on top of a Beam

  1. #1
    Associate Engineer
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    Oct 2020
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    Beam on top of a Beam

    Hi - new to the forum and hopefully this isn't too basic for the group...

    I have a 20ft span (running north-south) in an old barn where i'm updating the second floor. The original floor is supported by 22ft 3x8 joists (east-west) that have been reinforced at the mid-point with a triple 2x8 (running north-south). I plan to add a new LVL that will connect to and basically sit on top of the triple 2x8. Then i'll build a new subfloor using the new LVL and 2x10s.

    I can find beam calculators and work through the deflections and all that for the LVL and the 2x8s. My question for this group is how do i factor in the combined strength of both beams? I can't use a properly sized LVL by itself as it would be too deep for my purpose. So i'd like to use it undersized for the span and use the existing structure below it to provide additional strength.

    I have an architect who has given me an undersized LVL to use that he is comfortable stamping. This is more for my own education and curiousity as to how you would factor in the 2 beams together when calculating deflection of a uniformly loaded beam supported on both ends. Its also an old hay barn and saw much more dead weight than i'll ever put on it.

  2. #2
    Administrator Kelly Bramble's Avatar
    Join Date
    Feb 2011
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    Bold Springs, GA
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    2,353
    Quote Originally Posted by davidmrosner View Post
    I can find beam calculators and work through the deflections and all that for the LVL and the 2x8s. My question for this group is how do i factor in the combined strength of both beams? I can't use a properly sized LVL by itself as it would be too deep for my purpose. So i'd like to use it undersized for the span and use the existing structure below it to provide additional strength.
    If beams are separate, spacing should be closer and maximum loading is understood per beam, stress, deflection, code requirements calculated and compared to design requirements.

    If beams are connected together PROPERLY, beam area moment of inertia is recalculated and loading, stress, deflection are calculated with this data.

    Since we get a lot of question from non-engineers it can be challenging to give the most correct answer. The following webpage is being pushed to non-engineers doing the work themselves on non-regulated builds.

    https://www.engineersedge.com/beam_b...tion_13746.htm
    Tell me and I forget. Teach me and I remember. Involve me and I learn.

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