New evidence shows that hangers at risk from brittle failure on the Mania Suspension Bridge, which connects mainland Wales and the Isle of Anglesey, were recommended to be replaced over 30 years before concerns led to the closure of the structure last autumn. The 197-year-old bridge was originally designed by Thomas Telford. It consists of two 52.7m high masonry towers which support two sets of steel chains across the 176.7m main span. The approaches are formed of masonry arch viaducts, four spans on the Anglesey side and three spans on the Bangor Mainland side. The deck of the main span is suspended from the chains via vertical spiral strand hangers. In the side spans, vertical hangers also connect the chains to the masonry viaducts and this serves to control the profile of the chain and limit the horizontal movement of the roller saddles at the tower tops. The 176m-long road bridge was closed to all motorized traffic in October 2022 over concerns about the hangers. It was reopened with a 7.5t weight restriction in February, following a four-week emergency repair programmed carried out by Spencer Group. A technical briefing document, shared with NCE in February, stated that the issue which led to the closure center on an “unacceptable risk of brittle failure” in hanger sockets which were installed during a major upgrade of the bridge between 1938 and 1941. The document showed that 40 hangers were replaced between 1989-1991 but 202 were not.
However, it Has Now Been Revealed The Capacity Of The Hangers.
that were not replaced during the 1989 to 1991 work was questioned during structural investigations in 1991. A recommendation for the replacement of the remaining hangers on a rolling basis thereafter was made. Since then, no further hangers have been replaced. Isle of Anglesey County Council chief executive Dylan Williams said: “We are extremely disappointed and concerned. Had there been an appropriate maintenance programmed in place the recent bridge closure and resulting community impacts may well have been avoided. “Robust and resilient connectivity between Anglesey and the mainland is essential. “We remain hopeful that the outcome of the North Wales Transport Review, led by Lord Burns, will influence the Welsh government to take appropriate and immediate action.” Deputy Leader of Plaid Cymric and Member of the Sanded for Anglesey Run Werth said: “If 40 hangers were replaced around 1990 and there was a recommendation to replace the rest, then there should have been a programmed in place to change all the hangers over time. “It’s scandalous that successive governments didn’t make sure that the long-term wellbeing of the bridge was assured. “The way in which the bridge had to be closed with no notice last October was hugely problematic – we shouldn’t have been in a position where a decision to close it needed to be made that quickly.” In the coming months, work will see 168 of the existing hangers removed using a custom designed de-tensioning rig and replace them with new hangers. Once the new hangers are installed, the Menai Suspension Bridge will be able to reopen without restriction and the secondary fail-safe system and de-tensioning rig removed with only the new hangers remaining.