RMD Kwikform Iberica engineers develop a new innovative falsework solution to provide horizontal shoring on the development of the new line 9/10 of the Barcelona Metro.

 

When client UTE Gorg, a joint venture between Dragados, Acciona, Comsa and Sorigue, approached RMD Kwikform Iberica to provide a shoring system for works on the Gorg metro station in Barcelona, the challenge was well and truly set for its engineers to meet the project’s demanding needs. Once complete the line 9/10 will be the deepest line in the network and the longest line in Europe at a staggering 46.6 km.

 

Diego Martín of RMD Kwikform Iberica takes us through the project, the design, and the implementation of the falsework system that was used on the site.

 

“As a team of engineers, we needed to design a shoring system that would support the retaining walls in a vertical shaft. The walls themselves were nine metres deep into the ground and a total of 16 metres high, with a total length of 270 metres of wall in an enclosed shape to be shored. The obstacle was the irregular shaping of the walls and shaft; by irregular I mean there isn’t a completely straight wall in the entire design!”

 

“The loads involved in shoring these retaining walls were also very demanding, consisting of 75tn/m to be supported by our design. On such an unusual project and application the loads were worked out by the customer, using specialist CYPE software.”

 

“Early on it was clear that a ‘standard’ solution wasn’t going to withstand the loads, so our engineers had to take a more technical approach. The first key decision made was to prop the walls against each other, rather than against a vertical shoring solution. Thanks to the heavy duty support provided by our Megashor legs it was clear that we could achieve the basic first stage of this design by simply rotating a Megashor tower into the horizontal position to bridge the gap.”

 

Megashor towers had been used in this way before in similar projects but we had a lot of work to do to ensure that these towers could accommodate both the irregular geometry of the retaining walls and the inherent loads involved.

 

Using the Megashor shoring to prop directly from wall to wall requires adjustable screw jacks at one end of the horizontal tower. These screw jacks allow maximum contact between the shoring and the wall surface, and any minor adjustments in length can also be catered for at initial installation and over the lifetime of the project.

 

The longest Megashor brace we had would be 30 metres in length; this would be considered a significant size even with Megashor being used in its standard application as a tower. The challenge then, was to overcome loads of 75tn/m with such long props and meet the erection efficiency of the client.

 

Initially we needed to strengthen the Megashor shoring to help avoid any sagging or warping of the beams over such a big distance. In previous projects, we had used Superslim beams to this end but this system needed improvement so here we designed and fabricated a series of special triangular steel frames that could be attached directly to the Megashor beam, and run the length of each prop. A triangle being the strongest geometric shape made it a natural choice, but it also simplified the design, fabrication and final application of the triangular frames and increased the load capabilities of the Megashor towers, thanks to the no release joins between the Megashor beams and the frames.

 

The Megashor towers, now braced by the triangular frames required more development. We needed to provide extra support for this bracing to increase the load capacity and strengthen the joins between the individual Megashor brackets to improve the overall rigidity of the structure.

 

As a design team we felt that this required a unique piece of equipment to achieve the task at hand. The result was the creation of the telescopic tension members. These adjustable tubes have a load capacity of 27kN compared with the 6.5kN capacity of the tubes used on previous horizontal shoring projects. Using special plates, we positioned the telescopic tension members in a triangular formation from bracket to bracket throughout the design.

 

Once the design and fabrication of the new components was completed 270 tons of equipment was then shipped out to the site. The Megashor props were built on site, once in place the adjustable screw jacks were fixed into place on the solid retaining walls. Adjustments were made to the jacks to accommodate the uneven surface and ensure good contact and a strong fixing. The telescopic tension members could then be tweaked to adapt to all the different distances between props, giving rigidity and strength to the props and the required support to the retaining walls.

 

Overall, by introducing these two new shoring systems we improved the erection efficiency of the build by reducing the number of individual parts and substituting a large number of screws for pins. The flexibility of the design and materials also delivered significant cost efficiency to the overall project; the adjustability and its application during installation saved valuable man-hours (between 15% and 20% less) and allowed us to accommodate any changes to the overall build. This ultimately reduced programme time and the project was hired out to UTE GORG and delivered within budget.

 

The impact and application of this new solution on other projects is potentially immense. While both the triangular frames and telescopic tension beams were specially designed for this project, this design solution has now been adopted in all our horizontal shoring projects, replacing the old system. The fact is that this system can be used in basically any structure that requires Megashor towers, including vertical propping and façade retention systems.

 

Building Bridges

The €2,850m development works on the Barcelona Metro that are due for completion in 2013-14 is the latest in a long line of successful projects that RMD Kwikform Iberica have provided formwork and falsework solutions on for clients Dragados, Acciona, Comsa and Sorigue. These successful working partnerships have seen RMD Kwikform Iberica formwork and falsework utilised on the likes of the Madrid Metro, a bridge over the Segre and even more high profile structures such as the Basagoiti viaduct and the impressive Third Millenium Bridge. The latter being the largest suspended concrete arch bridge in the world.

 

 

 

 

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