Rayleigh wave based nondestructive evaluation techniques for structural health monitoring of concrete structures

Abstract

Much of the existing infrastructure in Korea has been in service for many years and continues to be used. However, due to a variety of physical, chemical, and environmental processes, concrete structures as well as other civil infrastructure may get deteriorated or damaged in unexpected way. Therefore, structural health monitoring (SHM) of these structures to provide the necessary maintenance has become critically important to our society and is an emerging technology in civil engineering. Especially nondestructive techniques that can detect, localize and characterize damage in the structure or assess the current condition of the structure are desired to develop for successful applications of SHM. The research detailed in this dissertation has complimentary efforts that seek to develop the nondestructive evaluation (NDE) techniques for concrete structures using Rayleigh waves. Those can be summarized as (1) analytical and numerical study of physical characteristics of Rayleigh wave propagation in solid media, (2) development of crack depth evaluation method in concrete structures, (3) development of improved Rayleigh wave velocity measurement technique, and (4) nondestructive strength gain evaluation of early-age concrete using Rayleigh wave velocity measurements. To provide necessary background through the research, physical characteristics of Rayleigh wave propagation are studied firstly by reviewing wave propagation theory and performing numerical simulations. Crack depth evaluation methods in concrete structures are presented in the first part of developments. These methods are based on the measurement of wave transmission in concrete structure. Self-calibrating technique is employed for reliable measurement of the wave transmission. Spectral energy method is proposed to estimate the depth of the crack from measured wave transmission function (TRF) in concrete slab. Experimental study to demonstrate the proposed method is performed on the rein...