Sika Wraps Up Town Ham Viaduct

The SikaWrap Strengthening System has been extensively used on the refurbishment of Town Ham viaduct.

The SikaWrap Strengthening System has been extensively used on the refurbishment of Town Ham viaduct, which was constructed in 1972 to carry the A417 over the River Severn flood plane and the rail link between Gloucester and Lydney.

This £1.5 million project is part of the Gloucester South West by-pass, currently being constructed by Norwest Holst.

Failure of the drainage systems and deck waterproofing had allowed the ingress of water and road salts, resulting in extensive spalling and delamination of the concrete columns, and high chloride levels.

A decision was taken on economic grounds to upgrade rather than demolish the bridge, with all design work being carried out by Halcrow, Gloucestershire County Councils term consultant engineers.

A number of columns had to be demolished, but many were saved using the SikaWrap system.

Specialist contractors, Laser Special Projects were employed to carry out all specialist works.

Seventeen of the supporting columns required strengthening due to the effects of bursting forces caused by the bearing support plates.

Sika Limited were able to offer a solution with their SikaWrap 103C, a wet wrap carbon fibre based structural strengthening system, which was applied in three layers to the top metre of the affected columns.

The wet wrap application method allows thicker fabric to be used which gives a higher tensile strength than conventional, thinner dry wrap systems, thus reducing the number of wrap layers required.

Other strengthening works involved the application of Sika Carbodur pultruded carbon fibre plates to the top of the cantilever section of the bridge deck.

This was to improve bending capacity on cantilever to allow the installation of containment parapets.

General concrete repairs to the spalling and delaminating areas was carried out using Sika concrete repair mortars.

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