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 Reporthttp://www.tms.org/pubs/journals/JOM/0112/...Eagar-0112.htmlAn 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., 2001http://www.tms.org/pubs/journals/JOM/0112/...erman-0112.htmlAnother site I frequented:http://www.iti.northwestern.edu/research/wtc/index.htmlWikipedia:http://en.wikipedia.org/wiki/Collapse_of_t...ld_Trade_CenterWorld Trade Center - Some Engineering Aspects - Civil Engineering - The University of Sydney
[info about the WTC's]:http://www.civil.usyd.edu.au/wtc.shtml911 Research:http://911research.wtc7.net/mirrors/guardian/WTC/WTC_ch1.htmNew Jersey Institute of Technology Civil Engineering Professor Details How the Towers Collapsed; the Impact of 9/11 on Civil Engineers, Professors, Students
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.
“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.”