Communications - Scientific Letters of the University of Zilina 2018, 20(4):63-68 | DOI: 10.26552/com.C.2018.4.63-68

Identification of Modal Frequencies From the Pre-Stressed Concrete Bridge Dynamic Response to Different Sources of Dynamic Excitation

Jozef Melcer¹, Jan Kortis², Lubos Daniel², Peter Fabo²

¹ Department of Structural Mechanics and Applied Mathematics, Faculty of Civil Engineering, University of Zilina, Slovakia

² Research Center, University of Zilina, Slovakia

The natural frequencies and mode shapes are unique characteristics of each mechanical structure. Their prediction is a crucial part of each dynamic experimental measurement. However, the proper identification of higher natural frequencies and mode shapes can be a problem, especially for big structures such as bridges. The reason is the need to excite the bridge in such a way that it responds in a free-vibrations mode shape. This paper describes three various sources of excitations, which are used to identify the modal characteristics of the pre-stressed concrete bridge. The impulse excitation, traffic load and ambient vibration are used and analyzed. In the case of the loading by a force impulse, modal shapes are also obtained. The study shows that the intensity and kind of the excitation has a noticeable impact on identification of modal frequencies. Finally, the results of the experimental measurements are used to calibrate the numerical model.

Keywords: dynamic excitation; modal frequencies; free vibrations; moving load; FRF function

Received: May 28, 2018; Accepted: July 9, 2018; Published: December 31, 2018  Show citation