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Old December 19th, 2012, 04:12 PM   #2241
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men on the boom of the Link Belt, maybe preparing to demob it.
Looks like you're right, boom is being taken down.
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Old December 19th, 2012, 06:03 PM   #2242
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Old December 19th, 2012, 07:22 PM   #2243
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Old December 20th, 2012, 12:06 AM   #2244
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Not to mention safer in the event that something catastrophic happens?

Asbestos is a nasty killer, yet Quebecers still want to mine the hell out of it XD
STill legal here?
In my country, it has been officially banned for use in buildings already for decades.
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Old December 20th, 2012, 01:35 AM   #2245
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STill legal here?
In my country, it has been officially banned for use in buildings already for decades.
It's not necessarily illegal, but it's not commonly used anymore. However, many older buildings still have it.
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Old December 20th, 2012, 12:12 PM   #2246
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image hosted on flickr

4 World Trade Center - 150 Greenwich Street by chrisswann26, on Flickr

image hosted on flickr

3 World Trade Center - 175 Greenwich Street by chrisswann26, on Flickr
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Old December 20th, 2012, 01:45 PM   #2247
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.. However, many older buildings still have it.
Same here. Contamination hazard during fires and delays + extra safety measures during demolition.
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Old December 20th, 2012, 01:55 PM   #2248
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It's good to see how much stronger the floor holding beams are compared to the trusses of the Twin Towers.
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Old December 20th, 2012, 02:06 PM   #2249
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The configuration of the structure is way more robust than what LERA envisioned for the twins.

Thanks for all the nice info I´m still curious though why most Asian supertalls use concrete structures and why these use steel. Is it the specific conditions on each site, or cost that determines?

Since the core parts that are concrete on new skyscrapers were drywall in the old twins, does that mean that the interior walls of the Empire State Building (elevator shafts and such) and the core walls in Sears tower is also drywall?

Last edited by Huskies; December 20th, 2012 at 02:55 PM.
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Old December 20th, 2012, 04:31 PM   #2250
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concrete is inherently inferior to steel. concrete's advantage is in compression.

concrete does not perform well in tension, moment, and shear, which is why we see so much rebar in concrete.

aside from being a better raw material, connection design for steel frames allows for a lot more options to meet forces.

we see the concrete encasement to supplement the steel and to act as 'even better' fireproofing. the purpose of the core itself is shear strength. The concrete portion is truely to create a secure area of the building that contains the transportation, utilities, emergency access in the event of a fire or whatever.

the twins were inherently weak because the core was small, unprotected, and required the outer wall to share the load. they used bar joists to hold the floors. Bar joists are garbage. The floors were actually prefabricated off site and set in place as panels. The purpose of this design was to create massive amounts of uninterrupted floor space.

The ESB is a traditional beam, column, brace frame building. The loads of the building area shared all over the place as it has a crazy amount of column lines. Its incredibly dense with steel. Its floor area ratio is incredibly stout for a building of that height.

Sears is not core driven, but it is much more traditional when compared to the twins. probably closer to the ESB

Last edited by thejacko5; December 20th, 2012 at 05:25 PM.
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Old December 20th, 2012, 04:37 PM   #2251
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Yes, on ESB the facing was actually brick, and each window is framed in steel panels. They used steel ornament, if you will, to cover up the interior brick facing and steel framing.
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Old December 20th, 2012, 04:41 PM   #2252
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the brick comment made me think of something else also.

they used to use brick as fireproofing for steel.
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Old December 20th, 2012, 05:21 PM   #2253
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Quote:
Originally Posted by thejacko5 View Post
concrete is inherently inferior to steel. concrete's advantage is in compression.

concrete does not perform well in tension, moment, and shear, which is why we see so much rebar in concrete.

aside from being a better raw material, connection design for steel frames allows for a lot more options to meet forces.

we see the concrete encasement to supplement the steel and to act as 'even better' fireproofing. the purpose of the core itself is shear strength. The concrete portion is truely to create a secure area of the building that contains the transportation, utilities, emergency access in the event of a fire or whatever.

the twins were inherently weak because the core was small, unprotected, and required the outer wall to share the load. they used bar joists to hold the floors. Bar joists are garbage. The floors were actually prefabricated off site and set in place as panels. The purpose of this design was to create massive amounts of uninterrupted floor space.

The ESB is a traditional beam, column, brace frame building. The loads of the building area shared all over the place as it has a crazy amount of column lines. Its incredibly dense with steel. Its floor area ratio is incredibly stout for a building of that height.

Sears is core driven, but it is much more traditional when compared to the twins.
Thank you for the info This is very interesting to read for me because I plan on studying engineering and the area that interests me the most in engineering is how to make buildings withstand catastrophes.
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Old December 20th, 2012, 07:58 PM   #2254
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My upload limit for flicker has been hit, so here are links to a model I made showing the corner structure of the ESB and the bricks, facade, and interior. Even if you don't have SketchUp you can use the in page "3D View" button at the top right corner of the preview image to rotate the model.
ESB Corner Model

I'll eventually upload my 3WTC model, but I'm using the construction images so I can't work ahead of the actual progress.
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Old December 20th, 2012, 09:57 PM   #2255
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Quote:
Originally Posted by thejacko5 View Post
concrete is inherently inferior to steel. concrete's advantage is in compression.

concrete does not perform well in tension, moment, and shear, which is why we see so much rebar in concrete.

aside from being a better raw material, connection design for steel frames allows for a lot more options to meet forces.

we see the concrete encasement to supplement the steel and to act as 'even better' fireproofing. the purpose of the core itself is shear strength. The concrete portion is truely to create a secure area of the building that contains the transportation, utilities, emergency access in the event of a fire or whatever.

the twins were inherently weak because the core was small, unprotected, and required the outer wall to share the load. they used bar joists to hold the floors. Bar joists are garbage. The floors were actually prefabricated off site and set in place as panels. The purpose of this design was to create massive amounts of uninterrupted floor space.

The ESB is a traditional beam, column, brace frame building. The loads of the building area shared all over the place as it has a crazy amount of column lines. Its incredibly dense with steel. Its floor area ratio is incredibly stout for a building of that height.

Sears is not core driven, but it is much more traditional when compared to the twins. probably closer to the ESB

Very nice post. I am an Architecture student and recently completed a course about structural systems and building materials, and think this info is very helpful. That's why I´m asking all this stuff, to learn, not to cause a stir


I understand that steel has many benefits towards concrete, but it seems like steel encased in concrete should be the optimum solution? Since burj khalifa has to face even more wind loads than this building, and so many huge skyscrapers are all being built in steel and re-bar completely incased in concrete, it does seem to be the "cutting edge" way of building, especially with the added fire resistance of concrete.

I do understand though that if a system was superior in every way it would be used everywhere, so it would be naive to think that the "burj khalifa/ shanghai tower etc" way is better in every way. I guess im curious about the reasoning behind each case and sort of "pros and cons" .

To ME it seems like the only advantage not casting everything would have is perhaps lower cost/ easier to build perhaps?. I just feel like building made of steel encased in concrete should be more resillient in almost every way than a building mostly just steel? These are just my thoughts so feel free to educate me.


(Do you know if the elevator shafts are made of drywall in Sears tower? i do understand that neither ESB or Sears have the core system of the old twins, but but still have elevator shafts.. )

Also, im guessing the fire resistance of Empire state building cant be much higher than the old twins, but the massive amount of interior columns would have probably held firm regardless if the plane had hit it instead? Really OT perhaps but im always saying that ESB would have held up better if it was hit so its nice to know if im completely wrong...


Im like that annoying kid now that asks a million questions, but the knowledge base here is is to good not to tap into
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Old December 20th, 2012, 10:58 PM   #2256
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Asking questions in never annoying. Education is the most important and most noble purpose of a forum

I would love to know whether Willis and ESB have drywall in such a major use as the Twins did?

Also, isn't not encasing a steel structure in concrete good against earthquakes? I mean, concrete is far more vulnerable to cracking and a cracked concrete shell would be additional load on the uncracked steel, with this cracked concrete being more or less useless because of its damage? I dunno, that's why I'd like to find out
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Old December 20th, 2012, 11:46 PM   #2257
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Quote:
Originally Posted by thejacko5 View Post
concrete is inherently inferior to steel. concrete's advantage is in compression.

concrete does not perform well in tension, moment, and shear, which is why we see so much rebar in concrete.

aside from being a better raw material, connection design for steel frames allows for a lot more options to meet forces.

we see the concrete encasement to supplement the steel and to act as 'even better' fireproofing. the purpose of the core itself is shear strength. The concrete portion is truely to create a secure area of the building that contains the transportation, utilities, emergency access in the event of a fire or whatever.

the twins were inherently weak because the core was small, unprotected, and required the outer wall to share the load. they used bar joists to hold the floors. Bar joists are garbage. The floors were actually prefabricated off site and set in place as panels. The purpose of this design was to create massive amounts of uninterrupted floor space.

The ESB is a traditional beam, column, brace frame building. The loads of the building area shared all over the place as it has a crazy amount of column lines. Its incredibly dense with steel. Its floor area ratio is incredibly stout for a building of that height.

Sears is not core driven, but it is much more traditional when compared to the twins. probably closer to the ESB
I will have to respectfully disagree with the assertion that "concrete is inherently inferior to steel". While steel has a stronger compression and especially stronger tensile strength, concrete is superior in other ways.

Concrete is cheaper. This can free up money for other aspects of the design.

Concrete can be pumped and poured with great ease. Many modern skyscraper have plumbing installed in the core that allows concrete to be pumped to where it is needed during construction. This is much quicker than trying to fasten a high number of steel building components.

Concrete provides fire protection. Even wood has a better fire rating than steel in some applications.

Concrete provides a continuous surface which is less susceptible to water infiltration.

Sound deadening. Residential buildings with concrete floors and unit walls enjoy near perfect sonic isolation from the neighboring units.

Exposed steel can require continual maintenance.

Concrete can provide mass to balance cantilevered structures.

Etc.


This isn't to say that concrete is better. It isn't "better". Rather that there are tradeoffs and neither are "inherently better".


The original question was about why Asian supertalls are using concrete instead of steel. That I don't know. If I had to hazard a guess it would be cost and availability of people skilled in designing and constructing steel structures. But that is just a guess.
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Old December 21st, 2012, 03:52 AM   #2258
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^

and around and around we go.

i cant disagree with a lot of what you said.

i'll leave it at, this is why we have the ongoing battle between the two materials

another benefit of concrete is that the labor is significantly cheaper.
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Old December 23rd, 2012, 09:29 PM   #2259
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Interesting note from kpdrummer82 on SSP

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Originally Posted by kpdrummer82
I got a word in from a worker on the site today that says since the core was not poured to fit an 88 story structure as of right now, it would take 9 months for a completion plan to even begin. Meaning if Larry did sign a lease right now, we would have to wait until August or September for it to even start construction towards 88 stories.
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Old December 23rd, 2012, 09:43 PM   #2260
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How is that possible, and wasn't it 80 stories?
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