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RE: Stucco or GWB as shear wall in seismic zone 4 (1997 UBC/2001 CBC)

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Bill,

I've seen illustrations and architectural details of the exterior stucco drip screed at the bottom of the wall that suggest that it may reduce or eliminate the connection of the stucco to the bottom plate and/or the foundation wall, thereby eliminating shear transfer of the stucco at the foundation.

 

Thanks, Dave. I’ll keep an eye on this detail (if I ever use stucco as a SW)

 

If GWB is used, then in the event of an earthquake or wind storm there will be architectural damage, such as to wall finishes at window corners.  Riverside is a windy place and without checking the seismic map I know it's fairly close to the San Andreas fault.

 

Based on my quick review of the seismic maps, Na and Nv are 1.

 

  One large event or several smaller ones could cost the owner more than a few wood shear panels.  If the loads are low the structure could be designed with a few sections of WSW, reducing the materials and labor cost.

 

That could be his choice.

 

What is the deflection of GWB at maximum lateral load?  Is the drift acceptable?

 

I know the first question is rhetorical since, AFAIK, there’s not a method to calculate the stiffness of GWB SWs. I would think that the drift would be acceptable considering the low load capacity and the relatively low aspect ratio, but that’s a guess, too.

 

Given the code and design issues raised here by others, I'd guess that most houses with windows would not satisfy design requirements for GWB as SWs.

 

That question wasn’t asked and I think I could figure that out on my own (when I get to that point).

 

I would recommend to the owner that he design a more durable building.

 

Again, that wasn’t the question.

 

Dave Gaines,

Pasadena, CA

 

            Regards,

 

T. William (Bill) Allen, S.E.

ALLEN DESIGNS

Consulting Structural Engineers
 
V (949) 248-8588 F(949) 209-2509

 

----- Original Message -----

From: Bill Allen

Sent: Thursday, June 22, 2006 6:17 PM

Subject: Stucco or GWB as shear wall in seismic zone 4 (1997 UBC/2001 CBC)

 

I haven't used stucco or GWB since Northridge, but a new customer is asking
me to look into it. If the loads are less than the capacity (even the
reduced capacity of GWB), I might have trouble justifying WSP just because
it "feels good".

 

Does anyone have evidence which would allow me to not use stucco or GWB as
SWs and still feel like I've tried to accommodate a customer's request?

 

Thanks,

 

T. William (Bill) Allen, S.E.

ALLEN DESIGNS <http://www.AllenDesigns.com>

Consulting Structural Engineers
 V (949) 248-8588 * F(949) 209-2509