Concrete structural health monitoring using embedded piezoceramic transducers

Abstract

Health monitoring of reinforced concrete bridges and other large-scale civil infrastructureshas received considerable attention in recent years. However, traditional inspectionmethods (x-ray, C-scan, etc) are expensive and sometimes ineffective for large-scalestructures. Piezoceramic transducers have emerged as new tools for the health monitoringof large-scale structures due to their advantages of active sensing, low cost, quickresponse, availability in different shapes, and simplicity for implementation. Inthis research, piezoceramic transducers are used for damage detection of a 6.1 mlong reinforced concrete bridge bent-cap. Piezoceramic transducers are embeddedin the concrete structure at pre-determined spatial locations prior to casting.This research can be considered as a continuation of an earlier work, where fourpiezoceramic transducers were embedded in planar locations near one end of thebent-cap. This research involves ten piezoceramic patches embedded at spatiallocations in four different cross-sections. To induce cracks in the bent-cap, thestructure is subjected to loads from four hydraulic actuators with capacities of 80and 100 ton. In addition to the piezoceramic sensors, strain gages, LVDTs, andmicroscopes are used in the experiment to provide reference data. During theexperiment, one embedded piezoceramic patch is used as an actuator to generate highfrequency waves, and the other piezoceramic patches are used as sensors to detectthe propagating waves. With the increasing number and severity of cracks, themagnitude of the sensor output decreases. Wavelet packet analysis is used toanalyze the recorded sensor signals. A damage index is formed on the basis ofthe wavelet packet analysis. The experimental results show that the proposedmethods of using piezoceramic transducers along with the damage index basedon wavelet packet analysis are effective in identifying the existence and severityof cracks inside the concrete structure. The experimental results demonstratethat the proposed method has the ability to predict the failure of a concretestructure as verified by results from conventional microscopes (MSs) and LVDTs.