This award provides funding for research to develop fusion models for non-destructive concrete structure diagnostics. The research will focus on two pervasive and significant defects found in concrete structures: delaminations and voids. The specific modalities considered are ground penetrating radar (GPR) and impact echo (IE). The intellectual merit is the development of innovative fusion models that embrace state of the art signal processing and imaging techniques for physically-based diagnostics of concrete structures. While both GPR and IE technologies have proven extremely useful, they can often be inconclusive and produce ambiguous results. The physics of the two methods are such that one (GPR) cannot directly detect the significant mechanical damage while the other (IE) cannot detect the important moisture, electrochemical, and physical conditions associated with damage. However, these two methods, which both provide depth measurements, complement each other. The proposed research seeks to jointly process the data from these complementary sources. This joint processing is expected to lead to more informative diagnostic information, and ultimately significant rehabilitation cost savings, than can be obtained from the two sources separately. The research effort is divided into three main thrusts. The Fusion Algorithm Development thrust includes defect definition, model development for electromagnetic and mechanical sensing sources, fusion model development, implementation of synthetic experiments, and analytical evaluation for fusion diagnostics capabilities and robustness with regard to real sensing environments. The Controlled Laboratory Experiment thrust will use laboratory concrete samples with voids in grouted tendon ducts and delaminations to generate controlled experimental data. Fusion and diagnostics models will be implemented and verified on controlled experiments. The Field Verification thrust will test in-service structural elements and compare results to other diagnostic studies. Northeastern University and the University of Illinois at Urbana Champaign bring expertise in structure diagnostics, data fusion, electromagnetic and mechanical wave modeling and nondestructive evaluation (NDE). Geophysical Survey Systems is a world manufacturer of GPR equipment and will provide equipment and expertise in field data collection and interpretation. The experimental partners, the German Federal Institute for Materials Research and Testing (BAM) and the U.S. Federal Highway Administration NDE Validation Center (NDEVC), will provide field samples, experimental models and field expertise. The NSF-funded Engineering Research Center for Subsurface Imaging and Sensing Systems (CenSSIS), will provide interdisciplinary expertise with imaging and signal processing strategies, student support, and interdisciplinary curricula, as well as educational and professional training opportunities through annual CenSSIS conferences. The broader impacts include the development of core theory that can be the basis for new technology development. Research will embrace an integrated and interdisciplinary team including faculty, international partners, practitioners, owners, graduate and undergraduate students (REU), and high school teachers. Advances will provide techniques and strategies for data fusion for other applications such as biomedical imaging and land mine detection. Student exchange with European partners will lead to international exchange of scientific culture. Graduate student support provided by the Northeastern Civil Engineering and Electrical Engineering Departments will integrate GPR and IE into the undergraduate laboratories.
