NEW YORK | One World Trade Center | 1,776' Pinnacle / 1,373' Roof | 108 FLOORS

[sterlippo1]

Originally Posted by SkyscrapersOfNewYork

at 800 feet it still barley makes an impact...God i love this city.

lol,me too but it is filling in that hole quite nicely

[DallasGreg]

Originally Posted by STR

There were 4 key design lessons learned from 9/11:

1) NIST concluded that if the fireproofing in the Twin Towers had stayed in place the buildings would not have collapsed. Therefore the proofing on steel sections is blast resistant. The concrete core will, naturally, be an excellent insulator for the steel within, allowing the fire to burn out long before endangering the structure.

2) Even if there was a failure at some point in the structure, such as the collapse of one floor, the WTC buildings are designed specifically to prevent progressive collapse. Progressive collapse is when a local failure causes a domino effect that results in the collapse of the entire structure. Progressive collapse is the cause of the failure of all 3 previous WTC office towers.

3) A specific lesson from the first 7WTC was redundancy in the columns. The failure of one single, important column lead to the collapse of the entire 47 story building. As such, any 2 columns in the new towers (including 2 adjacent columns) can be severed without compromising the structure.

4) The concrete core has an added advantage in that it shields the opposite side of the building in case of an airplane impact. Several columns were severed on the sides of the towers opposite of the impact points when hardened parts of the airliners (such as the steel and titanium engines) flew straight through the building, cutting exterior columns, core columns and escape stairways along the way and exiting the structure on the other side. Enclosing the stairways also largely eliminates the chance that all escape routes will be severed in an emergency.

The entire WTC is built to this specification. All 5 towers, as well as the memorial and the concourse. This spec is considerably heavier and more redundant than any other building of this size in the world. It is one of the main reasons why 1WTC will cost $3.3 billion, and the entire complex will cost roughly ~$20 billion. No one is going to come out and challenge the world by saying these buildings are airplane proof, as honestly an airplane impact is such a chaotic event with so many huge variables you really can't proof anything like an office tower against them (nuclear containment domes and other solid structures are another story, but I digress), but that was the goal.

The WTC is completely, utterly overbuilt and overly redundant. They will be standing there for the next 500 years, minimum.

Fascinating...

[dchan]

Originally Posted by steveve

well, from a design perspective, the old WTC's used reinforced steel on the exterior, (hence, no columns on the regular office floors), and since the planes obliterated the steel supporting columns on the exterior, the structure was weakened. the core of 1WTC is concrete for sure, and the floors are steel as far as i know (not sure if there's concrete filled in there as well), i'm not expert on construction though,

See STR's point number 1 in the last page. The fact is that designers of the original WTC towers designed them to specifically withstand the force of a jetliner crashing into it, specifically a Boeing 707. The crash would have left a huge hole in the exterior skin, but the force would have been redistributed around the hole to the intact columns.

Of course, the planes that crashed into the towers were larger Boeing 767s, but that's not the key point to the collapse. The key is the weak fireproofing much of the building's steel structure. Steel is a wonderfully strong material (it's far stronger unit-wise than concrete in both tension - obviously - and compression), but it's also susceptible to heat. More specifically, it becomes much weaker above a certain temperature, one which burning jet fuel exceeds. Once the fireproofing was destroyed, it was only a matter of time before the inferno within the towers would lead to the towers' collapse.

Of course, the ultimate key here is that you needed to save the lives of the 2500+ people who ultimately died on 9/11. In the original WTC towers, the cores consisted of the elevator steel columns and drywall, much of which was destroyed as the jetliners flew into the buildings. With the emergency stairways destroyed, the thousands of people in the floors above were trapped.

If a jetliner were to crash into the new WTC 1 after it's completed, there's a chance that the whole building will have to be demolished even if it remains standing after the crash. There would be simply too much damage to the building for it to be considered safe for its occupants as well as to the surrounding buildings, infrastructure, and pedestrians (see the Deustche Bank Building, which remained standing but was demolished for the same reasons). But there would be far fewer casualties because the heavily-built reinforced concrete core would remain intact, allowing everyone still alive after the crash to safely evacuate the building. That's the main reason to overbuild the new WTC buildings.

Originally Posted by Kanto

I'm new to this thread and, as was pointed out a few pages earlier, there is no FAQ

Interesting. You don't even know the basic structure that the new buildings will be constructed with, yet in the other thread (WTC hypothetical musings), you claimed you understood "the complexity of the site".

[OneWorldTradeCenter]

Good news to see the marketing of the building is going ahead

[toren1776]

Btw, what have they done to ensure that 1WTC can't collapse? Did they include concrete there or is it a steel structure like the old towers?

I obviously can't beat STRs explanation on this but I guess I'll chip in my five cents.

1.) The core of 1 WTC is massive when compared to the cores of the twins. It uses a special type of concrete that can only take 90 minutes to arrive from Brooklyn where it is made.

2.) On 9/11, the hijacked planes crashed into the towers at the north and south faces. Since the core of the twins was rectangular, the north and south perimiter walls of the twins were the farthest from the core,which induced tremendous damage to the steel. When the towers collapsed, it was the steel that failed first; the cores followed. Since 1 WTC tapers from the base to the top by 50%, there are less tenants at the higher floors (those most likely to be affected by a plane crash) which reduces the loss of life. This also puts less space between the outer perimiter of the building and its core, protecting the building from the fate of the twins.

3.) The base has a blast wall and has been moved away from the adjacent streets. These security measures were put in place to protect the building from a car bomb or an attack similar to the 1993 WTC bombing.

4.) The windows of 1 WTC are more blast resistant than those of the original twins.

[jsr]

Originally Posted by toren1776

I obviously can't beat STRs explanation on this but I guess I'll chip in my five cents.

2.) On 9/11, the hijacked planes crashed into the towers at the north and south faces. Since the core of the twins was rectangular, the north and south perimiter walls of the twins were the farthest from the core,which induced tremendous damage to the steel. When the towers collapsed, it was the steel that failed first; the cores followed. Since 1 WTC tapers from the base to the top by 50%, there are less tenants at the higher floors (those most likely to be affected by a plane crash) which reduces the loss of life. This also puts less space between the outer perimiter of the building and its core, protecting the building from the fate of the twins.

I'm not quite following point #2. The cores in the old WTC were rectangular, but not oriented in the same direction - separating the aeroelastic modes.

Why does placing the outer perimeter closer to the core walls improve the stuctural integrity in such a situation?

[toren1776]

Why does placing the outer perimeter closer to the core walls improve the stuctural integrity in such a situation?

The backbone of the twin towers were not the cores-it was the steel. On the other hand, the backbone of 1 WTC is the core. There is simply far less steel at the highest floors, but the size of the core stays the same. If a plane were to crash into the tower, it would do comparatively less damage to the steel and the core would sustain most of the impact. However, given how strong the core is it seems highly unlikely that its integrity would be compromised by the plane or the fire that would follow (As STR mentioned, the fireproofing on the steel is designed to be blast resistant, so if we would be dealing with another 737, the fire would be tiny in comparison to the 9/11 inferno).

If you look at these two diagrams, you will immediately notice the difference between the relative size of the cores and how the planes struck the sides of the twins where their perimeter columns were farthest from the core. Keep in mind that both towers have relatively the same size/profile.

Twin Tower Floorplan with Locations of Plane Impacts:


1 WTC (Freedom Tower) Floorplan:

[Traynor]

As jsr just mentioned:

The original towers' cores were oriented differently. One was East/West and the other North/South, yet the planes struck on only one of these axes. So you can take that variable out of your theory.

And the core on the new 1WTC gets smaller and changes shape, as it rises and fewer elevators are needed. So you can take that out of your theory as well.

[toren1776]

Yes, but the second plane hit the south tower at an angle, which means that it tore through just as much if not more steel than the first plane. So no, my theory still stands.

I see you are correct about the core being smaller towards the top, but the perimeter columns are still much closer to it then with the original twins and the core is far stronger as well.

[STR]

The new towers have roughly 45 foot spans from the core area to the perimeter. This was a deliberate decision, as 45 foot column free areas are the most commercially desirable. It was not related to safety, though they also avoided the extremely long spans found in 7WTC, as they discovered that fires would cause too much thermal expansion on such a long beam (note: the old 7WTC did not use floor trusses, as using beams allowed tenants to remove large sections of floor in order to add their own stairways between floors) and that expansion was the direct cause of failure for the critical column. The expanding beam pushed against the fire-weakened column until it failed.

Originally Posted by toren1776

The backbone of the twin towers were not the cores-it was the steel

The whole point of the Yamasaki designs was that they didn't have a backbone. The core carried ~50% of the gravity load, the perimeter carried the other 50%. Conversely, the exterior withstood 2/3 of the lateral load, with the remainder being distributed to the core via the hat truss on the 108-110th floors. The new design shifts a bit more of the load to the core, but it's still very much a distributed design. You don't really want a single backbone, as that makes for a single point of failure. You want as much redundancy as you can get.

More confusingly, I'm not sure I follow when you say "it was the steel". Of course steel failed, the buildings were entirely steel frame structures. There were no concrete shear wall in the core, only 2" thick drywall partitions used for fire resistance and functional separation (I'm sure we all prefer restrooms with walls). However, that's not why the exterior failed first. The specific reason why is in itself a long winded answer, I suggest skimming the latter chapers of NIST's WTC Report 1.6. In short, the floors of the towers started sagging due to the fire, and this in turn pulled inward on the perimeter columns, which were naturally weakened themselves. Eventually the perimeter columns, when deformed too much, gave way.

There is simply far less steel at the highest floors, but the size of the core stays the same.

The core, from bottom to top, reduces itself roughly 10 times, until you get to the upper floors where it covers roughly 1/3 of the (also reduced) floor space. In comparison to the core at the base, it's about 1/3 the size as well, as shown below.

[MadGnome]

With all the math and engineering around here, can someone explain to me how Conde Nast is leasing a million square feet on 22 floors? Are they counting the ceilings?

[upnotout]

Originally Posted by Bucktown718

[/FONT][/B]

Great shot! Somebody should totally photoshop the finished WTC in there!

By the way, why can't I see the American International Building? I see the Woolworth Building and 40 Wall Street. Is it obstructed or am I just blind?

[SkyscrapersOfNewYork]

Originally Posted by upnotout

Great shot! Somebody should totally photoshop the finished WTC in there!

By the way, why can't I see the American International Building? I see the Woolworth Building and 40 Wall Street. Is it obstructed or am I just blind?

i see them

[photoLith]

What strikes me most about that areal photo is how amazing the NJ sides skyline has gotten wow!

[STR]

Originally Posted by MadGnome

With all the math and engineering around here, can someone explain to me how Conde Nast is leasing a million square feet on 22 floors? Are they counting the ceilings?

It's a measure in gross square feet, which includes Conde Nast's "share" of the mechanical spaces. The actual occupied space will be somewhat less, but the gist of it is that ~1/3 of the tower's space has been leased to this one tenant.

[QuarterMileSidewalk]

Originally Posted by upnotout

Great shot! Somebody should totally photoshop the finished WTC in there!

By the way, why can't I see the American International Building? I see the Woolworth Building and 40 Wall Street. Is it obstructed or am I just blind?

It's in front of Chase Manhattan Plaza from that perspective. It just sort of blends in with the other buildings around it.

[NYguy]

Love the way it looms...

Whitebrowgigs

[NYguy]

http://www.nypost.com/p/news/local/manhattan/gz_tower_diagrams_on_web_INwnIIVlOwPe3YgexmIE9J

Detailed schematics of 1 World Trade Center posted online

By LOIS WEISS and CHUCK BENNETT
May 19, 2011


Detailed schematics of several floors of 1 World Trade Center -- a structure Police Commissioner Ray Kelly called the nation's No. 1 terror target -- were posted on the city's Web site along with a mundane leasing document.

Stamped "Secure Document -- Confidential -- For Official Use Only," the 17 detailed schematics can be downloaded right off the city's Department of Finance Web site by anyone.

But the PA said the documents were "scrubbed" of sensitive information about the building's electrical systems, plumbing, security and fire safety.

"The Port Authority provided scrubbed drawings to our consultants. While their default template is marked 'secure' and 'confidential,' the pictures in that frame are not," the agency said in a statement.

It blamed architectural consultant Beyer Blinder Belle for slapping the "confidential" stamp on the documents even though they are safe for public dissemination.

[MadGnome]

Originally Posted by STR

It's a measure in gross square feet, which includes Conde Nast's "share" of the mechanical spaces. The actual occupied space will be somewhat less, but the gist of it is that ~1/3 of the tower's space has been leased to this one tenant.

Maybe that has something to do with the $60? could there be one figure for your share of the whole building and another rate for the actual office space?

[scalziand]

Originally Posted by upnotout

By the way, why can't I see the American International Building? I see the Woolworth Building and 40 Wall Street. Is it obstructed or am I just blind?