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<p>The High Speed Railway (HSR) link Madrid - Extremadura crosses over River Almonte with a great arch viaduct of high - performance concrete. The main span of this structure is 384 meters.</p><p>This paper explains the exceptional techniques and structural analysis outside the usual engineering work that have been developed to reach its design and construction. These studies include the selection of the antifunicular arch axis taking into account construction process and train loads, geometric and material nonlinear analysis, dynamic analysis and aerolastic behaviour.</p>

<p>Two signature footbridges are introduced. Both built in Spain in 2006 and 2008, designed by Arenas &amp; Asociados and commissioned by the cities of Logroño and Zaragoza, represent different typologies and approaches to footbridge design, first one as a glazed closed and curved spatial steel truss, and the second one as a curved self anchored hanging bridge. They search to reach high quality architectural standards within a limited cost, and good integration in their urban environment.</p>

<p>This paper introduces two singular structures designed in the city of San Sebastian. The singularity of these bridges is based not on its dimensions or technical features, but in the way they adapt its design to local conditions. The 6th bridge over the Urumea River will be finished in 2010. This skewed urban bridge is 90 m long, with three spans of approx. 30 m, and 22 m wide. The bridge replaces an existing steel structure with historical values which is reused as a footbridge in a green area. It crosses the river parallel to the existing railway bridge, with associated visual and noise disturbances for the area. The new bridge in the area of Txomin-Enea over the Urumea River adapts to the different characteristics of the river banks. As the left bank will be a newly urbanized area with a green park following the river with walking and cycling paths. The structure uses two spans of 42 and 18 m, with the main span over the river and the side span over the new green area.</p>

<p>Hernani Viaduct is a 1226 long viaduct with two cable stayed spans of 120 m and 67.7 m. It will become the first cable stayed bridge for HSR (High Speed Railway) in Spain. Construction started in 2013 and will be finished by the end of 2015.</p> <p>Hernani Viaduct is part of the access railway line to San Sebastian in the North of Spain. This 1226 m long viaduct runs parallel to the Urumea River, crossing it three times with increasing spans (39,</p> <p>67.7 and 120 m) due to skew angle. Structure depth is limited by 500 year return period flood water level to 1.10 m below railway platform. This depth restriction forces us to adopt singular U shaped deck section and to add cable stayed superstructure for the 67.7 and 120 m spans. Construction is carried out using falsework. Temporary piers are placed every 30 m in the main spans and removed after cable stayed tensioning.</p>