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Mean of the Group of 4 Non-Overlapping Consecutive Test Results In N/mm^2

 
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Er. Surya
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PostPosted: Mon Apr 29, 2019 7:10 am    Post subject: Mean of the Group of 4 Non-Overlapping Consecutive Test Results In N/mm^2 Reply with quote

Mean of the Group of 4 Non-Overlapping Consecutive
Test Results In N/mm^2

Dear SEFI Forum Members.

Request your kind advice on how to group the average results obtained from mean of 3 cube specimens

say.

  
CUBE 1  

CUBE 2
AVG SAMPLE 1

CUBE 3
  
CUBE 4
CUBE 5 AVG SAMPLE 2
CUBE 6
  
CUBE 7
CUBE 8 AVG SAMPLE 3
CUBE 9
  
CUBE 10
CUBE 11 AVG SAMPLE 4
CUBE 12
CUBE 13
CUBE 14 AVG SAMPLE 5
CUBE 15
CUBE 16
CUBE 17 AVG SAMPLE 6
CUBE 18
CUBE 19
CUBE 20 AVG SAMPLE 7
CUBE 21
CUBE 22
CUBE 23 AVG SAMPLE 8
CUBE 24

Now the grouping of AVG SAMPLE will be...HOW?

1st non overlapping AVG SAMPLE (1+2+3+4)



2nd non overlapping AVG SAMPLE (2+3+4+5)
               OR
2nd non overlapping AVG SAMPLE (5+6+7+8)


Thanks in advance.
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badamsundararao
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PostPosted: Tue Apr 30, 2019 2:38 am    Post subject: AVERAGE Reply with quote

To my opinion average is required for set of three only and no need to go for further average.Elders have to confirm this.
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es_jayakumar
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PostPosted: Tue Apr 30, 2019 2:54 pm    Post subject: Reply with quote

IS Code 456 : 2000 stipulates :

16 ACCEPTANCE CRITERIA
16.1 Compressive Strength
The concrete shall be deemed to comply with the strength requirements when both the following condition are met:
a) The mean strength determined from any group of four consecutive test results compiles with the appropriate limits in col. 2 of Table 11.
b) Any individual test result complies with the appropriate limits in co1 3 of Table 11.

Going by "any group of four consecutive test results " in the above, the groups (1,2,3,4), (2,3,4,5), (3,4,5,6),....etc. shall hold good.
However, the heading of Col.2 of Table 11 stipulates "Mean of the Group of
4 Non-Overlapping Consecutive Test Results". Here, "Non-overlapping" creates confusion.
Ashok K. Jain, in his book "Reinforced Concrete - Limit State Design", in Example No.2.7.(c), has adopted moving mean of 4 results, ie., (1,2,3,4), (2,3,4,5), (3,4,5,6),....etc.

E S Jayakumar
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es_jayakumar
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PostPosted: Tue May 14, 2019 1:31 am    Post subject: Reply with quote

No further comments / clarifications were seen posted here, on this topic. A spread sheet prepared for checking the acceptance criteria as per the Codal provisions (moving mean concept) is attached.

E S Jayakumar



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TPS61
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PostPosted: Wed May 15, 2019 10:29 am    Post subject: acceptance criteria for cube strengths Reply with quote

The codal clause is quite clear. As stated by Jayakumar, the consecutive groups to be examined are (1,2,3,4), (2,3,4,5),(3,4,5,6) etc.
The average of each of these groups must meet the stated criteria.
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es_jayakumar
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PostPosted: Fri May 17, 2019 2:21 am    Post subject: Reply with quote

Sir,
What does the term "non-overlapping" in "Mean of the Group of 4 Non-Overlapping Consecutive Test Results" [Col.2 of Table 11] indicate ? This creates confusion.


E S Jayakumar
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TPS61
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PostPosted: Fri May 17, 2019 3:29 am    Post subject: acceptance criteria for cube strengths Reply with quote

I agree, the language is confusing.
I go by Logic which is : "average of any 4 consecutive strength results should...."
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Er. Surya
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PostPosted: Fri May 24, 2019 12:25 pm    Post subject: Reply with quote

Dear Members of SEFI


Request your kind views on Explanation of acceptance criteria on page- ( Page - 34,35,36,37,38 ) of SP-24

on page 37 of SP -24 towards the end (a) it states.

if  every  sample  is  to  the  right  of  C,
accept  each  of  the  sample.  (see  Fig.  E-3)


Where when referred C = Fck Characteristic Strength which for M25 would be 25 N/mm^2 after 28 days curing.
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es_jayakumar
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PostPosted: Tue Jul 30, 2019 2:59 am    Post subject: Re: acceptance criteria for cube strengths Reply with quote

TPS61 wrote:
The codal clause is quite clear. As stated by Jayakumar, the consecutive groups to be examined are (1,2,3,4), (2,3,4,5),(3,4,5,6) etc.
The average of each of these groups must meet the stated criteria.


But, Dr.N.Subramanian, in his book on Reinforced Concrete Design (PP-132) says "test result of one group should not be taken in another group too". This stresses on "non-overlapping" requirement.

E S Jayakumar



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