Multiple signal classification algorithm for non-destructive imaging of reinforcement bars and empty ducts in circular concrete columns

Multiple signal classification has been applied to inverse scattering problems. Here, we present a practical application of multiple signal classification related to civil engineering. The problem is to detect reinforcement bars and empty ducts in circular columns. With appropriate experimental design, multiple signal classification can be applied directly to detect reinforcement bars. However, it is extremely difficult to detect the empty ducts because of their small scattering strengths. We propose a simple two-stage MUSIC scheme capable of detecting empty ducts as well. The MUSIC shows good imaging results even in very high noise levels, upto 31%.