92 E. Cheynet et al. (HS1) 0 1 2 3 4 (HA1) 0 1 2 3 4 (HS2) 0 1 2 3 4 (HA2) 0 1 2 3 4 (VS1) 1 2 1.5 0.5 0 1 2 1.5 0.5 0 1 2 1.5 0.5 0 1 2 1.5 0.5 0 1 2 1.5 0.5 0 1 2 1.5 0.5 0 (VA1) (VS2) (VA2) (TS1) 5 10 15 20 (TA1) ζ (%) ζ (%) ζ (%) ζ (%) ζ (%) T(°C) 5 10 15 20 T(°C) Fig. 12.5 Modal damping ratios expressed as a function of the temperature for the first four lateral and vertical modes and the first two torsional modes, based on acceleration data recorded from July 2015 to December 2015 12.4 Conclusions The modal parameters of the Lysefjord bridge have been identified using AVT based on an automated SSI-COV procedure relying on several months of continuous acceleration records. Environmental effects were observed with a level of details that is scarcely available in the literature. In particular, the daily fluctuations of the eigen-frequencies were remarkably well captured as was the possible temperature-dependency of the modal damping ratios. A relatively large amount of acceleration data was accumulated, so that a statistical description of the influence of the mean wind velocity on the modal damping ratios could be achieved. The application of OMA using the automated SSI-COV method on other suspension bridges may provide a better general understanding of environmental influence on the modal parameters of such structures. The good agreement between the computed natural frequencies and the measured ones is encouraging for further investigation of full-scale measurement data using the automated SSI-COV method. The modal analysis also documented the non-linearity of the modal damping ratios and a possible non-negligible role of temperature effects on the modal parameters of the bridge. Further analysis will consider at least 1 year of full-scale measurements, and a more severe segregation of wind samples characterized by unusually high turbulence intensity indicating non-stationary fluctuations in excitation and response. Acknowledgment The authors are grateful to the Norwegian Public Road Administration for the support of and the assistance during the measurement campaign at the Lysefjord Bridge.
RkJQdWJsaXNoZXIy MTMzNzEzMQ==