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Re: Drop Panels

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With information provided (there might be something not readily apparent
without seeing the "whole" picture), I would say that additional bottom
bars strictly in the drop panel would NOT be necessary.  About the only
reason to place some additional bottom bars for the drop panel itself
would be is somehow you were using the column strip of the two-way slab as
a moment frame and you were somehow getting a positive moment at the
column, but since you say that drift is not an issue, this should not be a
worry in your case.

Additionally, if you were (and I don't think that you are) in a situation
where you needed some sort of reinforcement for the punching shear, then
you still likely would not need bottom bars, except as a "holder" for the
stirrups.  This is because the common methods for reinforcing a two-way
for punching shear involve either shearheads, stud rails, or stirrups, NOT
additional longitutinal bars.


Ypsilanti, MI

On Wed, 10 Jul 2002, Davin Weinhardt wrote:

> I guess my question wasn't clear. Aside from column strip (top) reinf.
> and aside from the 2 min. (bot) cont. bars, is there a requirement for reinf.
> at the bottom of the drop panel itself? Once again, there are no drift
> issues. The drop panel is proportioned per ACI. In other words, is
> there a problem with having 5 1/2" of unreinforced clear cover below
> the bottom layer of steel?
> Thanks,
> Davin
> PS The building in question was peer reviewed and came back from the
> building department with no comments. It's no wonder engineers get
> treated as a commodity when our own peers and plan checkers 
> thoughtlessly make comments about the integrity of another engineers 
> design. I only asked the question because most engineers throw in steel 
> just because.
>   ----- Original Message ----- 
>   From: Haan, Scott M. 
>   To: 'seaint(--nospam--at)' 
>   Sent: Friday, July 05, 2002 5:19 PM
>   Subject: RE: Drop Panels
>   If you have negative moment you need steel to resist it.  Also you need at least 2 continuous bottom bars in the column strip through the column core.  Also see ACI 318 Fig. 13.3.8.  Tell me the buildings you guys are designing without reinforcement in the drop panels so I can stay on the top floor.
>   Scott M Haan P.E. 
>   Plan Review Engineer 
>   Building Safety Division 
>   Development Services Department 
>   Municipality of Anchorage 
>   phone:907-343-8183  
>   fax:907-249-7399 
>   mailto:haansm(--nospam--at) 
>     -----Original Message-----
>     From: Lutz, James [mailto:JLUTZ(--nospam--at)]
>     Sent: Friday, July 05, 2002 2:20 PM
>     To: seaint(--nospam--at)
>     Subject: RE: Drop Panels
>     If there is no drift, and the moment stays negative over the panel area, then the drop panel is always in compression, and you shouldn't need steel in the drop panel. 
>      -----Original Message-----
>     From: Davin Weinhardt [mailto:yellowhumpy(--nospam--at)]
>     Sent: Wednesday, July 03, 2002 4:16 PM
>     To: seaint(--nospam--at)
>     Subject: Drop Panels
>       Just out of curiosity, how many would say that a
>       4" drop panel below a 9 1/2" two-way slab needs
>       reinforcement? What if I added that there is no
>       drift issues? If you still say yes, please state
>       why (references would be great)!
>       Thanks in advance,
>       Davin

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