Curved bridge for Dublin motorway upgrade

A major road widening scheme is underway along the M50 motorway, the Republic of Ireland’s busiest road. A number of junctions are being redesigned, one of which is junction N3 which has involved the construction of a new 115m-long steel bridge.

Due to the geometry of the new junction the bridge incorporates a curve and has a maximum skew of 60 degrees to the M50. This required a torsionally stiff deck and therefore a pair of trapezoidal box girders was selected for the main beams.

Structural engineer for the project Hewson Consulting Engin-eers, said using steel beams meant that road closures were kept to a minimum as large sections were brought to site and lifted in to place.

The new bridge, fabricated and erected by AMSE and requiring 550t of steel, has two spans both with a deck width of 13m and supported on a central pier.

The entire steel bridge was erected during four night time road closures involving tandem lifts with a 700t capacity mobile crane and a 350t capacity unit.