Return to index: [Subject] [Thread] [Date] [Author]

RE: 1970's Panelized Roof - Question

[Subject Prev][Subject Next][Thread Prev][Thread Next]
Dennis,

I don't know if this is a possible solution for a wood roof (since I do
mostly steel and concrete), but since someone else suggested it, then it
might just fit the bill.

You could create a grillage/platform level that would support the
mechanical units.  You can then design the framing for the grillage to
take all the loads back to the columns (or some other structural element
that is easier to reinforce or has extra capacity).

I have done this type of solution several times, including once where new
units that needed to be placed on a roof that was primarily comprised of
open-web steel joists.

HTH,

Scott
Ypsilanti, MI


On Mon, 11 Feb 2002, Dennis Wish wrote:

> Stan,
> The bearing walls are too far away (more than 20 feet) from where the
> units are placed. This might require larger units. However, you raise a
> good point as the problem in the calculations was that bending was
> excessive as I applied the concentrated load of two units at the center
> of the GLB Girder for worst case loading. Inasmuch as I can't get ten
> units axial on four columns, I can space them so that they lie closer to
> the columns and remove some of the bending stress by increasing the
> shear at the ends of the beam. There is definitely much more capacity
> available to me in shear than in bending.
> One problem still plagues me - based on current calculations, the
> Girders are already overstressed nearly 25%. I have not, as Roger
> suggested, considered any stress reduction for beam depth and I might
> look at this. Also, I have to have the contractor verify the actual size
> of the Girders as he gave me numbers that were rounded out. A 7" GLB
> could be either a 6.75" or if I recall, there used to be a 7.75" for an
> 8x GLB at one time. I don't think they are made any more, but will need
> to search my older AITC manuals. I suspect that they may be wider than
> narrower and if so, this will give me a bit more room on the bending
> capacity to work with.
>
> I will take into consideration all of the ideas I have received from the
> list members - they really help me seek creative alternatives to solving
> the problem (one of my main goals when Shafat and I started the list - I
> was scared of moving away from the big city where I had more
> accessibility to my peers).
>
> Thanks again.
>
> Dennis S. Wish, PE
> California Professional Engineer
> The Structuralist.Net Information Infrastructure
>
> Website:
> http://www.structuralist.net
>
> ."The truly educated never graduate"
>
> -----Original Message-----
> From: sscholl2(--nospam--at)juno.com [mailto:sscholl2(--nospam--at)juno.com]
> Sent: Monday, February 11, 2002 9:31 PM
> To: seaint(--nospam--at)seaint.org
> Subject: Re: 1970's Panelized Roof - Question
>
> Dennis
> Can you place the units over walls and/or close to exterior walls so
> that
> shear governs, in which case you can add some steel plates?
> This is a good example of why I do most of my work as the prime
> consultant so that I can dictate locations, etc. of loads such as this.
>
> Stan Scholl, P.E.
> Laguna Beach, CA
>
> ******* ****** ******* ******** ******* ******* ******* ***
> *   Read list FAQ at: http://www.seaint.org/list_FAQ.asp
> *
> *   This email was sent to you via Structural Engineers
> *   Association of Southern California (SEAOSC) server. To
> *   subscribe (no fee) or UnSubscribe, please go to:
> *
> *   http://www.seaint.org/sealist1.asp
> *
> *   Questions to seaint-ad(--nospam--at)seaint.org. Remember, any email you
> *   send to the list is public domain and may be re-posted
> *   without your permission. Make sure you visit our web
> *   site at: http://www.seaint.org
> ******* ****** ****** ****** ******* ****** ****** ********
>
>
> ******* ****** ******* ******** ******* ******* ******* ***
> *   Read list FAQ at: http://www.seaint.org/list_FAQ.asp
> *
> *   This email was sent to you via Structural Engineers
> *   Association of Southern California (SEAOSC) server. To
> *   subscribe (no fee) or UnSubscribe, please go to:
> *
> *   http://www.seaint.org/sealist1.asp
> *
> *   Questions to seaint-ad(--nospam--at)seaint.org. Remember, any email you
> *   send to the list is public domain and may be re-posted
> *   without your permission. Make sure you visit our web
> *   site at: http://www.seaint.org
> ******* ****** ****** ****** ******* ****** ****** ********
>


******* ****** ******* ******** ******* ******* ******* ***
*   Read list FAQ at: http://www.seaint.org/list_FAQ.asp
*
*   This email was sent to you via Structural Engineers
*   Association of Southern California (SEAOSC) server. To
*   subscribe (no fee) or UnSubscribe, please go to:
*
*   http://www.seaint.org/sealist1.asp
*
*   Questions to seaint-ad(--nospam--at)seaint.org. Remember, any email you
*   send to the list is public domain and may be re-posted
*   without your permission. Make sure you visit our web
*   site at: http://www.seaint.org
******* ****** ****** ****** ******* ****** ****** ********