Statistical evaluation of concrete compressive strength, a case study: reinforced concrete (RC) buildings constructed in Tabriz

The correct estimation of compressive strength of concrete plays a key role in evaluating the performance of reinforced concrete (RC) structures under gravity and seismic loads. According to the provisions of Chapter 9 of the Iranian National Building Regulations, sampling and performing compressive strength tests are required to determine the average compressive strength of concrete. In this study, by statistically studying the results derived from analyzing the archive of the compressive strength of concrete samples extracted from reinforced concrete (RC) buildings constructed over the past ten years in Tabriz, the values of statistical parameters affecting the average compressive strength of concrete such as the coefficient of variation (COV) and the standard deviation were calculated. The probability density function (PDF) and the cumulative distribution function (CDF) of the above-mentioned statistical parameters were determined for the purpose of comparison with the values provided in the Iranian National Building Regulations and other international standards as well as for use in future studies. The results show that in 30% of the buildings studied, the standard deviation of compressive strength of concrete exceeds the amounts presented in Chapter 9 of the Iranian National Building Regulations. A similar result is obtained in 18% of the high-rise buildings studied. The coefficient of variation of compressive strength of concrete in approximately 22% of the buildings examined is higher than the allowable values of FEMA356 (2000) and this problem was observed in a higher percentage of the low-rise buildings.