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Re: Cutoff Wall In Concrete Transition

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Gerard
Yes, you are right; my problem is not how to design a cut off wall( that one and for that matter any other element i can very well design given the problem description), my problem, as you rightly put is the confirmation of its necessity, from either structural or hydraulics point of view. This is required as a support reference to convince people who resist its adoption. If you followed my response to Roger Turk's query on the subject, you would be now fully conversant with its description. let me put it again. " at the outlet of box channel we have wing walls( to retain sloping earth outside), these wing walls are connected at the bottom with a slab-on-grade. But there is a stretch of this slab-on-grade (about 10m or 30 ft) which donot have wing walls and are simply resting elastically on soil. The wing walls , slab-on-grade & the cut off wall are known as TRANSITION, perhaps because they act as a medium to regulate water flow from a trained flow in a box channel to a comparatively untrained flow outside. At the ends of this slab-on-grade ( ends implying end in the direction of water flow, and on the two sides), we normally provide cut off wall for reasons as described earlier, i.e, to prevent or delay percolation of water beneath this slab-on-grade obviously with a view to inhibit damages to the transition. Iam sure now you know my problem. As for your comment on ability of our learned fellow engineers, i fully share your views especially on BILL POLHEMUS, who i notice is very agile in responding to almost every query on the list. But i was disappointed to observe his silence on this particulr issue. Hope this will provoke him & he would come up with his views also.
SYED FAIZ AHMAD
SENIOR STRUCTURAL ENGINEER
SAUDI OGER LTD
RIYADH, SAUDI ARABIA


From: "Gerard Madden" <gmadden(--nospam--at)mplusl.com>
Reply-To: seaint(--nospam--at)seaint.org
To: <syedfaiz23(--nospam--at)hotmail.com>,<seaint(--nospam--at)seaint.org>
Subject: Re: Cutoff Wall In Concrete Transition
Date: Thu, 31 May 2001 22:54:04 -0700

Syed,

Again, it sounds like you are asking about whether the wall transition is necessary, not how to design if indeed you determine its need. I was simply stating that structural engineers may nothave the "expert" opinion you seek to clearly state the transition's need and consequences when it's lacking. Your post made it sound like you already know why it's necessary and you were seeking confirmation. I realize it is a structural design issue - once you know it's necessary. I take it, from your previous posts, that you know how to do that part since it sounds like your are experienced and have a strong engineering sense.

By all means, you should not hesistate to ask this list and most any topic and you are likely to get an answer that is correct. People with knowledge on great many things beyond engineering,like Mr. Polhemus, are sure to provide you an unbiased open minded discussion the get to the "truth" of virtually any topic you can think of. He will also be able to trace the root of all the problems globally to the former president and his merry men. :)

respectfully.
-Gerard ( no mister :) )
Sam Francisco, CA
>>> syedfaiz23(--nospam--at)hotmail.com 05/31/01 17:51 PM >>>
Mr. Gerard
A cut off wall is a vertical wall at the end of the concrete slab-on-grade
in the outlet & inlet of the cross drainage structure. This cut off wall is
basically provided to prevent or delay water percolation beneath the slab.
Mind you, this concrete slab together with the cut off wall ( at the inlet
or outlet ) are termed as TRANSITION. Although its a hydraulic design issue
but its a structural problem as well. Many an engineer,  especially the
contractor's engineers donot understand its importance hence resist its
incusion in the shop drawing simply its cumbersome to build. My question
was therefore directed towards those experts who have the experience of
design & detailing of cross drainage structures ( who would understand this
issue better ) to advise me if this cut off wall was really necessary &
without which we could expect damages to the whole transition itself. Thank
you.
SYED FAIZ AHMAD
SENIOR STRUCTURAL ENGINEER
SAUDI OGER LTD.,
RIYADH, SAUDI ARABIA.


>From: "Gerard Madden" <GMadden(--nospam--at)mplusl.com>
>Reply-To: seaint(--nospam--at)seaint.org
>To: <seaint(--nospam--at)seaint.org>
>Subject: Re: Cutoff Wall In Concrete Transition
>Date: Thu, 31 May 2001 17:11:35 -0700
>
>Syed,
>
>You probably didn't get a response because your question appears to be more >of a hydraulic-fluids type question, not necessarily structural ... because >you are asking about the need for this cut-off wall. I for one, am not sure >what you are describing, sounds like a baffle or weir type of thing, but I
>forgot all that stuff the day after the PE exam and hope not to encounter
>it again. Just a guess, but is this something to do with the water hammer
>effect ???
>
>
>Check to see is ASCE has a similar list service with a greater percentage
>of experts in this field. I'd venture to guess that the vast majority on
>this list are experienced in buildings, bridges, and other above surface
>structures, so there are only a few who could help. Plus the fact that
>there are maybe 50 people who actually answer questions on this list which
>I believe has subscribers numbering in the 1000's.
>
>Good luck,
>-gerard
>
> >>> syedfaiz23(--nospam--at)hotmail.com 05/31/01 05:01PM >>>
>Fellow Engineers
>a week ago i had posted a question on the LIST about the afore mentioned
>subject, unfortunately i am yet to see any response on the same. Iam
>posting
>this question  again with a hope some expert will find time to respond
>appropriately.
>" iam designing & detailing a buried concrete box channel for storm water
>drainage. It has a oncrete transition both at inlet & outlet. From my
>experience i know every concrete transition should have a cutoff wall at
>the
>end. There is a resistance from some quarter for putting a cutoff wall in
>the shop drawing. According to them its not necessary. i seek opinion of
>the
>experts, on design of hydraulic structures, on this issue. Is cutoff wall
>necessary or not in a concrete transition for a cross drainage structure?"
>Thank you all in advance.
>SYED FAIZ AHMAD
>SENIOR STRUCTURAL ENGINEER
>SAUDI OGER LTD.
>RIYADH, SAUDI ARABIA.
>******
>
>
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