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Old March 24th, 2008, 07:23 PM   #5181
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i was up on the ob-deck of the la grande arche in la defense and the amount of security workers there was immense. And i think the ammount on the ob-deck of the BD will be even higher.
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Old March 24th, 2008, 07:31 PM   #5182
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Originally Posted by Old Town Resident View Post
I think what Firoz was asking was how they measure the deviation of verticality and horizontal movement from the X, Y and Z axis, in particular movement outwith the engineering tollerances.

And as Skymyhusband put it GPS is the answer, not simple trigonometry.
Er, no. GPS is nowhere near that accurate! They will use an optical laser system, maybe a theodolite but I'm not sure what they are actually called. Anyway, they just have to shine a laser up a liftshaft and they will have the means to precisely measure any horizontal deviation, as well as height. Not to mention laser range-finding could measure the height to millimeter accuracy
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Old March 24th, 2008, 08:05 PM   #5183
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because people do that on the empire state and other tall towers for fun and stupidty that's why.
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Old March 24th, 2008, 08:07 PM   #5184
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Quote:
Originally Posted by Doomlord_uk View Post
Er, no. GPS is nowhere near that accurate! They will use an optical laser system, maybe a theodolite but I'm not sure what they are actually called. Anyway, they just have to shine a laser up a liftshaft and they will have the means to precisely measure any horizontal deviation, as well as height. Not to mention laser range-finding could measure the height to millimeter accuracy
Er no, shining a light up a lift shaft with a thingy ma jiggy you dont know the name off, and compare with the accuracy of GPS.......duh.

So how does you thingy ma jiggy thing measure external walls, or are these walls considered to be in absolute parallel with the lift shaft and measured by another thingy ma jiggy thing.

Is the theodolite on at all times on building completion to monitor structural movement and powered by another imaginary source?

Last edited by Old Town Resident; March 24th, 2008 at 08:30 PM.
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Old March 24th, 2008, 08:41 PM   #5185
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Hi all.

Here is a link to a 12 page PDF on surveying for the Burj Dubai.

GPS and Tiltmeters are used. This is one of the best papers on the subject that I have seen.

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Old March 24th, 2008, 08:51 PM   #5186
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Hi all.

Here is a link to a 12 page PDF on surveying for the Burj Dubai.

GPS and Tiltmeters are used. This is one of the best papers on the subject that I have seen.

Thanks Fury

Heres a excerpt on the paper that I was about to post, and it does mention a thingy ma jiggy, so sorry Doomlord.

The Burj Dubai implements a procedure developed by Leica Geosystems using GPS observations combined with a precision inclination sensor to provide reliable coordinated points at the top of the worlds highest-rise building under construction in Dubai.

The movement of the structure creates several problems for precise survey; at a particular instant in time, theoretically, you need to know exactly how much the design centre line of the building is offset from the vertical axis and at that same instant you need to know the precise coordinates of the instrument. However a ‘mean’ position taken over a short period for both elements can provide a suitable solution.

GPS operating in static mode are being used to establish survey control at the upper levels. The system comprises a minimum of 3 GPS antenna/ receivers mounted on tall fixed poles at the top level of the formwork.

A tiltable circular prism is placed below each antenna and a Total Station instrument (TPS) is set up on the concrete visible to all GPS stations. The GPS plus TPS comprises a “measurement system”.

In static GPS mode, satellite signal data is received and recorded for a period of up to 1 hour. During this same period of time, the TPS instrument is used to measure a series of angles and distances to the prisms mounted below the GPS antennas. The TPS then measures to the reference marks placed on fresh concrete which are the reference points for control of the formwork as described in 1.4.1.
After completion of observations, data is returned to the office for processing. Computation of GPS antenna positions is carried out, processed against data from a Continuously.

The Core Wall Survey System (CWSS) uses NIVEL200 dual-axis precise clinometers (thingy ma jiggy) to accurately determine displacement of the tower alignment from vertical. Clinometers measure absolute tilt to +/-0.2” arc. This angular measure can be applied to the vertical distance of the clinometers sensor above the foundation raft to provide a computed plan displacement in X and Y at that elevation due to the tilt of the structure.

A total of 8 precise clinometers are to be networked at approximately every 20 floors up the tower as construction proceeds. Each instrument will be mounted in the center core wall in a boxout within the wall where casual disturbance is unlikely.
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Old March 24th, 2008, 08:52 PM   #5187
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thanks Fury, now i get what you ment. thanks for the PDF to. great stuff
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Old March 25th, 2008, 12:18 AM   #5188
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from today:

[IMG]http://i28.************/1fu72t.jpg[/IMG]
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Old March 25th, 2008, 01:14 AM   #5189
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Hi all.

Happy to help guys.

Here is some other info I have on BD surveying - all older but pertinant.













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Old March 25th, 2008, 01:22 AM   #5190
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Hi all.

Picasa - Bob - 08 03 01









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Old March 25th, 2008, 01:34 AM   #5191
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Wooow the photos are amazing and icredibles
Thanks FURY

Last edited by /-/_E_C_T_O_R 8§8; March 25th, 2008 at 01:39 AM.
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Old March 25th, 2008, 02:37 AM   #5192
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Quote:
Originally Posted by Slurms Mackenzie View Post
Overturning and base shear due to wind loads should be much much higher than those due to earthquake on a building this tall. The natural frequency of the building is very low, so an earthquake is not effective in mobilising the mass of the building.

Inertial forces (ie, earthquake) are far more effective at damaging shorter buildings with large plan areas.

At any rate, the structural engineers would have considered an earthquake load combination somewhere in their analysis (as for any other major building), but it almost certainly wouldn't have governed the design.
Exactly correct SM. Do you have a background in structures?
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Old March 25th, 2008, 03:02 AM   #5193
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Thanks Fury,

Not only is this the world's tallest building but what is that massive sprawling structure behind it? That thing is HUGE!!!!
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Old March 25th, 2008, 03:22 AM   #5194
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the worlds largest mall the pic is old, well not old old. but it's 23 days. and they put up two
6.4m sections in 23 days, which is quite fast. the height of the burj in that pic is 611.30m
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Last edited by helghast; March 25th, 2008 at 03:32 AM.
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Old March 25th, 2008, 03:25 AM   #5195
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the worlds largest mall
Thanks. I'll have to look it up. Interesting structure.
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Old March 25th, 2008, 07:17 AM   #5196
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thats an amazing pic! thanks for that. it really shows the development around the burj too!
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Old March 25th, 2008, 11:19 AM   #5197
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Jeez, that thing is incedible!!!!!

Still a good 150 metres to go as well
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Old March 25th, 2008, 12:13 PM   #5198
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In other news, construction foremen at Burj Dubai have reported a recent near-miss by Sputnik I, the Soviet-made first artificial satellite in orbit.
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Old March 25th, 2008, 12:17 PM   #5199
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Exactly correct SM. Do you have a background in structures?

Dead on!! Many times this is the reason why you are safer in a high-rise..

Look at what happened here in Los Angeles back in 1994... the majority of the structures that got damaged or destroyed, were shorter buildings with a decent sized footprint (3-4 story wood framed apartment buildings with the lack of shear walls). The apt. buildings of this type that did well, were retrofitted, bolted down, and had shear walls. CSUN was screwed because of the short squat buildings all over campus that were extensive in sq footage.

Most of the high rise buildings escaped without damage.. All of the really tall ones in Downtown LA were ok, but there were a few in the Valley near the epicenter that were red tagged and they were quite a site to behold because you dont often see tall structures that are soo earthquake damaged too often.

Most people believe it shakes harder the higher up you are (I used to think that too) but in theory, the building absorbs some of the earthquake shock and kills some of the shaking/swaying.

Still I cant help but to wonder how much if any damage would occur if there were a quake to strike nearby and give the Burj a good shake?
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Old March 25th, 2008, 12:24 PM   #5200
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because people do that on the empire state and other tall towers for fun and stupidty that's why.
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.
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