Reconstruction of the Butron Castle Arch Bridge

Abstract

Before the estuary of Plentzia, within one of the last meanders of the Butron river, the unique medieval castle of Butron can be found. It is located in the municipality of Gatika, in the Historical Territory of Biscay. The ancient masonry bridge connecting the castle and the opposite bank of the river, apart from being a hydraulic obstacle favouring the flooding of the alluvial plain in the area, presented a high risk of collapse, due to the scour of its right abutment. The local administration decides to reconstruct the ancient bridge, building a reinforced concrete deck arch bridge, with a single span of 23 m and a rise-to-span ratio of 1/6.57. This structural typology was chosen because of its ability for ensuring hydraulic section, and as a reminiscence of the ancient bridge. This humpback profiled structure is an example of an arch solving, in our days, a clearance in the range of very short spans.