The pylon spires of South Africa's Msikaba Bridge mega project are on their way up, soon to be almost 130 m high at each side of the deep river gorge. (Image source: Concor)

Concor Construction the contractor for the Msikaba Bridge in South Africa, has indicated that progress is continuing to be made on the project and they are now entering a highly technical phase

The erection of the bridge is part of the South African National Roads Agency Limited’s (SANRAL) N2 Wild Coast Project and is being constructed by CME JV, a partnership between Concor and MECSA.

“The last two years have been spent completing the four 21,000 t anchor blocks and progressing the elegant bridge pylons on each side of the gorge,” explained Laurence Savage, project director of the structure. “We are now entering some exciting but technically challenging phases.”

The next steps include the post-stressing of the anchor blocks to ensure the transfer of load exerted by the stay cables is well distributed. Embedded 14 m deep into each block, the post-stressing is profiled as a large ‘U’ shape to mobilise the dead mass of the anchor block being pulled up by the stay cable at the top. The post-stressing option is a modern and efficient strategy that reduces the need for reinforcement steel, according to Savage. The locally procured post tensioning strand cables at each of the 17 anchor points in each block are stressed up to around 500 t by a specialist company. The process is expected to take two to three weeks for each anchor point.

“The next major step will be installing pylon inserts into the pylon’s structure as it rises above the 86 metre mark,” Savage continued. “There are 17 inserts for each pylon; these are steel rings weighing 8 to 10 t each, which are concreted into place one after the other until the pylon reaches a height of about 122 metres.”

The pylon inserts are used as the anchors from which the cables run as back-stays to the anchor blocks, and as fore-stays to the bridge deck. However, Savage noted that not all the inserts have to be in place before the launching of the deck can begin. Careful planning will allow the deck launching to commence after the first five inserts are installed, which is likely to be in the second half of 2024.

Beyond this, another demanding aspect of the bridge’s latest phase will be the construction of the ladder deck. Being the first steel deck segment of the bridge, the ladder deck is to be cast in concrete into the foundation of the pylon and will be the largest continuous pour on site.

“We will cast 700 cu/m of concrete in a single pour, with a very strong 65 MPa mix,” Savage concluded. “This will also demand a high density of reinforcement steel, weighing 160 t.”

Learn more about the impact the Msikaba Bridge project is having in South Africa in the latest issue of African Review.

According to Rokbak, knowing the capabilities and limits of your hauler puts you in control. (Image source: Rokbak)

Rokbak, a ADT manufacturer, has provided a guideline on how to become a successful articulated hauler operator

Get ready to move:
Take control of the hauler and the daily work before the ignition has been switched on by making sure the truck is known inside out. It is important to have a thorough understanding of the truck's controls, capabilities and limitations. This includes knowing how to operate it efficiently and safely in various conditions.

Check things over:
At the start of the working day, prestart checks are essential. A diligent operator conducts routine truck inspections to make sure the truck is ready for work. They should check for pre-existing damage including identifying leaks and loose parts, the tyre conditions, lights and beacons are fully operational, full visibility through the windows and fluid and battery levels daily. Rokbak trucks have ground level test points and a fully tilting cab for quick, easy access when servicing. A thorough equipment walkaround before starting a shift can make a big difference, and it does not require a lot of time.

Know the limits:
Learn the worksite boundaries such as speed, ground bearing weight limits, travel direction, passing areas, width and height restrictions and no-go areas. Know the hauler’s capacity and ensure the truck’s working limits with regard to payload are understood. Furthermore, keep an eye on how many buckets the loader is dumping in the truck to stay within the safe operating limits of the ADT and avoid accelerated component wear through overloading. Rokbak provides an optional onboard payload system and exterior payload lights, which indicate to both the truck and loader operators whether the payload is on target or overloaded. This information is recorded and transmitted via the Haul Track telematics system.

Safe operation:
Follow all site operating procedures when driving the truck. Keep under speed and under control on gradients and check grade guides for safe and controlled descent speed. Correctly use differential locks – employing them when the operation is in soft or slippery ground conditions to maintain traction and control. Be aware of what equipment is on the haul route and what sort of traffic will likely be encountered.

Correct usage:
The Rokbak RA30 and RA40 articulated haulers have fully enclosed multi-disc brakes on all six wheels plus a retarder to deliver safe, consistent performance. Understanding the correct use of the retarder can prolong the life of the service brakes and reduce maintenance intervals for lower total cost of ownership (TCO). If required, make use of the transmission lock in range or manual shift modes to maintain a steady ascent or descent on gradients.

Stay alert:
A safe ADT operator stays alert to their surroundings, including other workers, vehicles and obstacles on site. They anticipate potential hazards and adapt their driving accordingly to maintain safety for themselves and others. Inevitably there will be challenges, such as navigating tight spaces. An alert operator can quickly assess situations, make informed decisions and take appropriate action to resolve issues while minimising downtime. Never operate an articulated hauler if feeling fatigued or unwell.

Keep an eye on targets:
Operating an articulated hauler requires attention to detail to ensure proper loading, unloading and manoeuvring of materials. While an integrated payload system can account for the number of loads moved, manually recording progress in relation to a target keeps productivity proceeding on schedule. For improved fuel efficiency, minimise heavy acceleration and aim to reduce unnecessary idle time whenever feasible.

Don’t ignore fault codes:
Critical information is delivered whenever system fault codes are triggered. If a Rokbak truck does develop a fault, the operator will receive a warning symbol on the dashboard. Faults should be reported when they occur as continuing operating could exacerbate the issue. Following the truck’s advice means increasing uptime by avoiding potential disruptions, and effective communication with site supervisors, co-workers and other equipment operators is crucial for coordinating tasks and ensuring smooth operations.

Finally:
At the end of a shift, follow the correct shutdown procedure. Allowing the truck to idle for a brief period at the end of a long workday enables the coolant to circulate through the engine. This helps to gradually lower the temperature, preventing potential damage from frequent ‘hot shutdowns’ over time. Adhering to the correct maintenance and start-up and shutdown procedures will help to keep operation costs low.

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