This project consisted of the demolition of a life-expired 2-span steel and reinforced concrete composite bridge over the M9 near Stirling in Scotland, and replacement with a single span composite bridge.
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This project consisted of the demolition of a life-expired 2-span steel reinforced concrete composite bridge over the M9 near Stirling in Scotland and replacement with a single span composite bridge. The new bridge is a 42 metre singe span structure consisting of in-situ concrete on steel I-beams with shear studs with an F3 fair-faced concrete finish. The parapets were cast into the bridge structure and bridge waterproofing was spray-applied. The bridge is founded on 24 bored piles 900mm in diameter and 18 m deep. The two deck beams were also lifted into place in a full road closure. The works included 350 metres of road realignment and the construction of crib walls to support the realigned Chartershall Road (as the bridge is 0.5m higher than the previous one). A contractor designed precast concrete crib wall retaining wall supported the increased height of the approach roads.
The main challenge on this project was to demolish the existing 2-span bridge with a ten hour road closure. Steel plates and stone were placed over the existing road surface to protect it during demolition. A total of eight 30-ton rock-breakers were used to demolish the bridge in order to complete the work within the road closure. Fitters were employed on stand-by to make sure that all of the plant would be working when required.
The road closures for the demolition and erection were planned and agreed with Transport Scotland and the emergency services and were advertised one month in advance. Coffey elected to bring the road closure for the demolition work forward by six weeks, as the main works programme had been resourced to allow construction work to start earlier than anticipated by the client team. This resulted in the project being completed 4 weeks early.
In order to minimise the length of the full road closure for the demolition of the M9 Chartershall bridge, the following traffic management operations were put into place:
- Work started forty-eight hours prior to the demolition works to create a haulage road from the main compound to the motorway hard shoulder to facilitate removal of material from site;
- Twenty-four hours prior to the demolition works, 35m of existing safety barrier was removed from the hard shoulders and central reservation in advance of demolition works.
Advance signage was used to alert motorists to the need to pre-plan their journeys which may have been affected by road closures. As a result of a proactive approach to stakeholder management by keeping stakeholders and the public informed, the client, Transport Scotland, received no complaints from motorists about the work.
To ensure a safe and efficient site during the demolition works, the following preventative measures were put in place:
- Plant locations during the demolition works were carefully planned and briefed;
- Personnel were not permitted within an exclusion zone when the rock breakers were breaking up the bridge deck, and communication was by a channel radio system.
- Supervisors carried air horns for emergency use to stop all work;
- Full high visibility PPE was worn by all personnel;
- Vehicles removing waste offsite were not overloaded.
The detailed design and implementation of the traffic management was subcontracted to Central Traffic Management Ltd, who have full accreditation for traffic management under the Highways Agency Sector Scheme.
To assist in the efficiency of the works, Coffey negotiated a private contract with a local landowner for our site compound area.