Low operating costs, easy maintenance and minimal disruption to train services were important considerations in the project to replace the life-expired but vital footbridge at Thornaby Station, UK. The solution was a slimmer and lighter bridge in which GFRP composite in particular played a decisive role.

A slimmer design and lightweight GFRP bridge deck meant that the overall weight of the bridge itself could be reduced, allowing the contractor to reuse the existing substructure and save significant capital costs.

Daniel Barnes, CEng MICE, Site Agent, Balfour Beatty UK:
"I had estimated that to fully demolish all the stone/brick piers and rebuild in steel, most likely with piled foundations, would have added £300,000 to the project. By making the new bridge steelwork weigh less than the existing construction through slender design of steel and using GRP, the bridge was allowed to sit on the existing stone/brick structures."

The existing steel bridge, dated back to 1895, was in poor condition due to corrosion, cracked masonry and even World War II bullet holes. But as the bridge is central to the town - it ties together old and north Thornaby - complete demolition was not an option.

Prestigious award

The new bridge won the prestigious ICE Robert Stephenson Award in the 'Medium Projects' category, among other things for the engineering work behind the project. Presenting the award, the judges said that Thornaby Station footbridge was: "An impressive project in which a close knit, quality based Partnering Team developed a scheme which met immovable deadlines yet was sympathetic to both residents and the built environment. Innovative design and construction solutions enabled the scheme to be delivered safely, on time and under budget." (www.ice.org)

Both the substructure and handrail are painted in an eye-catching blue, thereby creating an attractive as well as a safe way for station users to cross the busy railway.

Tight installation window

Thornaby is a busy station, which meant that the installation work had to be performed in a tight window of just six hours when train services would not be disrupted. Here too the light weight of the bridge decks was a distinct advantage as the decks could be lifted into position manually and machined on site using ordinary hand tools.

Quality and documentation key factors 

Fiberline is the world's only producer of abZ-approved structural profiles of pultruded GFRP, and can therefore document consistent product conformity with proven high quality. Safety is naturally a priority where construction of public bridges is concerned, and the decision to use a Fiberline bridge decks was a logical choice for the customer.

Extreme rigidity and long life

The new footbridge at Thornaby Station is a hybrid design with a steel substructure and GFRP bridge deck. The GFRP planks are corrosion and maintenance-free and thereby provide lasting watertight protection for the steel substructure, thus extending the service life of the bridge as a whole.

Christian Scholze, Technical Solution Manager at Fiberline:
"With a hybrid bridge you get an extremely attractive solution that unites the best qualities in each material at a competitive overall price. In this case, the rigidity of steel combined with the durability of GRP."

In addition, future operating costs are reduced as the bridge deck is resistant to both weather and salt impact and requires no maintenance.