Curves make for faster erections

The electrification of the Great Western Railway from London to Cardiff is aiming to improve reliability of the service and increase passenger capacity by 20%. One of the key components of the scheme will be provided by Barnshaws Metal Bending, which is supplying a number of anchor booms which are required to support the overhead cables.

Network Rail aims to use a high output plant system that will allow a more efficient installation system with minimal disruption to the rail network. This depends on all the materials that are required for each shift being ready and available on time. It also requires those components to be exactly as specified so that installation can be completed on time.

Anchor booms are used to support the overhead electrical cables that power the trains and they come in two basic designs, gantry and cantilever. The gantry style is slightly more complicated since there is an increased static load as well as the potential for higher wind loading. These have to be taken into consideration when designing the new components, along with the considerable specification list required by the rail industry.

Although they appear to be a simple support structure, in fact they are both kinked and cambered to provide additional strength. Previously the steel sections were cut to length and then welded together to provide the offset at each end of the booms.

In the past these booms were imported from Europe as IPE sections and the fabricator had to cut and weld each boom four times in order to achieve the correct shape for the finished boom section. By discussing the design requirements with Barnshaws, the fabricator was able to simplify the manufacturing process and make the product more cost effective.

Andy Tura, Structural Steels Team Leader, Barnshaws, comments: “We explained that it was possible to bend the IPE sections and achieve the same end results but without the need for any cutting or welding. The finished beam would have the required offset at each end as well as the slight camber as dictated by the specifications. Furthermore, we could deliver this for any length up to 23 metres, which would be sufficient to span the tracks for this part of the project.

By meeting the specification for the anchor booms through bending, rather than welding, Barnshaws was able to reduce the fabrication time as well as remove the welded joints in the beam and any associated heat stress that may have been induced.

For this particular contract Barnshaws delivered approximately 100t of kinked and cambered beams, all of which had to be delivered to meet the demanding schedule so that they could be installed within the specific construction windows.

The work between London and Bristol, including Newbury and Oxford is scheduled to be completed by 2016, with the route to Cardiff electrified by 2017.