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Bridge corrosion is linked to human urine


HUMAN URINE is threatening the safety of a major suspension bridge in the Caribbean, an Institution of Structural Engineers London meeting was told this week.

Mouchel project manager Raymond Hobbs said a recent inspection of the 45-year old, 175m span Puente Duarte Bridge in Santo Domingo, capital of the Dominican Republic, discovered major urine-linked corrosion below deck level.

'It seems there are few public conveniences in Santo Domingo, so pedestrians and cyclists crossing the bridge regularly relieve themselves against the four steel towers,' explained Hobbs.

After years being doused with urine, many rivet heads have completely disappeared, he said. The survey also highlighted widespread pitting up to 10mm deep in the steel and corrosion in the hangers and at the end of the suspended span. Worse still, Hobbs added, was the corrosion of the connections between a transverse girder and the ends of the mainspan truss.

Above deck level, although the paintwork was in bad condition, the inspection noted virtually no corrosion above a distinctive 'tidemark' at about waist height. 'This problem obviously dates back a long time, because there had been attempts to install 'splash plates', which had not worked,' Hobbs said.

'This is the first time I have ever heard of human urine causing such problems anywhere in the world - but the smell makes it easy to identify.'

Mouchel also concluded that the towers and suspension cables were badly under-designed and a major £15M strengthening operation was launched last year.

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