Good words and thoughts Ken. I liken this situation to every sprinkler design aspect I do; I do the 'leg work' and present it to a P. E., for verification. I feel like an X-ray technician in this regard-- I know how to run the machine, but I would not feel comfortable making any final diagnosis or plan of action with-out giving it to the Doctor first:)
> On Apr 4, 2014, at 8:21 PM, Parsley Consulting <[email protected]> > wrote: > > Jerry, > I appreciate the difficulty you're facing, and I don't envy that sort of > problem. Before I sought the services of a registered PE to certify the > hanger assembly, I'd spend a little time on the phone with the good people at > the hanger manufacturer, there are two of them located very close to us and I > would imagine they might be able to provide a listed assembly to accomplish > the support of the piping in the manner your example noted. > > Baring that, you have no alternative, Brad's math and guidance aside, but > to use the services of a PE. You can't use non-listed components unless > they're endorsed by a PE (9.1.2, 9.1.1.5.1). I take that back, you can do > anything you like, whether it's approved for installation by the AHJ is the > determinant, and if something happens, you're still wrong, particularly if > what you "design" fails. And it's relevant, I think to note that while Brad > has correctly explained the formula for calculating the required section > modulus for a cantilevered beam, the information he provided hasn't addressed > the means of fastening it to the structure, and the capacity of that means, > which is half the question. > > You're not an engineer, so why take that sort of liability on yourself? > Sure, from what I've seen of your submittals in the past you could do the > math just fine, but ask yourself this - can you defend it in court? If the > answer is "no", then a manufacturer is the first stop, and a PE is the next. > > Hope it works out for you. > *Ken Wagoner, SET > *Parsley Consulting*** > *350 West 9th Avenue, Suite 206 > *Escondido, CA 92025-5053 > *****Phone 760.745.6181* > Visit our website <http://www.parsleyconsulting.com/> > > *** >> On 4/4/2014 5:31 PM, Brad Casterline wrote: >> 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 > > _______________________________________________ > 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
