I am reading Alexander Tsoni's book on Calatrava's bridges and wanted to discuss the structural behavior of Calatrava's different motifs for suspended bridges.
Suspended structures as swing sets
When a child is suspended on a swing set, her weight is transferred into the supporting rope/cable/spring as tension. The tension then acts on the horizontal frame as downward point loads which are in turn carried into the vertical frame as compression loads into the ground.
The design of the suspension bridge is similar. The deck acts as the seat of the swing set, the arch or pylon as the frame and the cables act as the tensile element. With this basic design, the bridge can be designed with different configurations that act similarly.
Symmetric cables
Fig. Above: 3D view of Autodesk Revit Conceptual Model of Serreria Bridge(Click on picture to enlarge for all figures)
The Serreria Bridge in Valencia, Spain is a motif that uses a symmetric pylon to suspend the deck and stabilizes the pylon with symmetric back stay cables. In this case the symmetry is achieved with one pylon in the spine of the bridge.
Structurally, the curvature of the pylon is optimized to resist the static forces in the span of the bridge. The angle of the parallel cables is optimized to resist the counter-forces against the cable stays. Finally, the two back-stay cables provides additional stability to the pylon.
At both ends of the deck and the base of the pylon, foundation elements take the loads into the ground. At the abutments, rollers are designed to provide torsional support. At the base of the pylon, the connection is fully fixed by means of concrete box attached to the pile cap of the foundation element.
Fig. Revit Sheet showing interface of design software
Fig.Showing profile of deck new abutment.
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