The first use of column wrapping in the UK was in full swing on an M11 overbridge last week. Main contractor Balvac Whitley Moran is strengthening four 800mm diameter roadside concrete columns on the Coopersale bridge with up to 17 layers of Dupont's Kevlar fabric. This is normally used to make bulletproof vests.
Wrapping will make the columns more resistant to vehicle impact as well as enabling them to cope with 44t HGVs when they appear. But Agency structures design group engineer Ben Sadka said that the bridge was not seen as particularly vulnerable to vehicle impact.
'It's just good housekeeping, ' he added. 'The main work here is to strengthen the deck, which was found to have inadequate shear resistance. Wrapping the columns at the same time is a sensible precaution which adds only £45,000 to the overall project cost of £600,000.'