50 foot clear span steel beam in residential construction 2

[KevinChez]

I have a high end residential project with a 50ft x 50ft garage located under the upper two floors. I was going to design a couple of 50 foot deep W-beam's to avoid posts. They want to have room for 5-6 cars and a turntable.

Seems crazy to have a W24 or deeper. It is going to be so heavy. I doubt I can talk the client into posts due to the layout. But maybe costs/constructability will govern.

What are your thoughts on cambering this beam and what is an appropriate L/??? deflection criterion?

Thank you!

 

[lexpatrie]

Maybe.

It's kind of frustrating because this kind of question nobody seems to want to put down pencils and do actual calculations, and it's so readily calculable, but we are just missing the appropriate tributary widths and presumed weights and whatnot, (I get people hesitating, but if the OP wanted they could post their version for folks to kibbitz on).

I think either route is potentially fine, so long as it is done "correctly" and the degree of camber actually hits the suggested parameters (i.e. a deflection of 3/4" or greater actually spits out at 80% dead load), otherwise, camber is perhaps going to create issues with construction, and perhaps is not something 4 out of 5 dentists would do.

It could still work out in the field so I'm not going to issue a blanket condemnation (which I am perhaps somewhat known for in certain subjects). The brochure also claims beams that are shipped "lose camber", this is a longer span, so the L^4 in the deflection is larger than the L^4 in your previous "trouble" 32' beam.

 

[KevinChez]

Thanks for all the replies.

I would only consider camber if I went with a concrete on metal deck floor system. Wood frame above that. I figure I need the rigidity because the upper floors are offset from the foundation footprint.

It is in DD so I will let you know how it shakes out.

 

[dold]

It's kind of frustrating because this kind of question nobody seems to want to put down pencils and do actual calculations, and it's so readily calculable,

For god's sake just size the beam for the trib line load and keep deflection tight. Put a big steel beam in. Dont camber it and just spec mill bow up. Presumably you've got two levels of load bearing sheathed walls above so effectively you've got a vertical diaphragm that's going to take gravity load towards the ends of the beam anyway. Tell Arch they'll have to furr around it. If a beam with two floors of bearing wall above it is having vibration issues then sue me. Contractor can't install it then splice it at third points.

Hell of a lot of hand wringing in this one. /rant