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A stressed ribbon bridge is a tension structure (similar in many ways to a simple suspension bridge) in which the roadway follows a catenary arc between supports. Unlike the simple span the ribbon is stressed in compression, which adds to the stiffness of the structure (simple suspension spans tend to sway and bounce). The supports in turn support upward thrusting arcs that allow the grade to be changed between spans (where multiple spans are used). Such bridges are typically made from concrete reinforced by steel tensioning cables. Where such bridges carry vehicle traffic a certain degree of stiffness is required to prevent excessive flexure of the structure, obtained by stressing the concrete in compression.
The Maldonado bridge, located in Maldonado, Uruguay, illustrated externally below, was created by the engineer Leonel Viera (1913-1975) to span the Punta del Este. After placement of the principal cables, concrete tiles were placed to form the initial structure. The cables were then prestressed by loading sandbags upon the tiles, followed by final concretization. Removal of the sandbags then compressively stressed the concrete structure, enhancing its stiffness and durability under load. An identical bridge was later constructed parallel to the first.
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