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Re: Shear Flow

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Use QV/Ib where b is the width of the glulam.


-----Original Message-----
From: Gobo, Gina <ggobo(--nospam--at)>
To: 'seaint' <seaint(--nospam--at)>
Date: Monday, February 14, 2000 1:45 PM
Subject: Shear Flow

>I have question about composite beams:
>I have a wood glulam beam that I would like to reinforce by adding a steel
>channel to both sides. I am trying to find the shear flow at the channel to
>wd beam contact area so that I may figure our how many bolts I need to
>faster the composite beam together. I am using the formula f = QV/I, where
>is the maximum shear load on the beam, I is the moment of inertia for the
>composite section, and Q the first moment of inertia of the glulam beam
>is in contact with the channel = yA where, y is the distance from the
>centroid of the block of wd in contact with the channels to the neutral
>and A is the area of the same block of wd. If I am using a channel that is
>C12X20.7 and a 6.75X31.5 glulam, Q = ((12/2)-dist to neutral axis of entire
>section)*6.75*12=248in3. I = 17964.83 in4 and V = 48kips. f = 8kip/ft which
>seems very high.
>The shear flow that I get seems very high. Do I have to use the transformed
>section in order to get the shear flow? (i.e. transform the wd beam into an
>equivalent steel member in order to get the correct shear flow). Or, is
>using I of the composite section based on the geometry of the cross section
>Gina T. Gobo, E.I.T.
>Structural Engineering
>DLR Group
>Ph. 206.461.6000
>Fax 206.461.6049