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Beam camber spliced beam

Beam camber spliced beam

Beam camber spliced beam

(OP)
I recently detailed a 96' W36x256 with a camber of 1", the erector requested to splice into 32' pieces. I mistakenly left the 1" camber on the the 3 pieces. They have an "M" in the field, they will straighten out the 2 end beams, but they are asking me what the camber needs to be on the center piece, i am not sure if i am figuring it out right. My method is telling me 1/8" but i dont feel i am figuring it out right, any help is greatly appreciated.

RE: Beam camber spliced beam

Maybe a 1/2" camber in the middle third and a bevelled cut to the straight ends to provide a total camber of 1". A 1" camber on 96' will hardly be noticed.

Dik

RE: Beam camber spliced beam

A beam with a 1" rise over its full length will have a rise of (1/3)2 or 0.111" in the middle third if the curve is parabolic. As dik has stated, such a small camber will hardly be noticed. Any error in aligning the beam sections for welding at the third points will more than make up for any error in camber, so the calculation is theoretical but not very realistic.

Have you checked the beam deflection over a 96' span?

BA

RE: Beam camber spliced beam

Maybe the beam does not need field adjusting.

Dik

RE: Beam camber spliced beam

A W36x256 spanning 96' will deflect one inch under its own self weight. If it is supporting significant additional gravity load, it will sag a lot more than that. Perhaps the design needs to be reviewed.

BA

RE: Beam camber spliced beam

I'd sketch it out in CAD, should be a good double check of the camber you need.

I concur with BA, at just half of what I would expect the capacity of girder this to be it's deflecting 6 inches and very quickly exceeds even the most minimal deflection limitations. Your erector is smart; this thing would have likely folded itself into a pretzel if they tried to lift the full span.

Professional Engineer (ME, NH, MA) Structural Engineer (IL)
American Concrete Industries
https://www.facebook.com/AmericanConcrete/

RE: Beam camber spliced beam

Shop camber over 96' is probably close to that already, although if you sit it on the ground it will just sit flat under it's own weight as everyone else pointed out. From the shops standpoint, the camber is so small it is probably very difficult to achieve.

RE: Beam camber spliced beam

The ratio of beam span to depth is pretty larger. Beam deflection due to service limit states requirement may govern the design. I would double check the load and deflection calculation if I were you.

RE: Beam camber spliced beam

1" camber on a 96' beam = no camber at all. Won't be noticed and difficult to achieve. Side note: take a look at the bracing of the compression flange. It will need to be braced just to resist its own weight.

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