Operational Modal Analysis of a Bridge Subjected to Perceptible Vibrations

Bridge design must ensure that these structures are safe, serviceable, and durable. An important concern in serviceability is the comfort of bridge users. Vibration serviceability of existing bridges is required in order to prevent the motorists’ perception of an unsafe bridge and the possible economic and social impact of downtime after users’ complaints. However, little attention has been traditionally paid in the past to vibration serviceability of road bridges in the Italian structural design codes. Thus, bridges, particularly those characterized by slender structures, might be susceptible to vibration problems under traffic and wind loadings. In similar cases, Operational Modal Analysis can support the assessment of possible vibration serviceability problems by providing information about the dynamic properties of the investigated structure. The present paper describes the main outcomes of an extensive experimental campaign carried out on the San Marco Viaduct in Castellammare di Stabia, Southern Italy. Tests were aimed at the identification of the modal parameters of the bridge and at characterizing its performance with respect to vibration serviceability.