On The Physics of High Rise Building Collapses

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Source ~ http://www.europhysicsnews.org/articles/epn/pdf/2016/04/epn2016474p21.pdf

Europhysics News is the magazine of the European physics community. It is owned by the European Physical Society and produced in cooperation withEDP Sciences. It is distributed to all our Individual Members and many institutional subscribers. Most European national societies receive EPN for further distribution. The total circulation is currently about 25000 copies per issue.

Editor: Victor R. Velasco ; Science editor: Jo Hermans

About the Authors

Steven Jones is a former full professor of physics at Brigham Young University. His major research interests have been in the areas of fusion, solar energy, and archaeometry. He has authored or co-authored a number of papers documenting evidence of extremely high temperatures during the WTC destruction and evidence of unreacted nano-thermitic material in the WTC dust.

Robert Korol is a professor emeritus of civil engineering at McMaster University in Ontario, Canada, as well as a fellow of the Canadian Society for Civil Engineering and the Engineering Institute of Canada. His major research interests have been in the areas of structural mechanics and steel structures. More recently, he has undertaken experimental research into the post-buckling resistance of H-shaped steel columns and into the energy absorption associated with pulverization of concrete floors.

Anthony Szamboti is a mechanical design engineer with over 25 years of structural design experience in the aerospace and communications industries. Since 2006, he has authored or co-authored a number of technical papers on the WTC high-rise failures that are published in the Journal of 9/11 Studies and in the International Journal of Protective Structures.

Ted Walter is the director of strategy and development for Architects & Engineers for 9/11 Truth (AE911Truth), a nonprofit organization that today represents more than 2,500 architects and engineers. In 2015, he authored AE- 911Truth’s Beyond Misinformation: What Science Says About the Destruction of World Trade Center Buildings 1, 2, and 7. He holds a Master of Public Policy degree from the University of California, Berkeley.

Shortened Extracts

Indeed, neither before nor since 9/11 have fires caused the total collapse of a steel-framed high-rise—nor has any other natural event, with the exception of the 1985 Mexico City earthquake, which toppled a 21-story office building. Otherwise, the only phenomenon capable of collapsing such buildings completely has been by way of a procedure known as controlled demolition, whereby explosives or other devices are used to bring down a structure intentionally. Although NIST finally concluded after several years of investigation that all three collapses on 9/11 were due primarily to fires, fifteen years after the event a growing number of architects, engineers, and scientists are unconvinced by that explanation.

Steel-framed high-rises have endured large fires without suffering total collapse for four main reasons: 1) Fires typically are not hot enough and do not last long enough in any single area to generate enough energy to heat the large structural members to the point where they fail (the temperature at which structural steel loses enough strength to fail is dependent on the factor of safety used in the design. In the case of WTC 7, for example, the factor of safety was generally 3 or higher. Here, 67% of the strength would need to be lost for failure to ensue, which would require the steel to be heated to about 660°C); 2) Most high-rises have fire suppression systems (water sprinklers), which further prevent a fire from releasing sufficient energy to heat the steel to a critical failure state; 3) Structural members are protected by fireproofing materials, which are designed to prevent them from reaching failure temperatures within specified time periods; and 4) Steel-framed high-rises are designed to be highly redundant structural systems. Thus, if a localized failure occurs, it does not result in a disproportionate collapse of the entire structure.

Because the only loads present on 9/11 after the impact of the airplanes were gravity and fire (there were no high winds that day), many engineers were surprised that the Twin Towers completely collapsed. The towers, in fact, had been designed specifically to withstand the impact of a jetliner, as the head structural engineer, John Skilling, explained in an interview with the Seattle Times following the 1993 World Trade Center bombing: “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,” he said. “The building structure would still be there.”

Skilling believed the only mechanism that could bring down the Twin Towers was controlled demolition.

In general, the technique used to demolish large buildings involves cutting the columns in a large enough area of the building to cause the intact portion above that area to fall and crush itself as well as crush whatever remains below it. This technique can be done in an even more sophisticated way, by timing the charges to go off in a sequence so that the columns closest to the center are destroyed first. The failure of the interior columns creates an inward pull on the exterior and causes the majority of the building to be pulled inward and downward while materials are being crushed, thus keeping the crushed materials in a somewhat confined area—often within the building’s “footprint.” This method is often referred to as “implosion.”

The total collapse of WTC 7 at 5:20 PM on 9/11, shown in Fig. 2, is remarkable because it exemplified all the signature features of an implosion: The building dropped in absolute free fall for the first 2.25 seconds of its descent over a distance of 32 meters or eight stories [3]. Its transition from stasis to free fall was sudden, occurring in approximately one-half second. It fell symmetrically straight down. Its steel frame was almost entirely dismembered and deposited mostly inside the building’s footprint, while most of its concrete was pulverized into tiny particles. Finally, the collapse was rapid, occurring in less than seven seconds. Given the nature of the collapse, any investigation adhering to the scientific method should have seriously considered the controlled demolition hypothesis, if not started with it. Instead, NIST (as well as the Federal Emergency Management Agency (FEMA), which conducted a preliminary study prior to the NIST investigation) began with the predetermined conclusion that the collapse was caused by fires.

NIST was able to arrive at (its) scenario only by omitting or misrepresenting critical structural features in its computer modelling.[4] Correcting just one of these errors renders NIST’s collapse initiation indisputably impossible.

(Technical details ensue which you can read at the source magazine…)

The collapse mechanics discussed above are only a fraction of the available evidence indicating that the airplane impacts and ensuing fires did not cause the collapse of the Twin Towers. Videos show that the upper section of each tower disintegrated within the first four seconds of collapse. After that point, not a single video shows the upper sections that purportedly descended all the way to the ground before being crushed. Videos and photographs also show numerous high-velocity bursts of debris being ejected from point-like sources. NIST refers to these as “puffs of smoke” but fails to properly analyze them. NIST also provides no explanation for the midair pulverization of most of the towers’ concrete, the near-total dismemberment of their steel frames, or the ejection of those materials up to 150 meters in all directions. NIST sidesteps the well-documented presence of molten metal throughout the debris field and asserts that the orange molten metal seen pouring out of WTC 2 for the seven minutes before its collapse was aluminum from the aircraft combined with organic materials. Yet experiments have shown that molten aluminum, even when mixed with organic materials, has a silvery appearance—thus suggesting that the orange molten metal was instead emanating from a thermite reaction being used to weaken the structure . Meanwhile, unreacted nano-thermitic material has since been discovered in multiple independent WTC dust samples

As for eyewitness accounts, some 156 witnesses, including 135 first responders, have been documented as saying that they saw, heard, and/or felt explosions prior to and/or during the collapses. That the Twin Towers were brought down with explosives appears to have been the initial prevailing view among most first responders. “I thought it was exploding, actually,” said John Coyle, a fire marshal. “Everyone I think at that point still thought these things were blown up”.

Conclusion

It bears repeating that fires have never caused the total collapse of a steel-framed high-rise before or since 9/11. Did we witness an unprecedented event three separate times on September 11, 2001? The NIST reports, which attempted to support that unlikely conclusion, fail to persuade a growing number of architects, engineers, and scientists. Instead, the evidence points overwhelmingly to the conclusion that all three buildings were destroyed by controlled demolition. Given the far-reaching implications, it is morally imperative that this hypothesis be the subject of a truly scientific and impartial investigation by responsible authorities.

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Generally just Being. Nothing in particular, no claims to fame. I like gardening and the sea, nature, art in all forms from poetry to films and everything in between, and being in the company of my family.

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