Unconventional cable-stayed bridges: structural behaviour and design criteria

Under-deck and combined cable-stayed bridges are two relatively new bridge types that have been developed over the last 30 years. Most of these bridges have been constructed in Germany, Japan, France and Spain, and have been designed by outstanding structural engineers such as Leonhardt, Schlaich, Manterola, Virlogeux and Cremer. The main advantages of these bridge types are: their great structural efficiency; the small amount of materials that they require (allowing economic and sustainable proposals); their great construction possibilities, allowing an increase in the span range of certain construction methods; and their strong aesthetic characteristics owing to the different layouts that can be defined with the stay cables. This paper revises the structural behaviour and design criteria of under-deck and combined cable-stayed bridges, and summarises the main research contributions of the PhD thesis submitted by the author Dr Ana M. Ruiz-Teran, to whom the fib Diploma 2009 for Research (Young Engineers Award) has been recently presented for this work.