News: Eadon selected for Swedish bridge project

Following on from their success on the Humber Bridge, Rotherham-based design experts at Eadon Consulting have again been employed by C Spencer Limited to design gantries for the Älvsborgsbron in Gothenburg.

Eadon Consulting were the designer of the high level platforms required to carry out the majority of the works for the Humber Bridge Main Cable Dehumidification Project by C Spencer Limited. The movable gantries acted as a working platform to allow the main cables to be heat sealed in a polymer wrap along their entire length.

At just 933m long, the Älvsborgsbron is on a different scale to the Humber Bridge but presents its own particular challenges with respect to the design of the gantries.

The most noticeable difference between this and other suspension bridges is that the side spans of the bridge are viaducts so there are no hanger cables supporting the deck below and more importantly, not providing sideways support to the gantries in the case of storm winds.

Unlike other larger suspension bridges that Eadon staff have worked on, which have thousands of parallel wires making up the main cable, these cables are made of 85, 55mm diameter locked coil wires.

The projects are a pro-active move to prevent wire deterioration. Dry air is introduced into the steel cables to drive moisture out of the voids between the individual wires and reduce the level of humidity to below that which corrosion occurs. Work involves wrapping the cables with a polymeric material to form an air and water-tight sealed environment.

To make the cable section, round aluminium extrusion packs are laid around the outside of the cable which are secured by 4mm diameter wire wrapped tightly around the full length of the cable. Careful consideration has to be given to the gantry supports bearing on the cable in order not to cause damage.

Two gantry designs will be used on the Älvsborgsbron, one type on the main span and another on the side spans. The gantries are due to be installed in March 2011 with the main cable dehumidification project due to be completed before the winter.

Based on the Advanced Manufacturing Park (AMP) in Rotherham, Eadon Consulting is an engineering design consultancy working across a number of sectors, with expertise in mechanical, control, hydraulic and structural design.

Eadon Consulting website

Images: eadonconsulting.co.uk