Xi’an University of Architecture and Technology
With the increase of service age, the concrete strength of existing building structures shows the characteristics of multi-age degradation. A futher study on the change law of compressive strength of concrete with time under freezing-thaw environment was conducted. The ultrasonic-rebound combined method with concrete core amendment was used to conduct field tests on the existing building structures in Harbin, Jilin and surrounding counties and cities, and 924 sets of concrete compressive strength data were obtained. The measured intensity data is normalized and merged, and the Kolmogorov-Smirnov non-parametric test is used to perform hypothesis testing for all subsamples. The test results show that each subsample follows a normal distribution. On this basis, the relationship model of the mean and standard deviation of concrete relative compressive strength with age under freeze-thaw environment is established, which provides a reliable research basis for the comprehensive earthquake damage simulation and assessment of multi-age buildings in service.