Stress and damage localization monitoring in fiber-reinforced concrete using surface-mounted PZT sensors

Abstract

In concrete structures, damage is identified by the appearance of cracks on the surface. Monitoring the level of tensile stress in the material provides an indication of microcrack localization, which leads to the formation of a crack in the medium. In this study, the stress in the substrate leading to the localized cracking in a concrete substrate is evaluated using surface mounted PZT patches. The PZT patches are used in a local electrical impedance (EI) measurement mode and for distributed stress wave measurements. The EI measurements from PZT patches sensitively detect the tensile stress in the substrate. The localization of damage resulting in the formation of a crack in the concrete medium is detected sensitively by stress wave measurements. A frequency-dependent attenuation factor, which is independent of the intervening material effects is presented for quantifying the changes in the stress waves. The localization of microcracks leading to the formation of a crack is detected by the attenuation factor measurements of stress waves significantly before visual detection of a surface crack. The combined use of the EI measurement with the distributed stress wave attenuation allows for detecting stress and microcracking in the concrete leading up to the formation of a localized crack. The attenuation factor gives an indication of the crack opening once the crack is formed.