Transient response of thick rectangular bars subjected to transverse elastic impact

Abstract

The objective of the research presented in this paper was to study the transient response of thick rectangular bars subjected to transverse elastic point impact. It is shown that the transient response is composed of a number of resonant frequencies caused by cross-sectional modes of vibration. The individual modes and their corresponding natural frequencies were determined using plane-strain, finite-element models of rectangular cross sections. The effect of the cross-section aspect (depth/width) ratio on the natural frequencies is shown. Three-dimensional, finite-element models of rectangular bars were analyzed to determine the transient response caused by transverse point impact. To verify the results obtained from the numerical studies, experimental studies were performed on rectangular bars with aspect ratios of 0.60, 0.75, 1.33, and 1.67. The bars used in the experimental study were representative of full-scale concrete beams and columns—typical barlike structural elements. Excellent agreement was obtained between the numerical and experimental results. This paper is the second in a series of three papers aimed at understanding the transient elastic impact response of solid bars and bars containing flaws. Together these papers establish the basis for the use of the impact-echo method (a test method based on the use of transient point impact) for nondestructive testing of barlike structural elements.