When a guided wave is applied to a structural component in civil infrastructure, it is important to note the dimensions of the cross-section and the heterogeneity of the components. In this study, we proposed a wireless measurement system to measure the guided wave in the kHz frequency range. The guided wave was excited with an impact hammer. It was then received with wireless accelerometers at plural points. In order to enhance the accuracy of the guided wave testing, the propagation mode representing wave packets with different wave velocities is required. A semi-analytical finite element method was utilized to obtain the dispersion curve of the propagation mode. The numerically calculated and the measured dispersion curves showed good agreement for the I-beam metal specimen. The wave components with zero group velocity were observed in the measured dispersion curve. Investigations revealed that the components were caused by a natural vibration mode.
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