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RE: retail center lateral system (3 sided masonry)

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I thought that there were provisions to the diaphragm span ratio.  But, the only thing I found in 2003 IBC is in the empirical masonry design section (2109), which limits the span ratio to 2:1 for metal decking.  I think that's the first thing that hit me when I read your original post.  I would suggest adding making an interior partition structural, either masonry or a steel brace (chevron or x-brace) to reduce the span of the roof diaphragm...
Good luck convincing your co-worker...

Brian <bsh117(--nospam--at)> wrote:
Thanks for all the input!!

I have previously designed three sided structures with
the torsion being resisted by the end shear walls with
the resulting couple force. However, on this project,
I am concerned with the 300 ft dimension. The
building just "feels" too long for this type of

Thanks again for all your input!

--- "Sherman, William" wrote:

> Although I try to avoid buildings with one side
> completely open, I agree
> with Brian Smith that such designs are not that
> uncommon. For applied
> loads in the N-S direction, the center of rigidity
> is at the center of
> the shear wall on the west side. The applied loads
> cause torsion about
> that wall. The entire set of shear walls must then
> be accounted for -
> the torsion will be resisted by the the north and
> south walls, in the
> form of a couple. I would design the diaphragm to
> transmit the force
> couple to the north and south walls as well as the
> N-S shear reaction to
> the west wall.
> William C. Sherman, PE
> (Bill Sherman)
> CDM, Denver, CO
> Phone: 303-298-1311
> Fax: 303-293-8236
> email: shermanwc(--nospam--at)
> ________________________________
> From: Brian K. Smith
> [mailto:smithegr(--nospam--at)]
> Sent: Tuesday, May 09, 2006 8:43 AM
> To: seaint(--nospam--at)
> Subject: Re: retail center lateral system (3 sided
> masonry)
> Brian,
> Designing a 3-sided, open front structure is
> relatively
> common. There is some verbage in the IBC (2305.2.5)
> allowing it to be
> designed with a wood diaphragm. I do it all the
> time with metal deck.
> My approach is relatively conservative in that I
> assume the deck to be
> totally cantilevered from the back wall. I then
> check bending and shear
> deflections, moments, and shears using deep beam
> theory from Roark's.
> Brian K. Smith, P.E.
> ----- Original Message -----
> From: Brian
> To: seaint(--nospam--at)
> Sent: Tuesday, May 09, 2006 9:21 AM
> Subject: retail center lateral system (3 sided
> masonry)
> I need some help to settle an office dispute.
> Currently we have a 1-story retail center project
> in
> our office. The building is rectangular and
> approx
> 300 ft running in the NS direction and 90 ft in
> the EW
> direction. The entire East face of the building
> is
> storefront glass (300 ft) and wraps about 20 ft on
> the
> North and South faces. The rest of the building,
> which consists of the entire West face and the
> remaining portions of the North and South face, is
> contructed out of 8" masonry. The roof is
> constructed
> of joists, joist girders and metal deck and there
> are
> interior steel columns and steel columns at the
> storefront to support.
> Our differences come about for the lateral system
> in
> the long direction of the building. My co-worker
> would like to design this building without a
> lateral
> frame on the East face and rely entirely on the
> masonry shear wall on the West face. However, I
> believe that a lateral frame is required because I
> do
> not believe the metal roof deck can transfer the
> entire lateral force in that direction to the West
> face of the building.
> We are mainly dealing with lateral forces due to a
> basic wind speed of 90 mph.
> I would appreciate any other opinions out there.
> Thanks!
> Brian

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