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Re: Continuous Beams in Residential Construction

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Thanks for the comments.
I was looking for this piece of literature as I am
aware of the
problem but I wanted to give it to a person of the
architectural
persuasion who keeps trying to using continuous beams
of quite different lengths with no regard for uplift.
I have run into this problem twice in residential
construction, i.e. the bump or hump.
I had a large (2.5") hole drilled near centre and then
saw cut to it.
Seems to have worked Ok.

On 27 Nov 2002 at 6:02, Tim Allison wrote:

> Do you just specify the ½-depth cut, or are there calculations that go along with it?  I assume you are trying to avoid using a splice plate or some other connector by keeping the beam wood fibers partially intact.  What do you do to make sure the rotations, movement, etc. don't cause the
bottom half to split?
>
> >>> bcinc(--nospam--at)nanosecond.com 11/27/02 01:56AM >>>
>
> How about cutting the top of the beam vertically at least half of the beam depth, over the center support, in effect creating two simply supported spans?  I often specify this when dealing with residential beams, especially if it is not visible.  If they are visible, specify two separate beams.
The splice will be less noticible.
>
> Pat Clark
> ----- Original Message -----
> From: Tim Allison
> To: seaint(--nospam--at)seaint.org ; ghodgson(--nospam--at)vaxxine.com
> Sent: Monday, November 25, 2002 8:30 AM
> Subject: Re: Continuous Beams in Residential Construction
>
>
> I don't think my original message was sent.  Sorry if this is a re-post...
>
> A span up to 50% shorter than the longest span should not present problems with uplift for uniform loading.  I have not been able to find a specific document that addresses this.  However, most engineered wood manufacturers publish literature on their products and allow differences of 50% or
more; I'd be glad to point you to a few eng. wood sites for some confirmation of the 50%.  Alternatively, ASD (and others) publish equations for non-uniform span lengths and can be calculated by hand.  I don't believe there is a specific number that can be used, but from my experience 50% has
been safe.
>
> Tim Allison
>
> >>> ghodgson(--nospam--at)vaxxine.com 11/25/02 09:54AM >>>
> I have run into situations, particularly in house construction, where continuous beams of unequal length have been
> used.  Where there is a long span and a short span, you usually get a kick-up (uplift) at the end of the short
> span.  Unless you can hold the beam end down, you get a bump in the floor.  Consequently, I try to avoid these
> particular continuous beams.
>
> I read somewhere once, that to help avoid this situation, the continuous beam spans should not vary by more than
> 15%.  I would like to find that piece of literature again.  Can anybody help me with this?  Unfortunately, I don't
> remember if it was Canadian or American.
>
>
> Thanks,
> Gary Hodgson, P.Eng.
> Niagara Falls, ON
>
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