The Construction of the WTC Towers 1 & 2

The Construction of the WTC Towers 1 & 2

Exterior Framing

The first major structural subsystem was the exterior framing, which was a vertical square tube that consisted of 236 narrow columns, 59 on each face from the 10th floor to the 107th floor (Figure 3). There were fewer, wider-spaced columns below the 7th floor to accommodate doorways. There were also columns on alternate stories at each of the beveled corners, but these did not carry gravity loads. Each column on floor 10 to 107 was fabricated by welding four steel plates to form a tall box, nominally 0.36 m (14 in) on a side. The space between the steel columns was 0.66 m (26 in), with a framed plate glass window in each gap.
Adjacent columns were connected at each floor by steel spandrel plates, 1.3 m (52 in) high. The upper parts of the buildings had less wind load and building mass to support. Thus, on higher floors, the thickness of the steel plates making up the columns decreased, becoming as thin as 6 mm (¼ in) near the top down from as thick as 76 mm (3 in) at the lower floors. There were 10 grades of steel used for the columns and spandrels, with yield strengths ranging from 248 MPa (36 ksi) to 690 MPa (100 ksi). The grade of steel used in each location was dictated by the calculated stresses due to the gravity and wind loads. All the exterior columns and spandrels were prefabricated into welded panels, three stories tall and three columns wide. The panels, each numbered to identify its location in the tower, were then bolted to adjacent units to form the walls (Figure 4). Field panels were staggered so that every third panel was spliced at each floor level. The use of identically shaped prefabricated elements was an innovation that enabled rapid construction. (pg.7)

The second structural subsystem was a central service area, or core (Figure 3), measuring approximately 41 m by 26.5 m (135 ft by 87 ft), that extended virtually the full height of the building. The long axis of the core in WTC 1 was oriented in the east-west direction, while the long axis of the core in WTC 2 was oriented in the north-south direction. The 47 columns in this rectangular space were fabricated using primarily 248 MPa (36 ksi) and 290 MPa (42 ksi) steels and decreased in size at the higher stories. The four massive corner columns bore nearly one-fifth of the total gravity load on the core columns. The core columns were interconnected by a grid of conventional steel beams to support the core floors. (pg. 7&8)

.3.4. Concrete
Two types of concrete were used for the floors of the WTC towers: lightweight concrete in the tenant office areas and normal weight concrete in the core area and in the mechanical areas. Because of differences in composition and weight, the two types of concrete respond differently to elevated temperatures. While their tensile strengths degrade identically, lightweight concrete retains more of its compressive strength at higher temperatures.
The specified design strength for lightweight concrete was 20.7 MPa (3 ksi) and either 20.7 MPa (3 ksi) or 27.6 MPa (4 ksi) for normal-weight concrete, depending upon the floor location within the buildings. The actual strength of concrete at room temperature is greater than that measured from cylinders poured for testing during construction, referred to as 28-day cylinder strength, as concrete continues to strengthen with age. Methods for estimating changes in concrete strength with age are specified by the American Concrete Institute (ACI) 209 [11]. The actual compressive strength of WTC concrete slabs was estimated to be 38 percent greater than the specified design strengths: 37.9 MPa (5.5 ksi) for 27.6 MPa (4 ksi) normal-weight concrete and 28.3 MPa (4.1 ksi) for 20.7 MPa (3 ksi ) normal-weight and lightweight concretes.

3.5. Passive Fire Protection
Building codes require that elements that support loads are to be protected to achieve a specified fire resistance rating, expressed in hours. The WTC towers were classified as Class 1B, which required the columns to have a 3 h fire endurance rating and the floor system to a have a 2 h rating when tested in accordance with ASTM E 119 [12]. To achieve these ratings, the structural steel was protected with sprayed fire-resistive material (SFRM) or rigid fire-rated gypsum panels. Since application of SFRM to floor trusses was an innovative fire protection method in the 1960s, PANYNJ arranged for demonstrations to establish its feasibility for the World Trade Center [13]. In 1969, The Port Authority directed that a 13 mm (0.5 in.) thick coating of SFRM be used to insulate the floor trusses. This was to achieve a Class 1A rating, even though the preponderance of evidence suggests that the towers were chosen to be Class 1B. NIST found no evidence of a technical basis for selection of the 13 mm (0.5 in.) thickness.
In 1995, The Port Authority performed a study to establish requirements for retrofit of sprayed insulation to the floor trusses during major alterations when tenants vacated spaces in the towers [13]. Based on design information for fire ratings of a similar, but not identical, composite floor truss system contained in the Fire Resistance Directory published by Underwriters Laboratories, Inc., the study concluded that a 38 mm (1.5 in.) thickness of sprayed mineral fiber material would provide a 2 h fire rating, consistent with the Class 1B requirements.
In 1999, the removal of existing SFRM and the application of new material to this thickness became Port Authority policy for full floors undergoing new construction and renovation. In the years between 1995 and 2001, thermal protection was upgraded on 18 floors of WTC 1, including those on which the major fires occurred on September 11, 2001, and 13 floors of WTC 2 that did not include the fire floors.

Multiple approaches were used to insulate structural elements in the core. Those core
columns located in rentable and public spaces, closets, and mechanical shafts were enclosed in
boxes of gypsum wallboard. The amount of the gypsum enclosure in contact with the column
varied depending on the location of the column within the core. SFRM was applied on those
faces that were not protected by a gypsum enclosure. The thicknesses specified in the
construction documents were 35 mm (1.375 in.) for the heavier columns and 60 mm (2.375 in.)
for the lighter columns [13]. Columns located at the elevator shafts were protected using the
same SFRM thicknesses.(pg. 18 & 19)

Possible Airplane Crashes
An additional load, not required by any building codes, but stated by PANYNJ to have been considered in the design of the towers, was the impact of a commercial airliner. Documents obtained from PANYNJ indicated that the impact of a Boeing 707 or DC 8 aircraft flying at a speed of 268 m/s (600 mph) was analyzed during the design stage of the WTC towers. The life safety considerations following such impact were also addressed. One document stated that “…Analysis indicates that such collision would result in only local damage which could not cause collapse or substantial damage to the building and would not endanger the lives and safety of occupants not in the immediate area of impact.” No other documentary evidence on the aircraft impact analysis was available to review the criteria and methods used in the analysis of the aircraft impact into the WTC towers or to provide details on the ability of the WTC towers to withstand such impacts [9]. (pg. 6)

Twin Towers’ Designers Anticipated Jet Impacts Like September 11

Structural engineers who designed the Twin Towers carried out studies in the mid-1960s to determine how the buildings would fare if hit by large jetliners. In all cases the studies concluded that the Towers would survive the impacts and fires caused by the jetliners.

“We looked at every possible thing we could think of that could happen to the buildings, even to the extent of an airplane hitting the side… Our analysis indicated the biggest problem would be the fact that all the fuel (from the airplane) would dump into the building. There would be a horrendous fire. A lot of people would be killed. [But] the building structure would still be there.”~Lead WTC Structural Engineer John Skilling — The Seattle Times: (1993)

“The building was designed to have a fully loaded 707 crash into it. That was the largest plane at the time. I believe that the building probably could sustain multiple impacts of jetliners because this structure is like the mosquito netting on your screen door—this intense grid—and the jet plane is just a pencil puncturing that screen netting. It really does nothing to the screen netting.”~Frank A. Demartini, the on-site construction manager for the World Trade Center — (January 25, 2001)

In addition, investigators from NIST who examined the destruction of the WTC skyscrapers told The New York Times in 2007 that newly disclosed documents from the 1960s show that the new York Port Authority, the original owners of Twin Towers, also considered aircraft moving at 600 mph,slightly faster and therefore more destructive than the ones that did hit the towers.

WTC construction
WTC construction 2
WTC construction 3
WTC construction 4

Above a photo taken just moments after the “collapse” began. As is obviousthe huge plumes of pulverized concrete and steel beems, as well as full sections of box columns are being ejected some 70+ yards laterally from the frame of the buildings. It only took 10 seconds for the entire to collapse to the ground. This is practically ‘free fall’.

WTC tower collapse just seconds after initiation

Upper stories tipping mere seconds into collapse initiation.

Cardington Steel Fire Experiments

“In the mid-1990s British Steel and the Building Research Establishment performed a series of six experiments at Cardington to investigate the behavior of steel-framed buildings. These experiments were conducted in a simulated, eight-story building. Secondary steel beams were not protected. Despite the temperature of the steel beams reaching 800-900 C (1,500-1,700 F) in three of the tests (well above the traditionally assumed critical temperature of 600 C (1,100 F), no collapse was observed in any of the six experiments).
In building fires outside of such laboratory experiments, steel beams and columns probably never exceed 500º C. In extensive fire tests of steel frame carparks conducted by Corus Construction in several countries, measured temperatures of the steel columns and beams, including in uninsulated structures, never exceeded 360ºC.[3]”

Click to access MultistoreySteelFramedBuildings.pdf

The following information is from the most comprehensive and thorough tests yet done on the effects of fire on structural steel.
This study was cited in the NIST WTC Structure Report of 2002, in Appendix A, of that report. The same NIST report wherein the Appendix C was cited, that showed evidence of Thermite Arson on WTC7 steel samples.
The Cardington steel tests show why no multi-story steel framed building has EVER collapsed due to fire; not before 9/11, not after 9/11, and certainly not on 9/11.

© 1999 British Steel Technology Center

Cardington Steel Tests

9.1 Observed Behavior

The tests on the Cardington frame enabled the differences between the standard fire test and the actual behavior to be studied. This led to the conclusion that the cooler structure surrounding the heat effected members was extremely beneficial to the heated members. The maximum steel temperatures reached during the six tests at Cartington was in excess of 1100 °C. This occurred with no signs of structural collapse.
Using modern fire codes , which are based on the standard fire tests, failure (or structural collapse) was calculated at 680°C ; it is clear that the current level of safety is quite high.
Further work on quantifying the safety level and developing definitive design guidance, which will incorporate a more logical and economical approach to structural fire design. – pg. 64 text (pg. 73 PDF)

Every collapse theory generated by those who support the official narrative of the destruction of the WTC towers is based on the “accumulation of mass” hypothesis.
This thesis is utter nonsense, as I have pointed out time after time.
There was no accumulating solid mass.
The mass was particulates blown laterally outside of the frame of the buildings. This can be seen clearly in every single image of the towers being demolished.

FAQ #9: Were the Twin Towers Designed to Survive the Impact of the Airplanes?

When interviewed in 1993, Lead WTC Structural Engineer John Skilling told The Seattle Times:
Lead WTC Structural Engineer John Skilling was rightfully confident that neither the impact of a large passenger jet nor the ensuing office fires was capable of bringing down the Twin Towers
“We looked at every possible thing we could think of that could happen to the buildings, even to the extent of an airplane hitting the side… Our analysis indicated the biggest problem would be the fact that all the fuel (from the airplane) would dump into the building. There would be a horrendous fire. A lot of people would be killed. [But] the building structure would still be there.”

In 2001, Leslie Robertson, a WTC structural engineer who worked as a subordinate to Skilling, claimed that the Twin Towers were only able to withstand the impact of jet airplanes going no faster than 180 mph. However, not only are these statements contradicted by the design test results, they also contradict statements made by Robertson in 1984/1985, when he said that there was “little likelihood of a collapse no matter how the building was attacked.”

Critical Thinking – The 911 Conspiracy Discussion 

“Since the dynamic amplification factor for a suddenly applied load is 2, an intact floor below the level of collapse initiation could not have supported more than six floors. Since the number of floors above the level where the collapse initiated exceeded six for both towers (12 for WTC 1 and 29 for WTC 2), neither tower could have arrested the progression of collapse once collapse initiated. In reality, the highest intact floor was about three (WTC 2) to six (WTC 1) floors below the level of collapse initiation. Thus, more than the 12 to 29 floors reported above actually loaded the intact floor suddenly.” – NIST FAQ 12
. . . . . .
“Thus, more than the 12 to 29 floors reported above actually loaded the intact floor suddenly.”~NIST

Nonsense, they would have impacted the ENTIRE STRUCTURE BELOW suddenly. There was not just ONE intact floor below the presumed falling mass. The entire structure below was intact — some 81 intact floors for one tower, and 98 intact floors for the other.

This is a perfect illustration of why Newton’s Third Law of Motion proves the gravity collapse hypothesis wrong.
These facts are self-evident and axiomatic.

NIST and its booster club is trying to pull the wool over your eyes with their specious rhetorical nonsense.
The ONLY way to remove the intact structure from any presumed falling mass would be to blow them apart with explosives.
Evidence of nanothermetic explosives were found in the dust of the aftermath.
There can be no doubt that the WTC towers were destroyed by explosive demolitions.
The floor connections were blown apart by explosives. Period.
. . . . .
Now when I describe what WOULD HAVE HAPPENED if the upper structure fell on the lower structure, as the meeting portions grinding and crushing each other in an equal and opposite fashion due to Newton’s 3rd Law, I am NOT saying what DID happen. I am merely pointing out that the 3rd law of motion applied to the hypothesis of a gravity collapse, proves that the collapse would be arrested long before it became total.

The theory that jet fuel poured down the elevator shafts is untenable.
The elevators in the towers were staggered, with just one going from top to bottom. They were also self sealing to prevent the chimney effect. See FEMA Building Performance Study 2002
The amount of jet fuel that poured into the buildings during the crashes was miniscule compared to the size the the structures. Most of that fuel blew up in huge fireballs outside the buildings on impact.
If the towers were made to scale as 6 ft structures, the amount of jet fuel in the plane at that scale would be less than a thimble full.
The towers were essentially three separate buildings atop one another.


8 thoughts on “The Construction of the WTC Towers 1 & 2

  1. JOM
    The Journal of The Minerals, Metals & Materials Society (TMS)
    Editor: Justin Scott
    . . . . . . . . . .
    Why Did the World Trade Center Collapse? Science, Engineering, and Speculation
    Thomas W. Eagar and Christopher Musso
    JOM 53, December 2001
    The major events include the following:

    * The airplane impact with damage to the columns.
    * The ensuing fire with loss of steel strength and distortion (Figure 1).
    * The collapse, which generally occurred inward without significant tipping (Figure 2).
    . . . . . . . . . .
    A December 2001 paper, “Why Did the World Trade Center Collapse? Science, Engineering, and Speculation,” dismissed early reports about molten steel at the demolished World Trade Center. Dr. Thomas W. Eagar, a professor of materials engineering and engineering systems at the Massachusetts Institute of Technology, and his graduate research student, Christopher Musso, pointed out that the theoretical maximum temperature of a building fire (maximum 1000°C/1800°F) is not even close to the melting point of steel (approximately 1500°C/2750°F). And they noted that the observed black smoke emanating from the Twin Towers was consistent with a typical oxygen-starved building fire.
    Eagar and Musso concluded that the actual temperature most likely remained below 650°C/1200°F. In so doing, they dispelled the myth that the jet fuel could have made the fires unusually hot, noting that it was “highly unlikely” that the temperature rose above 800°C/1470°F.

    But because more recent reports confirm the presence of molten steel and molten iron both during and after the 9/11 event, it must be determined what actually melted those two metals and in so doing demolished two of the world’s tallest steel-frame skyscrapers.

    The Official Fired-Based Hypothesis Cannot Account for the Stream of Liquid Metal Pouring Out of the South Tower.
    . . . . . .
    Why Indeed Did the WTC Buildings Completely Collapse?
    By Dr. Steven E. Jones
    Click to access WhyIndeedDidtheWorldTradeCenterBuildingsCompletelyCollapse.pdf



  2. I now present to the candid world a series of links with the evidence and proofs of my assertion above:

    > The Construction of the WTC Towers 1 & 2

    The Construction of the WTC Towers 1 & 2



    > 9/11 IMAGES

    9/11 IMAGES

    > 2020 AD

    > Osama bin Laden Patsy 9/11

    Osama bin Laden Patsy 9/11

    > Military PSYOPS



  3. Conspiracy Theorists and Monological Belief Systems

    Kurtis Hagen

    Independent Scholar


    Recent scholarship has claimed to show that conspiracy theorists are prone to simultaneously believe mutually contradictory conspiracy theories, as well as believe entirely made up conspiracy theories. The authors of those studies suggest that this supports the notion that conspiracy theories operate within “monological belief systems”, in which conspiracy theorists find support for conspiratorial beliefs in other conspiratorial beliefs, or in related generalizations, rather than in evidence directly relevant to the conspiracy in question. In this article, I argue that all of that is either wrong or at least misleading.

    Click to access 7-Argumenta-Kurtis-Hagen-Conspiracy-Theorists-and-Monological-Beliefs-Systems.pdf



    1. Kurtis Hagen

      The Philosophy of Conspiracy Theories
      The philosophy of conspiracy theories is a subfield of applied epistemology.

      Over the last couple decades, a small group of philosophers began rigorously addressing the issue of whether or not conspiracy theories are a class of ideas, perhaps like miracles, that can be regarded as unwarranted simply because of the features by which they count as “conspiracy theories.”

      Two seminal essays stand out: (1) In 1995, Charles Pigden convincingly challenged the relevance of Karl Popper’s highly influential critique of “the conspiracy theory of society.” (2) In 1999, in the Journal of Philosophy, Brian Keeley explicitly addressed the aforementioned question of whether or not conspiracy theories may be dismissed in a way analogous to David Hume’s critique of miracles.

      Pigden’s arguments have stood up well, and his early essay has helped to legitimize the practice of taking conspiracy theories seriously in the academy. Keeley’s contribution is very different. Its value is in its stimulation of various responses, not in its own soundness or coherence, for it has been the subject of much criticism and disagreement.

      The result is that two schools of thought have developed, which have been labeled “generalism” and “particularism.” The generalists think that there are general reasons—though they disagree about what these are—on the basis of which conspiracy theories as a group can judged to be unwarranted, without even considering the particulars of individual cases. The particularist deny this, arguing that each conspiracy theory ought to be judged on its own particular merits.

      Obviously (to most people), the particularists are right. The reason this is (or should be) obvious is that all sides agree that some conspiracy theories have turned out to be true. The most often cited are: Watergate, Iran-contra, and Bush administration’s propagandistic effort to drum up support for the war in Iraq based on false pretenses.

      For more on the particularists, see: Conspiracy Theory Theorists.

      For abstracts of my own contributions see: My Work on Conspiracy Theories.

      Kurtis Hagen earned his Ph.D. in Philosophy from the University of Hawaii in 2002. He received a scholarship and then a postdoctoral fellowship supporting a total of four years of study and research in Japan. He then taught philosophy for eleven years at SUNY Plattsburgh, becoming Associate Professor and Chair of the Philosophy Department. He is now an independent scholar and author.

      Recent publications include Philosophers of the Warring States: A Sourcebook in Chinese Philosophy, and Conspiracy Theory: A Philosophical Defense.



      1. Is Infiltration of “Extremist Groups”1 Justified?
        Kurtis Hagen


        Many intellectuals scoff at what they call “conspiracy theories.” But two Harvard law professors, Cass Sunstein (now working for the Obama administration) and Adrian Vermeule, go further. They argue in the Journal of Political
        Philosophy that groups that espouse such theories ought to be infiltrated and undermined by government agents and allies. While some may find this proposal appalling (as indeed we all should), others may find the argument plausible, especially if they have been swayed by the notion that conspiracy theories (or a definable subset thereof), by their nature, somehow or another, do not warrant belief. I will argue that Sunstein and Vermeule’s proposal not only conflicts with the values of an open society, but is also epistemically indefensible. In making my case, I will adopt their
        favored example, counter-narratives about 9/11

        Click to access KurtHagen_IJAppliedPhilosophy_IsInfiltrationOfExtremistGroupsJustified.pdf



  4. Regarding the destruction of World Trade Center Twin Towers and Building 7, Sunstein and Vermeule might be tempted to point to the official reports of
    the National Institute of Standards and Technology (NIST). However, there are
    reasons a rational and well-informed person might be less than fully convinced
    by those reports as well. While there are many technical issues that have been
    raised by others, I will just list four that can be stated briefly. First, the Bush administration has been credibly accused of politicizing science—that is, corrupting
    science for political expediency.17 And, NIST was, after all, an arm of the Bush
    administration. Second, representatives of NIST were evasive about key issues,
    such as checking for explosives.18 Third, John Gross, a lead engineer involved the
    NIST report, denied being aware of any eyewitness accounts of molten steel at
    the WTC collapse sites, implied that he is unaware of any suggestive evidence,
    and expressed doubt that the necessary temperatures could have been reached.19
    And yet there are many well-documented eyewitness accounts of molten steel
    (which may have actually been iron), as well as video footage of what looks
    like molten steel flowing from the South Tower, supported by corroborating
    evidence of various kinds.20 (Indeed, the evidence of temperatures sufficient to
    melt steel is now quite strong.21 There should be an unbiased scientific discussion regarding how such temperatures were achieved, or at least a reasonable
    and open discussion of the evidence in question.) Fourth, in the “draft for public
    comment” version of their report on the collapse of Building 7, NIST asserted
    that the collapse rate was about 40% slower than freefall.22 David Chandler, a
    high school physics teacher, demonstrated in an online video that for over 100
    feet the building collapsed at very close to freefall acceleration, and he challenged
    NIST publicly on the matter.23 In the final version of their report, NIST conceded
    the point.24 Having been forced by clear and incontrovertible evidence into this
    astonishing concession, NIST then simply pretended that it doesn’t matter. This
    shows that there can be a kind of “self-sealing” quality to official stories too.
    Officials can deny or ignore evidence, just assert that their results are scientific,
    Is Infiltration of “Extremist Groups” Jand then end the discussion, refusing to have open and fair dialog or debate.
    And this is precisely what NIST has done.25
    Perhaps the real reason Sunstein and Vermeule think counter-narratives positing insider complicity in the events of 9/11 must be false is that they just seem
    too crazy. However, either there is an explicit demonstration of the craziness
    (which appears to be lacking) or else it is just an intuition. And, clearly, intuitions
    regarding the craziness of these ideas vary. As Sunstein and Vermeule themselves
    point out: “Among sober-minded Canadians, a September 2006 poll found that
    22 percent believed that ‘the attacks on the United States on September 11, 2001
    had nothing to do with Osama Bin Laden and were actually a plot by influential
    Americans.’”26 And roughly half of New York City residents accept, at least, the
    more modest “knew in advance . . . [but] consciously failed to act” counternarrative,27 otherwise known as “let it happen on purpose.” But perhaps it is
    only the unwashed half who espouse such beliefs. Sophisticated people, those in
    the know, or those with relevant expertise, Sunstein and Vermeule may assume,
    give no credence to such views



  5. 208 feet by 208 feet
    Each of the WTC towers had 110 stories. 1 WTC (the North Tower, which featured a massive 360-foot-high, TV antenna added in 1978) stood 1,368 feet high, and 2 WTC (the South Tower, which contained the observation deck) was 1,362 feet high. The length and breadth of the towers were 208 feet by 208 feet.


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