Sika CarboDur carbon-fibre plates were recently used to strengthen a service subway that carries both power and signal cables for the District and Circle Lines on the London Underground.
Metronet Rail SSL chose this innovative solution to upgrade the hundred-year-old subway, originally constructed using two main cast-iron OI beams with a cast iron plate spanning between them. The simplicity of using the light weight Sika CarboDur structural strengthening system allowed the work to be carried out during normal engineering night time hours, avoiding weekend possessions and disruptions to train services.
The Sika CarboDur Strengthening system used in this project comprised both pultruded and pre-preg carbon fibre plates, of various sizes and thickness, and a specially formulated cold cure, two-component epoxy adhesive.
Sub-contractors CRL vacu-blasted the underside of the cast-iron plate and OI beams to provide a suitable surface for the application of the SikaDur 30 structural adhesive.
Four Sika CarboDur DML plates, five millimetres thick and nine metres long, and specifically manufactured for this application using ultra high modulus carbon fibre, were bonded along the main cast iron beams. Smaller pultruded, lower modulus CarboDur CFRP plates were bonded to the underside of the cast-iron plate spanning between the cast iron beams to give extra strength.
The Sika CarboDur system is well established for such projects as strengthening the floors of buildings as well as bridges, and this is the most recent of many projects in it’s use to strengthen metallic structures for London Underground.
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