Tube beams set for strength test

Structural refurbishment work could win spin-off benefits from aerospace technology if tests for London Underground starting in a few weeks are successful.

Next month's static tests of the carbon fibre resin beams will be followed in November by dynamic loadings. The full-scale 7.8m long beams will be tested to destruction to examine their fatigue and durability performance before the designs are used in practice.

The lightweight beams are being developed for London Underground's structural replacement and strengthening work by a six-partner group backed by the Department of Environment, Transport and the Regions. The partners are: LU; Devonport Marine; the University of Southampton; the Defence Evaluation and Research Agency; Structural Statics and MSL.

In a second research project, the group is investigating how to use carbon fibre units to brace retaining walls, strengthen steel and cast iron beams, and strengthen masonry parapets. The University of Southampton's project leader, Dr Stuart Moy, said the aims "are all LU related but have wide application within the construction industry".

Moy said that the ultimate goal of the project is to create a design system to apply carbon fibre technology in beams.

The new 500kg carbon fibre beams are made by using vacuum suction to pull resin into the mould of the carbon fibre matrix. The lightweight units have been manufactured full-scale because "we can avoid scaling issues in design," said Moy.

The key dimensions of the full-scale units are their 1.5m width by 500mm depth. The dimensions for the test beams came from LU's needs in replacing beams in tunnels and stations, which should mean replacement work is easier for contractors working in confined spaces or where machinery cannot gain access.