Red Line South. Metro de Doha (Qatar). Estructuras singulares construidas in-situ de ancho o canto variable

The Doha Metro Red Line South runs on a viaduct along most of the line. At the beginning, the design consisted of typical precast spans, but external constraints made complex structures necessary. For this reason, several cast in-situ bridges were built. Some of them have variable width (either simply-supported decks or continuous ones up to three spans), whereas other bridges are of variable depth, so they can reach 59 m for a double track section and 75 m for single track. The most complex bridge is the variable-depth one for the double track railway because the structural behaviour depends on several resistant mechanisms.