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Re: Adding a mezzanine to a Masonry Building in Seismic Zone 4

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I just completed a mezz. in a fairly large tilt-up building with a 25 ft.
ceiling ht., to store car parts, in Corona, CA. I designed it to stand
alone, with wood shear walls just inside  the tilt-up exterior walls and
with a new footing around much of the mezz. I used cantilevered columns
with grade beams on the open front side.
 This was a design-build job and the contractor and I decided on this
prior to beginning the design.

Stan Scholl, P.E.
Laguna Beach, CA

On Wed, 16 May 2001 10:38:16 -0700 "Structuralist" <dennis.wish(--nospam--at)gte.net>
writes:
> I need to put together a proposal to add a wood frame mezzanine to an
> existing masonry building in Palm Springs. The building is more than
> 40-years old. The building is roughly a 3:1 aspect ratio (about 
> 100-ft x
> 35-ft) and the mezzanine (wood frame) will take up only about 1/3 of 
> the
> floor space (33' of the 100-ft width).
> The mezzanine will provide rooms which will be used for off space on 
> the
> first and light storage on the second floor. The mezzanine will 
> attach at
> the second floor diaphragm to the existing masonry building on three 
> sides.
> The masonry walls are 100% solid where the mezzanine occurs. One 
> side of the
> mezzanine is open at the second floor (it overlooks the first floor) 
> and the
> first floor walls will provide shear (lateral) resistance at the 
> open side.
> However, the second floor open side has no shear connection to the 
> roof.
> 
> I would normally have added the mezzanine dead load into the 
> existing roof
> dead load (adding about 5-psf over the entire roof), and 
> re-calculate the
> lateral analysis to the masonry walls to verify that they have the 
> capacity
> to resist the additional shear. At the open side of the mezzanine, I 
> would
> have calculated only the second floor diaphragm shear transfer into 
> the
> first story walls to resist drift. Considering that there the two 
> structures
> are tied together, does this seem like a reasonable plan? The 
> lateral load
> from the roof is distributed to the four masonry walls and would 
> include the
> weight of the mezzanine - but the open front of the mezzanine is the 
> only
> side unaccounted for that I would use the first floor shearwalls.
> 
> So here are a couple of questions for Zone 4 areas;
> 
> 1. Is it appropriate for me to simplify the design by using the 
> guestimated
> base shear (conservatively) at 0.186Wd to calculate the lateral load 
> caused
> by the mezzanine and verify all existing masonry walls to laterally 
> support
> the addition?
> 
> 2. Would I be expected to bring the structure into compliance with 
> the
> current code (near source values, full-compliance by flexible and 
> rigid
> design)?
> 
> 3. Would I be expected to use flexible design for the unsupported 
> side of
> the mezzanine based on the Simplified Static Design 
> [0.3ICa/(1.4R)]*Wd ?
> 
> 
> Regards,
> Dennis S. Wish, PE
> 
> 
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