Interpretation of Flexural Vibration Modes from Impact-Echo Testing

Abstract

The main goals of this study are to provide an improved interpretation of flexural vibration modes of delaminations in concrete bridge decks detected using impact-echo testing, and to develop a simple two-dimensional (2D) visualization scheme to show the areal extent of likely delaminated regions. To achieve those goals, the study consisted of three main tasks. The first was development of an analytical formulation that relates the fundamental frequency of the response to the geometry of delamination in a concrete plate. The formulation was developed from the thin plate vibration theory and numerical model simulations. The second task was the development of a simple model for predicting dynamic behavior (flexural vibration) of delamination in concrete plates. Finally, in the third task, the validity of the proposed model was verified through a comparison of the results from an experimental study on a near-real-scale concrete bridge deck and the results reported in prior studies. As demonstrated, the developed model enables better understanding and interpretation of the dynamic response of delamination in reinforced concrete structures.