Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Load question

  1. Jul 31, 2012 #1
    Will 3"od X .250" wall ASTM A500 Grade B square tubing safely carry a single point load of 180lbs. over a 12ft span.

    Thanks
     
  2. jcsd
  3. Jul 31, 2012 #2

    PhanthomJay

    User Avatar
    Science Advisor
    Homework Helper
    Gold Member

    It should, depending on proper end connection(s) design, but what's
    the application? Cantilever or supported at both ends? What safety factor do you need? Deflection limitations? PLEASE ELABORATE.
     
  4. Jul 31, 2012 #3
    We are suspending a speaker system in a gym. The tubing will span across 2 roof trusses and be bolted in place at each end. The speakers will be suspended using a "fly bar" that attaches to the speakers which is load rated by the speaker manufacture. The roof trusses should be more than enough to carry the load. I believe they are 5ft trusses. We like to have a 5:1 safety factor for suspended speakers. We always use load rated chain and shackles for hardware. Not sure how much deflection would be allowed, I guess that's what my question really is.

    Thanks
     
  5. Aug 1, 2012 #4

    PhanthomJay

    User Avatar
    Science Advisor
    Homework Helper
    Gold Member

    Yes, that will work. A quick calc with the speaker suspended at the middle of the span indicates a bending stress of less than 5 ksi which has a safety factor about 9 against yield and a deflection at mid span of less than 1/4". Be sure to connect the ends close to a joint on the trusses.
    Disclaimer: This author claims no responsibility for the proper design of the beam and its connections.
     
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook