Bridge CAT 3 Checker

Tender description

The new River Barrow Bridge is a constituent part of the proposed Athy Distributor Road. The alignment of the proposed Athy Distributor Road commences on the western outer edge of the town with a proposed roundabout junction on the N78, crossing the River Barrow, immediately south of an existing, disused railway bridge crossing , which also crosses the River Barrow, and terminates east of the town at the existing N78/M9 Link road roundabout. The primary function of the bridge is to carry the proposed carriageway over the Barrow River. The proposed bridge is a single span steel-concrete composite beam bridge spanning the full extent of the river. The span length measures 79.55m between supports and is equivalent to the total length of the existing railway bridge. The structure comprises four steel plate girders made composite with a reinforced concrete deck slab, which incorporates precast concrete units to minimise pouring operations over the watercourse. The depth of the steel beams is constant at 2.55m. The structural configuration is simply supported, straight with no skew at either end. The proposed structure is articulated at end supports. The abutments are reinforced concrete incorporating mechanical bearings and expansion joints at each end of the bridge. Mechanical bearings are proposed under each longitudinal steel girder at each end of the bridge. Longitudinal restraint to the bridge deck is provided by a fixed bearing at the west end of the bridge. Other bearings will be sliding guided or unguided bearings, depending on their location relative to the fixed bearing. The west abutment will be supported directly on competent bedrock and thereby direct bearing foundations are anticipated at the west support. At the east riverbank, alternating layers of Silt/clay and medium dense Sand/Gravels have been encountered and competent rock has been found at levels of 15 m bgl. Due to the presence of Clay/Silt materials below at shallow depth, the eastern abutment will be supported by 750 mm diameter bored pile