Adaptive Estimation of the <i>In Situ</i> Characteristic Concrete Strength

Abstract

For calculation of existing concrete structures on the basis of the partial factor format, the main representative value is the actual in-situ characteristic value of the concrete strength. When samples are tested, the concrete in-situ strength of the structure shall be determined, statistically if possible, from the test results. In accordance with EN 1990 the 5% percentile value is calculated on the basis of a unilaterally limited constant confidence level. It was found the in some case, estimation of the in-situ characteristic concrete strength taking a constant confidence level does not allow to adequately assess the reliability of the existing structures. A new estimator based on non-parametric statistical method was proposed for estimating of the in-situ characteristic concrete strength with a given arbitrary confidence level. The procedure that was proposed allows one to re-establish of the estimator pdf even with a very limited sample size. It is established, that the choice of the confidence level of the estimator should be based on the average reliability of the structure.