Structurae

The new IVth bridge over the Grand Canal, designed by the Spanish architect Santiago Calatrava, recently completed in Venice, is characterized by some original solutions in the Venetian panorama of traditional bridge design. Its stunning elevation, on a single 80m span depressed "Vierendeel" arch with a span/rise ratio of 1/16, implies an extraordinary challenge for the foundation system in the muddy Venetian soil. The cross section of the bridge presents an open star-shaped layout with a central triangular steel box girder, thus implying a remarkable torsional deformability. The loose mechanical properties of the Venetian soil, together with the peculiar intrinsic structural and geometric characteristics of the footbridge, imposed a careful revision of the original design and some modifications aimed at achieving a globally stiffer structure without any alteration to its external outfit. The footbridge was pre-assembled and loaded prior to erection trying to simulate its final condition in terms of external restraints. In this phase a monitoring instrumentation was installed in order to better investigate its response. The erection design was conceived in order to take into account the extremely bounding conditions of the project area.