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Re: Stiffness calcs for Moment Frames

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This looks like a Kleinlogel formula. Kleinlogel had a two volume set of
books containing formulae that appears similar to the formulae below. This
is from memory since these books belonged to my mentor (SE18xx). I have
tried to search for these books for my own library, but they are no longer
in print. Too bad.

Bill Allen

-----Original Message-----
From: Kathleen A. O'Brien <wildwoman1(--nospam--at)>
To: SEAOC Forum <seaoc(--nospam--at)>
Date: Monday, January 05, 1998 12:24 AM
Subject: Stiffness calcs for Moment Frames

I have in my possession  the following calculation for preliminary designs
of moment frames when we want to determine the drfit of a particular frame:

For pinned-at-base frames (and please excuse the crummy formatting):

        drift = P*H(squared)/6E  *(H/Icol + L/Ibm)

        where    P = load
                H= height of column
                L= length of beam
                Icol= I of column
                Ibm= I of beam

For fixed-at-base frames:

        drfit=P*H(cubed)/12EIcol * (3K+2/6K+1)

        where   K= Icol*H/Ibm*L
                everything else as above

Now here are my questions:

1.      Does anyone know where this comes from? It was something we used at
an office I worked in LONG ago. I feel a lot better using something when I
know how it was generated (this one looks as though it might have been
derived from the stiffness calc in the Amrhein masonry handbook).

2.      The K value - the document I have shows it as Ibm*H/Icol*L. I think
I (or possibly the person who gave me the formula) miscopied it, because it
wouldn't make sense to multiply the length of the column by the I of the
beam or vice versa(?) that would be like multiplying apples and oranges.

3.      Does anyone know of a more recent stiffness formula for moment
frames? We usually do moment frame calcs by hand (with some help from
Microsoft Excel) because:

        a) we are a small office and don't do that many moment frames.
        b) the ones we DO do are small and uncomplicated.

and it doesn't make sense to shell out beaucoup $$ for fancy shmancy

Kate O'Brien, P.E.
Simi Valley, CA