Nunnery Bridge supports the Steam Railway and footpath, spanning the river Douglas in the Isle of Man. The bridge is constructed in two forms. The main section is a bespoke half through steel truss, with a span of 26m, erected to replace the existing bridge in the 1970’s. The shorter span over the footpath is believed to be the original structure, constructed in the 1870’s and is a simpler girder and cross beam structure.
A number of isolated section loss and failure of areas of the paint coating were identified. To protect the asset it was recommended that, in addition to replacing corroded elements the structure should be fully repainted with an appropriate coating system to preserve the life of the bridge. A full refurbishment of the bridge is scheduled to be undertaken, commencing at the end of 2018. The bridge has been surveyed and a structural model assessed to ensure that normal loadings are not exceeding the structure’s actual capacity.
Burroughs have produced a design and package of works to refurbish the structure, with a paint specification giving 25 years to first major maintenance. Proposals include an upgrade to the current track supports across the bridge to reduce future maintenance requirements and an enhanced alignment. The scope of works includes relaying 300m of the track adjacent to the structure, fencing to prevent trespass, river bank stabilisation and tree removal immediately adjacent to the structure.