- 4 2 The Strength Of Concrete In A Structure In Situ Strength Is Frequently Measured Using Cores Drilled From The Str 1 (84.18 KiB) Viewed 18 times
- 4 2 The Strength Of Concrete In A Structure In Situ Strength Is Frequently Measured Using Cores Drilled From The Str 2 (25.64 KiB) Viewed 18 times
[4] 2. The strength of concrete in a structure in situ strength) is frequently measured using cores drilled from the structure. Five cores (4 in. in diameter and 6 in. long) without reinforcing bars were obtained from a structure near the UCD campus (many concrete batches were used for this structure). The individual core strengths (air dried) were 5950, 5850, 5740, 5420, and 4830 psi. Determine the equivalent specified strength of the concrete using ASTM C42 (Standard test method for obtaining and testing drilled cores and sawed beams of concrete). for = fore( FFFFⓇF) (ks..) Seven = ks Scis – 1.282, +V+V+V+V --- where, fcis = equivalent in-situ strength Score = core strength feeg' equivalent specified strength from the in-situ strength Fuar correction for length/diameter ratio = 0.87, 0.93, 0.96, 0.98 and 1.00 for l/d = 1.0, 1.25, 1.50, 1.75, and 2.0, respectively Fdia = correction for diameter of core = 1.06 for 2 inch core, 1.00 for 4 inch, 0.98 for 6 inch. Fr= correction for the presence of reinforcing bars = 1.00 for no bars, 1.08 for one bar, 1.13 for two. Fme = accounts for the effect of the moisture condition of the core at the time of the core test = 1.09 if the core was soaked before testing, and 0.96 if the core was air dried at the time of the test Fa=counts for damage to the surface of the core due to drilling = 1.06 ki = a factor depend on the number of core tests, equal to 2.40 for 2 tests, 1.47 for 3 tests, 1.20 for 5 tests, 1.10 for 8 tests, LOS for 16 tests, and 1.03 for 25 tests. ka = a factor dependent on the number of batches of concrete in the member or structure being evaluated, equal to 0.90 and 0.85, respectively, for a cast-in- place member or structure that contains one batch or many batches; and 0.90 for a precast member or structure n=number of cores after removal of outliers Scis = standard deviation of feis Vua = coefficient of variation due to length diameter correction, equal to 0.025 for 1/4 = 1, 0.006 for 1 d = 1.5, and 0 for 1/d = 2
V dia = coefficient of variation due to diameter correction, equal to 0.12 for 2 inch diameter cores, 0 for 4 inch, 0.02 fir 6 inch. V, =coefficient of variation due to presence of reinforcing bars in the core, equal to 0 if none of the cores contained bars, and to 0.03 if more than a third of them did V me = coefficient of variation due to correction for moisture condition of core at time of testing, equal to 0.025 Va=coefficient of variation due to damage to core during drilling, equal to 0.025