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RE: Elevator Shaft Design

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Bill,

My answers follow yours below ...


<<<
I have a project where the client would like to install an elevator shaft in
the middle of the floor plan of an existing historic building.  The building
is wood framed construction built in 1904, with diagonal floor sheathing,
and true dimensional lumber of course.  My questions are as follows:

1.  Do I need to perform a lateral load analysis of the building, and
distribute load to the 'new' shaft walls?  If so, do I have to use the
current code to develop the lateral loads or is there another method someone
can present?>>>

*****
If your new shaft walls are connected to the diaphragm and are capable of
accepting diaphragm shear, then yes, you need to do an analysis, you are
altering the load path and if it is in the middle of the diaphragm, your new
walls will be more heavily loaded that your perimeter existing walls.

I would use the current code normally. If your structure is indeed a
"Historic" structure, codes like the UCBC or ATC/NEHRP may be more
appropriate and could be applicable as the governing code. Also, if you are
in a major city, the local building code may have a reduction from the
current code (i.e. San Francisco lets you use 0.75 Vbase of the UBC Value
for historic structures). UCBC give diaphragm values for various types of
sheathing and also gives you reduced base shear coefficients (when compared
to 97 UBC).
*****

<<<
2.  The owner claims to have no knowledge as to whether the building is
already compliant or is exempt.  Does anyone have any leads as to where I
can obtain any direction on this subject?  When does a building have to be
brought into compliance, and when is it exempt?>>>

*****
if you are altering the load path, then you need to upgrade or analyze and
prove compliance. Also, I use the 5% rule that if you are increasing demand
to or decreasing capacity of any existing member by 5%, lateral or vertical
system, I upgrade or analyze and prove compliance. For exemptions, I;m sure
some of the plan checkers on the list can help you there.
*****

-gerard
SJ, CA

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