Structural design of a smart under-deck cable-stayed prestressed concrete viaduct: Theoretical basis and application to the Osormort viaduct

Under-deck cable-stayed systems have been extensively used in bridges to optimize the internal stress distribution, enhancing their structural performance. Although these systems provide highly contribute to counteract permanent loads, their efficiency to withstand live loads is reduced, thereby limiting opportunities for material savings. This effect is particularly relevant in concrete viaducts, where the relative stiffness of the deck with respect to the tendons is very high. This limitation can be overcome by using a smart under-deck cable-stayed system, which gradually modifies the tension in the stays as the live load increases, improving its performance. The smart behavior is achieved through the use of a linear actuator that replaces the midspan strut of a conventional under-deck cable-stayed bridge. This article starts by presenting the theoretical considerations on the structural design of these innovative systems. Then, the application of this technology to multi-span prestressed concrete bridges is evaluated using a numerical analysis. Specifically, the Osormort viaduct has been selected as a reference bridge for comparison purposes. This work quantifies the performance of the smart systems from different perspectives, including material quantities, CO2 emissions, and cost, for different portions of the live load compensated by the smart system. The comparisons reveal that the implementation of a smart system can optimize material quantity of the deck (concrete volume and internal prestressing), resulting in cost reductions of up to 15% and carbon emissions reductions of up to 9% compared to a conventional solution. In summary, this investigation provides a further confirmation of the potential of smart cable-stayed under-deck systems to significantly improve the structural performance of bridges while reducing material usage and costs.