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Re: Composite Beam Retrofit

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Greetings Mr. Francois,

If I understand your case correctly, one option for you is to:

1- Prop up the slab.
2- Demolish the 8"x14" beam also.
3- Recast a new R.C. beam 8"x22" with the required reinforcement to resist
the 51 kip-ft and 36 kip-ft.

I hope above is applicable.

Hasan Hindawi

----- Original Message -----
From: <marfra(--nospam--at)opus.co.tt>
To: <seaint(--nospam--at)seaint.org>
Sent: Sunday, 13 August, 2000 5:00 PM
Subject: Composite Beam Retrofit


>
> A Contractor has demolished a reinforced wall 41 feet long leaving an
> 8"x14" R.C. beam with 2No.4 bottom bars and No.3 bars at12" c/c spanning
> 41 ft unsupported. I can introduce 6"x6" m.s.tube columns at 12' c/c.
> The load above is a lecture hall and the factored bending moments for a
> 12' is 51 kip ft over supports and 36 kipft at mid span.
>
> The existing beam is therefore inadequate. W shapes are not readily
> available but I can get 8" x8"x5/16" tubing which I can rip into to 8x4
> channels. Head room is a problem.
>
> If i use the channels flat, cupping the underside of the beam fixed with
> epoxy anchors,can I assume that the beam fails over the supports and
> behaves as a simply supported beam, then design as a composite beam for
> mid span moments only.
>
> If yes the section is still inadequate if you ignore the 2 bottom bars
> in the existing beam. Can someone advise me how can i analyze the entire
> composite section inclusive the rebar,channel and concrete.
> Thank you
> mark Francois
>
>
>
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