VILOBÍ D'ONYAR & LA ROCA BRIDGES OVER THE A-7 MOTORWAY

These two bridges employ a new and innovative structural format known as the “strict box” composite system. It favorably combines the two most common composite bridges types: twin-girder and box-girder. This system has all the advantages of both types and none of their disadvantages and provides excellent durability and great ease and flexibility of construction whilst ensuring a pleasant visual appearance at minimum cost.

The leading design requirement was to concentrate the steel in 2 solid webs and let the bottom flange be a reinforced concrete slab of variable thickness (thicker at the piers and thinner at mid span) so to create a composite cross-section which takes advantage of the rebar installed in this bottom slab to resist the tensile stresses due to bending.