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RE: Input with regard to section 1633.2.4

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M. Bryson said the following:

"And how do you get the imposed forces? From the displacement, right? Then
you do have to design for the shear and bending from delta-M. However, I
think what you are trying to refer to is that you can skip calculating the
forces caused by delta-M and just conservatively provide ductile
detailing. Do you agree?"

If you provided the ductile detailing option, you don't need to design the
column for either the M or V resulting from delta-M.  If you do not provide the
ductile detailing, then you do.  This is spelled out in Section 1921.7 of the
UBC, although actually it is just a repeat of what is in the ACI.  In high
seismic zones it simplifies life to just specify ductile detailing for all
nonstructural columns and then not even bother to do the check - the detailing
is going to be required anyway.  So in that sense, I agree.

One problem that I personally have with the provision is that it sets no limits
on how much the difference can be between the strength provided and the
calculated forces. 4 time? 10 times?  Basically this is a function of the
width/height of the columns.  I tend to regard nonstructural columns as b/h of
around 8 or more.  If less, then I'm kidding myself by calling them not a part
of the LFRS.

regards, Martin

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