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Amendments to IS 456:2000

 
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Dr. N. Subramanian
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PostPosted: Tue Feb 02, 2016 5:59 pm    Post subject: Amendments to IS 456:2000 Reply with quote

Dear All,

Er Suresh had sent me a question reg. spacing of temp. reinforcement. Since it may be useful to others also I am giving my reply here.

In Clause 26.3.3(b) (2) [pp. 46 of IS 456:2000], it is written as distance between shrinkage and temp reinforcement bars shall not be more than 5 times the eff depth or 450 mm whichever is smaller. But as per Amendment 3 of Aug. 2007, 450 mm is changed to 300 mm.

Amendment 3 of Aug. 2007 may be found in the net
Note that there was an Amendment in 2013 also.This fourth amendment as given in UltraTech Cement Website is enclosed. Please check all the Amendments 1-4 and correct your code, if you purchased it in 2000.

Best wishes,
NS



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suresh_sharma
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PostPosted: Wed Feb 03, 2016 10:02 am    Post subject: Reply with quote

It means that no reinforcement be it temp, shrinkage or distribution shall not be spaced at less than 300mm. Whether ACI code has already implemented the above provision in their codes.
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es_jayakumar
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PostPosted: Wed Mar 02, 2016 7:18 am    Post subject: Reply with quote

Dear Sir,
As per the simplified curtailment rules at Fig. 9.5 of SP 34, we can curtail the alternate bottom tensile steel bars of a slab at 0.25L from the centre of the connected beam. Then, this spacing will go beyond the 300mm restriction, when the spacing of main bars is more than 150mm c/c. Is it permissible ?

Regards,
E S Jayakumar
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sknsrinivasan
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PostPosted: Wed Mar 02, 2016 10:11 am    Post subject: Reply with quote

Dear Jayakumar

   As far my Knowledge The tension reinforcement should be placed at Middle strip only. That Bar shall extent lower part of slab ( Into Edge Strip bottom) with in  0.25l at continuous edge and 0.15 discontinuous edge This code provision D.1.4

If you are felling the spacing will be more than 300mm in Edge strip  you can provide the slab bottom bar support center to center this is  engineer justification only. But code not mentioned any thing spacing and minimum reinforcement for edge strip But Top bar will take care of edge strip moment. I think you know very well why you are asking this question I dont know

The Code Restricted only Bottom Bar at Middle strip top bar at Edge strip

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N.Srinivasan
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suresh_sharma
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PostPosted: Wed Mar 16, 2016 5:37 am    Post subject: Reply with quote

Dear Mr. Srinivasan,
As per the revision talked about in this thread, any type of rft be it shrinkage, temp, distribution, the spacing should not be more than 300 mm. What you are talking about is the structural rft. How far it is prcticable to achieve 300mm for all rft. and what is the trade practice?
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sknsrinivasan
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PostPosted: Wed Mar 16, 2016 5:57 am    Post subject: Reply with quote

Dear Suresh sharma

   My Reply only Er jayakumar post only. Pls refer Jayakumar post and My post

Regards
N.Srinivasan


suresh_sharma wrote:
Dear Mr. Srinivasan,
As per the revision talked about in this thread, any type of rft be it shrinkage, temp, distribution, the spacing should not be more than 300 mm. What you are talking about is the structural rft. How far it is prcticable to achieve 300mm for all rft. and what is the trade practice?
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es_jayakumar
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PostPosted: Wed Mar 16, 2016 7:31 am    Post subject: Reply with quote

Friends,
I hope we would better confine the subjected spacing within 300mm c/c to take care of temperature, shrinkage etc.

E S Jayakumar
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sknsrinivasan
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PostPosted: Wed Mar 16, 2016 9:09 am    Post subject: Reply with quote

Dear Jayakumar

  What you told that is correct. Generally all structural elements the maximum distance between two consecutive bars not more than 300mm any ware at any cost Design engineer should keep this in their Mind if we want to restrict the spacing 300mm in edge strip
  
   a) If the design spacing more than 150mm, Run the bottom bar up to center to center of support
    b) If the design spacing less than 150mm we can curtail the bottom bar as per code. this is only for economical purpose  

   If we do like this Bend up bar option we can not provide. we can adopt straight bar option only
  In Flat slab also we can not curtail alternate bottom bars in Middle strip The above points for Top Bar also so the code need to rearrange the detailing option of slab This is my opinion


Regards
N.Srinivasan         

es_jayakumar wrote:
Friends,
I hope we would better confine the subjected spacing within 300mm c/c to take care of temperature, shrinkage etc.

E S Jayakumar
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