Msikaba Bridge
The Msikaba bridge is a cable-stayed bridge, currently under construction, spanning the Msikaba River, near Lusikisiki in the Eastern Cape Province of South Africa. The bridge forms part of the N2 Wild Coast Road (N2WC) project, which aims to improve the travel time between Durban and East London for light and heavy freight vehicles.


Earmarked as one of the government’s strategic infrastructure projects, construction is already proving its worth through the promotion of economic activity, community development, service delivery and job creation at both a regional and provincial level. President Ramaphosa visited the site in September 2021, stating that the project would generate between 21,000 and 28,000 indirect jobs during construction and 8,000 direct full-time jobs once completed.


SMEC was appointed as the lead partner in the HVA Joint Venture to oversee design and supervise construction.



One of the key aspects of the bridge is its two identical, inverted Y-shaped, reinforced concrete pylons. Each of the 127 m tall pylons comprises two inclined legs, straddling the roadway below, and a tall cylindrical spire. The spires have a diameter of 6 m at the bifurcation, where the two legs meet, tapering to 4.5 m at the top. Anchored into each pylon are 17 pairs of main stay cables (connected to the deck) and 17 pairs of back stay cables (anchored 130 m behind the structure).


Grouting trials for anchor blocks

Pre-stressing grout trials were also a vital part of the construction verification process. Full-scale grouting trials were conducted on site to ensure high quality bonded tendons and the durability of structure. The longest tendon was simulated with the maximum curvature and steepest incline to test the equipment, methodology and operators.


The anchor blocks are 49 metres long, 10 metres wide and 17 metres deep, containing over 5,980 m3 of concrete, weighing approximately 15,500 tonnes. Each group of back-span cables are anchored in a buried concrete gravity anchor. U-shaped prestressing tendons extend the full depth of the anchor blocks to provide structural capacity to activate the full deadload of the anchor blocks. The anchor blocks unique shape provides maximum interlock with the in-situ rock mass, ensuring maximum efficiency in lateral bearing capacity to resist tension from the stay cables.


Composite deck

The composite deck, spanning 530 m and supporting a dual 2-lane carriageway, comprise of two box girders connected by transverse truss like cross frames. The deck is simultaneously constructed from both banks, each side comprising of 17 deck segments typically 15 m long. The composite steel and concrete deck of the main bridge is 22.8m wide and includes foot walks to the outer edges of the deck.


The composite deck is highly flexible and structurally indeterminate. An analytical model was created with more than 300 stages to determine the erection sequencing and methodology. The erection engineering included a stay cable tuning exercise to optimise the force effects in the structure as well as the monitoring of displacement in each construction stage to verify the final deck profile.


Wind testing

The bridge design was subject to full wind tunnel testing to ensure the aerodynamic stability during the in-service condition. The Contractor was also required to undertake wind tunnel testing of the deck at various stages during construction.


Concrete thermal modelling and monitoring

Large volume concrete elements (Anchor Blocks, Pylon Bases, and Ladder Decks) were modelled to determine the maximum peak temperatures and peak differential temperature range needed to avoid any thermal cracking. Thermocouples were then installed into the concrete to monitor temperatures during the hydration process. SMEC closely monitored the concrete hydration process to ensure tensile stress remained within the range of the approved temperature gradients.


deck span
of earthworks cut

Temporary work solutions to fast-track construction

The remoteness of the project as well as the logistics of travelling from the northern side to the southern side – a three-hour drive – means that a cable way has been installed as part of the temporary works. A mono-rope cable system, equipped with a six person cabin is being used to transport people and small amounts of material from one side to the other. The cable car takes only eight minutes to traverse the gorge resulting in a significant time saving for all crew on site. The project has also been aided by an agreement between the South African National Roads Agency (SANRAL) and the Magwa Tea Estate, the biggest tea estate in the Southern Hemisphere. Magwa has provided 8ha of land for the Engineering teams accommodation camp which houses the majority of SMEC’s site staff.

Structural health monitoring system

A structural health monitoring system was installed to monitor the bridge in its permanent state. The system comprised a modular design, which could be expanded, if required.  Data sensors included Static Strain Gauge, Thermistors, Stay Vibration sensors, Biaxial Accelerometers, Tilt Meters, Displacement Transducer, Anemometer as well as various weather sensors. A GPS was installed at the top of the pylon structure to monitor real-time movement and the impact of temperature gradients.


The support pylons reach heights close to 85 m and held by four anchor blocks, completed at the end of 2023. Erection of the complex deck is scheduled to start in the second quarter of 2024. Once complete, the route will be 69km and 85km shorter than the current N2 and R61 routes, respectively, and, owing to its shorter and flatter alignment, between 1.5 to three hours faster for light and heavy freight vehicles.


Talk to one of our specialists about our role on the Msikaba Bridge Project.