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Re: wood panel wall aspect ratios: shear transfer around openings

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>That said, I'll bet most engineers just eyeball it unless 
they get caught by a plan checker who really knows his stuff.

Well, I have to agree with you on this one.  I rather find it very
challenging to compute forces on panels with different width each side of
the opening and very shallow dimension above the header.  It  even gets
worse when the size of the opening gets like 7' wide between the panels.  I
think if you try SEAOC design manual approach you will find that the shear
values get really high above the opening especially for shallow depth above
the opening, 12 inches or less. 
 Personally, I stay away from it whenever I can.  Thus far I saw some
clever spread sheet out put that points out final answers with no clear
direction or formula of how the final answers were obtained.  I am curious
if any body has developed a spread sheet to share with the interested
parties on this list.

Samir Y. Ghosn, PE
Harris & Associates
 At 10:25 AM 11/26/2002 -0800, you wrote:
>Scott-
>The recent SEAONC wood design seminar included an excellent presentation 
>on this subject by Doug Thompson.  The analytical method is Ed 
>Diekmann's and is published in the Fahey/Williamson book. Kelly was sort 
>of Ed's protégé and is no doubt well versed in the the calculation. The 
>intent of this method is to provide a rational method for analyzing the 
>shear flow around an opening in a shearwall with 2 tiedowns( and 
>coincidentally allows a way around the 2:1 aspect ratio problem for some 
>walls).
>
>Ben's understanding of the method is incorrect. His suggestion (and 
>yours) creates a statically indeterminant system in which the relative 
>deflections of tiedowns, shearpanels, and strapping would determine the 
>internal load distribution--something well beyond our meager design 
>capabilities. At low load levels the forces would certainly head for the 
>stiffest elements--your 2 "extra", interior tiedowns.  Depending on the 
>wall geometry and relative stiffness these tiedowns could be quickly 
>overwhelmed. No question about it though, the analysis is a PITA. One of 
>this days I'll try to do a spreadsheet.
>
>The perforated analysis by Dolan/Sugiyama/BOCA etc. is intended for 
>unreinforced openings and is now limited to long walls with 4' panels at 
>each end.
>The reason for Ed's analysis is the fact that the shear in the panels 
>above and below the window can easily exceed the "pier" shear and unless 
>you do the calc's there is really no way to design the sheathing/nailing 
>schedule.  That said, I'll bet most engineers just eyeball it unless 
>they get caught by a plan checker who really knows his stuff.  I 
>occasionally just use the empirical "perforated shearwall" method and 
>add some eyeballed strapping above and below the window--quick and safe 
>(but conservative).
>Chuck Utzman, P.E.
>
>
>
>
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