Experimental vs operational modal analysis: A flyover test case

Abstract

Expo 2015 is about to begin and the theme will be Feeding the Planet, Energy for Life. This exhibition will be focused on the nutrition issue but it is also important because of its economic benefits for the country, mainly for the development of the infrastructures necessary to support the event. For instance, one of the most strategic construction site is the BreBeMi highway connecting the cities of Brescia, Bergamo and Milan, which will host the exhibition. This paper will present a comparative discussion about a BreBeMi flyover, crossing the Oglio river, which was deeply studied by means of operational modal analysis, experimental modal analysis and finite element simulations. The bridge is made by hollow core prestressed elements with unbounded tendons, supported by hollow core circular piers. Friction pendulum isolators are used at the supports to disconnect the deck from the piers as for seismic actions. The FE model was tuned by the comparison of the eigenvalues and eigenvectors computed by a linear modal analysis and the data obtained by the experiments. The results show the good correlation between the model and the real structure in terms of frequencies and mode shapes. Moreover this bridge is a remarkable test case to compare benefits and drawbacks of using operational and/or experimental modal analysis.