The Fourth Bridge over the Grand Canal in Venice: From Idea to Analysis and Construction

The new fourth bridge over the Grand Canal, designed by the Spanish architect Santiago Calatrava, which was recently completed in Venice, is characterized by some original solutions in the Venetian panorama of traditional bridge design. Its stunning elevation, on a single 80 m span depressed \u201cVierendeel\u201d arch with a span/rise ration 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. A set of full-scale static tests of the structure was carried out before and after the erection to check the behavior of the bridge