I, too, would think that all the published weights of these buildings are for the above ground structures. That is certainly the number of interest for potential energy calculations. And, yes, I think 500,000,000 kg each for WTC 1 and 2, may not be too bad a number, but I still wonder about the live load vs. the dead load. With over 30 years of continuous operation, the Twin Towers were being loaded up with more and more junk all the time. Desk top computers wern't even invented when the Twin Towers were built! Was anybody keeping track of the increasing floor loading? NF

There is another way to estimate the mass of one WTC Tower. That is from the mass of the rubble pile. Because ground zero clean-up contracts were based on a specific WEIGHT REMOVED, there are good records of the mass of material removed from the WTC site after 9-11......

Values ~ 1.7 million tons for the entire site are usually quoted, but this includes WTC 1, 2, 3, 4, 5, 6 and 7. If we let the mass of WTC 1 = x and assume:

Mass WTC 2 = x
Mass WTC 3 = 1/4x
Mass WTC 4 = 1/4x
Mass WTC 5 = 1/4x
Mass WTC 6 = 1/4x
Mass WTC 7 = 1/2x,

we have:

Mass of all the buildings at the WTC site = 1.7 million tons = 3.5x,

in which case x, the mass of a Twin Tower = 485,700 tons

The following information is available at a number of websites - try disaster.pandj.com for example:

The initial debris estimate (at ground zero) included 125,000 tons of glass, 250,000 tons of steel, 450,000 cubic yards of concrete..... By July, 2002, 1,462,000 tons of debris had been removed.

Could this figure for the amount of glass possibly be correct?

I'm not an engineer or physics major, but...with the information below, my question would be: What is the maximum live weight load the building could
actually sustain.....remove the central core and then calculate the load based on the remaining square footage....And what's reasonable???

I watched the towers being built as I went back and forth every few months from Long Island to Princeton, and was struck by the relatively spindly central column structure. I remember seeing the entire steel skeleton on central tubes.

towers have in-house engineers for this.

old typewriters are not lighter than computers.

in fact, if you recall, the standard case was cast iron, before plastic came into vogue.
old cheque cutting machines were very heavy, old adding machines were quite heavy....
steel filing cabinets used to be MUCH more massive than they are now(i have an old 4 drawer one,and HOLYCRAP, it must weigh two hundred pounds!), and all records were on paper back then, whereas now, you can fit an entire library in the palm of your hands, and paper records are nowhere near as voluminous as they once were, because of magnetic storage.

i don't buy that they were more loaded than thirty years ago, and considering all the vacancies in the towers, i think they were far less loaded.

oh yeah, and those standard old office desks made of thick hardwood weighed MUCH more than your run of the mill tube metal, tin and chipboard desk of today.

Yah, reams of paper are and were heavy. CRT monitors are dinosaurs. I think the point is the dynamic crunch, a momentum crunch, of several, or more than several, floors.

Hi all,

I'm not a theorist who is linked with any of the usual "conspiracies" movements or theories, but there is a paper I read a while back which carried some weight in its professionally published explanations and doubts, remaining unanswered publically and professionally, as far as I know, by the relevant bodies with the authority, time and need to.

I am quite surprised that this topic remains in continuation on peoples mind, nevertheless, here are the links and sources, that I hope can come in handy to this discussion of yours:

Why Did the World Trade Center Collapse? Science, Engineering, and Speculation
Published in JOM by Thomas Eagar and Christopher Musso, 2001
Feature: Special Report
http://www.tms.org/pubs/journals/JOM/0112/...Eagar-0112.html

An Initial Microstructural Analysis of A36 Steel from WTC Building 7
Published in JOM by J.R. Barnett, R.R. Biederman, and R.D. Sisson, Jr., 2001
http://www.tms.org/pubs/journals/JOM/0112/...erman-0112.html

Another site I frequented:
http://www.iti.northwestern.edu/research/wtc/index.html

Wikipedia:
http://en.wikipedia.org/wiki/Collapse_of_t...ld_Trade_Center

World Trade Center - Some Engineering Aspects - Civil Engineering - The University of Sydney [info about the WTC's]:
http://www.civil.usyd.edu.au/wtc.shtml

911 Research:
http://911research.wtc7.net/mirrors/guardian/WTC/WTC_ch1.htm

New Jersey Institute of Technology Civil Engineering Professor Details How the Towers Collapsed; the Impact of 9/11 on Civil Engineers, Professors, Students:
http://www.njit.edu/v2/News/Releases/254.html

Now I've tried to register, but at the place I'm in, I think the IP address given out has already been taken from someone else registered here, so I can't I'm afraid (don't posses Internet at home).

From the first paper (I've seen general acceptance of) some quotes and not so of others.

[i]"skyscrapers in that they were to be very lightweight "

"With a 700 Pa floor design allowable, each floor should have been able to support approximately 1,300 t beyond its own weight. The total weight of each tower was about 500,000 t. "

"The floor below (with its 1,300 t design capacity) could not support the roughly 45,000 t of ten floors (or more) above crashing down on these angle clips. "

"a 500,000 t structure has too much inertia to fall in any direction other than nearly straight down."

"To a structural engineer, a skyscraper is modeled as a large cantilever vertical column. Each tower was 64 m square, standing 411 m above street level and 21 m below grade. This produces a height-to-width ratio of 6.8. The total weight of the structure was roughly 500,000 t, but wind load, rather than the gravity load, dominated the design. The building is a huge sail that must resist a 225 km/h hurricane. It was designed to resist a wind load of 2 kPa—a total of lateral load of 5,000 t."

"lightweight “perimeter tube” design consisting of 244 exterior columns of 36 cm square steel box section on 100 cm centers"

"In the upper floors there is as much as 40,000 square feet of office space per floor. The floor construction is of prefabricated trussed steel, only 33 inches in depth, that spans the full 60 feet to the core, and also acts as a diaphragm to stiffen the outside wall against lateral buckling forces from wind-load pressures."

"Since the mass of the combined towers is close to 1000000 tons, finding evidence will be an enormous task."

"First tenant occupancy of the 110-story north tower (WTC 1) was in December 1970, and occupancy of the 110-story south tower (WTC 2) began in January 1972. The other WTC buildings were constructed during the 1970s and into the 1980s, with WTC 7 constructed just north of the WTC site in 1985. WTC 3, located immediately west of the south tower, was a 22-story hotel operated by the Marriott Corporation. WTC 4 and 5 were nine-story office buildings, and WTC 6 was an eight-story office building. WTC 7 was a 47- story office building. The seven-building complex provided approximately 12 million square feet of rentable floor space occupied by a variety of government and commercial tenants"

"Height: 1,368 and 1,362 feet (417 and 415 meters)
Owners: Port Authority of New York and New Jersey.
(99 year leased signed in April 2001 to groups including Westfield America and Silverstein Properties)
Architect: Minoru Yamasaki, Emery Roth and Sons consulting
Engineer: John Skilling and Leslie Robertson of Worthington, Skilling, Helle and Jackson
Ground Breaking: August 5, 1966
Opened: 1970-73; April 4, 1973 ribbon cutting
Destroyed: Terrorist attack, September 11, 2001"

"There is no question that an important, yet overlooked, hero of 9/11, was the structural redundancy built into the framing of the Twin Towers," says Schuring. "Structural redundancy means there are multiple load paths to sustain the building weight. This redundancy provided precious time for thousands of workers to escape. And although it's not technically feasible to design a skyscraper to be invulnerable from impact by fully fueled jetliners, as design professionals we must develop improved details and systems that provide ever-greater protection against progressive collapse such as what occurred at the WTC site"

"On September 13, 2001, the cover of the New Civil Engineer in the UK consisted of a picture 1 WTC during its collapse with a single word written across it: "unthinkable". "Just hours earlier, it had been genuinely inconceivable that structures of such magnitude could succumb to this fate."

"Leslie E. Robertson, the lead structural engineer on the team that designed the towers, wrote that "The events of September 11 are not well understood by me . . . and perhaps cannot really be understood by anyone." As NIST would also conclude"

"It was estimated by the Port Authority that the population of the WTC complex on September 11, 2001, was 58,000 people. "

"It was assumed in the 1960s design analysis for the WTC towers that an aircraft, lost in fog and seeking to land at a nearby airport, like the B-25 Mitchell bomber that struck the Empire State Building on July 28, 1945, might strike a WTC tower while low on fuel and at landing speeds."

"Boeing 707 considered by the designers, weighed 263,000 pounds and the Boeing 767s that hit the towers weighed about 274,000 pounds. This is a difference of 4%. ...Incidently, the maximum takeoff weight for a Boeing 707 is 336,000 pounds. The maximum takeoff weight for a Boeing 767-200ER is 395,000 pounds."

"1,000,000 t of rubble will require 20,000 to 30,000 truckloads to haul away the material. The asbestos fire insulation makes the task hazardous for those working nearby. Interestingly, the approximately 300,000 t of steel is fully recyclable and represents only one day’s production of the U.S. steel industry. Separation of the stone and concrete is a common matter for modern steel shredders. The land-filling of 700,000 t of concrete and stone rubble is more problematic. "





I've heard many allegations that people are just "making up" facts here, and have no evidence, method or support at all- (such as mass).

As I can already see, I bet theres many individuals who've been at this, bickering, contending or otherwise defending certain views since 9/11 itself, that are on here thus should be very well educated in all its information.

Some aspects seemed contradictory, however, on a general search, around the University websites, in the Departments of Civil Engineering, the figure taught, quoted and told to students was usually 500,000t.

I realize on the Internet, people can often feel very bold, unchalant and emotionless to be able to act recklessly in any manner that suits them to others, usually vitriolic.. BUT I don't want to be a part of that thankyou, as I'm not here for gain, fame, blaming and hating.

Hope it helps somewhere in your figures required.

Lord Kelvin:
“I often say . . . that when you can measure what you are speaking about, and express it in numbers, you know something about it; but when you cannot measure it, when you cannot express it in numbers, your knowledge is of a meager and unsatisfactory kind; it may be the beginning of knowledge, but you have scarcely, in your thoughts, advanced to the stage of science, whatever the matter may be.”

Previously, many have used the 500,000 t mass without checking it.

I have done a preliminary calculation of the mass and PE in wtc1. I am working on better supporting calculations and references. I am aware of a number of issues but I believe my preliminary result to be very close. Please see my paper published as a letter at the Journal of 911 Studies.

...journalof911studies.com/letters/wtc_mass_and_energy.pdf

Can't post a link.