OT: curvature of the earth and buildings--was g-dElson right?

"Proctologically Violated©®" wrote in message news:%EK7h.32$ snipped-for-privacy@newsfe10.lga...

Interesting concept, (I've often pondered it myself), but swallowed up entirely in the tolerance (or margin for error).

You could argue, f'r'instance, that any one "vertical" strut would indeed have the earth-centre-pointing vector contained entirely within itself, unless it was considerably less than 1/2" thick.

-- Jeff R. (pass me another beer)

You're preaching to the choir here. :) Read the claims in the original thread. goodgawd....

I would ASSume that how they are actually constructed would be that the imaginary centerline of the building's core would be constructed plumb and the building would be squared to that. Therefore there would be no "tipping moment" as WRT the earth's gravity all outside walls would be leaning in equally. However, I haven't personally built anything bigger than a large shed, so I dunno.

IRL it seems that most tall buildings have terraces and therefore the upper floors are smaller in areas than the lower floors discussion above notwithstanding.

nate

Ya know , there's something to this . I read once of a (oblong , and big !)tank/fountain/whatever , that was supposed to have an even volume of water falling over the edge all the way around . Kind of a water curtain effect . They forgot to include the curvature in their calcs , the thing was only overflowing in the middle ! Don't recall how they solved it , but I recall pics of it "after mods" . T'was wayyyy cool .

Coriolis force?

You are correct. I guess ahm in my alarmist mode. :)

And you are correct about terraced buildings. This is actually required in some areas by the urban planners, as well as setbacks for these tall buildings. The reason can be plainly seen ( or not seen!) by parts of very lower Manhattan, where walking on the sidewalk is much like being in the bottom of a goddamm well--you see the sun only when it is directly overhead! Ergo, the terracing. Oh, and the area of the top floor would be 16,040, not 16,400: 400.05 x

I don't know whether I don't know whether these buildings are actually designed this way, but I'll bet they are BUILT this way. The reason is, they use LEVELS when putting the walls up! So, the walls have to diverge by that tiny amount. You'd never be able to measure it on one floor, but if you were to carefully measure the walls over a few floors, I think they might show the divergence.

Ahh, I can't measure that one, because it is too far off the local vertical!

Jon

I dunno about the other stuff but one interesting fact of tall buildings is sway. There are different methods to minimize this sway. The sway is caused mainly by wind and earthquakes. In Seattle one building has a method for controlling sway that I think is unusual. One floor partway up the building is occupied by a concrete slab on bearings. The motion of the slab is controlled by servos. The slab is moved to compensate for building movement. I've always wondered what would happen if the wires for the servos were reversed. ERS

This is done in a cupla tall buildings, WTC as well, iirc. A terrorist w/ a mech eng degree could calc the resonant frequency of the building, and fool w/ the damping device, to have it reinforce, rather than dampen, and then the g-d building would likely break off at the root. FBI: not endorsing, merely pointing out that this could happen, so's y'all can do yer jobs betterer.

"Proctologically Violated©®" wrote in message news:%EK7h.32$ snipped-for-privacy@newsfe10.lga...

The Boeing plant in Everett, WA is about .6 miles long according to my odometer. You can see the curvature of the earth in the ramp in the front of the building, and if you look just right at the building from an approaching highway you can see the curvature of the roof to match. Haven't been on the roof but once, and I wasn't looking for that when I was up there. Since the building is actually many separately constructed building joined together by semi-flexible joints and floor plates between buildings for earthquakes and natural ground movement, you can't see the curve inside the building unless you put your head to the floor and look from one end to the other in the main aisleway inside. It's .3 miles deep, and arranged so that there are two buildings front to back and six or so longways. I imagine that if you could somehow measure the centerline of the posts that hold up the walls and roof, you might be able to measure the difference in span between the floor and the roof structure.

Properly constructed buildings are built with parallel lines, not truly "plumb" lines in the strictest sense. The alignment is done with optical instruments calibrated to set benchmarks which which ignore the divergence that you describe. If tall buildings were built with plumb bobs, perhaps the divergence would be more of a problem, but then, where would you hang the plumb bob from?. Large civil structures, such as bridges, are often subject to this divergence due to their large size. Bridge towers will indeed be further apart at the top than the bottom due to the earth's curvature.

Sorry, can't comment on tipping moments.

No , the water surface actually was curved to match that of the earth . The tank (for lack of a better word) lip was straight ... therefor it was only flowing over the edge in the middle .

Negative edge

I'm curious as to the project that you can't recall, think...

Must be long and done with a laser. I've wondered for years what the limitation of a water level is.

Actually, while the subject of your post is rather silly, there is only one application of which I am aware where the curvature of the earth plays any significant role in the alighnment of vertical structures. That unique situation is the ROTHR (Relocatable Over The Horizon Radar) antennas. It's kind of an interesting case to engineer. Then to, rememeber that the ROTHR system bounces RADAR signals off the ionospher to a sea surface that reflects them back though the same reflection and propagation path to the receiver, over round-trip distances in excess of 3,000 miles. The spatial orientation of the antenna array is therefore very critical, rivaling a micrometer in accuracy.

The deal here is that to phase the scanning beam correctly, the vertical transmission towers spaced over a distance measure in miles must be precisely parallel to each other. Not vertical, but precisely parallel.

Erecting a tower vetically is a trivial effort requiring only a plumb line or its modern, more precise instrumentation equivalent. Erecting an array of tower space over miles is a challenging engineering effort due to the curvature of the earth -- you cannot use a plumb line reference.

What is important to realize is that the ROTHR towers are located a considerable distance apart, and not in the 50-yard proximity of the footprint of a very large skyscraper. So, who cares if the four structural members of the building are not precisly parallel. They're certainly sufficiently parallel and vertical enough for both government work and civilian construction.

Harry C.

Proctologically Violated=A9=AE wrote:

The problem with the Sears Tower was its asymmetric construction. There were multiple rectangular structural elements all bolted together, but each section terminated at a different height. Thus, when they got to the highest center section, they found that the very top of the building was cockeyed (leaning in one particular direction).

A similar analogy would be a man coming home from work while each of his say 5 children jump on him and hang on at different levels. If the children weigh enough, the man is going to have difficulty standing straight.

I briefly worked in the Sears Tower earlier in my lifetime and up above the 100th floor was not a good place to be during the big storms that occasional hit Chicago with 40 - 50+ mph winds. The building swayed so much that hanging light fixtures would swing swing back and forth.

Beachcomber

Proctologically Violated©® wrote: (all the stuff cliped since everyone has already read it)

I understand that the builders of very wide water falls as in shoping centers etc, also have to take into account the curvature of the earth to make the water a uniform thickness over the falls. ...lew...

Holy Mother of God! They'd have to be pretty *wide* all right!

-- Jeff R.

More likely the contractor's excuse for shooting only two marks and the chalk line sagging.

Yes, pretty wide. The widest I can think of is the reflecting pool at=20 the Christian Science Center in Boston, which is 686 feet long. The=20 water spills over a granite curb that surrounds the entire pool. The=20 earth's curvature over 686 feet is only 1/32". Walking through the plaza=20 on a windy day it's obvious that on this scale the wind is a much=20 greater influence than the earth's curvature.

Ned Simmons