Bridge, Coimbra

A bridge of two halves

COIMBRA (PT) - Arup's Advanced Geometry Unit founder Cecil Balmond and engineer António Adão da Fonseca are responsible for the recently inaugurated, 275-metre-long bridge across the Mondego river in the Portuguese city of Coimbra. The form stems from Balmond's desire to make it possible to 'walk over that stretch of water and linger, stop and start.' That brought him to the idea 'to have two halves for the bridge, with neither meeting in their journey across water: two curves that would slip past each other. The middle then would become a crossover zone, not just for pedestrians but also for structure.'

In the event, the design has become a symbol for a tragic love affair that took place in Coimbra in the early fourteenth century, between the future king of Portugal and Algarve, Pedro I, and Inês de Castro, who was murdered by Pedro's father, King Afonso IV, two years before Pedro's ascension.

As Adão da Fonseca explains, the extremely flat-arched bridge consists of 'a central parabolic arch and two lateral arches supporting the deck. The rise of the central arch is 9.36 m for a 110 m chord, resulting in a shallowness ratio of 1/12. Longitudinally, the deck extends through two ramps with a constant inclination of 4%.'

The balustrades of the bridge consist of facetted panes of coloured glass in a seemingly random carbon steel framework.