Bridge-inspection services

Tender description

Transport Scotland wishes to appoint a suitably experienced contractor to undertake an internal inspection and investigation of the main suspension cables on the Forth Road Bridge. 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 an internal inspection and investigation of the main suspension cables at the Forth Road Bridge. These works are due to commence on site in April 2018 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 main span is 1006 metres long with side spans each of 408 metres. The deck is an open steel truss with an orthotropic stiffened plate on the main span and a reinforced concrete slab on the side spans. The suspended truss is supported by two aerially spun cables each of approximately 590 mm diameter. Following work which had been undertaken in the USA, the first internal inspection of the main cables on the Bridge was undertaken in 2004 following the recommendations of NCHRP Report 534 (Guidelines for Inspection and Strength Evaluation of Suspension Bridge Parallel Wire Cables). Each of the main cables was opened in 5 locations (3 low level and 2 high level). The low level locations were accessed from scaffolds and the high level locations from specially constructed steel platforms. Following the inspection, the strength of the cables were evaluated using the NCHRP Brittle Wire model. In 2006 an acoustic monitoring system was installed on the main cables of the Bridge to monitor the number of wire breaks in the main cables. In 2006, a contract was also awarded to install a dehumidification system to the main cables. This involved sealing the main cables to make them air tight and then pumping dehumidified air through the voids, between the individual wires which make up the cables. The 2nd internal inspection of the main cables was included within the main cable dehumidification works contract to allow the condition of the cables to be ascertained prior to the commissioning of the dehumidification system. This project was completed towards the end of 2009. In 2012 the 3rd internal inspection of the main cables was undertaken. This involved unwrapping a total of 8 No panels to allow inspection of the internal wires. The principal elements of the proposed works will comprise, but will not be limited to: — Refurbishment, modification, load testing and certification of purpose designed cable gantries; — Refurbishment and testing of a purpose designed cable compactor and wrapping machine; — Provision of detailed method statements; — Installation and removal of cable gantries and access cradles; — Erection and removal of low level scaffolding platforms; — Removal and reinstatement of main cable elastomeric wrap; — Removal, reinstatement and recommissioning of main cable dehumificiation and acoustic monitoring equipment; — Unwrapping of the main cables including the removal of lead and zinc waste; — Cable wedging; — Wire sampling and splicing; — Cable compaction and wrapping; — Provision of as-constructed information; — Provision of Health and Safety File.