ASTM A500 Grade B Square Tubing: Safely Supporting 180 lbs. Over 12 ft.

[Jaman]

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

 

[PhanthomJay]

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.

 

[Jaman]

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

 

[PhanthomJay]

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.