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Re: RTU loads on joists

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Jim,

For new construction, we typically factor up all the loads the mechanical
people give us by 50%, and then design accordingly with a straight tributary
distribution, or as someone else pointed out we take the maximum corner load
and design for 150% of that at each location.

May sound really conservative, but in my experience mechanical loads
continue to increase throughout the design process :-).

If you are trying to figure a retrofit application it is a different story.

Paul Feather PE, SE
pfeather(--nospam--at)SE-Solutions.net
www.SE-Solutions.net
----- Original Message -----
From: "Jim Kestner" <jkestner(--nospam--at)somervilleinc.com>
To: <seaint(--nospam--at)seaint.org>
Sent: Thursday, September 19, 2002 2:01 PM
Subject: RE: RTU loads on joists


> We always do it by requiring a field welded web member. It is next to
> impossible to get exact locations from mech. contractors or suppliers and
> even if you do, substitutions more than likely will make the info.
invalid.
>
> Jim K.
>
> -----Original Message-----
> From: Effland, Greg [mailto:geeffland(--nospam--at)butlermfg.com]
> Sent: Thursday, September 19, 2002 8:04 AM
> To: seaint(--nospam--at)seaint.org
> Subject: RE: RTU loads on joists
>
>
> That (use KCS joists) is a good idea but keep in mind that they are not
> designed for chord bending from concentrated loads.  refer to the comments
> on page 27 of the 2002 SJI tables which states:
>
> "As is the case with standard K-, LH- and DLH-SERIES
> Joists, chord bending due to concentrated loads must be
> addressed. In the case of concentrated loads, the specifying
> professional shall handle them in one of two ways: 1)
> specify on the structural drawings that an extra web must
> be field applied at all concentrated loads not occurring at
> joist panel points, or 2) provide exact locations of all concentrated
> loads for which the joist manufacturer shall provide necessary
> reinforcement."
>
> HTH,
> Greg Effland, P.E.
> KC, MO USA
>
> -----Original Message-----
> From: Andrew D. Kester [mailto:andrew(--nospam--at)baeonline.com]
> Sent: Thursday, September 19, 2002 7:17 AM
> To: seaint(--nospam--at)seaint.org
> Subject: RTU loads on joists
>
>
> One other alternative of using steel beams to support mechanical loads
(this
> can make connections to joist-girders a pain) is the KCS Joist. It has
> similar sizes and load capacities of a K Series, but it is designed for a
> flat moment and shear envelope. So it does not matter where you put the
> point loads or increased uniform loads, as long as you have checked it for
> max M and V. We just started specifying these and wish we would have done
it
> a while ago. Although we do not do much northern work, I think these would
> be especially useful for snow drift loads.
>
> Although this does not completely solve Jim's problem because he has an
RTU
> that spans 6 joists. One other option, if possible, that may help you, is
to
> see if the ME will change the orientation of the RTU to run parallel with
> the RTU so you can just overdesign 2-3 joists rather then 6+ joists. A lot
> of the time our ME's are flexible and they may just not realize the impact
> it has on the structure and will gladly change it.
>
> Good luck,
>
> Andrew Kester, EI
> Longwood, FL
>
>
>
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