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Concrete T-Beam

Concrete T-Beam

Concrete T-Beam

(OP)
Section 8.12.4 of the ACI 318-08 code seems to be saying that a T-beam flange can't be less than one-half the width of the beam. This seems awfully restrictive, and unreasonable. I'm not sure what the significance is of being "isolated beams in which the T-shape is used to provide a flange for additional compression area". What other reason would you have for treating it as a T-beam? What is the significance of "isolated"... what does it mean? Does anybody understand the thinking on this provision?

RE: Concrete T-Beam

I think an isolated T beam is one where the slab is not poured monolithically with the beam. A case where you physically only have a certain width, not arbitrary code required eff. flange width.

RE: Concrete T-Beam

That's not correct, slick.  An isolated T beam is generally a precast beam, and the provisions are just to prevent the use of very thin flanges.  The exact same provision has been in the code since at least the 1963 version.  

RE: Concrete T-Beam

(OP)
Thanks for the replies, but I'm still a little confused. I guess the precast is made composite with the slab using shear connectors cast into the precast... is that the idea?

RE: Concrete T-Beam

To the best of my knowledge, precast single tees went the way of the dodo.  Double tees are made composite with a roughened surface - no steel.  I'd have another look at this for high seismic, but for mild areas, this is standard.

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