Task Order from PDF framework for 612093 A46 Guys Cliffe Interchange

Descriptions

A46 Guys Cliffe IC contains two underbridges that carry the dual carriageway Warwick bypass over the interchange link roads with the A429 and B4115. The two bridges are single span simply supported structures with composite decks comprised of pre-stressed beams and 200mm thick slabs cast upon permanent formwork between beams. The end supports are reinforced concrete cantilever abutments, which are constructed in two sections and separated by a movement joint at the centre line. Each abutment is flanked by reinforced concrete tapered wing walls.

The deck is free to move at the south end and fixed at the north end. In November 2003, secondary Open Box Beam (OBB) Vehicle Restraint Systems (VRS) were installed on both sides of both structures to protect the existing substandard BACO Aluminium parapets (P1 System). The OBB barrier is flared back and connected into the Tensioned Corrugated Beams (TCB) barrier apart from ramped OBB barrier on the departure end of the South Bridge. This secondary OBB has substandard set-back and working width.

The bridge records indicate that both bridges were re-waterproofed in 1993 by Acrylic and Polyurethane spray over the entire deck and again in 2003 with spray applied system at the verges only (on top of new C50 verge concrete) in conjunction with parapet protection works (OBB barrier installation). This is based on the 2003 Contract Drawing contained within IAMIS (S.22.002/A) and service life can be considered for minimum 35 years. The existing deck waterproofing at the North Bridge was damaged on both the northbound and southbound carriageways during a resurfacing intervention in 2013.

The waterproofing remains in its damaged state. Following the option study undertaken by Kier to address the damaged waterproofing at the north bridge and the substandard secondary protection at both bridges, an addendum to the Options report was submitted. The addendum VRS replacement option on both bridges is to replace the VRS with new N2 W1 metal VRS and to replace the current verge with a new reinforced concrete plinth with cast-in cradles to form a fixing for the VRS and resin anchoring steel 'U' bars into the bridge deck.

For the North Bridge, waterproofing will be sprayed from the new plinth, under the kerb, across the carriageway, and shall form a joint with the existing central reserve waterproofing in the channel fronting the kerb. For the South Bridge, waterproofing will be sprayed from the new plinth, under the kerb, and shall form a joint with the existing carriageway waterproofing in the channel fronting the kerb. A departure from standards has been approved for the new VRS to have reduced setbacks. An asbestos survey and adhesion testing of the existing waterproofing will be undertaken in Stage 3.