Design of a High Speed Rail Arch Bridge over the Alcántara Reservoir (Spain)

The Almonte River arch bridge over the Alcántara Reservoir, which is part of the Madrid- Portuguese Border High Speed Rail (HSR) link, is a challenge for bridge design, engineering and construction. Its 384-m main span will make this major project become the largest HSR arch in the world and the largest railway bridge in Spain. With the aim of giving response from the design stage to the specific problems of a HSR crossing with large span and length, a formally and structurally innovative design has been used: the arch, linked to the deck at the crown, has an octagonal section with variable depth and width in its central 210 m, from where it splits itself into two legs with irregular hexagonal section until its springings. The design joins together structural efficiency, out-of-plane stability (as HSR horizontal deflection limits require), improved response to wind loads (as exhaustive wind tunnel tests have proved), transparency, aesthetics and durability.