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Widening of a historic masonry arch bridge

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Widening of a historic masonry arch bridge
Barcelona, February 09, 2018

The widening of Monistrol Bridge over the Llobregat River, on the BP-1121 local road, in the town of Monistrol de Montserrat (Province of Barcelona), was successfully completed in April 2017, four months ahead of schedule. In 2014 the owner, Diputació de Barcelona, decided to widen the bridge to improve capacity and enhance, safety for both vehicles and pedestrians. Pedelta provided design engineering and contract administration services for this project.

The bridge was originally built in the 13th century and was partly blown up in the Spanish Civil War in 1939. The structure consists of four masonry arches of different lengths – 13 m, 17.5 m, 27.1 m, and 38.7 m. The key project challenge was how to widen the platform from 7.9 to 11.3 m, while keeping the visual appearance of the bridge. The proposed solution was to implement a minimal intervention by widening the platform with a concrete slab sitting on the fill between the spandrel walls. The concrete deck consists of partial depth precast concrete slabs topped with a continuous concrete layer. Safety barriers and pedestrian railings were designed with minimal and clearly differentiated elements to visually lighten the intervention.

Ultimate analysis of equilibrium was used to assess structural safety of the existing arches. The widening and rehabilitation project preserves the existing historic arches, masonry walls and exterior wall supports. Several elements of the existing masonry bridge were repaired, including the arches, the spandrel walls, the abutments and the wingwalls.