A massive 375-metre-long incrementally launched bridge over the Usutu River, the Siphofaneni Bridge is an infrastructure development that has transformed the lives of communities in eSwatini. The bridge forms part of the 23 km St Phillips Road upgrade project, which was undertaken with the support of the European Union to reduce transportation costs for sugar farmers in the country.
There are three bridges across the Usutu River downstream of the new one, two of which are single-lane low-water structures. The third, a high-level bridge, is approximately 30 km downstream, which the community would have to use in the past, during flooding of the river.
Zutari was commissioned to carry out preliminary and detailed design, and to provide assistance with tender evaluation and construction supervision for the project.
The width and nature of the Usutu River, the largest in the country, meant that a formwork structure could not be used to build the bridge, and an incremental launch construction method was chosen. What made the Siphofaneni Bridge different from typical incrementally launched bridges was the use of reinforced concrete instead of concrete post-tensioned with concentric cables for the launch phase.
The conventional method of building bridges follows the principle that the concrete should not be allowed to crack and tensioned concentric cables are used to prevent cracking in the concrete. It requires the services of a specialist subcontractor coming to site weekly for several months to install and stress the cables. Such a service is expensive and rare when working on remote sites.
The cost-effective solution adopted by Zutari was to go against convention and allow the deck concrete to crack in the construction stages by using reinforced concrete.
“It is humbling to be part of a project that is not only technically excellent, but will help the people of eSwatini for years to come”
The cost-effective solution adopted by Zutari was to go against convention and allow the deck concrete to crack in the construction stages by using reinforced concrete. A specialist subcontractor was only needed once the deck was in place, to close all cracks with final stage post-tensioning.
The new bridge, which was officially inaugurated in June 2017, has a large impact on the region’s community, as well as the country’s economy. School children and local people use the bridge to access schools, shops, and clinics. Farmers can safely transport their sugar cane to the mill across the river, even during times of flooding.
“It is humbling to be part of a project that is not only technically excellent, but will help the people of eSwatinid for years to come,” said Louis Steyn, Zutari Professional Civil Engineer.
The project won the Most Outstanding Project in Structural Engineering award at the 2017 South African Institution of Civil Engineering (SAICE) Awards.
*The Aurecon Africa business has been officially renamed Zutari as at 21 July 2020. Zutari acquired Aurecon Middle East on 20 November 2020.