Floating structures will enable safe complementary construction in future metropolises

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Floating structures will enable safe complementary construction in future metropolises

11 June 2018
In the coming decades, sea levels will rise due to climate change while the population of many coastal cities will grow. At the same time, the built environment will need new alternatives for dense residential areas. Floating structures are one possible solution to these challenges.

Urbanisation is a global megatrend also in Finland. Floating structures offer new opportunities both for coastal cities and areas of flood risk, such as riversides. People could live increasingly above water.

“As the world’s population is concentrating in cities, lack of space is becoming an increasingly alarming problem around the world,” says Sweco’s Project Manager and specialist in modelling urban areas, Kari Nöjd. “In Finland, lack of space isn’t as big of a problem as it is in Asia, but we still have a lot of potential for building above water. In Finland, we have a lot of sheltered urban coasts, whereas areas with powerful currents are not suitable for floating structures.”

According to the forecasts of the Finnish Meteorological Institute, rain volumes in Finland will grow by 25 per cent in the next 100 years. Total rainfall and wind velocity will also grow.

“Floods will become more common in the lowlands, and at the same time the hours of wet time, meaning hours when the air humidity is over 80 per cent and the temperature is above zero, will also increase,” says Sweco’s leading specialist Jyri Nieminen. “It’s important to use the forecasts even now when evaluating the corrosion risk of steel structures and the moulding of wooden structures. Coastal construction also needs to take increasing windiness, diagonal rain and storms into account.”

Innovations from the maritime and aviation industries to structural engineering – frost, ice and earthquakes pose local challenges to engineering

Light weight and the control of mass are critical in the engineering of floating structures. Steel or concrete pontoons that can sustain the environmental stress are used in the bottom of floating structures.

“We have learned about structural engineering from the maritime industry, among others,” Nöjd says. “However, floating buildings will always be connected to the city’s infrastructure, such as the waste management, potable water and district heating systems. This way, sewage won’t burden the environment any more than it does on land. I believe we can find new ideas for engineering floating structures also from the aviation industry, which is pondering all the same questions.”

Changing conditions place strict requirements on the physics of the materials.

“With floating structures, the conditions are exceptional compared to traditional construction: the higher air humidity, the wind loads, the salt levels and the long-term rise of the sea level all need to be considered,” Nöjd says. “Regional differences are also relevant. For example, ice during the winter months is a challenge at Finland’s altitude levels, while in Asia it’s earthquakes.”

New innovations in the building services engineering of the floating residential area in Dubai

Sweco has been involved in many flood protection projects in countries such as the Netherlands, Denmark and Indonesia. Sweco also participated in the engineering of the ”North Deck” residential island which was transported from the Rauma shipyard to Dubai in pieces.

“Engineering floating structures in Dubai forced us to create brand new concepts as there were no suitable solutions in the Finnish building codes, for example,” says Antti Hänninen, Sweco’s specialist in building services engineering.

A holistic view on lifecycles and analysing different options together with the various engineers and designers is essential when planning floating structures.

“Water is both your friend and enemy when it comes to floating structures. That’s why it’s important to spend time on simulating different options and analysing the data before starting the design process. For example, glass surfaces transfer the heat load indoors in hot climates, which is why you need a solution that balances window quality and the size of the cooling system. In Dubai, we came up with a ventilation system that uses three times less energy than normal systems.”

Attention to safety solutions and the use of resources

When building on water, it is particularly important to plan the use of resources.

“In Dubai, water is one of the scarcest resources, so we developed a solution where the condensation water from the cooling system is cleaned through reverse osmosis and transformed into domestic water. During the project, we also used concepts commonly used in freight ships, such as using ballast tanks underneath the swimming pools of the houses. Thanks to the tanks, the floats stay in balance when the pools are emptied.”

Safety is also an absolute requirement for building above water.

“The island uses a split bilge system where one part acts as a maintenance system and removes condensation water from the pontoons like in sailboats. We also used a ‘maritime classification’ and designed an emergency bilge system that removes water in case of a leak.”

The solutions used in Dubai and elsewhere in the world can also be applied to Finland.

“Sweco is now offering comprehensive expertise, thanks to which we can take the different energy economy factors of different floating locations into account when planning heating and cooling solutions,” Hänninen says. “For example, seawater can be used to condensate the cooling systems instead of the hot outdoor air in Dubai, while in Finland you can use the system in reverse: the heat energy from lakes can be used for heating floating homes.”