Need a book? Engineering books recommendations...
Return to index: [Subject] [Thread] [Date] [Author]
Re: Sanitary Structures
[Subject Prev][Subject Next][Thread Prev][Thread Next] To: seaint(nospamat)seaint.org
 Subject: Re: Sanitary Structures
 From: Jim Kestner <jkestner(nospamat)somervilleinc.com>
 Date: Wed, 10 Feb 1999 16:13:00 0600
Chris:
I assume that you are doing this by ACI 350. To get about the same resteel that we used to get by WSD, they introduced the addtional 1.3 factor that gets you pretty close on the first time around. I developed some tables years ago that I still use today which give me the capacity and the Z factor at full stress level for different slab / wall thicknesses, bar sizes, covers and spacings. All I have to do is proportion the req'd Zfactor (95 or 115) by 1.3 and the ratio of req'd capacity to the actual capacity. You then just pick the bar and spacing from the chart. This method is very fast. If I have something unusal that is too difficult to analyze by hand, I use Visual Analysis / Design to model it by finite element and let the computer design everything including checking working stress levels and Zfactors. I hope this answer is helpful to you.
Jim Kestner, P.E.
Chris Towne wrote: I do a lot of concrete tank design and I was wondering how other engineers tackle the problem of cracking. The process I go through is vigorous and time consuming, but I feel it is necessary. Step 1: Find Steel that satisfies phiMn >= Mu Step 2: Find the actual steel stress (unfactored) Step 3: Find the maximum spacing for that steel stress and bar size that satisfies Z <= 115 k/in. Step 4: If that spacing is less than I found in Step 1, I shorten my spacing and perhaps change bar size and go to Step 3. I repeat steps 3 and 4 until I have the most economical section that satisfies both strength and cracking. I've found out that most of the time if the steel stress is under about 24 ksi, cracking is ok. I was wondering if others just use working stress design and make the whole process simpler. I was taught using ultimate strength and I feel the need to check it even though it never governs. Chris Towne, E.I.T. 

 References:
 Sanitary Structures
 From: Chris Towne
 Sanitary Structures
 Prev by Subject: RE: Sanitary Structures
 Next by Subject: Re: Sanitary Structures
 Previous by thread: Sanitary Structures
 Next by thread: RE: Sanitary Structures
 About this archive
 Messages sorted by: [Subject][Thread][Author][Date]