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  #1  
Old Posted Mar 21, 2012, 8:18 PM
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The Case for Skyscrapers Made of Wood

http://www.theatlanticcities.com/des...comeback/1554/

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The Case for Skyscrapers Made of Wood

Samuel Medina
2:56 PM ET
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Since the invention and development of steel and concrete, the combination of which would spawn the birth of the skyscraper, wood as a building material has been marginalized as simple construction ephemera, used to form concrete or to structure building frames advanced with the expressed purpose of producing single family homes or large estates and to furnishing their plush interiors.

Wood fell out of vogue in a large part because of its vulnerability to fire, probably the single greatest factor in restricting use of the material to smaller structures. But change is coming, writes CNN, as wood has become transformed by a handful of dedicated engineers and architects – Shigeru Ban most notable among them - and put to use in the service of large-scale structures like Michael Green‘s proposed “Tallwood” skyscraper in Vancouver.


Photo courtesy of Michael Green

The plans for the 30-story tower are among a small group of “woodscrapers” being proposed throughout the world, which all had to overcome stringent building codes. Explaining the motivation behind his design, Green says that wood construction at such scales is decidedly cheaper than standard-industry methods and, more importantly, much more energy efficient, given the large amounts of CO2 expended in the manufacturing of steel and concrete and the extent of their large carbon footprints. Conversely, wood traps carbon dioxide throughout a building’s life cycle, and, if sustainably harvested from controlled and well-managed forests, can prove to be a renewable resource.

...
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  #2  
Old Posted Mar 21, 2012, 10:37 PM
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Nice idea,but can wood support the weight of a building in the same way steel does? After all, isn't that another reason why the latter became the predominant component for building skyscrapers?
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Old Posted Mar 22, 2012, 5:59 AM
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As the posted article notes, wood has a poor resistance to fire, which led some cities to ban wood construction for taller structures, particularly in Chicago and New York where modern skyscrapers were developed. Since wood was banned as a structural material in these main skyscraper markets, the tools and strategies for designing skyscrapers with wood were never really developed.

Strength wise, wood fares fairly well. In compression, wood is actually about as strong as concrete, while being much lighter. Wood also compares favorably to steel, since although steel is much stronger, it's also quite heavier. Wood's light weight is an advantage in earthquake prone areas.

Here's a chart of the strength to weight ratio(ksi/SG) for some varieties of wood and steel and concrete.

Data from http://workshopcompanion.com/KnowHow...d_Strength.htm

Other difficulties with designing with wood are that the strength changes with moisture content and direction of grain. For a lowrise structures, it's ok to overcome these uncertainties with deliberate overbuilding, but for a skyscraper, it's necessary to have a more consistent material.
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Old Posted Mar 22, 2012, 6:22 AM
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Well then, this may be the time for Vancouver to actually be another innovator city in the development of the skyscraper. North America has enough land to develop tree farms to grow the species that will be needed to build many of these "woodscrapers".
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  #5  
Old Posted Mar 30, 2012, 2:23 AM
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Originally Posted by scalziand View Post
As the posted article notes, wood has a poor resistance to fire, which led some cities to ban wood construction for taller structures, particularly in Chicago and New York where modern skyscrapers were developed.
Not necessarily true...and damn is this a headache to prove it when it comes to building codes into Chicago. Try converting a warehouse built of wood into a high school!! It can be done, despite that code doesn't allow it.

Heavy timber actually has self insulating properties. If you've ever chopped through a thick log that's been burning in a fireplace, you'll find the core unburned. Usually heavy timber exposed in building fires can maintain its strength and unlike steel, not warp and bend from heat that would cause stress on the rest of the structure.

Basic fireinsulating solution is the same. Encase the columns in several layers of sheetrock.

If there's ever is a fire, replacement of members is fairly easy. It's resilient construction to damage.

Where you hear all the bad stories is when a house or apartment built out of 2x4's and 2x10's burns to a crisp....obviously because the stud-wall construction has thinner members, and more edges to catch fire.

Some of the drawbacks to wood construction will be flooding, pests, and mold. I realize there's tons of treated wood products out there that claim to defeat all of these problems, but I question the longevity of resistance, and I still have not done enough research on their health effects. Basically, I don't know what kind of treated wood is required for high-rise construction versus a low rise...which we know has little or no EQ issues.

Basically, I'm only convinced on engineering and life safety part of it which are the biggest hurdles to win over skeptics. I'm happy with the sustainability aspect too.
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  #6  
Old Posted Mar 30, 2012, 1:49 PM
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And what happens if the big bad wolf shows up? Wooden skyscrapers would be more than likely be susceptible to hurricanes and stuff.
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  #7  
Old Posted Mar 30, 2012, 9:51 PM
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Originally Posted by M II A II R II K View Post
And what happens if the big bad wolf shows up? Wooden skyscrapers would be more than likely be susceptible to hurricanes and stuff.

In japan they have what one might call proto-skyscrapers. Their called pagoda towers and while I will admit their not that tall. They have more in common with modern skyscrapers than your typical wooden structure in that they are both earthquake resistant (some actually have tuned mass dampers) and hurricane resistant ( Japan gets hit with bigger hurricanes than we do e.g. typhoon tip).

As Hayward said the main issue is fire-proofing. Several pagoda's of antiquity have been destroyed by fire.

http://www.jappleng.com/articles/vie...da-and-history


http://en.wikipedia.org/wiki/File:Horyu-ji09s3200.jpg
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Old Posted Mar 31, 2012, 12:06 AM
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Actually wooden skyscrapers could probably take place in developing or undeveloped countries. Since these nations have a lower GDP they can afford to construct a wooden skyscraper. Wood would serve as a fine gap between traditional houses and steel skyscrapers.
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Old Posted Mar 31, 2012, 5:04 AM
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Originally Posted by M II A II R II K View Post
And what happens if the big bad wolf shows up? Wooden skyscrapers would be more than likely be susceptible to hurricanes and stuff.
It probably wouldn't be a good idea in areas with a lot of hurricanes...or even humid weather. Even if the building isn't damaged by strong winds, water that's seeped into the walls will do the rest. Sure, plenty of wood buildings have been fine in places like Florida. But how does one easily swap out a ton of moldy lumber and keeping a tall building plumb and level after repair.

And tornado areas...don't even think of it. Even Steel buildings don't fare well.

Maybe someday reinforced concrete will become more sustainable. There's GFRC, but it's usually limited to decorative elements and cladding.
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Old Posted Mar 31, 2012, 3:01 PM
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And then there's termites and other unwanted guests.
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Old Posted Apr 1, 2012, 4:49 AM
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So do you guys think these buildings would be best built in higher elevations?
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  #12  
Old Posted Apr 24, 2012, 11:59 PM
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Termites, fire-prone, highly work-intensive maintenance-wise.

Just three examples why "highrise" wood structures should not be considered.

Interesting exercise, tho.

But with future hybridization in genetics and farming, who knoww what they will come up with.

I think some sort of plastic structure is much more likely than wood.

I didn't even realize until a few years ago that the "periodic table" of elements has increased so much siince I was in school, so who knows what new element/material will be created in the future.

Plas-steel, a combo of concrete/steel/plastic? All I know is we'll all be pleasantly surprised...
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Old Posted Apr 29, 2012, 1:25 PM
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Still haven't seen anybody talk about how they plan to address the fire issue. Tall wood buildings certainly are not allowed by building codes here.

Somebody mentioned large timbers, fireproofing, etc. But if you do all of that, you lose the weight and cost advantage, which was the whole point in the first place. We do a fair bit of timber construction here (in the mountains), but it's not cheap. Not the same thing as wood construction at all.
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Old Posted Apr 30, 2012, 12:02 PM
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It's very cool, but I'd personally never want to live or work in a wooden skyscraper. Also, one, by itself, might have minimal fire hazard, but a "forest" of them - that would be truly terrifying.
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Old Posted May 4, 2012, 12:51 AM
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Steel and concrete would still be in the infrastructure, and wood will probably be just the cladding (and that's still unfeasible). I also see glass on the building render in Vancouver.
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Old Posted May 4, 2012, 4:04 AM
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Heavy timber isn't all that much more dangerous than steel, which will deflect and fail when exposed to fire. Of course, our solution is to fireproof steel. It's done the same for wood. If code permits highrise woodframe construction, you'll usually encase members in several layers of sheetrock. You can usually achieve some pretty high fire ratings by building up around the columns. If heavy timber is used, the outside surface of the wood will form a protective char and maintain quite a bit of strength and rigidity, even after the fire is extinguished. Of course that is worst case scenario. Usually the sprinkler system will knock out the fire before things get worse.

Again, my fear IS the exposure to water. Like any material it's a problem but with wood you have more problems besides weakening strength, like mold, insects, and chemicals.

I imagine the entire building envelope is glass with aluminum framing with some wood planks projected over the glass for aesthetic reasons. If code allows, you can pour concrete over a wood structure. It's done all the time here in Chicago to boost fire ratings. They'll go into old wood frame factory buildings and just start pouring over the old floor to level things out a bit and provide some extra protection.
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Old Posted May 9, 2012, 8:31 PM
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Interestingly in Germany on Grosser Feldberg, a mountain in Hesse, there is since 1950 a high-rise like telecommunication tower whose upper section consist of wood, without metallic parts! See http://skyscraperpage.com/diagrams/?buildingID=41551 .

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Old Posted May 10, 2012, 8:45 PM
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Interesting idea, but as a Floridian it freaks me out. We stopped using wood for structural purposes a while ago. I understand that wood can be treated, but I wonder if you lose some of the benefits from that.


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Old Posted Jun 6, 2012, 7:01 PM
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Wood That Reaches New Heights

By HENRY FOUNTAIN
Published: June 4, 2012

LONDON — Among the many apartment buildings in the London borough of Hackney, the nine-story structure on the corner of Provost Street and Murray Grove stands out, its exterior a mix of white and gray tiles rather than the usual brick.


William Pryce
WITH THE GRAIN, AGAINST THE GRAIN At the nine-story Graphite Apartments in London, structural elements involve many layers of spruce fused together.

But it’s what’s underneath this cladding that makes the 29-unit building truly different. From the second floor up, it is constructed entirely of wood, making it one of the tallest wooden residential buildings in the world.

It was built three years ago using laminated spruce panels, up to half a foot thick and 30 feet long, that were fabricated to precise specifications in Austria, shipped across the English Channel and bolted together on site to form the exterior and interior walls, floors and roof. Even the stairwells and elevator shafts are made from these solid panels, called cross-laminated timber, which resemble supersize plywood.

Developed in Europe in the 1990s, cross-laminated timber, or CLT, is among the latest in a long line of “engineered” wood products that are strong and rigid enough to replace steel and concrete as structural elements in bigger buildings. Already popular in Europe, CLT is only beginning to catch on in North America, where proponents say buildings made with the panels could be a cheaper and environmentally friendly alternative to structures made with those other materials.

...

Codes in Britain allow more flexibility, said Anthony Thistleton, partner in the London architectural firm of Waugh Thistleton, which designed the Hackney building, formerly called Stadthaus and now known as the Graphite Apartments. “It’s perhaps the only place that we could have broken this ‘timber ceiling,’ ” he said.

Waugh Thistleton has designed a second CLT structure, a four-story commercial and residential building, now under construction nearby, and an eight-story apartment block is within walking distance, making Hackney a hotbed of cross-laminated timber design.

Last month, construction began on a 10-story CLT apartment tower in Melbourne, Australia. Some proponents think buildings made from the panels could be even taller. “In the U.K., I’m convinced that it will hit 12, 13, 14, maybe 15 within a couple of years,” said Craig Liddell, formerly commercial director with the British division of KLH, the Austrian company that made the panels for the Graphite Apartments. Others say that hybrid structures, perhaps with timber panels built around a concrete core, could reach 30 stories.


http://www.nytimes.com/2012/06/05/sc...pagewanted=all
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