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RE: Lateral Deflection of Masonry Wall Building

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I'm developing specifications for a pre-engineered building which will
include some masonry veneer walls. I'm currently planning on specifying a
drift limit of H/200 under full design wind load (at service load levels).
This is somewhat of a compromise vs tighter drift limits and design at lower
wind recurrence levels. I prefer to design at full wind load, so I decided
to use a "moderate" drift limit. (I don't want to expect repairs for winds
in excess of 10-year winds.) In my opinion, H/100 at 10-year wind speeds is
not stringent enough. I've heard that drift limits of H/200 are not that
uncommon (Ref NCMA TEK 5-5A). 

William C. Sherman, PE 
(Bill Sherman) 
CDM, Denver, CO
Phone: 303-298-1311
Fax: 303-293-8236
email: shermanwc(--nospam--at)cdm.com


> -----Original Message-----
> From: rlewistx(--nospam--at)juno.com [mailto:rlewistx(--nospam--at)juno.com] 
> Sent: Friday, November 28, 2003 7:11 PM
> To: seaint(--nospam--at)seaint.org
> Subject: Lateral Deflection of Masonry Wall Building
> 
> 
> 
> Several years ago I asked this question and got a good 
> response.  I was thumbing through my 2000 IBC the other day 
> and came across Table 1617.3 - Allowable Story Drift.  For 
> masonry cantilever shear wall the allowable story drift is 
> 0.010*h which is equal to h/100.  For other masonry shear 
> wall buildings the allowable story drift is 0.007*h which is 
> equal to h/142.  Now I know this is in the seismic design 
> section but Section 2108.5.1 refers to this table for story 
> drifts in the general strength design section.  I don't have 
> the text in front of me but I know there is an AISC manual on 
> low-rise steel construction that would agree with these high 
> sidesway values for masonry wall construction with steel framing.
> 
> From my post several years ago I came away with the 
> conclusion that most engineers design for wind sidesway of 
> h/400 to h/500 using the 10 year wind when masonry walls are 
> present for the majority of the building.  As I wrote in 
> other post I sent on slender wall design, I have a 
> pre-engineered metal building with a 30 feet eave height.  
> The exterior walls will be masonry.  H/100 for this condition 
> is a 3.6" sidesway.  This seems too much for me.  H/400 would 
> knock this down to 0.9".  I know this will increase the steel 
> cost, but it seems to me that this is more appropriate for 
> this conditions.  
> 
> What other opinions are out there regarding sidesway of 
> pre-engineered metal building with masonry exterior walls?
> 
> Thanks.
> 
> Rich
> 
> 
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