A new multi-span arch bridge over the Piave River in Venice:conceptual design and structural optimization

摘要

Not infrequently, building yards of important infrastructures take remarkably long time to be accomplished and are characterized by several interruptions and resumptions. This is the case of the bridge over the Piave river in San Dona, an outstanding 500m arch structure on five bays of 100m each, located in a strategic area just outside the city of Venice-Italy. The interruption of the construction works was, for the case mentioned, contemporary to the introduction of a new regulation, the O.C.P.M. n 3274, concerning seismic design and seismic classification of the National territory. This fact, since the original project was characterized by a massive box girder concrete deck on pile foundations (thus not conceived for horizontal loads at first), gave rise to the necessity of starting with an updated design aiming to achieve a much lighter composite steel and concrete box girder deck. The new deck was connected to the already built piers by means of non conventional steel-to-concrete connections ensuring hogging moment resistance at supports, and it is characterized by a sophisticated aesthetics and by an optimized distribution of structural material obtained through an iterative design-and-check process. In the following paper, the structural optimization process aiming to reduce the weight of the superstructure of the bridge will be presented. This study follows a previous one based on a manual ESO (evolutionary structural optimization) performed into a FEM model (Zordan T. et al. 2010), for which all computer automatic procedures were been replaced by a step-by-step iterative process controlled by the designer. Now this results are compared to the ones coming from a totally automatic ESO procedure performed with Ansys V.12 software, and a semi-automatic procedure, that use Ansys topological optimization's results for identifying shape finally defined by the user himself.