Synthetic Aperture Radar Imaging and Image Analysis in Civil Engineering
— Challenges and Opportunities
Dr. Tzuyang Yu
Associate Professor, Department of Civil and Environmental Engineering, University of Massachusetts Lowell
Portland cement concrete (PCC) is the most widely used artificial and engineering material on Earth. In civil engineering, PCC is used for buildings, bridges, tunnels, airports, roadways, pipelines/culverts, waterways, dams/levees, nuclear power plant containers, ports, etc. In general, concrete structures are expected to achieve 50~75 years (or longer) of design lifespan. In such a long lifespan, their aging and deterioration process becomes very difficult to predict. As a result, sensing and monitoring techniques from nondestructive evaluation/testing/inspection (NDE/T/I) and structural health monitoring (SHM) have been used by civil engineers to prevent sudden failures of concrete structures from happening.
Among existing NDE/T/I and SHM methods, electromagnetic (EM) sensors such as ground penetrating radar (GPR) and synthetic aperture radar (SAR) represent a unique approach for surface and subsurface inspection of concrete structures. EM sensors can interrogate concrete structures for material degradation, delamination, and cracking with a flexible penetration depth and a versatile resolution. Both contact (ground coupled) and non-contact (air-coupled, remote sensing) inspection of concrete structures can be achieved by using EM sensors. Since PCC is a multi-phase porous cementitious composite, phase change inside PCC can be detected by EM sensors and used for condition assessment.
In this seminar talk, application of SAR imaging and image analysis of several multi-phase porous cementitious composites are presented. Problems like subsurface delamination and moisture content estimation in PCC systems are investigated by using SAR images. Subsurface delamination in concrete structures can be used as an indicator for aging or overstressing. Moisture content of concrete structures regards the cement hydration level and short-term strength development of concrete, as well as the phase-distribution (solid, gaseous, and liquid) inside concrete and its long-term durability.
Challenges in using SAR images for assessing the condition of concrete structures are discussed, along with research opportunities presented in the area of image analysis and pattern recognition for researchers and engineers outside the civil engineering community.