Quantitative evaluation of SIBIE procedure and case studies

The impact-echo method is well-known as a nondestructive test for concrete structures. Methodologically, frequency spectra of elastic waves that are generated by a mechanical impact and propagate in concrete are applied to evaluate the thickness or to locate internal flaws in concrete. Occasionally, spectra analyzed contain so many peak frequencies that resonant frequencies associated with locations of defects are marginally identified in practical applications. A procedure named as stack imaging of spectral amplitudes based on impact-echo (SIBIE) is developed to compensate this drawback and to visually identify locations of defects at a cross-section. In order to evaluate the feasibility of the procedure, three stages of the impact-echo of applying the impact, detecting waves, and identifying peak frequencies are examined. Based on the results, case studies on grout performance in prestressed concrete and surface cracks at delaminated areas in a concrete pier are conducted and the applicability is demonstrated.