Modal identification of a double-curvature concrete arch dam under natural excitation: analysis of the accuracy achieved with different types of accelerometers

Abstract

At present time, the accurate estimation of modal properties of large civil structures (e.g. buildings, bridges, chimneys, wind turbines) can be easily achieved by applying state of art output-only modal identification methods (e.g. SSI-cov, SSI-Data, p-LSCF) to the data obtained with ambient vibration tests performed with appropriate sensors and data acquisition systems. However, when dealing with massive structures like concrete dams, the signals are very low (of the order of micro-g) and the signal to noise ratio very challenging in terms of modal identification. In this context, this paper describes an investigation developed on the Alto Lindoso dam (a double curvature arch dam in the North of Portugal, 110 m high) with the purpose of analysing the level of accuracy achieved, in terms of modal identification with the alternative use of different type of accelerometers (force-balance, piezoelectric, MEMS), developing a complete ambient vibration test along the dam crest.