Construction of the Msikaba Bridge near Lusikisiki in the Eastern Cape – which started in earnest in late 2019 – is advancing steadily and the project should be complete in the last quarter of 2024. The Msikaba Bridge, which will span the 198 m deep Msikaba River gorge, forms part of the South African National Roads Agency Limited’s (SANRAL) N2 Wild Coast project and is being constructed by the CME JV, a partnership between Concor and MECSA, both 100% black owned Grade 9CE South African construction companies.
The bridge’s four huge anchor blocks are now at a very advanced stage of construction, over 50 % of the concrete for the bridge’s two 127 m high pylons has been poured and the complex deck construction phase of the project is about to start.
The project is also maintaining its impeccable safety record. It recorded 3 million Lost Time Injury (LTI) Free hours on 21 October 2022, a major achievement given the challenges that construction presents, including working at both at extreme heights and at depths of up to 20 m in excavations.
Commenting on Msikaba, Concor’s Laurence Savage, who is project director, says the cable-stayed bridge – which he describes as “iconic” – is probably the most complex structure of its type ever to be built in South Africa and probably in Africa.
“At 580 m in length, it will the longest cable-stayed bridge – in terms of main span – in Africa and it will have the second longest main span of any bridge on the continent. At 192 m above the floor of the gorge, it will also rank as one of the highest bridges in Africa, only exceeded by the Bloukrans Bridge at 216 m and, once it is completed, Mtentu at 223 m,” he says.
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. The pylons are back-stayed into the anchor blocks by 34 pairs of cables – 17 on either side of the gorge.
With the anchors blocks approaching completion and the legs of the pylons – which make up the first 20 m of the pylon structures – already complete, the focus of the project going forward will be on the construction of the circular pylon spires and the composite steel and concrete bridge deck.
The spires taper from a diameter of 6 m at the point where they start (the top of the inclined legs) to 4.5 m at their full height. To construct them, the JV is utilising a custom designed, four-level, 15-m high climbing formwork system. The pylons are both expected to be fully complete in September 2023. Construction of the bridge deck is an exercise which has to consider the significant wind loads that can sometimes occur at the site, where winds can gust up to 80 km/h.
The first 24 m of the deck on either side of the gorge is a reinforced concrete ladder deck that is cast into the first steel deck segment, known as deck segment zero- DS0. Because of crane access restrictions, DS0 will be slid laterally into place before reinforcement is installed and concreted. The remaining segments, DS1 through to DS17 on either side, will be installed using the free cantilevering method, with each segment being installed in sequence.
To place the deck segments in position, two gantries will be used, one on either side of the gorge. These are large 160 ton assemblies, each roughly the size of a tennis court in surface area. They will launch the deck segments – which have an average weight of 84 tonnes – out over the gorge and then rotate 90degrees, lower, align with and then connect them with the previous segments. Closure at the mid-point of the deck is expected to be achieved in Q2-2024.
An interesting aspect of the project is the close ties that have been forged by the CME JV with local communities. “We have worked very hard – and at considerable cost – to ensure that the project has the full support of surrounding communities and that the benefits stemming from construction are localised to the greatest extent possible,” says Savage.
Not only has the CME JV recruited about 70 % of its workforce locally – all of whom have been subjected to intensive on-site training – but it has also identified and supported a host of local SMMEs, around 40 in all, who have been appointed as sub-contractors and suppliers.
A view from the South pylon across the Msikaba Gorge to the North pylon.
The South area preparing for the arrival of the deck segment in November 2022.
Preparation for the deck segments.