Required Section Modulus for cantilevered will be the force (pounds) times the distance (inches), divided by the stress (15,000). The force is the weight of the water-filled pipe plus 250. The distance is 4" in this case. Not hanging at 15' just means the force will be less, i.e, if you have these unistrut at 7'-6", the weight will be half that if they were 15'-0, but you still have to add 250 lbs to get the force. Please post your results so we can all look at them, and be prepared to be criticized for not hiring a structural engineer. The 4x thing you mentioned will also be cleared up because with regular trapeze it is half the force times half the distance. Brad Casterline
> On Apr 4, 2014, at 6:56 PM, "Jerry Van Kolken" <[email protected]> wrote: > > I have a retrofit project where I structure will not allow us to install > beam clamps. The existing hangers are unistrut clamp to the beams and > extended 4" out to allow rod a ring to be attached. I would like to use a > similar assembly but I don't know how to calculate the loading to determine > the size of the unistrut. I've heard some stuff about 4x the section modulus > based on the trapezes table in NFPA. > > > > I was also wondering if there is a adjust the section modulus if you are not > planning on hanging at 15'-0"? > > > > > > Jerry Van Kolken > > Millennium Fire Protection Corp. > > 101 Copperwood Way, Suite H > > Oceanside, CA 92058 > > (760) 722-2722 FX 722-2730 > > > > _______________________________________________ > Sprinklerforum mailing list > [email protected] > http://lists.firesprinkler.org/listinfo.cgi/sprinklerforum-firesprinkler.org _______________________________________________ Sprinklerforum mailing list [email protected] http://lists.firesprinkler.org/listinfo.cgi/sprinklerforum-firesprinkler.org
