Design and Engineering
The Frank Sherwin Bridge, completed in 1982, was designed by DCC engineer Richard Fowler and built by Irishenco Ltd. Construction commenced in October 1980 with a total cost of £1.8 million.
The bridge took over from the old Seán Heuston Bridge because of its inadequacy to meet traffic demands with only two lanes and a restricted load limit of two tons. The new bridge has four lane capacity used in a one way system. The structure is a three span bridge with in-situ reinforced concrete deck. The central span measures 22m with two equal side spans of approximately 14m.
An in-situ reinforced concrete bridge was chosen for simplicity of construction, cost and aesthetics. It has two rows of three in-situ river piers so as to give the bridge an open appearance for what is a quite short three span structure.It is also for this reason that the piers are set back from the face at the bridge.
The abutments are of reinforced concrete supported on steel encased, in-situ concrete piles encased. These piles were driven to the limestone bedrock. Rock anchors were provided at the abutments to “hold down” the structure by means of the tension force in the cable.
A sheet piled cofferdam was used for the construction of each set of river piers. The piers are reinforced concrete cast, in-situ formed into a complex geometrical shape. The bridge deck is of solid reinforced concrete construction, the deck width is 19.7m over the three spans. The thickness of the deck varies to create a curved soffit, with the maximum depth of slab being 0.71m. Two finishes were applied to the sides of the deck, the lower half is finished using growth ring boards while the top half is finished using precast panels of impregnated Scottish and Wicklow granite dust. A steel parapet railing is used with forked posts to complement the pier shape and deck soffit profile.