Olifants River Bridge

Enhancing the N7 crossing with an innovative bridge design that combines traditional arch forms with modern materials and construction techniques.

Client

South African National Roads Agency Limited (SANRAL)

Project date

2013

In 2013, SANRAL appointed Zutari to improve the Olifants River Bridge and associated works on National Route 7, Section 4 (N7/4), from Km 47.1 to Km 48.9. The N7 is a vital economic link between South Africa and Namibia, supporting both tourism and freight transport.

The opportunity

The existing road faced challenges including limited pavement structure, substandard horizontal and vertical curves, steep grades, and a narrow cross section, which could not accommodate increasing traffic volumes. A major constraint was the existing bridge over the Olifants River, which lacked sufficient horizontal clearance and structural capacity to support heavier traffic if the road were widened. The only feasible solution was to re-align the road over this section, requiring a new bridge adjacent to the existing structure.

What we did

The existing bridge spans the main waterway with an arch of nearly 100 m. The new bridge adopts a similar arch form to maintain aesthetic continuity and improve functionality. A continuous deck with integral piers minimises high-maintenance items such as expansion joints and bearings.

The design required careful balancing of contradictory requirements. Piers had to be large enough to resist vertical loads from the deck while remaining slender to avoid attracting excessive horizontal forces. For the shorter piers supported on the arch, a concrete hinge detail was introduced at the top, a technique developed 120 years ago, to reduce stiffness and design moments.

The project also prioritised community involvement, employing all required unskilled labourers locally and implementing several skills training programmes. This approach maximised the number of skilled individuals available for future projects.
The bridge combines an ancient structural form with modern materials and analysis techniques, resulting in an aesthetically pleasing and functional structure.

The outcome

The new Olifants River Bridge successfully improved traffic flow and safety on the N7. The project reduced maintenance requirements, enhanced structural capacity, and provided long-term benefits to the local community through skills development and employment.

The project demonstrates how thoughtful design, engineering innovation, and community engagement can come together to deliver a landmark infrastructure upgrade with lasting impact.

“The Olifants River Bridge uses an ancient structural form in an innovative way, making use of modern materials and analysis techniques to provide an aesthetically pleasing structure.”

Hennie Niehaus

Zutari Project Controls Manager

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