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N2 Wild Coast Toll Road megabridge projects, South Africa – update

An image showing off-loading of the second box girder for the South Bank segment zero at the Msikaba bridge

An image showing off-loading of the second box girder for the South Bank segment zero at the Msikaba bridge

Photo by Sanral

13th January 2023

By: Sheila Barradas

Creamer Media Research Coordinator & Senior Deputy Editor

     

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Name of the Project
N2 Wild Coast Toll Road (N2WCTR) megabridge projects.

Location
The bridges will be built over the Msikaba and Mtentu river gorges, both near Lusikisiki, in South Africa’s Eastern Cape province.

The Msikaba bridge is located on the N2, which connects the Western Cape, Eastern Cape, KwaZulu-Natal and Mpumalanga provinces, and traverses the cities and major towns of Cape Town, George, Gqeberha (formerly Port Elizabeth), East London, Mthatha, Durban and Ermelo. This includes a new greenfield section of 112 km between Port St Johns and Port Edward, including the two megabridges and several additional major river interchange bridges.

Only the new greenfield section of the project will be tolled. None of the sections between East London and Mthatha or between Mthatha and Ndwalane, near Port St Johns, will be tolled. The public participation process for the tolling of the greenfield section of the road is yet to start.

Project Owner/s
South African National Roads Agency Limited (Sanral).

Project Description
The Msikaba and Mtentu bridges form part of the N2WCTR project.

The 580-m-long Msikaba bridge will be the longest main span bridge in Africa – constructed using the cable-stayed method – and the second-longest main bridge span in Africa after the Maputo-Catembe suspension bridge, in Mozambique. With a deck height of 194 m above the river valley, Msikaba will become the third-highest bridge in Africa and the 133rd-highest in the world. The Msikaba bridge cable-stay design will ensure that the construction of the bridge will have no direct impact on the pristine gorge environment almost 200 m below, which is one of the environmental requirements in building the bridge.

The 1.13-km-long Mtentu bridge, which includes a 260-m-long main span, will be one of the longest main-span-balanced cantilever bridges in the world. Only ten prestressed concrete girder bridges worldwide have a main span of 260 m or longer. Reaching heights of more than 220 m above the river valley, it will displace the Bloukrans bridge, in the Western Cape, as the highest bridge in Africa and the southern hemisphere. The 141-m-tall Pier No 9 (equivalent to a 40-storey building in height) will also be the tallest bridge pier in Africa and the southern hemisphere.

Being one of the longest main-span-balanced cantilever bridges and one of the highest bridges in the world makes the construction of the Mtentu bridge a technically highly challenging project. The remote location and local social dynamics add to this complexity.

Potential Job Creation
So far, the Msikaba project has created work for 137 unskilled local labourers and 372 jobs for skilled persons, of whom 190 are locals.

Capital Expenditure
The Msikaba bridge project will cost an estimated R1.65-billion and the Mtentu bridge project R3.5-billion.

Planned Start/End Date
The N2WCTR project started construction in 2011. However, the major greenfield portion of the route between Port St Johns and Port Edward started construction only in 2016.

Construction of the Msikaba bridge is expected to be completed at the end of 2024.

Provided that there are no significant delays on the Mtentu bridge project, the construction period is estimated to be 49 months, including a four-month mobilisation period.

Latest Developments
Work has started on the Msikaba bridge deck.

“The pier includes its major foundations to support the downward pressure from the cables, as well as the abutment and gallery next to the piers, this is where the deck starts and is joined to the base of the pier,” Sanral N2WCTR project manager Craig McLachlan says.

“The two massive anchor blocks on each side, each half a soccer field long and buried four storeys into the ground, all must be substantially complete before work on the deck extending out over the gorge can start,” he explains.

The second segment will be transported from Mpumalanga to Msikaba this January.

The entire deck comprises 36 segments, with 18 segments on each side. Each segment comprises two box girders and two truss girders. It takes three trucks to transport each segment and, in total, it will take 108 truck delivery trips, including four abnormal loads for the four boxes for segment zero at North and South sites. 

Segment zero on each side is not connected to any cables but is attached to the abutment and supported from below until it is connected upward to Segment 1. Segments 1 to 17 on each side each have two cables (attached one on either side). Each box segment will be supported or held up by these two cables leading up to the 127-m-high pier with two corresponding cables connected back down to the anchor blocks.

“With the exception of segment zero, which can be assembled in situ, each segment will be assembled on the bank, then carried between the legs, launched out above the gorge, rotated 90°, brought back and attached to the proceedings segment, or for the first segment to the embankment.

“The segment then has two cables attached, one on each side. The cable is attached to the spire and another corresponding set attached to the anchor block. A thin steel and concrete composite deck is then cast. The process is repeated till the decks meet in the middle,” McLachlan outlines.

All steel used to manufacture the material for the deck is 100% South African.

The deck segments are being built (cut and welded) in Middelburg, Mpumalanga.

The first four big boxes will be transported using abnormal loads, but the girders and remaining boxes can be delivered using normal trucks.

When joined together, the two large boxes on each side of the deck segments will form two separate 290-m-long box girders that provide the longitudinal support and stiffness for each half of the bridge. This means there will be a joint at the midpoint of the bridge so each half of the 580-m-long bridge is an independent structure.

The smaller truss girders linking the boxes are stiff compound steel structures that provide the main cross support between the longitudinal box girders and provide twisting stiffness or rigidity.

Together, the longitudinal box girders and cross truss girders form a very large ladder shaped steel structure upon which the (combination steel and reinforced concrete) deck plate lies and upon which the four-lane highway will run.

Key Contracts, Suppliers and Consultants
Concor Mota-Engil, a joint venture between Concor Construction and MECSA Construction (Msikaba bridge contract); HVA Joint Venture (Msikaba and Mtentu bridge consultants comprising CH2M and SMEC); V3 Consulting Engineers (lead consultant – Ndwalane to Ntafufu and Kulumbe to Mtamvuna river); ERO Engineers (lead consultant – Ntafufu to Bambisana turn-off); Naidu Consulting (lead consultant – Bambisana turn-off to Lingeni); Aurecon Rohm consortium (lead consultants – Lingeni to Msikaba); Knight Piesold (lead consultant – Msikaba to Mtentu); and KBK Engineers (lead consultant – Mtentu to Kulumbe).

Contact Details for Project Information
Sanral project manager Craig McLachlan, tel +27 41398 3200 or email MclachlanC@nra.co.za.

Edited by Creamer Media Reporter

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