The 177.5 m Blackburn Pedestrian Bridge is one of the longest cable-stayed pedestrian bridges in Africa. Coupled with its uniquely shaped pylon and aesthetic lighting, the structure is a landmark project in South Africa.
The project was constrained by two rigid deadlines: the FIFA 2010 World Cup and the opening of the new King Shaka International Airport. Even minor oversights could have caused extremely costly delays.
Bridge deck dynamics - Built-in wind-resistance
The long span solution required serious consideration of the bridge deck dynamics. Past lessons learned from wind-induced galloping at the Tacoma Narrows Bridge and footfall-induced side sway at the London Millennium Bridge were taken into account.
A wind-expert was consulted to ensure there were no site-specific wind-related issues. Potential for the deck shape to contribute to deck sway or resonance and pinging in cable stays were investigated along with footfall-induced vibrations, vertically, laterally and torsionally using 2D and 3D models.
Both South African codes and developing international structural design concepts were consulted to ensure a stable bridge deck. The detailing also required technical expertise and careful attention to detail. The protection to the cable stays are a critical element as the loss of support through vandalism or terrorism could cause the collapse of the bridge.LED aesthetics - Lit up for longer
Because of the unique nature of the bridge, both safety and aesthetic lighting were designed. The final scope of works comprised the installation of cutting edge LED lighting which provided both safety lighting and decorative lighting. The benefits of the LED lighting was a reduction of electrical consumption costs to 10% of the original proposal and an increase in the expected life of some of the larger globes from 900 hour to 20,000 hours.