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I Strength of materials in a reinforcing being for garage

  1. Apr 27, 2017 #1
    I have a 30 by 30 pole barn type garage that is my workshop where I am trying to restore an old 68 Mustang of my grandfather who passed away. The trusses are 2x4 and are four feet apart. My thinking was to create a beam that runs perpendicular to the trusses about 10 to 15 feet from the edge. The beam would be a little above the bottom chord and would tie the bottom chord of the trust to it with those special construction hangers you can buy. I would add additional two by fours two this theme from the supporting outside wall.
    The goal of all of this is to enable myself to install some OSB on top of this so that I can store some of these extra parts of Grandpa's and get them up out of the way.
    I have no ceiling in this garage only very thick insulation and a plastic Vapor Barrier underneath the bottom chords of the trusses.
    I have thought about sistering two by sixes with plywood in the middle and running it the 30 feet as I said or I found online how to make something that is supposed to be pretty sturdy but seems weird to me. They take a 2x4 or 2x6 laid flat one for the top of the beam and one for the bottom of the bean they are connected on the sides with plywood every two feet inside there is a 2x4 or 2x6 on end attaching the bottom member to the Top member. It looks like they would not be very strong with the solid wood lane flat like that instead of on edge but they had calculation tables and such inside of the article, I know ideally I would use several 2 by 12 or something else but I do not have any and money is an issue. I do not have a ceiling as I said and I am not worried so much about the flexion like you would if you had a drywall ceiling.
    The other thing I thought about doing is I have a lot of scrap steel tubing that I have kept over the years I have about 30 feet of either 3 inch or 4 inch square tubing they are in 10 foot sections but I have the ability to weld them together to make 30 feet worth of tubing in one piece. I think the thickness of the tubing is 3/16. No matter what I have to do all this myself as I have absolutely no help.
    Also I have Amish Neighbors and live in the country so I do not have a lot of building codes like you would worry about in most big cities. However I like doing things right if at all possible I appreciate any help you can provide
  2. jcsd
  3. Apr 27, 2017 #2

    Stephen Tashi

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    Science Advisor

    Only a structural engineer can give you good advice about modifying your shop and it would take more information that you have provided.

    My advice is not to get involved in a large construction project just to store car parts. Use your resources to build yourself some large shelves. Better yet, clean out the shop and get rid of clutter that "might be of use some day", but also might not.

    Perhaps you are not a pack rat. However, if you have a 30 ft by 30 ft shop and you are short of room to store some car parts, the natural way to imagine the situation is that the shop is full of junk.

    For people with pack rat tendencies (like myself), large horizontal spaces are a psychological trap. They soon with get covered with clutter - that includes tablesaw tops, tables, chairs, and areas of the floor. (And I have friends who have half their beds covered with junk, leaving them only the other half to sleep in!)
  4. Apr 27, 2017 #3
    Among the many ways I failed to put my physics B.Sc to work, I worked in a truss plant for 5 years. Most of my time was spent building trusses and supervising the workers but I did take a truss design course and spent some time designing trusses. I currently do construction ... including occasional pole buildings.

    One thing just about all trusses I was involved with at the truss plant and have seen elsewhere have one thing in common: they are designed to support a large "live load" on top - usually just a winter's worth of snow - but only a very small "dead load" on the bottom chord. The dead load is things like the insulation you mentioned, ceiling lights, and then a layer of drywall or thin steel, etc. In my area, trusses might be designed for dead loads of perhaps 2 or 3 lb/sq ft on the roof and ceiling and live loads of up to 40 lb/sq ft on the roof but 0 on the ceiling.

    Truss plates are not cheap so manufacturers try to use the smallest plates possible and place them precisely. Thus the plates connecting the truss webs to the bottom chord are sized and positioned to deal with the webs pressing down onto the bottom chord. They are NOT sized/positioned to deal with forces trying to pull the bottom chord down away from the webs. When a truss is designed for a significant live load on the bottom chord - such as in attic trusses - the bottom chord's lumber dimensions and the plate sizes increase dramatically.

    However, your top chord IS designed for a live load pressing down onto the webs and then through the webs to the bottom chord. Thus, if you want to hang an unplanned-for and non-trivial load from your trusses you are better off hanging it from the top chord.
  5. Apr 27, 2017 #4


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    Staff: Mentor

    As already mentioned, we cannot help you with your project. Get competent help from a structural engineer who can wotk with you on-site. Thread is closed.
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