Journal Published Online: 27 March 2014
Volume 42, Issue 3

Forced-Vibration Testing and Experimental Modal Analysis of a Steel Footbridge for Structural Identification



Dynamic characteristic identification provides an important insight about structural behavior of steel structures. The experimental modal analysis is used to detect dynamic characteristics and consists of several phases. First, forced-vibration tests are carried out, spectral functions are produced, dynamic characteristics are determined by analyzing processed spectral functions, and, finally, analytical models are calibrated or updated depending on experimental analysis results. In this study, forced-vibration testing is conducted on the steel footbridge by using an impact hammer. Low-amplitude broadband excitations are applied using an impact hammer to excite the bridge. The excitation force and measured responses are processed by passing them through a band-pass filter to obtain frequency-response functions, cross-power spectra, auto-power spectra, power spectral densities, and spectrograms. The system-identification procedure is based on input–output measurements. The obtained system-identification results are compared with the analytical results, which were obtained in a different previous study. A very good agreement is observed, thus providing a reliable set of identified modal properties (natural frequencies, damping ratios, and mode shapes) of the structure. The good correlations between analytical and experimental analyses show that no anomalies are detected along the structure. The experimental mode shapes are similar to what is expected from this type of structure. There is not any unexpected mechanism that changes the dynamic characteristics of the system.

Author Information

Şahin, Abdurrahman
Yildiz Technical Univ., Dept. of Civil Engineering, Istanbul, TR
Bayraktar, Alemdar
Karadeniz Technical Univ., Dept. of Civil Engineering, Trabzon, TR
Pages: 19
Price: $25.00
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Stock #: JTE20130166
ISSN: 0090-3973
DOI: 10.1520/JTE20130166