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RMD Kwikform shares British engineering knowhow to build Rustenburg bridge in South Africa

RMD Kwikform has used its British expertise and standards to help deliver a South African road bridge – sharing knowledge and learning lessons along the way.

We all know that the UK construction industry has very high standards and skillsets when it comes to health & safety and engineering design.

So as more businesses look to expand in a global construction marketplace, collaboration between teams from different countries to share ideas and innovation will become increasingly important, particularly for developing countries.

Not only can this approach help to secure additional revenue, it can also help to highlight the success of new construction methods developed for projects overseas, which can then be used in the UK market.

Hanging deck innovation

One such project that really highlights this opportunity is the recent construction of a bridge in South Africa.

The 60 m-long structure was built over the N4 highway using a completely new hanging deck solution, designed in collaboration with RMD Kwikform’s UK and South African engineers.

The bridge is part of a major £5.8m upgrade of the R24 tolled highway through Rustenburg in the North West Province of South Africa, where main contractor Lonerock Construction is widening the section from two to four lanes.

“The bridge was being constructed over an extremely busy toll road with a minimal number of closures allowed to maintain revenue for the concessionaire”

This project had a very tight deadline, and in addition to all of the new road surfaces, the bridge was being constructed over an extremely busy toll road with a minimal number of closures allowed to maintain revenue for the concessionaire.

In addition, at least 200 trucks a day needed to be able to pass below, all serving the regional mining industries.

Lonerock contracts manager Louis Van Der Walt was keen to use a new construction method that would reduce the impact of construction activities on surrounding areas, one that removed the need for additional traffic management, lane reductions and closures.

Tough learning curve

After being introduced to specialist bridge construction subcontractor Tzandeboo Construction, RMD worked with its South African engineers to provide drawings of the new building method, which allowed the bridge to be constructed while suspended in the air.

It was an interesting learning curve for Lonerock Construction, as it had not built a bridge this way before. It wasn’t until the bridge piers were already in place that Tzandeboo took on the bridge construction element of the project.

To provide a solution swiftly, the design team worked in conjunction with RMD’s engineering team here in the UK and South Africa. With such a large project, it was vital to combine knowledge of bridge work and experiences on past projects.

The solution involved hanging the deck on tie bars from five heavy-duty megatrusses, each weighing 34 tonnes.

The megatrusses were made up of RMD’s Megashor shoring, steel Superslim soldier beams and steel bracing members, with steel beams forming the bottom and top of each megatruss. The Megashor was also used to form a total of 10 supporting towers.

With the size of the abutments at each end of the bridge calculated to support the forces of a total of five towers and five megatrusses, the Tzandeboo Construction team had to cast each structure from the ground up.

Each of the supporting towers were constructed in-situ and propped using Superslim soldiers, topped with a large steel beam that supported two special connector components, and finally braced with a steel Superslim soldier beam. Once in place, each of the megatrusses assembled next to the bridge structure were lifted using a 550-tonne mobile tower crane and secured to the towers.

Precise calculation

Site safety was crucial, particularly due to the live highway, so RMD included integrated walkways with Ultraguard edge protection into the final design.

This allowed the site team to install the numerous tie bars required to hang the bridge deck formwork, made up of steel Superslim soldier primary beams and timber GTX secondary beams.

One of the challenges faced when designing the solution was the sheer weight of the megatrusses, and a 2 per cent slope across the bridge deck for drainage. Marius Els, RMD’s senior engineer in South Africa, knew the team had to get the positioning exact and obtain the right levels for each support.

“It was vital that we combined our knowledge of bridge construction and shared our experiences on past projects in order to create a solution together”

To make fine adjustments while on site, RMD incorporated Megashor jacks into the design to accommodate the sloping platform. As this was a new design, only recently introduced to the contractor before work began, the site team underwent training and the erection team was supported throughout the process.

The bridge deck was cast 710 mm above the design level in one pour, using 953 cu m of concrete. This process took place while trucks were using the N4 section of the road.

Once the concrete had been cured and stressed, the Tzandeboo Construction team was then able to remove the megatrusses, with the deck supported on shoring at both ends of the bridge. The site team was then able to complete the deck before it was jacked down to the final level.

Preferred design

Tzandeboo Construction was initially presented with an alternative design at the start of the process – a formwork design using steel super beams for deck support and two scaffold towers at either side of the live N4 Highway.

Its focus was to reduce the need to close the highway, so RMD’s design was adopted, particularly as the hanging deck solution was similar in cost to the previous super beam approach.

This project has succeeded in opening up the South African market to more innovative ways to construct bridges and other civil projects. RMD’s South African team has already received enquiries for similar projects across the country.

RMD believes this to be a breakthrough method of construction that highlights how collaborative working on a global scale can bring new and innovative thinking to different markets.

Overseas success should also be acknowledged more by the UK market, bringing solutions, such as this type of bridge construction, into the UK with confidence in order to deliver projects in a commercially effective way.

Ian Fryer is engineering director at RMD Kwikform

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