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Old February 14th, 2015, 06:28 PM   #5261
Otie
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Quote:
Originally Posted by Hudson11 View Post
as opposed to 1 WTC where the first 20 floors might as well be the core. The core gets smaller after this.
After the podium, the core only gets smaller to the extent of bumping the western section of the core (which houses the elevator banks serving the trading floors and an egress stairs -relocated), north and south faces will remain the same (distance between glass and core wall is of 45ft) until they reach a setback.
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Old February 14th, 2015, 08:37 PM   #5262
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But the progress is very slow and I hope they will go faster soon, because I suppose that my favourite 2WTC won't start till they finish the "3" tower...
No, it doesn't have to do with completing 3WTC. For building 2WTC what they need is to find a large tenant. Once they find it, they will resume construction, whether 3WTC is completed or not.
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Old February 18th, 2015, 11:24 PM   #5263
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Core forms were raised today. Steel construction can't be too far away now. I wonder if they will wait until third tower crane gets put in.

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Old February 19th, 2015, 02:58 AM   #5264
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Should be anytime now. There are a lot of steel bits on the deck, albeit mostly smaller pieces.
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Old February 19th, 2015, 04:13 AM   #5265
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Why didn't they put evergreens in the WTC memorial?
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Old February 19th, 2015, 08:06 AM   #5266
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You think people want to walk though pine trees?
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Old February 19th, 2015, 02:21 PM   #5267
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This building has been a stump for so long, i can wait to finally watch it rise
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Old February 19th, 2015, 03:16 PM   #5268
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No need to wait. It's rising.
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Old February 19th, 2015, 03:36 PM   #5269
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Why is it that in NYC they still use structural steel to construct floor spaces instead of forming and pouring reinforced slabs like the rest of the world?
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Old February 19th, 2015, 07:49 PM   #5270
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Quote:
Originally Posted by Aalecki View Post
Why is it that in NYC they still use structural steel to construct floor spaces instead of forming and pouring reinforced slabs like the rest of the world?
This is not only in NYC but pretty common in the US and around the world.

Basically for similar depth/width ratio, steel beams can span longer distance than concrete beams (unless post-tensioned concrete is used but that is a whole different story). So for unobstructed floor plans (such as for office with "open space" layout) and increased spacing between the columns/walls, steel construction is better.

Concrete shear walls is more advantageous for the lateral loads resisting system (both for stiffness and economic reasons), which is why a concrete core and steel floors makes sense for a lot of buildings.

Of course there are other factors such as historic/cultural: concrete has been invented in France where its use developed and generalized over Europe and is still favored to this day. In the US the steel industry "boomed" to support the war efforts, after which the steel manufacturing capacities were geared more toward the construction (there was also a lack of infrastructures to produce cement and concrete), so the steel construction was favored for large skyscrapers. In other "emerging" countries (Emirates, Qatar), both systems are used.

Nowadays it's mostly an economic question: construction in concrete is likely to be quicker, less expensive and the best choice in a country with a "weaker" (or not well established) steel trade and stronger concrete trade, and vice-versa.
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Old February 20th, 2015, 05:00 AM   #5271
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Formwork and formwork platforms on the west section of the core are finally coming off. This part could take a while...

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Old February 22nd, 2015, 10:36 AM   #5272
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Wow! Look at that core rising! I've only been out of the city for six weeks and it is already so much taller than it was when I saw it!
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Old February 24th, 2015, 02:10 AM   #5273
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They've finally begun raising the inner segments of the core scaffolding, after delaying so for several days. Weather perhaps?
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Old February 24th, 2015, 02:24 AM   #5274
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That and a combination of them being in a mechanical/transition segment.

By the way, they aren't using scaffolding. It's a self-climbing platform system
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Old February 24th, 2015, 02:36 AM   #5275
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I don't understand how being at a mechanical section hinders progress. There isn't a major core reconfiguration (elevator shafts remain the same, HVAC shafts are built separately, and the core walls basically are extruded the way up). Any reasonable explanation?
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Old February 24th, 2015, 02:40 AM   #5276
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As for a detailed explanation, you probably know better than me. I just gave a broad reason.

Also, the last Favco M720D should be coming in about a week or two.
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Old February 24th, 2015, 01:01 PM   #5277
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Mechanical floors have additional reinforcing and bracing to manage the latteral movement of the building.
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Old February 24th, 2015, 06:13 PM   #5278
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There is no significant change in the core before the 12th floor, where the West bank will stop. As a matter of fact the structural drawings for the core are the same for each floor between 7-10.

The only change above 12 is that the west bank will stop and the core will be square (before additional setbacks on the North and South sides at higher floors).

As Otie correctly pointed, there is no reconfiguration in the sliding formwork that would require a significant down time since all the openings for the elevators and MEP are the same. They do have to install link beams and embedded plates for the connections of the future steel beams, but that's the same as before.

More than likely, the slowdown is due to the extreme cold in the last couple of weeks: it is difficult to pump concrete at low temperature, and in addition high-strength concrete shall cure in a specific temperature range (above 50F for at least the first 3 days after placement) because low temperatures could freeze the pore water in the concrete mix before the hydration (chemical reaction/hardening of concrete) occurs. There are systems to heat the forms to maintain the concrete at the right temperature and other admixtures that can be used, but it will increase the setting time and there is only so much that can be done when the outside temperature is 15-20F...
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Last edited by NYStruct; February 24th, 2015 at 06:31 PM.
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Old February 24th, 2015, 06:20 PM   #5279
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Quote:
Originally Posted by weidncol View Post
As for a detailed explanation, you probably know better than me. I just gave a broad reason.

Also, the last Favco M720D should be coming in about a week or two.
I would be extremely surprised to see that Favco M760D installed in the next two weeks - I'd wager my paycheck that it will not be happening.

An "official" decision has yet to be made regarding the use of the Wolff 700B or the Favco M760D.

The Favco M760D would also need a shorter deck configuration which has not yet been approved for use in NYC.
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Old February 24th, 2015, 07:21 PM   #5280
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Quote:
Originally Posted by Aalecki View Post
Why is it that in NYC they still use structural steel to construct floor spaces instead of forming and pouring reinforced slabs like the rest of the world?
The real question is why doesn't the rest of the world use steel

Steel is better and the US has a huge steel industry so it makes economic sense.
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