New milestone for South African bridge

The Msikaba Bridge project in South Africa has reached a new milestone as the legs of the bridge’s south pylon have now been hydraulically jacked apart.

The stay cable bridge will span the 198m deep Msikaba Gorge (Photo: Concor Construction)

Once completed, four lanes of vehicles and a pedestrian walkway on either side will pass beneath the legs.

The 580m stay cable bridge on the new N2 toll road between Port Edward and Umtata forms part of a Wild Coast project by the South African National Roads Agency Limited (SANRAL) and is under construction by the CME JV (joint venture) – a partnership between Concor Construction and MECSA Construction.

“These two legs make up the first 20m of the inverted Y shaped pylon,” says CMEJV project director Laurence Savage.

“The jacking apart of the legs countered the bending moment at the bases of the cantilever legs. In layman’s terms, the jacking eradicated the effect of the legs bending towards each other; as engineers would see this, the legs are effectively vertical due to the jacking process.”

The Msikaba bridge includes two pylons that will stand 128m high on each side of the gorge. The pylons will support the bridge deck using a network of 34 cable tendons strung through their upper reaches.

“These cables then run from the top of the pylons back into anchor blocks located 100m to the rear of the respective pylons,” adds Savage. “Each of the four anchor blocks is made up of over 1,600 tons of structural reinforced and mass concrete and extend 17m – the equivalent of six storeys of a building – into the ground.”

The preparation for the jacking took three months of planning and analysis, while the setup was conducted over nine days with the jacking process being complete in less than eight hours from commencement.