Investigation of concrete compressive strength of existing buildings depending on number of core samples

Concrete strength is one of the most critical parameters that affect the seismic performance of reinforced concrete constructions. One of the common methods to determine the concrete compressive strength is to take core samples from structural members. However, the number of taken core samples-based on the size of the construction–is important for reliable results, especially in old constructions. This study aims to investigate the possibility of determination of the concrete compressive strength values of existing buildings using lower number of core samples than the required number of cores. For this purpose, experimental results of core samples taken from 148 slightly or moderately damaged reinforced concrete buildings during 2011 Simav Earthquake. Concrete compressive strength values based on 15 different sets obtained by using 50% and 70% of the core samples of each building are compared. The compressive strength values calculated from the sets were compared with the average compressive strengths of all core samples to investigate accuracy of estimation of compressive strength with using lower number of core samples. The study also investigates whether there is a significant difference between samples taken from a single story (i.e. ground story) compared to the whole building. It is concluded that the use of %50 of the required core samples is possible for the rapid assessment or large-scale field investigation studies when the obtained concrete strength is equal to or greater than 8 MPa. However, additional core samples to complete 70% of the code required samples are required for concrete strength values lower than 8 MPa.