Frequency Spectrum Analysis of Impact-Echo Waveforms for T-Beams

Abstract

Numerical and experimental studies were performed to assess the transient impact response of 11 T-beams with various dimensions and aspect ratios. Numerical modeling was performed using a three stage finite-element modeling procedure which included modal analysis, resonant analysis, and three-dimensional transient dynamic analysis. The response at impact locations on both the top centerline of the flange and the bottom centerline of the web was investigated. Physical models of three of the beams were constructed in the laboratory to determine the physical response of the beams when subjected to a transient impact and to verify the numerical results. Relationships between the fundamental frequencies and the frequencies of higher cross-sectional modes of vibration were established for the various aspect ratios. Shape factors were derived from the numerical and experimental results. The practical significance of the results is demonstrated for a project where impact-echo testing was used to nondestructively assess the condition of a decommissioned concrete T-shaped girder.