Probabilistic Analysis and Time Variation Model of Concrete Compressive Strength in Existing Buildings

Abstract

Probabilistic analysis and time variation model of concrete compressive strength in existing buildings were conducted based on relevant site testing data. The data were collected from rebound hammer (RH) method and core test method. There were 73,840 of RH test data and 4,149 of core test data. First, the data were normalized through dividing by the cube strength, to eliminate the concrete grade effect. The probability distribution analysis showed that the normal distribution is more suitable than the log-normal distribution. Moreover, it was found that the mean value of the core test data was higher than that of the RH data. Further, regression analysis on the data was carried out, and two quadratic functions were adopted to capture the time variation models of the compressive strength based on the RH data, and the core test data, respectively. Furthermore, some more data were obtained by the Genetic algorithm-back propagation (GA-BP) neural network method, and the time variation models were accordingly updated including the new data. Finally, the relationship between the RH model and core test model was discussed, and two approximately linear curves existed from 0 to 30 years and 31 to 60 years. Hopefully, this probabilistic analysis and the time variation model can be helpful in the assessment of the bearing capacity and evaluation of structure reliability in concrete structures.