Return to index: [Subject] [Thread] [Date] [Author]

Re: Cutoff Wall In Concrete Transition

[Subject Prev][Subject Next][Thread Prev][Thread Next] Thank you very much Mehrotra. You have a good point there. Thank you once again.
SYED FAIZ AHMAD



From: "R.P. Mehrotra/engg" <rp.mehrotra(--nospam--at)eil.co.in>
Reply-To: seaint(--nospam--at)seaint.org
To: seaint(--nospam--at)seaint.org
Subject: Re: Cutoff Wall In Concrete Transition
Date: Fri, 01 Jun 2001 16:22:47 +0500

For any hydraulic structure there is the problem of 'scour' associated.
If the natural flow of stream is obstructed, it indulges in scouring of
the bed (and/or the banks). The question or the problem bothering you is
best answered as

The wing walls train the stream to the required section and before it is
actually channelised, a concrete floor, as apron, is made to reduce the
scour depth. You may be aware that for all hydraulic structures the
depth of foundation is to be measured from the scour depth.

The outer wing walls (without the apron) channelise the flow. Thence
after apron with wing wall takes over.

Trust this would be of some help.



Regards


RP Mehrotra
Manager (Engineering - Structural)
ENGINEERS INDIA LIMITED
New Delhi INDIA

----- Original Message -----
From: "syed faiz ahmad" <syedfaiz23(--nospam--at)hotmail.com>
Date: Friday, June 1, 2001 3:35 pm
Subject: Re: Cutoff Wall In Concrete Transition

> 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.
> > >******
> > >
> > >
> > >*
> > >*   This email was sent to you via Structural Engineers
> > >*   Association of Southern California (SEAOSC) server. To
> > >*   subscribe (no fee) or UnSubscribe, please go to:
> > >*
> > >*   http://www.seaint.org/sealist1.asp
> > >*
> > >*   Questions to seaint-ad(--nospam--at)seaint.org. Remember, any email you
> > >*   send to the list is public domain and may be re-posted
> > >*   without your permission. Make sure you visit our web
> > >*   site at: http://www.seaint.org
> >
>
>_______________________________________________________________________
__
> >Get Your Private, Free E-mail from MSN Hotmail at
> http://www.hotmail.com.>
> >
> >*
> >*   This email was sent to you via Structural Engineers
> >*   Association of Southern California (SEAOSC) server. To
> >*   subscribe (no fee) or UnSubscribe, please go to:
> >*
> >*   http://www.seaint.org/sealist1.asp
> >*
> >*   Questions to seaint-ad(--nospam--at)seaint.org. Remember, any email you
> >*   send to the list is public domain and may be re-posted
> >*   without your permission. Make sure you visit our web
> >*   site at: http://www.seaint.org
> >
> >
> >*
> >*   This email was sent to you via Structural Engineers
> >*   Association of Southern California (SEAOSC) server. To
> >*   subscribe (no fee) or UnSubscribe, please go to:
> >*
> >*   http://www.seaint.org/sealist1.asp
> >*
> >*   Questions to seaint-ad(--nospam--at)seaint.org. Remember, any email you
> >*   send to the list is public domain and may be re-posted
> >*   without your permission. Make sure you visit our web
> >*   site at: http://www.seaint.org
>
>
________________________________________________________________________
_
> Get Your Private, Free E-mail from MSN Hotmail at
> http://www.hotmail.com.
>
> *
> *   This email was sent to you via Structural Engineers
> *   Association of Southern California (SEAOSC) server. To
> *   subscribe (no fee) or UnSubscribe, please go to:
> *
> *   http://www.seaint.org/sealist1.asp
> *
> *   Questions to seaint-ad(--nospam--at)seaint.org. Remember, any email you
> *   send to the list is public domain and may be re-posted
> *   without your permission. Make sure you visit our web
> *   site at: http://www.seaint.org
>


*
*   This email was sent to you via Structural Engineers
*   Association of Southern California (SEAOSC) server. To
*   subscribe (no fee) or UnSubscribe, please go to:
*
*   http://www.seaint.org/sealist1.asp
*
*   Questions to seaint-ad(--nospam--at)seaint.org. Remember, any email you
*   send to the list is public domain and may be re-posted
*   without your permission. Make sure you visit our web
*   site at: http://www.seaint.org

_________________________________________________________________________
Get Your Private, Free E-mail from MSN Hotmail at http://www.hotmail.com.


* * This email was sent to you via Structural Engineers * Association of Southern California (SEAOSC) server. To * subscribe (no fee) or UnSubscribe, please go to:
*
*   http://www.seaint.org/sealist1.asp
*
* Questions to seaint-ad(--nospam--at)seaint.org. Remember, any email you * send to the list is public domain and may be re-posted * without your permission. Make sure you visit our web * site at: http://www.seaint.org