Engineering - Bridge strengthening

We were asked to help strengthen a motorway bridge to enable one of the heaviest loads to travel the roads in Britain to cross it to reach its destination. Our solution had to ensure that the bridge could support a combined weight of over 450 tonnes.
We used FD808, a two-part epoxy resin, to attach a steel plate to the underside of the bridge.
Both concrete and steel surfaces were cleaned by shot blasting, holes were drilled in both, and long threaded bars fixed into them. The steel plate was suspended on these bars by screwing nuts underneath the plate, leaving a gap of 0.5m. The adhesive was then applied to both concrete and steel mating surfaces and the steel brought up to the concrete by fastening the screws. After the adhesive had cured the bars were sawn off. FD808 was specially formulated for this type of application. It offers

• good bond strength
• ease of workability
• good tolerance to damp conditions, and
• fast curing characteristics necessary for on-site operations.

Normally the adhesive is supplied in a tin into which, when required for use, the correct amount of FD808 hardener is poured from the accompanying polythene bottle. Once mixed, due to its limited pot life, the adhesive must be applied immediately.

As work on this bridge was on such a large scale the resin was supplied in drums and the resin was applied in sections, with excess adhesive squeezed out from one section being applied to the next. To achieve optimum curing temperature the sides of the bridge were shrouded in tarpaulins and gas heaters placed beneath: this enabled temperatures of 15-18°C to be maintained and curing to complete in 24 hours.

In all 816 metres of 400 x 100mm structural steel plate was attached to the bridge, using 4.5 tonnes of adhesive - believed to be the largest amount of adhesive ever used for a single application.

The whole operation was successfully completed within the specified time of 12 weeks.

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Formulated Resins Ltd
Unit 3, Malbern Ind Est,
Greg Street, Reddish
Stockport, SK5 7BX, UK
Tel: 00 44 161 480 2121
Fax: 00 44 161 480 4445

© Formulated Resins Ltd 2004

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