Bridge construction work

Description

Transport Scotland wishes to appoint a main Contractor to replace the Truss End Links with a new sliding bearing arrangement at the Forth Road Bridge. The works comprise of strengthening of the main towers to accommodate the installation of a new bracket, complete with sliding bearing to be fixed to the tower beneath the end post. There are 7 truss end link locations requiring these replacement works. The main span truss currently has a temporary repair installed to provide an additional support system to provide a secondary load path for the deck loads and allow for the future replacements. Three of these, phase 2 repairs, temporary works will require dismantling, altering and installation on the side span locations. The North East main span location will have been completed as part of the advanced buildability trials. It is intended that the Contractor will complete the works in accordance with the Employer's Design.Temporary works will be designed and provided by the Contractor. Transport Scotland is an agency of the Scottish Government and contracts in the name of and on behalf of the Scottish Ministers. Transport Scotland has identified the requirement to appoint a Main Contractor to undertake repair (Phase 3) works to the Truss End Links at the Forth Road Bridge. These works are due to commence in Spring 2017, for a period of approximately 6 months. The Main Contractor will be procured through a competitive tender procedure, in accordance with the restricted procedure as stated in the Public Contracts (Scotland) Regulations 2015. Due to project complexity, the project requires to be performed by a single contractor and as such shall not be divided into lots. To be considered for this contract economic operators are required to complete the European Single Procurement Document ESPD in accordance with this Contract Notice. Economic operators shall be evaluated in accordance with the Public Contracts (Scotland) Regulations 2015, on the basis of information they have provided within the (ESPD). Project Details The Forth Road Bridge spans the Firth of Forth and carries the A90 Trunk Road between Fife and Lothian. The bridge consists of two approach viaducts and a suspension bridge which forms the main section of the structure. The bridge carries two 7.3m wide carriageways and two 4.6m wide footway/cycleways. The bridge deck is supported by transverse cross girders which in turn span onto a longitudinal stiffening truss, this is connected to the tower via the truss end links which are pinned to the bottom chord of the stiffening truss and to the tower where it is connected through two steel cantilever brackets which protrude through the tower. As the truss end links or Pendle bearings are pinned at each end this allows longitudinal articulation of the stiffening truss. The Phase 3 strengthening project consist of the installation of a sliding bearing at the bottom of the longitudinal stiffening truss beneath the end post. This bearing is supported on a new steel cantilever bracket, which requires concrete strengthening within the tower. The bridge operating company, Amey, on behalf of Transport Scotland are currently undertaking advanced buildability trials for the phase 3 works, economic operators are invited to attend site visits throughout the buildability site trial phase. A contractor is sought to replace the remaining seven truss end links with the new sliding bearing arrangement. The principle elements of the works will comprise:-The fabrication and installation of the permanent Phase 3 solution at the NW Main Span, SE Main Span and SW Main span-Alterations and relocation of the Phase 2 repairs at the NW Main Span, SE Main Span and SW Main span to their respective side spans.- The fabrication and installation of the permanent Phase 3 solution at the NE Side Span, NW Side Span, SE side Span and SW side span Internal strengthening is required in the tower to support the new bearing support bracket, made up of reinforced concrete inside the outer cell bolted through the tower using MacAlloy bars. Following the internal strengthening and the load transfer on to the new bearing and bracket, the Phase 2 repairs can be removed and relocated to the side span locations to allow the Phase 3 repairs to be carried out. There will be temporary access required to allow for modifications to the tower to accommodate the works, the installation of the steel reinforcement within the tower, the concrete pour into the tower cell, the removal/reinstallation of the phase 2 works and the installation of the permanent access stairs and platforms.It is proposed that the materials will be delivered to site via barge and lifted into place using a winch on the top chord or existing bracket. The concrete will be pumped from the carriageway under an overnight night carriageway closure using a contraflow traffic management system on the bridge.