Residential Steel Design

[engineer817]

I am designing a residential steel and composite concrete slab structure? Does anyone have any information on what an acceptable initial deflection for steel beams would be? I know that in commercial applications, it you does not matter due to a higher tolerance allowed by finishings i.e suspended ceilings. A house however could be unforgiving with a much more strict allowable deflection criteria. I was trying to keep the initial deflection to 0.75 in. I know that the the floor will be poured flat, but I wanted to know if anyone just had a reference on construction deflections. Thanks.

 

[kkoloj]

When I design beams for custom homes, I look at deflection but I also consider vibration due to walking. A typical criteria I use to design steel beams is that the depth should be at least L/20. This, I believe, comes from one of AISCs steel tips booklets. For deflection, I will try to keep it around L/360 to L/480 for TOTAL loading (DL + LL).

 

[scottiesei]

Don't forget to take into account that load bearing walls below will be framed to the bottom of the floor/roof system. There is nothing worse than a falling cieling line or crushed dry wall at the tops of walls!

 

[engineer817]

This house is a full steel frame with a composite concrete floor system. I am looking for the allowable initial deflection (construction deflection). Do you know any publications or articles that disuss allowable construction delflections. Thanks.

 

[scottiesei]

I would think that construction deflections would be an OSHA thing.

 

[scottiesei]

Final LL and DL deflections would be local code i.e: FRC, IBC, UBC, etc. And of course, these are all minimums. Discuss with the contractor the materials and systems going below the steel and the order of their installation and make a "judgement" based on your research. You can also discuss with the owner/contractor the cost increase of increasing sections to limit deflections vs. the possiblity of falling cieling lines etc. Document everything! CYA

 

[engineer817]

Thanks. I think that is the best solution. Make an agreement with the architect and contractor on an allowable deflection.