Field applications of IE and SASW methods to concrete structure

Abstract

As growing up of the industry, concrete structures have become bigger and older. The strength estimation and safety assessment of concrete is getting more important for the maintenance of existing structures, and have been studied in various civil engineering practices, including rebound hammer, probe penetration, ultrasonic pulse velocity (UPV), maturity, and cast-in-place cylinder. Among those, the wave velocity based methods are very attractive because of its cost effectiveness, nondestructiveness and simple configuration. The UPV method has been widely used for evaluating the strength of concrete structures, but it is hard to get the exact velocity because the wave propagation velocity is calculated by direct travel time measurement. Impact Echo (IE) is a non-destructive test for obtaining internal flow, thickness and quality of structure using P-wave reflections. Spectral Analysis of Surface Waves (SASW) method has been used for determining shear wave velocity profile in layered media. This thesis focused on the development of the instrument for IE and SASW methods and field applications of IE and SASW methods for assessment of concrete structures. The optimized testing system was developed by considering the characteristics of each method and the testing program for IE and SASW tests were developed based on Matlab. In the IE method, P-wave velocity was determined in the frequency domain with the known wall thickness. In the SASW method, dispersion curve which is the relation between phase velocity and wavelength (or frequency) is determined. Then the representative average surface wave velocity was found using a sequence of statistical operations and P-wave velocity is derived using the Poisson\`s ratio of concrete structure. To verify the feasibility of the IE and SASW methods, field tests were performed. Both IE and SASW methods were performed to make a relation between P-wave velocity and concrete strength on four wall-type concrete structures hav...