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Re: Strengthen wood beam -help

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If you are not intending any composite action, as indicated by placing the
plates on the sides of the existing beams, then you simply need enough
fasteners to transfer the tributary 140 lb/foot from the beam into the pair
of side plates, and then at the ends, to transfer the reactions in each side
plate back into the beam and thence to the supports (assuming it is not
practical to transfer the reactions in the side plates directly into the
supports).

As someone else indicated, you will need sufficient fasteners along the top
edge of the side plates to prevent locally buckling.

Rather than risk a headache-inducing exercise, I would space the proposed
screws (a good choice) at 12 inches along the top edge and 24 inches along
the bottom edge to get the load into the side plates, and find some way to
get the 800 lb. reactions at the end of each side plate into the supports,
either through the beam or directly, and declare victory.

Mark D. Anderson PE
Anchorage

>From the "other U of  I" (Idaho)


----- Original Message ----- 
From: "Stanley E Scholl" <sscholl2(--nospam--at)juno.com>
To: <seaint(--nospam--at)seaint.org>
Sent: Friday, June 11, 2004 12:57 PM
Subject: Re: Strengthen wood beam -help


>
> I should have learned about this about 40 yrs. ago at U. of Illinois
> but----
> I must strengthen a couple of 4x8 roof beams at 3ft. oc. spanning 21 ft
> which are deflecting too much (and which are overstressed)
> I propose adding 1/4" x 7.25" plates on each side- after jacking up the
> beams, and using Simpson 1/4" x 3" SDS screws to attach the plates to the
> beams to make a Flitch Beam.
> Can anyone tell me the best method of determining if these screws will be
> adequate and what spacing should be used?
> I have designed the plates to take all the load.
>
> Stan Scholl, P.E.
> Laguna Beach, CA
>
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