Wood has long been touted as a building material for high-rise buildings. The highest specimen in Norway reaches 85 meters into the sky. Now a Japanese company duo claims to have developed a construction method for 350 meter high skyscrapers. The construction group Nikken Sekkei and the wood processing group Sumitomo Forestry have jointly developed a composite beam construction method in which wooden beams and reinforced concrete ceiling panels are combined.
The innovation consists in a new construction of the wooden beams, which allows spans of around twelve meters. That is twice as long as previous wooden beams. In addition, the beams are less deep, which means that the storey height and thus the material requirements can be reduced. This should make the wooden constructions particularly suitable for medium-sized and very high buildings.
The recipe consists not only in the lamination technique, but above all in the surface of the beam, which resembles a saw. Every 25 centimeters, the engineers sawed in a shallow, sinking indentation that is up to 3.5 centimeters deep. 16 mm thick hexagonal screws are drilled into the middle of the indentations. Then the reinforced concrete ceiling is applied.
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Due to the sawtooth pattern, the composite construction then forms a particularly strong structure. The companies said it was not inferior to conventional steel and reinforced concrete structures. In addition, the method requires only a tenth of the steel screws used on smooth beams to hold the concrete slab in place.
The idea for the project came to Sumitomo Forestry as a gift for the company’s 350th anniversary, which is to be celebrated in 2041. In 2018, the timber company therefore launched the W350 project, which was intended to develop the technology for a 350-meter high-rise building. They chose Nikken as their partner. The goal of the wood experts is now to realize a wooden megacity with all the attributes, such as high-rise buildings, by the deadline.
(Image: Sumitomo Forestry / Nikken Sekkei)
At the same time, the method should help to reduce greenhouse gas emissions in the construction sector to zero on balance by 2050. Japan has large fallow carbon dioxide sinks that could be used for this: the industrial forests planted after the war. Their use collapsed in the 1960s when the first GATT Free Trade Round Japanese wood became more expensive than imported.
The use as a building material for small single-family houses was also a relatively small market. Through the mass use of wood, also for large buildings of all heights, the duo hopes to expand the market so much that the use of coniferous forests is worthwhile again. This would also do Japan a service in terms of health. In the spring, the giant trees that have grown old emit huge clouds of pollen, which have made pollen allergies a widespread disease. Younger forests would reduce the sneeze waves. Health.