R21/N1 Incrementally Launched Bridge, South Africa
Tshwane's “flying saucer” interchange
A 240 m long incrementally launched bridge provides a directional ramp joining the R21 North to the N1, and forms part of the Gauteng Freeway Improvement Project. The bridge spans eight existing carriageways and was constructed without any disruption to the traffic below.
A special requirement was for the geometry of the bridge to follow an exact circle in space. Aurecon’s design solution included using long constant section circular piers for aesthetic and clearance reasons.
An aesthetically pleasing structure has been realised through the innovative use of reinforced and prestressed concrete, and the resulting bridge is an asset to South Africa’s road network. The launched composite deck consists of an open steel box girder with a concrete slab on top.