Tokyo To Build 350m Tower Made of Wood (theguardian.com)

A skyscraper set to be built in Tokyo will become the world's tallest to be made of wood. From a report: The Japanese wood products company Sumitomo Forestry Co is proposing to build a 350 metre (1,148ft), 70-floor tower to commemorate its 350th anniversary in 2041. Japan's government has long advertised the advantages of wooden buildings, and in 2010 passed a law requiring it be used for all public buildings of three stories or fewer. Sumitomo Forestry said the new building, known as the W350 Project, was an example of "urban development that is kind for humans," with more high-rise architecture made of wood and covered with greenery "making over cities as forests." The new building will be predominantly wooden, with just 10% steel. Its internal framework of columns, beams and braces -- made of a hybrid of the two materials -- will take account of Japan's high rate of seismic activity. The Tokyo-based architecture firm Nikken Sekkei contributed to the design.

Comments

I'll believe it when I see it...

[Pollux]

When I read this, I immediately wondered why it was even possible to build a 1,100 ft tall wooden building, more than eight times taller than the current record for the tallest wooden building. This Guardian article goes into more detail about the engineering of tall wooden buildings, and cites this Canadian Wood Council case study for some of its information. In short, the wood materials to be used are highly specialized fireproofed laminate composites. Calling the finished product wood is like calling Splenda sugar; just because it's a derivative of the original doesn't mean it's the same thing.

From an engineering perspective, a skyscraper undergoes incredible stresses. The building has to be capable of supporting itself and all the weight within it. It has to withstand the tremors of earthquakes, the forces of wind and water, and not lose its strength over time, even as it's exposed for decades to UV rays. The building materials need to have a unique combination of sheer strength, tensile strength, and compressive strength. A combination of steel and concrete give you all three. But natural wood is inconsistent. Flaws like knots and cracks in the grains weaken its sheer strength. Wood has great tensile strength in the direction of the grain, but is very weak against the grain. And it works the opposite way with compression. The only way to overcome these weaknesses is with laminates, which are very expensive (currently, due to the lack of demand) to produce.

Not to mention wood burns much easier.

My personal opinion is that there are some architects trying to get name recognition by coming up with something unique. I hope anyone considering to fund such imaginations take a lesson from the Spruce Goose and use wood when it's advantageous, not avant garde.

Re:Fireproof?

[hey!]

Well, consider the 67.3m Grenfell Tower which burned spectacularly last June, killing seventy people. The tower was reinforced concrete, but it was the decorative polyethylene cladding that transmitted the fire at deadly speed, and the interior apartment furnishings that actually killed people.

So it's quite possible for a concrete building to become a fire trap; it's the superficial bits that are the risk. Massive wooden structural members might burn in theory, but like an over-large log they wouldn't catch fire quickly.

So I should think that a large wooden building could in principle be engineered to be for all practical purposes as fire safe as concrete building. The problem is knowing that something is safe in practice. Engineering is as much about the application of experience as it is induction from general principles. So if you build far beyond the limits of experience, you can never be quite certain of the behavior of a system.