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RE: 12" Hollow Core Plank Span

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I’ve designed the Hollow plank for 17 feet two way system as the main logic of the Hollow plank is that the concrete in the tension zone has a less priority in the strength and other


aspects but on the contrary for longer span pre stressing  v will face that creep problem may be arranging the strand drape height at certain locations may rectify the problem, I am


expecting but I am not sure, if this leads to wrong opinion just forgive me.







Phani Krishna...

Senior Design Engineer,

Lnt GES.


-----Original Message-----
From: Rich Lewis [mailto:seaint04(--nospam--at)]
Thursday, June 05, 2008 7:31 AM
To: seaint(--nospam--at)
Subject: 12" Hollow Core Plank Span


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.




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