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Re: 12" Hollow Core Plank Span

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I did a design with 12" precast planks and a 3-1/2" conc topping.  It was on the limit for vibration from standard footfall.  And this was for an office loading of 50 psf.  i haven't heard of the occupants getting "seasick," as the office furniture will dampen the vibrations.  However, at a span of 44', be very aware of it, as that is very much a serviceability issue.  good luck.

On Wed, Jun 4, 2008 at 7:00 PM, Rich Lewis <seaint04(--nospam--at)> wrote:

I've been asked to design a building that has precast hollow core plank spanning 44 feet.  I'm looking for some guidance from others who have experience in longer span using hollow core plank.  My past experience has primarily been 8" plank in spans under 30 feet. 


Technically, by the span tables, 12" plank will span 44 feet.  It takes a lot of prestressing to get it there.  My concern is with serviceability issues.  With using lots of prestressing am I likely to see upward creep in the plank, or is the gravity dead load usually enough to overcome upward creep?  Has anyone experienced this before.  What practical issues should I consider when using longer span floor plank?


Thanks for your insight.




David Topete, SE