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Building bridges: Engineering charity chief on how UK firms can help

A key figure at a US engineering charity that has set up in the UK has spoken to NCE about the important work the charity does and how companies here can get involved.

Ian Firth, chief operating officer at consultancy Flint & Neill, is also trustee at charity Bridges to Prosperity, which works in developing countries to connect rural communities to vital healthcare, education and economic opportunities.

“The UK arm will facilitate tax-efficient donations to support the vital work that Bridges to Prosperity does with poor rural communities around the world, building bridges to provide much-needed access across impassable rivers,” he said.

The charity asks companies to donate $50,000 (£33,000) and lend 10 volunteers for two weeks to help build a bridge. The employees are expected to pay their own flight, accommodation and other costs while they are there, and they work alongside charity staff and local community members to build the bridge.

“$50,000 buys the bridge and all the services that are needed to get it built,” said Firth. “However, the cost can be split between companies if required.”

Flint & Neill and Balfour Beatty are co-funding and co-staffing a bridge project in Gaseke, Rwanda, in July this year.

Firth said that despite all the costs involved for employees, the opportunity to carry out the work was extremely popular.

“We had 20 applications for only fives paces,” he said.

There are two basic types of bridge which the charity uses, according to Firth: a simple suspended bridge for when the river banks are high enough that the centre of the span remains above flood level, and a suspension bridge which is used where flood water inundates the banks and the deck has to rise above it.

“The design is done by Bridges to Prosperity in the US. They’re a standard design which has been developed,” he said. “The span and the local conditions vary but the basic principles are the same.”

London-based Arup senior structural engineer Kayin Dawoodi is a trustee and a technical advisory board member for the charity and has worked to develop a design tool that tailors the basic bridge design to the local conditions and technical requirements.

Firth said the engineers helped with the more complex aspects of the construction of the bridge and in return got a sense of empowerment that can be hard to get in the normal working environment.

“With some of the technologies involved with the erection of the towers – stressing of the cables, working at height and using harnesses and other safety issues – there are some skills that won’t normally be experienced by the local population,” he explained.

“But also it gives the volunteer company something meaty to get their hands on. It gives the staff a fantastic opportunity to learn what it’s like to work in that kind of environment.”

To find out more about how you can get involved, contact info@bridgestoprosperity.org.

Bridging the gap

Two types of bridges are used by Bridges to Prosperity: a suspended bridge and a suspension bridge.

The charity has agreements with companies who supply cables and bridge components to use surplus materials at reduced cost. Companies such as Hilti have supplied tools to the areas to aid the construction process.

The design life of the bridges depends on the location as conditions can often be hot and humid, causing corrosion or degradation of the secondary elements. However, the structures have been known to be used for 12 years and with proper maintenance the life could be extended. An important element of the design is the scour protection of the foundations to ensure that the bridge is not undermined during its life.

Suspended

This is a basic bridge with typically four steel cables sharing the loads. Construction of the foundations and anchor blocks, the termination point for the cables on either side of the bridge, is completed prior to the volunteers arriving on site. The upper cables pass over the small towers on concrete saddles, with bent bar hangers connecting the lower cables to form the deck. A chain link fence infills the panels. Steel cross beams between the lower cables support the timber boards.

Suspension

Cross section through suspension bridge

Cross section through suspension bridge

This is used where there is a risk that the river will flood and the deck is required to be higher above the water level. The bridges have a steel tower made out of pipe on either side of the river, whose height depends on the span. Two main cables made up of typically two or three strands pass over the towers and are suspended between the supports. The deck is then hung from the main cables. Erection of the towers is done with ropes and cables, using a Tirfor (portable manual hoists) or manual winch. The bridges typically span 50m to 80m but can be up to 120m long.

Building bridges: Engineering charity chief on how UK firms can help

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