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# in situ specified strength from cores2

## in situ specified strength from cores

(OP)
I am Italian, so not much familiar with ACI 214.4R-10.
Chapter 9 : determining an equivalent f'c value for evaluating structural capacity of an existing structure
My concern on formula (9.4)
1 - V values to be input in formula not as % but %/100 (decimal numbers), correct ?
2 - V values are referring to many cores : for Vl/d it is suggested to choose the correspondent (l/d)min that is the max Vl/d
3 - for Vdia I make linear interpolation for intermediate core diameter (provided that all cores have same diameter. If not what happens ?)
4 - for Vmc and Vd : obliged choice

Any comment will be appreciated. Thanks

PS : I am elaborating an excel file including all the procedures for assessment of in situ specified concrete strength from core (EN 13791, EN 1990, BS 6089, ACI 214, ACI 562, method of Pucinotti, Steenbergen, Cestelli Guidi, Masi, Holos). AS soon as I can I will post said file for free download (and, may be, for help from Your side)

### RE: in situ specified strength from cores

I'm not a strong advocate of coring samples... too often coring just 'clouds' the issue. That being said, I don't have a copy of 214, and if I can get into the office today, I'll take a look at the formula.

It's kind that you would provide a copy of your work and is much appreciated.

Dik

### RE: in situ specified strength from cores

(OP)

ACI 562M-13 formula (6.4.3) refers to CAN/CSA S6-06 2006. In formula the coeff V = coeff of variation of the core strengths : is this V coeff to be deemed as standard deviation of the core strengths or as per Bartlett/MacGregor (1995) table 4 (there called as Vws)?

Any help appreciated

### RE: in situ specified strength from cores

If you can be a little more specific... there are just too may links to Vsub...

V = coefficient of variation
VAL = coefficient of variation for live load analysis method
VI = coefficient of variation for dynamic load allowance
VL = coefficient of variation for live load
VR = coefficient of variation for resistance
VS = coefficient of variation for total load

kc = factor to modify coefficient of variation of concrete core strengths (Table A14.1.2)

A14.1.2 Concrete
The compressive strength of sound concrete shall be determined from the strengths of cores obtained
from the components being evaluated. The core tests shall be conducted in accordance with
CAN/CSA-A23.2.
The strength of cores smaller than 100 mm diameter shall be adjusted to approximate the equivalent
strengths of 100 mm diameter cores. The appropriate strength-correction factor shall be determined from
cores of both diameters obtained from the components being evaluated.
It may be assumed that the strengths of 100 and 150 mm diameter cores are equivalent.
The equivalent strength of 100 mm diameter cores shall be increased by 8% for cores soaked 40 h in
water or reduced by 5% for cores dried 7 d in air before testing.

The equivalent specified compressive strength, fc’, used for evaluation shall be calculated as follows:

fc 0 9fc 1 1 28 kcV n 0 0015 2 0 5 ...I can copy the formula as a *.pdf if that's what you're looking for... text copy is really ugly.
. . /

where is the average core strength, modified to account for the diameter and moisture condition of the
core, V is the coefficient of variation of the core strengths, n is the number of cores tested, and kc is
obtained from Table A14.1.2.

Table A14.1.2
Coefficient of variation modification factor, kc
(See Clause A14.1.2.)
A14.1.3 Reinforcing steel
Coupon specimens for determining the yield and ultimate tensile strengths of reinforcing steel shall be
tested in accordance with CAN/CSA-G30.18. At least three coupons, taken from different bars, shall be
obtained from the components being evaluated.
The yield strength, fy, used for evaluation shall be calculated as follows:
where and V are, respectively, the average value and coefficient of variation of the yield strengths, and ks
is obtained from Table A14.1.1, in which n is the number of strength tests.

n kc
2
3
4
5
6
8
10
12
16
20
25 or more
2.40
1.47
1.28
1.20
1.15
1.10
1.08
1.06
1.05
1.03
1.02

You can piece this together or I can *.pdf a copy.

Dik

### RE: in situ specified strength from cores

It appears to be OK, but, with the exception of a cursory use, I'm quite unfamiliar with the ACI concrete code. There may be someone on the forum that can provide a more definitive review.

Dik

### RE: in situ specified strength from cores

robyengIT:

ACI 562-16 was recently issued and V is stated as the coefficient of variation of the core strengths (sample standard deviation divided by sample mean).

The old V-table based upon number of concrete batches had been replaced, I understand.

The kc table of values has not changed.

### RE: in situ specified strength from cores

(OP)

Assessment of in situ concrete core strength

As promised I am attaching the documentation (software and formulas data sheets) of few different procedures (U.S.A. - Canada - UK - Italy) for the assessment of the in situ hardened concrete strength. The software (Open Office Calc format) is not protected, or better the pwd is revealed, so that anyone can modify it according to his own need (no copyright).
For the U.S.A./Canada sheet I am waiting for any suggestion, mistake/bug done, etc so that to release a final program (we are Italian, not so much familiar with these codes).
Thanks again to Dik and Ingenuity for previous help and to my colleague Reversi, whose review has been indispensable.

### RE: in situ specified strength from cores

Roby... excellent post... wish I could give you a couple of stars... gone through a bit of it and will finish up on the weekend.

Dik

### RE: in situ specified strength from cores

Roby:
I went over your spreadsheet on the weekend... looks great, I didn't find any exceptions. Good work, and thanks for sharing.

Dik

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