SUMMARY A novel optico‐acoustic sensing system based on digital image correlation (DIC), guided ultrasonic waves (GUW), and acoustic emission (AE) and its application in detecting breaks on seven‐wire steel strands is presented. The implementation of the emerging optical nondestructive testing (NDT) method of DIC in parallel with established acoustic NDT techniques enables the cross‐correlation/validation of in situ recorded information related to progressive damage accumulation, which is the focal point of this research. To the authors' best knowledge, it is the first time that full field strain accumulations have been obtained on the surface of the seven‐wire strands. Furthermore, acoustic waveforms and their extracted features are found complementary to full field strain measurements and prove capable to detect damage initiation in critical structural sites (‘hot spots’). To demonstrate the potential of the novel NDT system, pristine and prenotched strands were loaded using a mechanical testing frame while simultaneously recording DIC, GUW, and AE data. The DIC and GUW were acquired and excited at specific load intervals to avoid overlapping of GUW with AE activity. The reported DIC results directly reveal strain accumulations at the notched areas prior to breaking, whereas AE waveforms and related features show sudden changes at time instances that correspond to wire breaks. In addition, the GUW signals show a decrease in their amplitude upon progressive load of the strands and wave speed variations. Detailed post‐processing of the acoustic results was performed to cross‐correlate recorded information from novel optico‐acoustic sensing system and create methodologies for effective data filtering, alignment, synchronization, and fusion (through unsupervised pattern recognition techniques) that could lead to robust damage identification in structural health monitoring applications. The results demonstrate for the first time that the use of full field strains in correlation with acoustic techniques visually validates the damage source location and, in turn, enhances the damage predictive capabilities of each NDT method for prestressed and post‐tensioned cables found in stay cable bridges. Copyright © 2013 John Wiley & Sons, Ltd.

Summary This paper presents a hybrid non‐destructive testing (NDT) approach based on (non‐contact) infrared thermography (IRT), (passive) acoustic emission (AE), and (active) ultrasonic (UT) techniques for effective damage assessment of partially grouted concrete masonry walls (PGMW). This hybrid monitoring approach could be implemented for the health monitoring of concrete masonry structures. The implementation of this system assists the cross validation of in‐situ recorded information for structural damage assessment. NDT was performed on PGMW subjected to cyclic horizontal loading. The obtained IRT, AE, and UT results successfully monitored the progressive damage process throughout the loading history. Copyright © 2014 John Wiley & Sons, Ltd.

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This paper presents a data fusion approach based on digital image correlation (DIC) and acoustic emission (AE) to detect, monitor and quantify progressive damage development in reinforced concrete masonry walls (CMW) with varying types of reinforcements. CMW were tested to evaluate their structural behavior under cyclic loading. The combination of DIC with AE provided a framework for the cross-correlation of full field strain maps on the surface of CMW with volume-inspecting acoustic activity. AE allowed in situ monitoring of damage progression which was correlated with the DIC through quantification of strain concentrations and by tracking crack evolution, visually verified. The presented results further demonstrate the relationships between the onset and development of cracking with changes in energy dissipation at each loading cycle, measured principal strains and computed AE energy, providing a promising paradigm for structural health monitoring applications on full-scale concrete masonry buildings.

This article demonstrates the potential of the digital image correlation (DIC) method to provide accurate full-field deformation measurements and successfully monitor the development of damage during seismic excitation of a partially grouted reinforced masonry building. The building was subjected to a sequence of earthquake ground motion records using the Large High Performance Outdoor Shake Table at the University of California, San Diego. The DIC setup was capable of measuring surface deformations of the single-story building with high frame rate cameras located at a distance greater than 50 ft away. The accuracy of the measurements was assessed with data obtained using mounted displacement transducers. The full-field deformation data collected by the DIC system was capable to detect strain localization patterns associated with the onset of wall cracking before it could be shown by the displacement sensor data or by post mortem visual inspection. The research findings reported herein demonstrate, for the first time to the authors' best knowledge, the potential of in situ monitoring of actual structures for damage induced by non-stationary loading profiles using optical metrology.