Two new types of bridges: under-deck cable-stayed bridges and combined cable-stayed bridges — the state of the art

At least 20 cable-stayed bridges have been built over the last 30 years that cannot be classified under existing typologies for cable-stayed bridges. These structures represent two new types of cable-stayed bridges that we herein define as "under-deck cable-stayed bridges" and "combined cable-stayed bridges." The evolution of these new bridge types is explored through consideration of the different proposals and structures that have been built throughout this period, pointing out the innovations made in each of them. In this paper we propose a new classification system for bridges prestressed by means of tendons into which these two new bridge types will fit. Studies that have been made of these structural types are also highlighted. On the basis of the aforementioned, we describe the state-of-the-art for these structural types, compiling and cataloguing information, documents, and knowledge that were previously highly dispersed. Lastly, we make a critical analysis of the current situation and draw some k...