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Megatalls Discussions of projects under construction at least 600m/2,000 ft tall.



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Old March 25th, 2008, 04:24 PM   #5201
Slurms Mackenzie
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Quote:
Originally Posted by melkor View Post
Exactly correct SM. Do you have a background in structures?
Yes...I'm a structural engineer, working in London, but from Australia. Although people may not realise it, in Australia earthquake is the governing consideration on most medium-rise buildings. For every building I designed there that was 2 or more stories, earthquake governed over wind.

But, once you get to supertall heights, the structure frequency becomes way too low to correspond to any earthquake frequency response spectrum, so the inertial effects aren't as severe. So wind then becomes the governing criteria.

You just have to imagine holding a very tall, flexible object and shaking it very quickly at the base. It simply won't resonate because it wants to move at a much slower rate. But if you slowly move the base back and forth, you might start to get some resonance happening and some big sway movements. Earthquakes apply fast base movements which are good at causing resonance in a short, rigid structure.
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Old March 25th, 2008, 04:26 PM   #5202
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Hi Indica. Yes I think in an earthquake I would rather be in a large modern building that has been designed for earthquake resistance, rather than something dodgy like a house which may or may not have been designed for anything.

The idea that is continually implied on this site is that a taller or 'more extreme' structure is less safe than a more conventional one (comments like 'it's too tall - it's gonna fall over!). In reality, buildings are designed to building codes which mandate a certain safety factor no matter what the structure is. So, theoretically, a building in San Francisco will be designed for a certain seismic load and one in, say, Chicago will be designed for a smaller siesmic load. The safety margin for each will probably be about the same and therefore the probability of either collapsing due to earthquake will be roughly the same. But people intuitively think it is safer to be in a building in Sydney 'because they get smaller earthquakes'. This is incorrect - that building will have been designed for a smaller load and therefore not be safer. The safety margin will be the same.

The logic behind structural design is rigorous, yet it seems that the public generally don't understand the whole concept of safety factors. At any rate, the Burj is so high-profile that I think an even higher level of scrutiny and safety would have been applied to it than usual. To remove the complexity of seismic analysis from the discussion, I would just say that generally, under any conditions, wind or whatever, I would feel safer in the Burj than I would in a small apartment block or an ordinary old house.

Last edited by Slurms Mackenzie; March 25th, 2008 at 04:41 PM.
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Old March 25th, 2008, 06:02 PM   #5203
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buildings in Dubai have to be able to withstand at most 5.0 magnitute earthquake.
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Old March 25th, 2008, 08:15 PM   #5204
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Originally Posted by Indica View Post
It's a rumour in most cases...


It was found that if you dropped a quarter from the ESB obs deck, that it WOULD NOT land with enough force to kill somebody (contrary to popular belief) because the updrafts will more than compensate for the speed at which the quarter is falling. In other words, by the time that quarter makes it to the ground, its not really going to be able to hurt anybody.

Nothing to do with updrafts, but the correct result. It's due to terminal velocity which is caused by air resistance; terminal velocity is the maximum speed something will move under gravity in our atmosphere, so a penny dropped from a 100m tall building will move the same speed as one dropped from an aircraft. If you dropped a penny from space, it would accelerate to a much higher speed, then burn up as the atmosphere tries to slow it to it's terminal velocity (this is why the space shuttle needs a heat shield). The terminal velocity of a penny is not much faster than you can throw one (in the order of 100mph), try throwing a penny at someone, it'll annoy them but aint gonna leave too big a bruise.
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Old March 25th, 2008, 08:17 PM   #5205
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awesome pics fury!

March 21st, flickr from Peter VG:

[IMG]http://i28.************/2i14yw.jpg[/IMG]
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Old March 25th, 2008, 08:21 PM   #5206
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@indica, I wasn't really thinking about hurting people so much rather than all the loogies :P
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Old March 25th, 2008, 08:30 PM   #5207
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Quote:
Originally Posted by joobn View Post
buildings in Dubai have to be able to withstand at most 5.0 magnitute earthquake.

Ah, but what do you mean by "withstand" ?

There is a wide misunderstanding that buildings complying with building codes will "withstand" earthquakes up to a certain intensity without damage. Not so. The building codes are designed to maximise the occupants' chances of survival - it's impossible to guarantee that the building will emerge undamaged.
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Old March 25th, 2008, 08:38 PM   #5208
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From early morning today, still no 7th floor steel

[IMG]http://i28.************/24xicyt.jpg[/IMG]
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Old March 25th, 2008, 08:53 PM   #5209
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from the dubai devlopment thread
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Originally Posted by victorPP View Post
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Old March 26th, 2008, 12:16 AM   #5210
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^if i was from another planet and flying past, i would land at the base of burj dubai and ask- take me to you leader.
great shots
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Old March 26th, 2008, 12:17 AM   #5211
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current status

i found this intersting pic
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"If you put the empire state building on top of the Sears Tower then it's reasonable to say you'll be in the neighbourhood," Mr Baker says.
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Old March 26th, 2008, 12:23 AM   #5212
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Quote:
Originally Posted by helghast View Post
i found this intersting pic
Wow man, That is magnificent
Too bad i've seen that image about 100 times already.........
But i guess others have not, so still a good contribution!

Owh, does anyone know when the two "normal" cranes are going to be removed and the last crane is going to be assembled?

(this had probably already been said, but i don't have the time to read hunderds of pages.......)
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Old March 26th, 2008, 12:51 AM   #5213
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^lol

Well seems updated with the current hight, thanks for that.
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Old March 26th, 2008, 01:01 AM   #5214
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hahaha

Ive seen it 100 times too harm

Its a couple of years old now, lifted from a BBC article on the BD. I laugh every time I see it due to the scaling on the graph being totally off!! It should not really be used to compare the BD to the other structures as its not indicative of the real difference in size between them.
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The Pearl Tower observation deck will always be the best one to visit. After all, it's the only one from which you won't be able to see the Pearl Tower...
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Old March 26th, 2008, 01:15 AM   #5215
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Quote:
Originally Posted by helghast View Post
i found this intersting pic
This diagram has like 2 big errors on it ><

for a start the tip of the Taipei 509m not 620....

and the Petronas Twin towers have a spire which is its max height. like 452m or summin. not 510m. ect ect

The rest are okie tho.

Last edited by Ember-To-Ashes; March 26th, 2008 at 01:21 AM.
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Old March 26th, 2008, 01:59 AM   #5216
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Wow this is really interesting.
Seems that it have been posted in such one of those sundays newspapers.
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Old March 26th, 2008, 04:08 AM   #5217
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^yeah pretty pathetic diagram. looks like the "artist" has put taipei101 and petronas towers spire heights at roof heights first and then added spires on? lol

sounds like im due for next update.
look out for April f00ls day ;-)
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Old March 26th, 2008, 04:26 AM   #5218
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Quote:
Originally Posted by helghast View Post
i found this intersting pic
Here's to another 200m.
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Old March 26th, 2008, 04:42 AM   #5219
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Quote:
Originally Posted by CULWULLA View Post
...look out for April f00ls day ;-)
hehehehe

Domen
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The Pearl Tower observation deck will always be the best one to visit. After all, it's the only one from which you won't be able to see the Pearl Tower...
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Old March 26th, 2008, 05:01 AM   #5220
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I have a question about the Burj's facade, from what I understand, this building will have apartments, but the building looks like a corporate tower with a smooth glass curtain with no windows or balconies. These apartments will have no windows at all? no way for fresh air to enter?
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adrian smith, burj dubai, burj khalifa, downtown, dubai, dubai tower, emaar, megatall, middle east, rascacielos, sarajevo construction, skyscraper, spire, tallest, uae

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