A problem which caused the sudden closure of the Menai Bridge in north Wales could have led to "catastrophic loss of life", engineers ruled at the time. In October of last year it was decided that the 197-year-old bridge would close to traffic after issues with the span hangers were detected during routine maintenance.
NorthWalesLive reports that a technical briefing document shared with New Civil Engineer has now shed more light on what exactly led to the closure. In the document it reportedly states that the issue centred 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 briefing document, which was based on analysis by engineering and architecture consultancy Cowi, reportedly said that "were a given hanger to fail in a brittle manner [...] the impulse loading from this event had the potential to cause brittle fracture in adjacent hangers, leading to a progressive and disproportionate collapse of the bridge deck".
Read more: Third Menai crossing in Welsh Government's project pipeline following bridge's closure
It added: "Due to the inherently unpredictable nature of brittle fracture, it is extremely difficult to accurately determine the probability of such an event, but the analysis showed there was a credible risk of an unzipping failure of the bridge deck. Such an event may have led to catastrophic loss of life and was thus considered an unacceptably high consequence event that could have credibly occurred."
Following its closure in October all traffic was diverted to the neighbouring Britannia Bridge, leaving only pedestrians and cyclists to use the bridge. After four weeks of work the bridge was reopened to restricted loads on February 2. The first phase of temporary mitigation has seen work to strengthen the historic bridge's hangers.
According to the Welsh Government they are working closely with UK Highways A55 Ltd alongside engineering firms Spencer Group and Cowi to develop a plan for "longer-term remedial" work to take place and with "minimal disruption" to bring the Menai Suspension Bridge back to full capacity. This work is anticipated to start in late summer, according to the government.
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