[SML] Unistrut safety factor specs?

[PATRICK MCCREARY]

Beams and column members are rarely given safety factors - rather they 
are rated for deflection. Failure in a connector or hardware item is 
just that - failure being torn apart, crushed, etc. - failure in a beam 
or column is a function of deflection. If you're planning something, 
best to use 1/360 of span, which, for all practical purposes, is a 
safety factor over 1/180 of span of about 2. Deflection ratios are based 
somewhat on usage - 1/360 being ideal for flat office/living 
room/occupied floors, 1/180 being tolerable for such things as warehouse 
racks, etc., where a bit of sag doesn't bother what's riding on them.

Patrick

On 2/26/2015 2:54 PM, Stephen Lee via Stagecraft wrote:
>
>
> Yes, I believe we're talking about the same concept.
>
> My confusion is coming from a lot of the other load ratings in the 
> catalog having a safety factor mentioned. For example, page 67 lists 
> some crush load ratings, and lists a safety factor of 2.5 (which I 
> assume means that the actual tested minimum load before failure is 2.5 
> times the stated maximum allowable load).
>
> Page 80 for general fittings says "Design load data, where shown, is 
> based on the ultimate strength of the connection with a safety factor 
> of 2.5, unless otherwise noted".
>
> The pipe hangers on page 128 list a safety factor of 5, etc...
>
> However, the max loads for the strut itself don't have a safety factor 
> listed. I kind of doubt that the loads they have listed are the 
> ultimate failure strength, but it doesn't say one way or the other.
>
> There's gotta be something I'm missing...
>
> Stephen Lee
>
>
>
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-- 
G. Patrick McCreary
Technical Director
Department of Theater and Dance
Indiana University of Pennsylvania

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