THEME: BUILDING AND CONSTRUCTION

Small country big bridges

Photo: COWI

Thousands of bridges, among them some of the world’s largest, have been designed by Danish engineers. And a range of new projects, which will yet again extend the limits of the possible, are in pipeline.

By Morten Andersen

5 kilometre long steel cables with a diameter of more than one metre. A concrete deck, carrying a four-lane motorway with emergency lanes and two train tracks, spanning a distance of more than three kilometres without the need for supporting piers.

These are the impressive dimensions of the world’s longest suspension bridge, which crosses the Messina Strait connecting Sicily and Calabria on the Italian mainland. The bridge, which has a free span of 3,300 metres, has been designed by COWI consulting engineers, who had a practice run at home in Denmark with the East Bridge of the Great Belt Link, which with its free span of 1,624 metres, is now ousted into second place.

The company is also the holder of the world record for cable-stayed bridges with China’s Sutong bridge, which has a span of 1,088 metres.

If you are puzzled that engineers from a small country – representing less than a thousandth of the world’s population – are those you seek out when the world’s largest bridges are to be designed, it might help to take a look at a map of Denmark. With its many islands, fjords, straits and sounds, Denmark was born with a need for bridges.

Box girders and cable dampers

In the 1930s the country had its first wave of bridge construction with the Little Belt Bridge, the Limfjord Bridge and the Storstrøm Bridge as the most significant examples. World War II put a temporary stop to proceedings, but in the period from 1970 to 1985, activities blossomed again with the Farø Bridge, the Vejle Fjord Bridge and a new bridge over the Little Belt. The 1990s saw two landmark projects: The Great Belt Link, which set a world record for suspension bridges, and The Øresund Link, a cable-stayed bridge with a main span of 490 metres – a world record for a cable-stayed bridge carrying both a motorway and a railway.

The path was thereby paved for the creation of more of the world’s largest man-made structures.

Besides building on their experience from one project to the next, which gradually enabled the Danish engineers to handle slightly larger projects, they benefited from rapid technical developments.

It became possible to produce increasingly longer and thicker steel cables, just as it became possible to mould elements in concrete so that costs were kept down while ensuring consistent quality and high reliability.

With the construction of the new Little Belt Bridge in the 1970s, COWI for the first time introduced aerodynamically designed closed girders for cable-stayed bridges. Inside the closed girders a continuous dehumidification of the air takes place, which prevents corrosion. The concept is standard today.

Another significant development is dampers for bridge cables. In certain wind conditions a cable can start to oscillate, the process becoming exacerbated until
a point can be reached where the entire construction collapses. The larger the bridge, the longer the cables and thus the greater the risk. The first generation of dampers featured cables fixed in a cylinder filled with viscous oil which could absorb some of the mechanical energy. In recent years, development work has started on new types of damper which actively counteract oscillations in the cables. Research scientists at the Technical University of Denmark have supplied the theoretical foundation for dampers of this type, which have been used for the Sutong Bridge, the world’s longest cable-stayed bridge.

Major project on the way

The next world record could very well be on the way. Together with Germany’s Obermeyer, COWI is competing with another consortium, which includes the Danish consulting engineering company Rambøll, to supply the right solution for a fixed link that can connect Denmark and Germany via the Fehmarn Belt. The competing consortium is preparing a proposal for a tunnel, while COWI/Obermeyer will be bidding with both suspension and cable-stayed bridge proposals.

“The project contains major technical challenges, because everything about the Fehmarn project is larger and more complex compared to the fixed links across
the Great Belt and Øresund. A bridge will – regardless of whether it is a suspension bridge or a cable-stayed bridge – become the world’s longest combined road and rail connection. The construction will probably require some of the largest cranes and other types of equipment the world has ever seen,” says Lars Hauge, director of the bridges division at COWI.

In addition to the technical challenges, the Fehmarn construction will also need to accommodate a major environmental requirement, since the project must not disturb the biological balance in the Baltic Sea. Or more precisely, it must neither increase nor decrease the inflow of water from the North Sea and the Kattegat to the Baltic Sea.

“It will be enormous”

Regardless of the solution chosen for the Fehmarn Belt, Danish engineering is set to play a significant role in major bridge construction projects in the future. In Doha, Qatar, COWI is collaborating with the Qatar-Bahrain Causeway Consortium on connecting the island state of Bahrain with the mainland neighbouring country of Qatar. At 40 kilometres, the Friendship Bridge will be the world’s longest and will comprise a four-lane motorway as a natural extension of the King Fahd motorway connecting Bahrain and Saudi Arabia. When the link is completed – according to plans, in 2013 – the travelling time will be shortened from the current five hours, where part of the journey takes place through Saudi Arabia, to just half an hour.

The project will be subject to strict environmental requirements, including provisions to protect a threatened species of large marine mammal, the Dugong.

Not quite as long, but in many ways still a landmark project, will be the coming fixed link between Yemen and Djibouti. The 28 kilometre link will cross the Bab El-Mandeb Strait, which is part of The Red Sea, and so connect the Middle East with Africa. The western part of the strait is more than 20 kilometres wide with water depths of 300 metres.

1. Great Belt Link
2. Little Belt (two bridges)
3. Limfjord Bridge
4. Storstrøm Bridge
5. Farø Bridge
6. Vejle Fjord Bridge
7. Øresund Link (links Sweden and Denmark)
8. Fehmarn Belt (future project to link Germany and Denmark)

According to COWI’s calculations, the link should have at least three spans, each of about 2,700 metres – in other words each of the three spans will be only slightly shorter than the Messina Link’s world record of 3,300 metres.

“The concrete pylons will be set in foundations at a depth of 300 metres, and will have to reach a height of 400 metres above the water. This will be necessary
in order to carry the ultra long spans of the suspension bridge. So each pylon will be 700 metres in overall height. It will be enormous,” says Henrik Andersen, COWI’s Head of Major Bridges.

The East Bridge of the Great Belt Link has a free span of 1,624 metres. When opened in 1998 is was the longest suspension bridge in the world.

Photo: Scanpix

Future bridges of reinforced plastic

Manufactured in advance: A 40 metre bridge for pedestrians and cyclists spans the very busy railway in the Danish town of Kolding.

Photo: Fiberline

The Danish company Fiberline Composites is pioneering the use of carbon fibre and glass fibre for bridge construction. Since the company´s first bridge was erected in 1997, more than thousand small bridges and six large road bridges have been built in Europe.

By Morten Andersen

Steel and concrete are the materials one especially associates with Danish traditions in bridge building, but at the western end of the island of Funen, there is a rapidly growing company, Fiberline Composites, which is successfully introducing completely new materials to the world of bridge building – composites based on carbon fibre and glass fibre, which have already established applications in yacht hulls and wind turbine blades.

In 1997, Fiberline A/S supplied the deck and profiles for Scandinavia’s first bridge made of composite material. The 40 metre bridge for pedestrians and cyclists spans the very busy railway in the Danish town of Kolding. Fiberline’s solution was chosen because it could be manufactured in advance, so that it was only necessary to interrupt rail traffic briefly during the construction. In fact it happened just three times, all during the night at weekends.

Since then more than a thousand pedestrian and cycle bridges, where the composite material has been used for the bridge deck, have been installed in the Netherlands, and over 30 in other European countries. The material has also been used for larger bridges for heavy traffic.

This began with an EU supported project, where from 1992 to 2002 Fiberline together with European partners developed the first bridge decks that could withstand heavy traffic. Today the company has six references, the most prominent being a bridge installed across the M6 motorway in Manchester, UK.

“What especially made Britain’s Highway Agency choose composite material was that the bridge could be completed in another location and then lifted into place, so that the traffic only needed to be interrupted briefly. The M6 is very busy motorway, and a lengthy interruption would have caused chaos.

At the same time, the Highway Agency’s calculations showed that the bridge was only five per cent more expensive than a conventional solution. The investment was quickly recovered, since a bridge made of composite material is easier to maintain,” says Finn Jernø, head of communications at Fiberline.

Near Barcelona in Spain, a bridge made of composite material has also been chosen to ensure minimal interruption of high-speed trains, just as the German highway authorities have chosen a similar solution in Friedberg at Hessen. In Russia there are several projects planned, because the material is highly resistant to the large quantities of road salt used in winter.

“Obviously, when you introduce a new material, there is a certain conservatism that needs to be overcome, and people in the industry also have to learn to work with the material. But many bridges have been erected using the material, and we certainly expect that the number will grow strongly. And who knows – perhaps we will also see composite material applied in the major bridge projects one day,” says Finn Jernø.

As composites become more routinely used and volumes increase, the cost of bridges built with these materials will gradually reduce, and this will help promote their application in bridge construction. In addition, climate considerations will play a role since energy consumption from production of composite material is significantly lower compared to steel and concrete.

Airport of the future

Danish companies collectively cover practically everything involved in the construction of airports. Now they are developing a shared vision

By Morten Andersen

Low environmental impact. Sustainable use of resources. Optimal exploitation of space. Maximum flexibility.

These are the four key concepts in ’The Airport of the Future’ development project initiated by the Danish Airport Group, which is part of the Danish Export Association. The group comprises more than 40 Danish companies, whose businesses range from engineering consulting to baggage handling systems and other types of equipment for air traffic control, security and maintenance.

“Although the companies each have their niches in airport construction, they share a common denominator in environmental considerations, resource exploitation and Scandinavian design. We are now developing this so we can supply a total concept.

In addition we gain more “muscle” when we collaborate, which enables us to bid for major projects,” says Michael Niels Thorsen, sales director in Integra A/S and chairman of the Danish Airport Group.

Airports are national symbols

COWI consulting engineers is the world’s eighth largest consultant in the airport sector measured by revenue generated abroad, so it has a lot of weight in relation to many of the other companies in the Danish Airport Group.

“Since our work as consultants lies early in the process, we often hear about projects a couple of years before the companies which supply equipment. But one should never be so high and mighty as to think there is no benefit in collaborating with others. Often we are the ones who tip the others in the group, but if we can just get a couple of contacts from them in return, then that’s fine,” says project director Ejner Christensen of COWI.

The Danish companies never present a complete package, he points out:

“Airports are national symbols, especially in the capitals. The airport terminal is the first impression that visitors gain when they arrive in a country for the first time. We typically team up with a local architect so that the airport gets a visible local touch.”

But in the underlying functionality one can build on elements from previous projects. According to Ejner Christensen, Danish companies in the airport sector are good at being flexible in their solutions.

“Creative thinking is necessary when you need local distinctiveness and functionality to form a synthesis. That is a Danish strength.”

In addition, it is a distinctive Danish speciality to think of energy, climate and environment.

“For example, we are consultants on a new terminal in Oslo, Norway, where the winning parameter was that our solution was better thought through in the energy area,” says Ejner Christensen.

Sub-optimal start to climate discussions

Green developments in airports will come more onto the agenda, the COWI director believes, since the entire aviation industry has an image problem with regard to climate impact. One of the reasons is that the industry has not managed to create a common strategy for communication and so has become an easy target.

“In reality, the industry only emits about two per cent of global CO2, but listening to the debate you would think that it was 20 per cent. Many companies have started to change course however. Airports account for only a small proportion of the CO2 emissions from air traffic, while the aircraft themselves account for 90-95 per cent. But it is important that airports do their bit to keep emissions down, so they help correct the poor image the industry has acquired,” states Ejner Christensen.

The Danish Airport Group was founded in 2005 and has been busy from the start. When the group was founded, Danish companies were already able to supply practically all the products and services that are needed in an airport – from the consulting engineering work to helping disabled people round the airport and getting runways quickly repaired.

“Working together is new to us. Some of the companies are also competitors, but we have cleared that hurdle. All members of the group take part in developing a consistent idea of how airports should evolve,” says group chairman Michael Niels Thorsen.

You can find a full list of all the members of the Danish Airport Group on http://www.dk-export.dk

The baggage will overtake its owner

Today air passengers wait for their baggage, but soon it will be the time it takes for passengers to get from one aircraft to another that will be the limiting factor in airports

By Morten Andersen

“Our objective is to transport baggage as quickly as possible, so that it will be the time it takes for travellers to get from the arriving aircraft to the departing aircraft that will be the limiting factor for how quickly transfers are executed.”

So says sales director Henrik Cort of Crisplant, which develops and supplies complete systems for baggage handling in airports.

Regarding transfers, airports are competing on the shortest possible connection time, i.e. reducing the time needed between connecting flights. Today an airport typically requires a margin of one hour to guarantee that passengers from one aircraft can board another. Baggage is still the limiting factor, but there are rapid developments happening in this area.

If you fly from Copenhagen Airport via Munich International Airport to Singapore Changi Airport – three airports where Crisplant has supplied baggage handling systems – information about the baggage is automatically sent from the scanner in Copenhagen to the corresponding systems at the other airports. This ensures that the baggage is handled quickly and securely at the transfer airport.

At the same time, the speed of baggage conveyor belts has increased. The fastest systems today move baggage at 10 metres per second – equivalent to 36 kph or 22 mph.

“Today it is mainly relevant for larger airports with several terminals where baggage runs in tunnels. But in the future, it will probably become the standard,” says Henrik Cort.

The combination of intelligent transport systems and high speed has led to some airports cutting down the minimum connection time to half an hour.

“It gives them a competitive edge over other airports, and that race will continue,” says the sales director.

In contact with each suitcase

Crisplant, a company in the Beumer Group, is among the world’s leading suppliers of advanced systems for baggage handling in airports. Its list of references includes Munich International Airport, New Doha International Airport (Qatar) and Singapore Changi Airport.

“New solutions in the security area are a trend that will dominate the airport of the future,” asserts Henrik Cort.

“Regarding systems for baggage handling, you will for example see that a suitcase which cannot immediately be approved but needs further investigation, will be electronically labelled in a way which 100% guarantees that it is not put on board the aircraft until it is declared safe.”

There are also systems to ensure that the location of each suitcase is known, so that it can easily be removed from the aircraft’s hold if the passenger does not turn up at the gate.

“It results in significant costs for both airlines and airports each time a suitcase is sent off, even though the passenger did not reach the gate – or the opposite. It actually happens frequently, but it will not happen in the airport of the future,” says Henrik Cort.

The solution has already been developed. An electronic label, known as an RFID (Radio Frequency Identification) tag, can be built into the labels that the baggage is given at check-in. Unlike ordinary labels, information can be continuously transferred to an RFID tag. So if the passenger does not appear at the gate, a message can be sent to the tag which stops the suitcase from being placed on board the aircraft. And if it is already on board, it is easy to find and remove. It will also be possible to reroute the suitcase if a certain aircraft cannot take off and the passengers need to board another aircraft.

Budding green trend

Finally, there is an environment and energy trend. Crisplant’s transport systems use linear motors. These are electric motors in which the iron core is replaced by rotating permanent magnets. In this type of motor, heat loss is significantly lower. That reduces electricity consumption in itself. At the same time it saves on ventilation because the components do not become so hot – a further saving. In total, there are energy savings of up to 75 per cent with Crisplant’s linear motors, which translate into similar savings in CO2 emissions. And the savings have been achieved almost without additional cost.

“We decided at an early stage that all our systems should be provided with this type of motor. We thereby gained economies of scale, which means that the price for the motor is only marginally higher than the price for conventional electric motors,” says Henrik Cort.

On the question of whether the low energy consumption carries weight with customers, the sales director answers:

“If everything else is equal between you and a competitor, and you have the extra green features, then that can be what wins you the order. We are starting to see however that some airports are attaching great importance to having a green profile. Helsinki is probably the best example.

And we are also seeing a trend towards many airlines seeing the environmental profile as a big issue.”