Tee-beam stanchion (onto a T-beam chord)

Discussion in 'Boatbuilding' started by netjaws, Jul 14, 2019.

  1. netjaws
    Joined: Jan 2004
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    netjaws Junior Member

    Long time lurker, first-time poster. (For construction).

    Needing to intersect two (2) structural tees (in any case—but for this one in particular, a load-bearing stanchion onto its supporting bottom chord)... C may be optimal, but multiple have merit—what do you think they are?

    Diagonals (and supporting brackets) omitted for clarity.
     

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    Last edited: Jul 14, 2019
  2. jehardiman
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    jehardiman Senior Member

    The joint design and structural orientation is based upon the loads and moments needed to be carried. In your drawings A is similar to B but totally different from C. Additionally, you really need to decide if you need a 3-corner intersection, as they are not preferred (see Design of Weldments by Lincoln Electric). If it is truly a stanchion, un-balanced sections are also not preferred (see Design pf Ship Structure by SNAME).
     
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  3. netjaws
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    netjaws Junior Member

    I don't suppose mentioning a "desert-isle" scenario would impress anyone coming after; but somewhere in between that and textbook ideality must lie any number of less than-preferable solutions to real world design problems... and would an angle-doubler appease just such a discerning eye?
     

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  4. jehardiman
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    jehardiman Senior Member

    What material? How thick? What process? Can you edge prep? And just for complete clarity on terms, is this a bulwark stanchion (cantilever "to structure") or a deck stanchion (compression "in structure")?
    I could just send you to the handbooks which fully detail weld design requirements, structural efficiency requirements, etc... but I will highlight some points....
    1) Welds "in" structure should be 100% efficient. This means full penetration welds only
    2) Partial penetration fillet welds are never 100% efficient because they are crack starters.
    3) Never weld stresses into a corner, always use a mousehole leaving the bending stress weld continuous. Use light sealing plates for watertightness.
    4) Built-up sections should not have a flaying surface.

    Edit, just noticed and changed "toy" to "you"...I hate having old slow fat fingers.
     
    Last edited: Jul 15, 2019

  5. Ad Hoc
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    Ad Hoc Naval Architect

    In addition to JEH's summary above you should also:
    5) Establish the load paths and ensure there are adequate load paths for transferring the load to surrounding structure.
    6) Establish what the design allowable stress will be - which takes into account the duty, environment and any possible fatigue aspects of the joint - and design to that, with the procedures noted.
     
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