Barge structural details: pillars

Discussion in 'Boat Design' started by Vinassman, Jul 23, 2012.

  1. latestarter
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    latestarter Senior Member

    Your English is usually so good that I had not noticed you were from Spain and this is a second language.

    The confusion is down to the use of words. In English a pillar is usually stone and would not work well off vertical. The term for a vertical post in steelwork is a column.
    In structures the term for a member in compression is a strut and if in tension a tie. This applies no matter what angle they are at.

    On its own an inclined strut would fall over but if you provide something to lean against at the top and stop it sliding at the bottom it will work.

    When I was referring to a truss it was the struts within it rather than the overall frame.

    Steelwork with an I section comes in columns whose height and width are the same and beams which are higher than their width. Engineers are free to use either at any angle. Almost any structure can act as a column or a beam but may not be efficient at both.

    Ad Hoc has just posted while I was writing this, his explanation about your other queries is much clearer than I would manage.
     
  2. TANSL
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    TANSL Senior Member

    Thank you very much, latestarter, for taking your time to clear my confusion. I am convinced that you, Ad Hoc and my selfI speak the same language on the concept of structure is concerned, and only semantic makes it seem that there are differences.
    With respect to English, I'm used to using the rules of the Classification Societies and they all talk about "pillars". Indeed I have always understood that a "column" was the name that was given to the pillars in the construction of buildings. Perhaps, I wonder, is a difference between UK English and U.S.
    Thanks again for your explanations.
     
  3. Ad Hoc
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    Ad Hoc Naval Architect

    This is not only confusion in terminology but also disciplines, or rather fields of engineering.

    Whilst you're correct, these definitions are not correct in naval architecture :(

    A pillar is defined as a structural member that is supporting a load from a deck load to another; generally between 2 or more decks. The pillar is, as I'm sure you're aware, simply to reduce the spans and thus design a structure that is not so heavy/large/expense. So in boats/ships these pillars are used in compression. (Although on rare occasions they can be in tension too - a tie bar).

    Pillars are generally of round section of square section. Unlike the classical Beam-columns one finds in steel work, these, in naval architecture, do not exist in that definition, nor usage.

    This is not to say they are never used. Since on some very large car ferries between decks they sometimes use I-beam sections, but generally they are square section. But still called a pillar not a column. Just to make things worse and more confusing! :eek:
     
  4. TANSL
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    TANSL Senior Member

    Totally agree, once again.
    Just add a review. The pillars in I try to avoid problems due to condensation that may occur inside the pillars of closed shape. As you well know, the material inside the pillar contributes little to the moment of inertia of the section and therefore, as posble, if working in compression, must be avoided.
     
  5. latestarter
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    latestarter Senior Member

    I live and learn ..... lots on this site. It as well that my canoe will not have pillars or columns. :D
     
  6. Ad Hoc
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    Ad Hoc Naval Architect

    Just for completeness:

    Pillars - DNV.jpg Pillars - LR.jpg

    :p
     
  7. Zeek
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    Zeek New Member

    The truss/stanchion arrangement is basically a lighter (sometimes) substitution for a bulkhead. It also might be easier to fabricate. The stanchions break the un-supported length of the deck transverses or girders and allow them to be smaller in size. From a rule standpoint, ABS will also allow the stanchion to break the un-supported length of the bottom frame/girder as long as a diagonal brace is added. Without the brace, and the bottom member could not be sized as being supported by the stanchion, and the length would extend until the next point of a support which would probably be a bulkhead or the side shell.

    The pillars are considered beam-columns, because the are supporting both compressive loads and the end moments of the deck or bottom members. Without the brace, the moment on the pillar would be amplified and would decrease the strength capacity of it.
     

  8. SamSam
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    SamSam Senior Member

    Not knowing anything about it, but let me suggest that it's not a beam or a truss in the sense that the ends are supported and the load is only from the top, as in a beam or a truss. It is more like a bulkhead and transfers loads from any direction, elsewhere. It creates a self supporting two dimensional shape that works with other support systems such as beams, girders, stringers and skins to create a self supporting three dimensional shape like a barge, boat or airplane.
     
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