Summary An important issue in impedance‐based damage monitoring is to deploy sensors in proper positions in which damage‐sensitive impedance responses can be captured effectively. In this study, a full‐scale multi‐strand anchorage is analyzed to determine optimal locations of piezoelectric sensors for impedance‐based monitoring of locally damaged strands. First, stress variations of the multi‐strand anchorage are experimentally measured to estimate the anchorage behavior under the effect of locally damaged strands. Strain signals are examined for axial, circumferential, and radial stress components under the variation of prestress forces. Second, a finite element analysis is made on the multi‐strand anchorage to back up the experimental findings. Third, a damage‐sensitive structural model is interpreted for the local strand breakage. Finally, impedance responses sensitive to local strand breakage are experimentally examined for a few scenarios simulated in the anchorage system. PZT (lead zirconate titanate) sensors deployed on the anchor head and the bearing plate are evaluated to comparatively determine ideal regions of interest for impedance monitoring. The results show that the greater stress variation yields the greater variations in impedance responses and the near‐top and near‐anchor heads are ideal regions of interest for damage‐sensitive impedance monitoring.

In this paper, a piezoelectric sensor-embedded smart rock is proposed for the electromechanical impedance monitoring of internal concrete damage in a prestressed anchorage zone. Firstly, a piezoelectric sensor-embedded smart rock is analyzed for impedance monitoring in concrete structures. An impedance measurement model is analyzed for the PZT (lead zirconate titanate)-embedded smart rock under compression in a concrete member. Secondly, a prototype of the smart rock embedded with a PZT sensor is designed in order to ascertain, sensitively, the variations of the impedance signatures induced by concrete damage in an anchorage zone. Thirdly, the performance of the smart rock is estimated from a numerical analysis and experimental tests. Variations in the impedance signals under compressive test cases are analyzed in order to predetermine the sensitive frequency band for the impedance monitoring. Lastly, an experiment on an anchorage zone embedded with the smart rocks and surface-mounted PZT sensors is conducted for the impedance measurement under a series of loading cases. The impedance variations are quantified in order to comparatively evaluate the feasibility of the sensor-embedded smart rock for the detection of internal concrete damage in the anchorage zone. The results show that the internal concrete damage was successfully detected using the PZT-embedded smart rock, thus enabling the application of the technique for anchorage zone health monitoring.

This study investigates the feasibility of smart aggregate (SA) sensors and their optimal locations for impedance-based damage monitoring in prestressed concrete (PSC) anchorage zones. Firstly, numerical stress analyses are performed on the PSC anchorage zone to determine the location of potential damage that is induced by prestressing forces. Secondly, a simplified impedance model is briefly described for the SA sensor in the anchorage. Thirdly, numerical impedance analyses are performed to explore the sensitivities of a few SA sensors in the anchorage zone under the variation of prestressing forces and under the occurrence of artificial damage events. Finally, a real-scale PSC anchorage zone is experimentally examined to evaluate the optimal localization of the SA sensor for concrete damage detection. Impedance responses measured under a series of prestressing forces are statistically quantified to estimate the performance of damage monitoring via the SA sensor in the PSC anchorage.

In this study, a piezoelectric-based interface technique for impedance measurement is presented to monitor local strand breakage in multi-strand anchorage systems. Firstly, a hoop interface-based impedance measurement model is designed based on stress behaviors of the multi-strand anchorage. Coupled dynamic behaviors between the lead zirconate titanate (PZT) interface and the target tendon anchorage are interpreted to determine sensitive frequency ranges under local strand breakage. Next, a prototype of the PZT interface is designed to fit into the target multi-strand anchorage to monitor the stress variations induced by local strand breakages. Dynamic characteristics of the PZT interface are numerically analyzed to sensitively catch impedance signals in predetermined frequency ranges. Finally, a series of damage scenarios are tested on a full-scale multi-strand anchorage system to evaluate the feasibility of the PZT interface for monitoring a series of strand-breakage cases. Impedance responses of the PZT interface prototype are analyzed to determine damage-sensitive frequency ranges. Linear tomography of root-mean-squaredeviation (RMSD) indices is utilized to localize damaged strands.

This study investigates the feasibility evaluation of smart PZT-embedded sensors for impedance-based damage monitoring in prestressed concrete (PSC) anchorages. Firstly, the concept of impedance-based damage monitoring for the concrete anchorage is concisely introduced. Secondly, a prototype design of PZT-embedded rebar and aggregate (so-called smart rebar–aggregate) is chosen to sensitively acquire impedance responses-induced local structural damage in anchorage members. Thirdly, an axially loaded concrete cylinder embedded with the smart rebar–aggregate is numerically and experimentally analyzed to investigate their performances of impedance monitoring. Additionally, empirical equations are formulated to represent the relationships between measured impedance signatures and applied compressive stresses. Lastly, an experimental test on a full-scale concrete anchorage embedded with smart rebar–aggregates at various locations is performed to evaluate the feasibility of the proposed method. For a sequence of loading cases, the variation in impedance responses is quantified to evaluate the accuracy of smart rebar–aggregate sensors. The empirical equations formulated based on the axially loaded concrete cylinder are implemented to predict compressive stresses at sensor locations in the PSC anchorage.