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RE: Strengthen wood beam -help

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I agree, deformation is key. 
 
There is a bunch of work on vertically laminated wood assemblies that was conducted at the University of Wisconsin in cooperation with the USDA Forest Products Laboratory in the early to mid nineties by Bohnhoff, Chiou, Williams, and Moody.  This was both experimental and numerical in nature.
 
See the following link for a list of papers on vertically laminated spliced and unspliced members under bending.
 
http://bse.wisc.edu/profiles/faculty/bohnhoff.html
 
 
Regards
 
Greg
 
Gregory D. Williams, Ph.D., P.E., S.E.
Manager of Engineering
FWS Design Builders
 
 
-----Original Message-----
From: struct(--nospam--at)att.net [mailto:struct(--nospam--at)att.net]
Sent: Friday, June 11, 2004 5:09 PM
To: seaint(--nospam--at)seaint.org
Subject: RE: Strengthen wood beam -help

I wonder why there should be any shear flow along the vertical planes since the plates are on the sides, not on the top and bottom.

 

I think compability of deformation should be the criteria, i.e. both the steel plate and 4x8 will have to deflect equally. This criteria will give you the share of loads carried by the steel plates and the force to be transferred by the screws.

 

Suresh Acharya, S.E.


 

-------------- Original message from "David Fisher" : --------------
> Damn U of I guys...always need the Purdue engineers to help them out...
>
>
>
>
> Stan:
>
> Wouldn't the standard shear flow equation apply here?
>
> ([VQ]/[It])
>
>
> This should give you the horizontal shear in the bolt line
>
> (required between point of zero and maximum moment) as a function
> Of effective depth...
>
>
>
> Divide by the fastener capacity to determine the number of bolts...
>
>
>
> Or, do what Frank Lloyd Wright did when his engineering "fell short"
> As it often did...
>
>
> Use offset wire on each side to "post-tension" the wood section...
>
> (Think he did this on the Hanna house in Palo Alto)
>
>
>
> Good luck!
>
>
> David L. Fisher SE PE
> Fisher + partners
> 372 West Ontario
> Chicago 60610
>
> 312.573.1701
> 312.573.1726 fax
>
> 312.622.0409 mobile
>
> www.fpse.com
>
> -----Original Message-----
> From: Stanley E Scholl [mailto:sscholl2(--nospam--at)juno.com]
> Sent: Friday, June 11, 2004 3:58 PM
> To: seaint(--nospam--at)seaint.org
> 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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