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Re: IBC Wood Shearwalls

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Paul:

My interpretation (for what it is worth) is that the intent of the 40%
allowable increase for the allowable wood shearwall values under wind is
due to the different nature of the loadings.  For seismic (as you are
aware), you are more interested in a ductile response and don't want that
"brittle" failure.  For wind, that is not the case.  As such, I believe
the code writers intended to allow an increased wind capacity as in theory
a wood shearwall under wind loading is seeing a more monotonic, "static"
type loading.  As such, it should be able to develop a higher capacity.

Now, I have nothing official to back that up.  The only thing that
supports it is that I know for SIP shearwalls the ICC Acceptance Criteria
has two different testing requirements for shearwalls.  One is a
non-cyclic load (i.e. non-ductile) type test and the other is the newer
cyclic loading protocal.  The older method is permissible for wind and low
seismic uses (SDC A, B, & C in IBC "speak"), while the newer method is
permissible for all SDCs in the IBC.  And from my understanding, a SIP
shearwall tested and detail per the older method can much easier develop a
large allowable capacity than when tested by the newer method.  This is
largely due to different "goals"...the older method bascially is after
maximum strength/capacity, while the newer method is "after" a ductile
response.  I have never gotten a response from those in charge to my
question of if the capacities done under the newer method will be
permitted to be increased by 40% along the lines of the IBC provision.
The newer method is a "seismic testing" method after all, so it would make
sense to me...assuming that I have the reasoning for the 40% increase
correct.

HTH,

Scott
Adrian, MI


On Mon, 21 Aug 2006, Paul Feather wrote:

> What is the opinion regarding whether or not section 2306.4.1 (40%
> increase in shearwall allowable shear for wind design) is compatible
> with section 1605.3.1 Load Combinations?
>
>
>
> Or would section 2306.4.1 be considered a material increase?
>
>
>
> Us UBC people do not have any provision for increased allowable
> capacities in the shearwall tables for wind design.
>
>
>
> Also, is the .6D with .7E combination an errata?  Load combinations with
> E have never been less than .85D.
>
>
>
> Thanks
>
>
>
> Paul Feather PE, SE
>
> pfeather(--nospam--at)SE-Solutions.net
>
> www.SE-Solutions.net
>
>
>
>
>
>

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