Keywords: Fisher information matrix, Genetic algorithm, Optimal sensors placement, Movable bridge ABSTRACT Bridge structures are very critical elements within a complex transportation system, and movable bridges are especially important because they allow to the traffic to cross active waterways granting passage to ships that would otherwise be blocked by the structure. Therefore, the reliability assessment as well as the health monitoring of movable bridge structures are challenging issues and deserve a lot of attentions as the socio-economic consequences due to structural failures and/or temporary unserviceability states may be invaluable. In this perspective, experimental and analytical technologies can be successfully integrated to obtain a field-calibrated finite element model, thus ensuring more consistent decision processes. Moving from these considerations, the paper addresses the optimal sensors placement for the dynamic monitoring of a historic swing bridge in Taranto (Italy). After a brief description of the bridge, both CAD and FE models are illustrated. Subsequently, the considered strategies for sensors positioning are presented. Finally, these techniques are adopted in order to identify the best locations for the available sensors. Comparative analyses are performed to evaluate advantages and drawbacks of the obtained results in the aim to support the experimental design for this special structure. 1 INTRODUCTION 1.1 Case study: the “St. Francesco da Paola” bridge in Taranto (Italy) Taranto is a coastal city located in the southern part of Italy, in the Apulia region, in front of the Ionian Sea. The city is characterized by a hydrologic system based on two basins close to the Ionic coast. An inner, semi-enclosed basin with lagoon features – named “Mar Piccolo” – is connected with the outer basin (named “Mar Grande”) through two canals, namely the “Navigabile” canal and the “Porta Napoli” canal. The inner basin “Mar Piccolo” is divided into two inlets – named first and second inlet – which have a maximum depth of 13 and 8 m, respectively (Figure 1). The actual swing bridge over the “Navigabile” canal – the “St. Francesco da Paola” bridge (Figure 2) – was opened to traffic more than fifty years ago, on March 10, 1958. This swing bridge was built with two equally armed movable portions and each of them rotates about one vertical axis. Figure 1. Location of the “Navigabile” canal The structural health as well as the functionality of the opening system are crucial because the bridge has a central role within the local transport network. The actual structural reliability of the bridge is substantially unknown because it has not been investigated previously by using modern simulation-based numerical Dynamic monitoring of the “St. Francesco da Paola” swing bridge in Taranto: optimal sensors placement techniques Giuseppe Quaranta Department of Civil and Environmental Engineering, University of California, Davis. One Shields Avenue, 95616 Davis (CA), U.S.A. Giuseppe Carlo Marano, Francesco Trentadue Department of Environmental Engineering and Sustainable Development, Technical University of Bari. Viale del Turismo 10, 74100 Taranto, Italy. Giorgio Monti Department of Structural and Geotechnical Engineering, Sapienza University of Rome. Via A. Gramsci 53, 00197 Roma, Italy.