Wood The Best Material For Skyscrapers!

[Eclipse Now]

Do you agree? Please listen to the podcasts below.

 

This ABC podcast architect Michael Green unpacks how ‘new’ wood is cheaper, safer, and stronger than steel and concrete for building Skyscrapers!

http://abc.com.au/rural/telegraph/content/2011/s3159230.htm

 

One cubic meter of wood stores 1 ton of Carbon. Imagine fast-growth trees of 10 to 15 years sequestering all that Carbon to house the next 3 billion people who need homes!

 

* He uses Aspen and Birch trees that are shredded and the fibres glued together

* (Note: glue can come from our rubbish tips!)

* Trees are only 10 to 15 years old when harvested

* Apart from the foundations, wood can replace the use of steel and concrete in buildings and becomes the new structural backbone of the skyscraper!

* Huge wood beams are now 20m long by 2.5m wide by 85mil thick

* Wood weights half as much as concrete which improves the strength of the building in an earthquake

* Wood buildings have survived earthquakes better than heavy steel and concrete buildings

* Can lead to an enormous reforesting business worldwide, and an enormous sequestration of Co2!

* As a material the wood is more expensive but …

* It so drastically reduces the labour costs associated with buildings as it can go up so much faster.

* EG: It takes a week to pour a concrete floor in a skyscraper before the next floor can be constructed. Michael Green has seen wood skyscrapers that can build 6 floors a day!

 

Here is his TED talk.

[joekgamer]

* Huge wood beams are now 20m long by 2.5m wide by 85mil thick

* Wood weights half as much as concrete which improves the strength of the building in an earthquake

 

Even with how light wood is, that would weigh more than the equivelently strong steal beam.

 

* Wood buildings have survived earthquakes better than heavy steel and concrete buildings

 

Because they are generally shorter/wider.

 

* Can lead to an enormous reforesting business worldwide, and an enormous sequestration of Co2!

 

Or a boon to the deforestation buisiness, and environmental collapse.

 

* It so drastically reduces the labour costs associated with buildings as it can go up so much faster.

 

But it takes much longer to make. 15 years for a wood beam vs less than a day for a steel one.

 

* EG: It takes a week to pour a concrete floor in a skyscraper before the next floor can be constructed. Michael Green has seen wood skyscrapers that can build 6 floors a day!

 

Who would build a skyscraper with concrete floors above the first floor?!

 

Two more points: steel doesn't rot, and wood shatters. Wood would last maybe a few decades at most before their beams rot, while steel buildings would last centuries with proper maintenace (painting/sealing the beams, etc). Also, steel bends, so in high winds towers can sway. A wood one would break because wood is brittle. Wodo can be sawed through by a saw/chainsaw that would barely scratch a steel beam.

[Turtle]

Do you agree? Please listen to the podcasts below.

 

This ABC podcast architect Michael Green unpacks how ‘new’ wood is cheaper, safer, and stronger than steel and concrete for building Skyscrapers!

http://abc.com.au/rural/telegraph/content/2011/s3159230.htm

 

certainly an attractive alternative even if not a replacement.

 

* EG: It takes a week to pour a concrete floor in a skyscraper before the next floor can be constructed. Michael Green has seen wood skyscrapers that can build 6 floors a day!

 

pouring the floors does not interupt building the frame above.

 

 

 

But it takes much longer to make. 15 years for a wood beam vs less than a day for a steel one.

that is not a valid comparison. first, while it does take 15 years for a crop of trees to mature, when you have 15 plots or more you have a more-or-less continuous harvest. second, the ore for the steel has to be mined & transported & that is time & money, not to mention not sustainable as is the tree growing.

 

 

 

Who would build a skyscraper with concrete floors above the first floor?!

erm...just about everyone!?

 

Skyscraper

•7 In a steel-skeleton building, floors are constructed on the layers of horizontal bracing. In other building designs, floors are supported by horizontal steel beams attached to the building's core and/or support columns. Steel decking (panels of thin, corrugated steel) is laid on the beams and welded in place. A layer of concrete, about 2-4 in (5-10 cm) thick, is poured on the decking to complete the floor. ...

 

Two more points: steel doesn't rot, and wood shatters. Wood would last maybe a few decades at most before their beams rot, while steel buildings would last centuries with proper maintenace (painting/sealing the beams, etc). Also, steel bends, so in high winds towers can sway. A wood one would break because wood is brittle. Wodo can be sawed through by a saw/chainsaw that would barely scratch a steel beam.

 

:doh: wood buildings can & do last for centuries. steel rusts as sure as wood rots. wood doesn't bend? ever used a bamboo fishing pole? how about a steel one. :doh: steel can be sawn through as easy as wood.

 

here's a blurb on plans for the tallest wood building in the woorld.

 

Plans for the World's Tallest Wooden Building

Norway plans to construct a wooden building 16-17 stories tall with carbon neutral construction techniques. The Norwegian Barents Secretariat will use it for a cultural center for the nation’s northern coast. It will house a library, a theatre, and art studios in its approximately 10,000 square meter interior space and will highlight sustainable development:

 

The idea is to construct a building which will be CO2-neutral, where the concept of the cycles of nature will be preserved. The innovative solutions on modern wooden constructions will stand as a token of the level of competence in the region, says architect Reiulf Ramstad.

 

As far as I have been able to determine, the record for tallest wooden building in the world is currently held by the 43-meter tall St. George’s Cathedral in Guyana.

 

[Eclipse Now]

Awesome points Turtle. Can someone please explain sheer to me? Is that a term used to describe the amount of force as a building, and its weight, respond to wind? Michael Green said that the larger wooden buildings responded better to earthquakes etc as they were lighter. This seems counter intuitive to me, but I'm not a scientist or architect. :huh:

[joekgamer]

General shear stressThe formula to calculate average shear stress is:

 

[t=f/a]

 

where

 

τ = the shear stress;

F = the force applied;

A = the cross sectional area.

 

http://en.wikipedia.org/wiki/Shear_stress

 

However, this does not explain how a material reacts to sheer stress. A metal beam bends. A wood beam shatters/breaks.

 

From the official statistics, available at the CN Tower website (www.cntower.ca):

 

In a 120 KPH breeze, there is this much sway:

 

Antenna mast (highest part): 1.07 meters (about 3 1/2 feet for you Yanks)

 

SkyPod (Upper observation deck): .46 meters (1 1/2 feet, about)

 

Lookout (Open observation deck): 22.9 centimeters (9 inches)

 

It has to move. The only alternative would be to engineer these parts to withstand the tremendous forces (wind, gravity, shear, compression and precipitation) and you'd still have one inescapable fact: these things are held up in the sky on a stick. Remember moving things with a lever in grade school? The longer the lever, the more the mechanical advantage. The Skypod is on a lever 1100 meters long - how much force to make it topple if the lever were one stiff piece? That's why there's some "give" in it - to destroy the mechanical advantage and keep the tourists alive, happy and spending money. That's what keeps Toronto green.

 

http://www.straightdope.com/columns/read/1590/do-tall-buildings-sway-in-the-wind

[CraigD]

Do you agree [that wood is the best material for skyscrapers]?

Wood's an wonderful material, but it's a bit disingenuous, I think, to compare tall wood buildings with tall steel or reinforced concrete ones.

 

The planned world’s tallest wood building Turtle linked is 17 stories tall. The 1902 steel frame Flatiron Building is 22, the 1931 steel frame Empire State building, 102, and the current world’s tallest Burj Khalifa, 163, the bottom 156 reinforced concrete, the top 7 steel frame. Though the term “skyscraper” is a vague one which can in fairness be applied to a building of as few as 5 stories in a town with few or no taller buildings, when I hear of a 21st century building called one, I think of something at least several multiples of 20 stories tall.

 

I suspect there are reasons other than cost and tradition that wood buildings over a few stories are rare. Typical compressive strength for reinforced concrete is 3000-6000 psi, which increases with age. Typical compressive strength for wood is from a few hundred to around 1000 psi. This means that wood columns need be at least 2 times as wide as concrete to support the same load. Wood is less dense than concrete – a good structural wood has a specific gravity of about 0.6 vs 2.4 – about the same as the ratio of their compressive strength – so wood isn’t not out-of-the question for very tall buildings, but would take some radical, untried engineering to pull off.

 

Wood also ignites much more easily than concrete, and burns with more heat. Though I’m sure the engineers of the planned 17 story building in Norway are taking designing special precautions, the prospect of such a wood building burning is awful to consider. :(

[Eclipse Now]

Wood is less dense than concrete – a good structural wood has a specific gravity of about 0.6 vs 2.4 – about the same as the ratio of their compressive strength – so wood isn’t not out-of-the question for very tall buildings, but would take some radical, untried engineering to pull off.

 

What does gravity have to do with it? If the building material is lighter then isn't there less weight from the floors above to have to support?