Construction World January 2023

A view over the South pylon.

A view from the South pylon across the Msikaba Gorge to the North pylon.

are well-known for making aesthetically pleasing bridge structures and Msikaba is no exception. As Savage says, “The bridge, which will accommodate a dual two-lane carriageway, has an extremely slender design which will make it very pleasing on the eye. Moreover, it does not disturb in any way the natural environment of the gorge.” The bridge is being built from both the north and south banks of the gorge and comprises two identical ‘halves’, each spanning 290 m, which will meet mid-point over the gorge. Each half is supported by 17 pairs of cables attached to 127 m high inverted Y-shaped concrete pylons, one on each side of the gorge, which are essentially tapered circular shafts that straddle the roadway by means of inclined legs. The pylons are back-stayed into the anchor blocks by 34 pairs of cables – 17 for each half – which are positioned 130 m behind each pylon. Commenting on progress on the project thus far, Savage says that an important milestone was reached in April 2022 when the south pylon legs were hydraulically jacked apart. These two legs make up the first 20 m of the pylon and were built without any lateral support as free cantilevers. The jacking apart of the legs countered the bending moment at the bases of the cantilever structure placing them into a ‘straight’ position before they are joined together. With both pylon legs and the bifurcation section above the legs now completed, the focus is now on the construction of the pylon spires and the first lift on the south spire started in November 2022. The JV is utilising a custom-designed 15 m high climbing formwork system for spire construction. This provides four levels for concrete, fixing, curing and cleaning. It

Steel fixing of the bifurcation lift soffit slab in October 2022.

A bird’s eye view of the steel fixing on the bifurcation lift soffit slab.

31 CONSTRUCTION WORLD JANUARY 2023