Email this article The collapse of WTC 7: A re-examination of the “simple analysis” approach
DOI: https://doi.org/10.20528/cjsmec.2016.02.004
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Although the events of that tragic day happened 14 years ago, there remain nagging questions of why the 47 storey WTC 7 steel framed structure collapsed, when it was NOT hit by an airplane. We will review the official rationale of how the collapse events started, and why, in our opinion, the explanation is judged to be wrong. Then, we will proceed with another scenario that says “Okay – let’s assume that the two critical storeys did sustain extremely hot fires, so much so that 2/3rds of their columns totally lost axial resistance capability”. We then proceed to employ Newton’s laws to inquire whether there was sufficient gravitational potential energy due to live and dead loadings in upper and lower floors to overcome the resistance offered by the remaining columns, together with floor slabs known to have been pulverized to reduced particle sizes by surface to surface crushing. Our conclusion suggests that Newton’s laws of motion and energy conservation considerations would have had to have been violated to explain that building’s total collapse within a debris pile several storeys high.
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References
Abdalla HM, Karihaloo BL (2003). Determination of size-independent specific fracture energy of concrete from three-point bend and wedge splitting tests. Magazine of Concrete Research, 55, 133-141.
http://dx.doi.org/10.1680/macr.2003.55.2.133
Bazant Z, Zhou Y (2002). Why did the world trade center collapse? – Simple analysis. Journal of Engineering Mechanics, ASCE, 128(1), 2-6; Addendum, 128(3), 369-370.
http://dx.doi.org/10.1061/(ASCE)0733-9399(2002)128:3(369)
Bazant ZP, Le J-P, Greening FR, Benson DB (2008). What did and did not cause collapse of the WTC twin towers in New York. Journal of Engineering Mechanics, 134(10) 892-903.
http://dx.doi.org/10.1061/(ASCE)0733-9399(2008)134:10(892)
Bond FC (1952). The third theory of comminution. Mining Engineering Journal, 193, 484-494.
Cantor IG, Structural Engineers (1985). Structural Drawings of 7 World Trade Center.
Doering International Corporation (2011). Grinding Media Size Formula – Work Index for Different Materials According to Bond. Sinn, Germany.
Dunbar D, Regan B (2006). Debunking 9/11 Myths – Why Conspiracy Theories Can't Stand Up to the Facts: An In-Depth investigation by Popular Mechanics. New York Hearst Books.
Eloranta J (1997). The efficiency of blasting versus crushing and grinding. Proceedings of the 23rd Conference of Explosives and Blsting Technique, Las Vegas, Nevada, 1-7.
Greening FR (2006). Energy Transfer in the WTC Collapse. WTC Report, 3 pages.
Griffin DR (2010). The Mysterious Collapse of World Trade Center 7. Olive Branch Press, Chapter 6, 125-144.
Korol RM, Sivakumaran KS (2012). Energy absorption potential of light weight concrete floors. Canadian Journal of Civil Engineering, 39, 1193- 1201.
http://dx.doi.org/10.1139/l2012-107
Korol RM, Greening F, Heerema P (2015). Performance-based fire protection of office buildings: A case study based on the collapse of WTC 7. Challenge Journal of Structural Mechanics, 1(3), 96-105.
Korol RM, Sivakumaran KS (2014). Reassessing the Plastic Hinge Model for Energy Dissipation of Axially Loaded Columns. Journal of Structures, 2014, 795257.
http://dx.doi.org/10.1155/2014/795257
NIST (2008a). Final Report on the Collapse of World Trade Center Building 7. NIST-NCSTAR 1A, National Institute of Standards and Technology, Gaithersburg, Md.
NIST (2008b). Structural Fire Response and Probable Collapse Sequence of World Trade Center Building 7, NCSTAR 1-9, National Institute of Standards and Technology, Gaithersburg, Md.
NIST (2008c). Draft for Public Comment, WTC Investigation, NCSTAR 1-9.
Sivakumaran K, Korol R, Fan X (2014). Energy absorption potential of concrete floors containing secondary (shrinkage and temperature) reinforcements. Frontiers of Structural and Civil Engineering, 8(3), 282-291.
http://dx.doi.org/10.1007/s11709-014-0269-3
