High Accurate Detection of Inclined Cracks in Concrete Structures Using an Acceleration Pickup

Abstract

The present paper proposes a detection method of inclined cracks in concrete structures using an acceleration pickup. The sensor on the concrete surface observes the stationary waves inside the structure whose frequencies depend on the distance to the crack (or to the bottom of the structure). The method can recognize the profile of the inclined crack with a high precision by the following two procedures. The first is to model the sensor output as an output of a linear dynamic system with an unknown parameter and measures the accurate propagation distance from the sensor to the crack by applying a maximum likelihood method at each inspection point. The second is to use a least squares method considering the reflection efficiency of the elastic waves at the inclined crack and the directivity characteristic of the sensor.