
Tokyo to build 350m tower made of wood - markgavalda
https://www.theguardian.com/cities/2018/feb/16/plyscraper-city-tokyo-tower-wood-w350
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jakewins
Fire safety in wooden structures is interesting. A friend who does research in
the area explained that, in some ways, wooden beams are simpler to engineer
than steel beams when dealing with fire.

The goal, engineering wise, is to put a number on a given structure - how many
hours can it burn before it falls?

A steel beam will maintain most of its strength up to the point it suddenly
becomes soft and loses all of it. The exact point in time this occurs is hard
to predict, because it varies substantially with several variables.

A wood beam will maintain the full strength of the beam, minus the average
thickness of wood that is burned off per hour, which is a reasonably well
known quantity.

This makes it simple (though not easy, of course!), relative to steel
structures, to put a number on a wooden structure - "this building can burn
for 2 hours before it is no longer safe for firemen to try to put it out from
inside".

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tbabb
The question is: how does the number for a steel structure compare to that of
a steel one?

~~~
bch
This doesn't answer the question, but on topic: I was working with a building
engineer who described a situation where a car engine caught on fire
underneath a buildings (large, extended) eve that was built with steel beams,
and they did melt, obviously necessitating a lot of fix-up work. He reckoned
though that if the beam was built of wood, in that situation you'd just have
to clean of some blackened material and carry on business-as-usual.

He also said that of steel, perfect glass, and wood, glass was (strength to
weight) the strongest material (I don't remember if this was in compression,
or tension, or ...), but it's so affected by its environment (chemically,
physically (a scratch)), there's really no such thing as perfect glass, so
it's moot.

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tromp
Currently under construction is this 73m tall residential wooden tower in
Amsterdam:

[https://hautamsterdam.nl/en/](https://hautamsterdam.nl/en/)

The name HAUT appears to be a play on the Dutch word for wood (HOUT) and the
french word for tall (HAUTE).

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mikeash
Note that “haute” is the feminine form, and the masculine version of tall is
just “haut.”

~~~
tromp
Thanks for pointing that out. Now I learned that "cuisine" is feminine.

~~~
Epholys
No, adjective like "haut" change according to the noun it describes and most
of the time by appending a "e". A "tour" (the feminine word for tower) will be
"haute". An "arbre" (the masculine word for tree) will be "haut". "Cuisine" is
a general noun so it does not change, even if it ends with a "e". There are
not a masculine or feminine cuisine, it's just a cuisine :).

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ibz
> "Cuisine" is a general noun so it does not change, even if it ends with a
> "e". There are not a masculine or feminine cuisine, it's just a cuisine :).

"cuisine" is definitely a feminine noun. There is no such thing as a "general"
noun. Also, it is the adjective that changes to match the noun, not the other
way around.

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oever
Here's a site with more information on wooden skyscrapers. It has a design for
a wooden empire state building.

[https://www.metsawood.com/global/Campaigns/planb/cases/woode...](https://www.metsawood.com/global/Campaigns/planb/cases/wooden-
skyscraper/)

~~~
swampthinker
Very interesting! But there is quite literally zero cross-bracing in that
structure, which leads me to believe this was designed by an architect and not
a structural engineer.

~~~
ansgri
Do architects nowadays not have to be competent structural engineers? If so,
it would amuse me greatly: how can you be entrusted in drawing new building
shapes if you have no clue on their feasibility?

In other words, have the word 'architect' devolved into a 'building (exterior
& interior) designer'?

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nakedrobot2
Architects these days often seem to be large scale sculptors who inflict
strange shapes on people who then have to live in or around them, without
regard for engineering or human psychology.

~~~
cjalmeida
Not really "these days". Unliveable spaces has a good longstanding tradition.
Just check Le Corbusier and Niemayer works.

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steve19
They plan on finishing it in 2041, more than two decades away. I think this
sounds far more like a marketing ploy than an actual building project.

~~~
Yetanfou
People working in forestry are used to planning long-term, what you sow or
plant now will be reaped by the next generation. They just planted the
building and are now waiting for it to grow to harvestable size.

~~~
sitkack
I would love for humans to plant Red Woods and Iron Woods that would someday
be harvested. They take so long to grow that they are not replaced, an
ultimate testament to selfishness.

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steve19
You would enjoy reading about this forest:

[https://www.atlasobscura.com/places/visingso-oak-
forest](https://www.atlasobscura.com/places/visingso-oak-forest)

Ultra long term planning is hard.

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KhanMahGretsch
Japan is unrivaled in building long-lasting wooden structures using only
joinery (no nails, screws). This allows the wood to expand and contract
harmoniously without cracking. Multi-story buildings (temples are a great
example) have “floating” stories than may shift several feet during an
earthquake, all kept together with a freestanding “spine” mounted only to the
ground.

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pimmen
Is it harder to build this thing resistant to earthquakes than if it was made
out of steel and concrete?

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armada651
So Tokyo is finally going to build a Skytree made of actual wood this time?

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prostoalex
Having just paid for a termite inspection, are infestations not a risk?

~~~
baud147258
I first read that as thermite and I asked myself how does it work with wood
buildings. (even if, as per this thread, wood is better regarding heat)

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foobarbazetc
Is there a good article on fire safety in these buildings?

~~~
anonymous5133
Curious as well. Seems like it would be a death trap and help spread the fire
more.

~~~
yawniek
Actually wood buildings are safer in case of fire if done right. New
techniques (can't find the link) are able to control the way fire spreads and
how fast it burns far better, also iirc because the heat that develops is
lower.

~~~
tmas
Safer? Than steel or brick?

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alkonaut
Yes. The reason is slow and predictable burn that doesn’t affect the
structural integrity until it has burned for a very long time. Even without
special fire proofing, glulam burns at less than 1mm/minute.

The idea behind a fire safe high rise isn’t that it can’t burn but that when
it burns it doesn’t collapse until people have left. That’s why the integrity
is measured after 30min burn, 60min burn etc. As a wood beam burns the
charring limits the oxygen supply of the fire, slowing the burn.

Steel beams require fire proofing and high temperatures or compromised fire
proofing makes them structurally unsound which can cause unpredictable
catastrophic failure (this happened in both of the WTC towers).

~~~
mongol
Is really collapse the the main danger to consider when a fire happens? I
would think that when a building collapses from fire, many people in the
building would already be dead from smoke and heat. If a wooden building would
stand longer but be smoke filled earlier, I am not sure it can be said to be
safer.

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evgen
Everything else around your structural elements are going to be putting out
smoke that will kill occupants regardless of whether the structure is steel or
wood in situations like this. You worry about collapse for cases when the fire
on a lower level traps occupants above, and the more time you can buy to
control the fire or evacuate the better.

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m3kw9
Adhering to fire codes must be big part of the costs. How do you fireproof
some crazy dude just decides to throw a Molotov cocktail at it?

~~~
mseebach
I don't remember the details, but on a previous article on wooden skyscapers,
it was explained how the engineering of the wood, which is also required for
the necessary structural strength, made it very dense and practically
incombustible. Fire proofing is an inherent quality, not something that's
applied and thus could be done poorly.

IIRC.

~~~
DasIch
Wood also just burns, slowly. Steel might not burn but as it gets hot it loses
structural integrity very quickly.

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faragon
"The W350 tower will be mostly wood, and 10% steel."

Wood and steel.

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imtringued
You might as well call it a steel tower at this point.

Steel is heavy but it's also very strong. You don't need a lot of it to build
something. A pure steel building actually ends up being lighter than a
concrete building because of this.

~~~
Sharlin
Steel has a great tensile strength but an average compressive strength at
best. It's prone to buckling. Concrete is the exact opposite. In a skyscraper
you need great tensile _and_ compressive strength in different structural
elements. This is why reinforced concrete is such a big deal. The properties
of steel and concrete naturally complement each other.

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incompatible
I have a certain dislike for wooden houses because a) they seem to have high
maintenance requirements, since wood as an organic material is often attacked
by fungi, mould, or insects b) the ones I've lived in were old buildings
lacking insulation and draughty, thus freezing in winter. That could be fixed
with insulation of course.

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jotm
Bricks (everywhere, internal walls and all) and concrete (for the floors) are
the best - no stupid squeaking, nothing to rot, nothing to break, great
soundproofing, good thermal insulation if done right, will last a long time
provided no natural disasters. Not even expensive depending on the region.

That said, I don't get the point of a wooden skyscraper. I'd guess it's
earthquake resistant, and it's not actual natural wood but a mix of synthetic
materials and wood.

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swampthinker
Bricks and concrete are absolutely not the best. They have terrible insulation
properties, poor sound absorption, and cost more than wood structures.

Wood is an overall superior construction material if you can use it, and I
think you're misunderstanding the pressure treatment process. It's normal wood
placed in a vacuum chamber so preservatives can seep into the lumber.

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MertsA
Don't forget, brick and mortar also holds moisture and is porous. This can
lead to spalling in cold weather and rotting whatever's behind it in warm
weather.

[https://www.youtube.com/watch?v=k1m5VShzxYs](https://www.youtube.com/watch?v=k1m5VShzxYs)

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y123y
It's just a proposal/advertisement of one company.

