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The structure
Trowbridge Town Bridge is a listed 18th century three span limestone masonry structure carrying the two lanes of the A366 over the River Biss. Prior to strengthening the live load rating was 12.5 tonnes.
The problem
Analysis of the structure revealed that although the two side spans had sufficient unstrengthened capacity, the deformed profile and flattened crown of the central span was found incapable of achieving the 40/44
tonne HA loading requirement without first some form of strengthening intervention. The bridge contained numerous services and carried a high volume of traffic through the town centre.
The solution
So as not to disrupt traffic and to avoid internal services, contactors TST of the Isle of White carried out the drilling and installation from below. In total 32 6xS10 multibar anchors of 2.7 and 2.8 metres in
length were installed by diamond drilling the 65mm cores from the adjacent arches.
Upon completion, Wiltshire County Council commented upon the financial savings made and also
upon the short time undertaken to strengthen the structure over the original proposal for saddling.
Traffic flow remained undisrupted throughout the process.
Typical section revealing drilling from adjacent arches.
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