Bridging the gap

Bridge construction in the UAE is beginning to use state-of-the-art techniques. Hugo Berger visits the Saadiyat Bridge Island project in Abu Dhabi to learn about the cutting edge methods being used by the workforce.
Bridging the gap
By Hugo Berger
Sat 12 Apr 2008 04:00 AM

Bridge construction in the UAE is beginning to use state-of-the-art techniques. Hugo Berger visits the Saadiyat Bridge Island project in Abu Dhabi to learn about the cutting edge methods being used by the workforce.

Abu Dhabi is striving to become the cultural hub of the Middle East.

Central to this vision is the development of Saadiyat Island.

The methods usually used to build bridges here are simple; nobody has tried these complicated methods before.

The island - which translates as island of happiness - has been extended by a comprehensive landfill programme.

It will provide additional space for the further development of Abu Dhabi and also an idyllic holiday destination.

It will also include a host of cultural attractions to boost the city's artistic credentials.

But all the cultural attractions would be pointless unless there is proper infrastructure to support them.

In order to form a connection between the island and the mainland the authorities are creating Saadiyat Bridge.

At 1,455m long and 60m wide, it is one of the largest bridge projects in the world.

It will provide enough space for ten car lanes, as well as two railway tracks.

The bridge is being constructed by a consortium formed by Ed Züblin AG and Saif Bin Darwish Civil Engineering Contractors.

The engineers for the project are Parsons.

The firm is constructing eight foreland piers in the west and 11 more on Saadiyat Island itself to support the three pre-stressed concrete hollow boxes.

These have spans which range between 45 and 135m.

The main bridge itself has a span of 200m, with an overhead clearance of 26m, carried by two V-shaped 20m high sets of triple identical pier sections.

The inclination of each of the twelve individual supports is 27.45 degrees.

Philipp Holzmann, technical manager, Peri Formwork Shoring Engineering, said the incline of the bridge was presenting the biggest challenge.
He says: "We are concentrating on the V-piers which are very complicated because of the incline structure.

"They are around 20m high. As it is so high up and in the middle of the water it requires a lot of technical know-how.

"The incline of the bridge also makes it much more complicated. If it was straight or vertical it would be a lot simpler."

The Peri formwork and scaffolding solution for the inclined individual supports consists of two sets of VARIO GT 24 side formwork, a 7.76m wide, forward-inclined VARIO formwork element with integrated working platforms as well as a reverse-inclined raised formwork unit.

This is based to a large extent on rentable standard material taken from the VARIO GT 24 girder wall formwork system and SLS heavy-duty spindles.

Due to the large supporting angle, the high concreting loads are carried on the externally-positioned reverse-inclined formwork mounted on Peri-Up shoring.

Holzmann says that the simplicity of the Peri-Up system was making a complicated job manageable.

He says: "The design for the bridge was done in Germany because it was complicated."

"We used Peri-Up for the scaffolding to support it because it is very flexible, which is its advantage over many systems."

Despite the complex nature of the job, Holzmann insists that the workforce has been able to cope with the work.

He says: "What I heard from the site was that it was quite easy to train them, because the system is designed to be easy."

"The methods usually used to build bridges here are often very simple; nobody has tried these complicated methods before."

"The know-how is simply not here and labour is so cheap they usually go for the simple way."

"The size of the projects and the short timeframes given is also making people choose the simplest way of construction."

"But we did not want that for the Saadiyat Bridge."

Part of the steel girder framework installed by the contractors which cantilevers over the sea - steel profiles over 900 millimetres high - provides a safe support surface and reliable load distribution.

The structure and the dimensions of the Peri-Up modular scaffolding system make it possible to adapt load bearing construction to the forces which are transferred from the formwork.
It uses 1.5m-wide shoring towers, which are connected to form long supporting frame sections.

Short 25cm long ledgers contribute to the bundling of the standards at the points where the loads are applied.

Thus, the individual load-bearing capacity of 40 kilonewton (kn) per leg can be virtually multiplied at will, even for higher loads in the system without any time-consuming coupling of the scaffold tubes, as well as being adapted to the required load size.

In connection with the high ledger of the Peri-Up scaffold nodes, the scaffolding sections remain sufficiently stable in all situations.

This means large scaffold units can be moved very quickly without their dimensional stability being impaired in any way.

In the UAE, Peri has worked on numerous high-profile projects, including the Emirates Towers in Dubai and the Grand Mosque in Abu Dhabi.

But Holzmann says working on a bridge presents a series of new challenges.

He says: "The method to build a bridge is very different from that you would use to build a normal structure."

"The interesting thing about the Saadiyat Bridge is that it is using techniques which have never been seen in the UAE before."

"One of these is the incremental launching. In Europe this is quite common, but it is the first time it has been used in the UAE."

To move the sections, 7m by 3m individual supports are constructed with four climbing steps which have concreting heights of 4.7m, as well as by 2.44m in an outward direction in each case due to the pier inclination.

The Peri concept therefore means that the supporting frame construction is pulled outwards on the steel girders after striking has been completed as though being guided along rails.

For the supporting and platform levels, three tower modules - each with a 2m base and a 4.65m extension height - are coupled together.

The time-saving connection is carried out by means of a standard component taken from the Peri Up programme and the Peri section spindle.

The extension units can therefore be accurately adjusted to the required height.

Through the extensively dimensioned moving units, using in part special cross-beams for the Vario wall formwork elements, both the formwork and scaffolding can be brought to the next cycle.

This means the altogether 48 casting segments can be very cost-effectively constructed with only four sets of formwork.
The Peri system will be used for other construction phases as well - for both abutments, the numerous bridge piers in the foreland area through to the superstructure formwork.

For the subsequent construction of the pre-stressed concrete hollow boxes, three different building methods are used:

• the western foreland bridge for the incremental launching method;

• falsework will be used for the superstructure on Saadiyat Island in the east; and

• the balanced cantilever method will be used for the large spans in the middle section of the bridge.

As Abu Dhabi catches on to the construction boom, the use of ground-breaking techniques look set to become the norm.

The workforce only has two years to finish the project, but Holzmann was confident this could be met.

He says: "The bridge is almost 1.5km long, which is very long, but everything is on schedule at the moment."

"Because we are using advanced techniques, it is making a complex job a lot easier. It is a difficult job, mainly because of the size of the project and the short timescale, but we are working fast to make sure we meet the deadlines."

Saadiyat Island fact file• The bridge will be 1,455-long and 60m wide, carrying five lanes of traffic in both directions and two railway tracks.

• It will have eight foreland piers and 11 piers on Saadiyat Island to carry the span.

• The contractor is a joint venture between Germany's ED Zublin AG and the UAE's Saif Bin Darwish.

• Peri is the main consultant.

• The bridge is due for completion in 2010.

• The developer is the Abu Dhabi Tourism Development and Investment Company (TDIC).

• The project is one of two bridges and a tunnel connecting the island to the mainland.

• The total cost of the bridge and the 10-lane highway is US $184 million (AED 676 million).

• The overall project, costing $27 billion, will be built in three phases with completion earmarked for 2018.

• It will include 29 luxury hotels and 8,000 villas, housing up to 170,000 residents.

• There will also be branches of the world-famous art galleries, the Guggenheim and the Louvre, a performing arts centre and a concert hall, a campus of New York University and a golf course designed by Gary Player.

• The project is divided into six districts: Cultural District, Saadiyat Park, Saadiyat Beach, South Beach, Al Marina and The Wetlands.

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