At the time of its construction, this was the largest infrastructure project underway in Abu Dhabi. it will allow traffic to run from North to South, connecting the Abu Dhabi Airport to Saudi Arabian border and East to West easing congestion from Al Ain to Abu Dhabi City.
Replacing the current two lane interchange that was just too small to cope with the increase in road traffic, the new Mafraq Interchange consists of four lanes in each direction, two main arched flyovers known as R5 and R6 and two smaller main deck bridges known as Bridge 10.
For primary contractor China Civil Engineering & Contracting Co, the main challenge of the project was the rapid construction of the three bridge structures. With two bridges measuring 980m in length and climbing up to 22m high and a third measuring 300m. The key to delivering the project on time and budget was the use of combination of formwork and shoring equipment from RMD Kwikform Middle East.
In addition to 100,000m³ of Rapidshor, special components were designed and manufactured for the wing walls, with Superslim primary and GTX secondary Beams used to form the support for the plywood deck structure. With a total of 2,260 metres of bridge to construct, China Civil Engineering and Contracting Co. opted to part purchase and part hire the equipment required for the job from RMD Kwikform, as the Rapidshor system could then be reused on future projects.
With 100,000m³ of Rapidshor needed to complete the job, the Mafraq Interchange represented one of the most significant projects undertaken using Rapidshor in the Middle East. For the two arched flyovers R5 and R6, constructed simultaneously, approximately 50,000m³ of Rapidshor was used for each structure. The product was then re-used to construct the first span of Bridge 10, with approximately 15,000m³ of Rapidshor fully decked out, which on completion was then re-used to construct the second span.
But the challenges posed by the project delivery were not to the supply of Rapidshor as Elpidio Aspillaga, RMD Kwikform’s Sales Engineer explains:
Logistically managing the sourcing and transportation of 100,000m³ of Rapidshor was a complex task, however as a business we are used to working on large scale projects of this nature, so the demands of this project were well within our experience and capabilities.
The real challenge however came with the design of two bespoke formwork and shoring solutions for the project. The first required our engineering team to design a new solution to allow the overall system to follow the wing profile of the bridge. to make this as easy to achieve as possible, a cranked Superslim Soldier was created, with 440 units fabricated to a tight deadline order to complete the task.
Because the deck edge was in parts over 22 metres off the ground and had to flow with the curvature of the bridge designed, the formation of the Superslim Soldier deck edge shoring had to take into account how it would be supported by the Rapidhor shoring, whilst being able to form the correct angles required to allow the deck edge to be poured.
In order to achieve this, our engineering team had to connect regular Superslim beams and the cranked Superslim Soldiers together at non uniform angles, whilst ensuring structural integrity at all stages in order for the desk edge support to withstand the concrete pressures. To make the connection a standard pin connector was used to attach the Superslim Soldiers together.
The whole approach was designed to speed up to construction process cycle time, allowing China Civil Engineering & Contracting Co to erect the forms at ground level in completed side units. This made for very little adjustment of the units when they were placed along the bridge edge shoring. On a long repetitive bridge such as this one, reducing cycle time was very important. By using a cantilever design, the side units could be removed early in the striking process and reassembles at the next stage of construction, speeding up the process dramatically.
Having solved the connection challenged, because the Superslim beams were now rigidly connected to each other, the overhanging Superslim beam at the tip of the deck edge shoring had to be further supported, as the horizontal and vertical forces placed upon the beams by the concrete would not have been held by the beam alone.
Therefore a second part of the deck edge support system had to be designed to brace the Superslim beams against each other. The solution to this requirement was the design and fabrication of 440 specially oversized turnbuckles. They were created to deliver a longer prop with a larger diameter tube, increasing the capacity as the standard RMD Kwikform turnbuckle units were not long or strong enough for the task at hand. The new turnbuckle was designed to be able to vary in length between 2400mm and 2700mm in order to cope with variations between each Superslim section and to allow for small adjustments once the units had been lifted into place.
In order to speed up the erection process, the wing form sections were assembled on the ground, then lifted into place using Alshor Plus C Hook, previously used on the contruction of the Damac Towers in Dubai. Crane operated, the Alshor Pluc C Hook can safely lift and remove sections minimising the need to work at height be relocating the wing forms.
Using the Alsor Plus C Hook meant the wing forms only had to be assembled once, and could be moved and reused on a separate section of the bridge, without having to be rebuilt. This resulted in insignificant programme time and cost savings across the project to its conclusion.