DoT bridge repair 'headache'

The Department of Transport is wasting tens of millions of pounds a year patching up road bridges as a costly penalty of its 'cheapest is best' design philosophy.

Anthony Biddle of the Steel Construction Institute says that the DoT recognised 30 years ago that the longest lasting bridge would be a structure with integral decks and piers and a handful were built on the fledgling M1 motorway.

But the policy was abandoned in favour of building the cheapest bridge.

'Instead we got bridges with expansion joints,' said Biddle, manager of SCI's civil engineering division. 'The trouble is that they leak: salt-laden water from the road gets in and corrodes them, the chloride breaking the bond between the reinforcements and the concrete. The damage goes to the heart of the structure.

'The DoT then moved to composite bridges which were better. However, they have a bearing problem. Corrosion causes bearings to seize up and the bridge won't roll properly over its abutments, with the result that you get forces that break the bearing from the concrete. 'The DoT is faced with a major headache because bridges with a design life of 120 years are falling apart after just 25 years. Patching up will cost billions. It was only recently that the DoT realised it was badly wrong.'

A DoT survey confirmed its worst fears, though it has yet to take action. But contractors anticipate a new guidance note from the DoT by the end of this year.

l The SCI is pressing hard for the use of fully threaded bolts. On a typical medium-size building, 180 different bolts would typically be used - SCI says this could be cut to just three different sizes if bolts were fully threaded, with one size accounting for 90% of all the bolts used.