Spontaneous Collapse Mechanism of World Trade Center Twin Towers and Progressive Collapse in General
Publication: Journal of Structural Engineering
Volume 148, Issue 6
Abstract
The collapse of the World Trade Center (WTC) Towers during the terrorist attacks on September 11, 2001, remains one of the most tragic catastrophes in the field of structural engineering. This paper first reviews a mathematical model that explains the process of the total collapse of the Twin Towers and shows that the downward collapse progression below the impacted floors was spontaneous. The model is based on a continuum description of the motion of the crush front and captures various types of energy dissipation during the collapse. The predictions of this model match all the observations, including the video records of the first few seconds of motion of both towers, the seismic records of the collapse durations for both towers, the mass and size distributions of comminuted concrete particles, and the fast expansion of dust clouds during collapse with the booms generated. This catastrophe provoked general interest in other types of progressive collapse of buildings. This is the subject of the second part of this paper, in which a three-dimensional stochastic computational model for the collapse of RC frame buildings is presented. The occurrence probabilities of different collapse patterns are predicted. The model is further extended to investigate the delayed collapse behavior of RC frames. The results of the analysis shed light on the emerging trend of probabilistic analysis and design of structures against progressive collapse.
Get full access to this article
View all available purchase options and get full access to this article.
Data Availability Statement
The computer code and simulation data generated from the study are available from the corresponding author by request.
Acknowledgments
J.-L. Le acknowledges partial financial support from the Nuclear Engineering University Program of the Department of Energy under Grant DE-NE0008785 to the University of Minnesota. Z. P. Bažant acknowledges partial financial support under NSF Grant CMMI-2029641 to Northwestern University.
References
Abboud, N., M. Levy, D. Tennant, J. Mould, H. Levine, S. King, C. Ekwueme, A. Jain, and G. Hart. 2003. “Anatomy of a disaster: A structural investigation of the World Trade Center collapses.” In Proc., 3rd Forensic Engineering Congress, 360–370. Reston, VA: ASCE.
Alashker, Y., H. Li, and S. El-Tawil. 2011. “Approximations in progressive collapse modeling.” J. Struct. Eng. 137 (9): 912–924.
Aycardi, L. E., J. B. Mander, and A. M. Reinforn. 1994. “Seismic resistance of reinforced concrete frame structures designed only for gravity loads: Experimental performance of subassemblages.” ACI Struct. J. 91 (5): 552–563.
Bao, Y., and S. K. Kunnath. 2010. “Simplified progressive collapse simulation of RC frame-wall structures.” Eng. Struct. 32 (10): 3153–3162. https://doi.org/10.1016/j.engstruct.2010.06.003.
Bao, Y., S. K. Kunnath, S. El-Tawil, and H. S. Lew. 2008. “Macromodel-based simulation of progressive collapse: RC frame structures.” J. Struct. Eng. 134 (7): 1079–1091. https://doi.org/10.1061/(ASCE)0733-9445(2008)134:7(1079).
Bažant, Z. P. 2001. “Why did the World Trade Center collapse?” SIAM J. Math. Anal. 34 (8): 1–3.
Bažant, Z. P., and M. Jirásek. 2018. Creep and hygrothermal effects in concrete structures. Berlin: Springer.
Bažant, Z. P., J.-L. Le, F. R. Greening, and D. Benson. 2008. “What did and did not cause collapse of WTC Twin Towers in New York.” J. Eng. Mech. 134 (10): 892–906. https://doi.org/10.1061/(ASCE)0733-9399(2008)134:10(892).
Bažant, Z. P., and M. Verdure. 2007. “Mechanics of progressive collapse: Learning from World Trade Center and building demolitions.” J. Eng. Mech. 133 (3): 308–319. https://doi.org/10.1061/(ASCE)0733-9399(2007)133:3(308).
Bažant, Z. P., and Y. Zhou. 2002. “Why did the World Trade Center collapse?—Simple analysis.” J. Eng. Mech. 128 (1): 2–6. https://doi.org/10.1061/(ASCE)0733-9399(2002)128:1(2).
Boumakisa, I., G. Di Luzio, M. Marcon, J. Vorel, and R. Wan-Wendner. 2018. “Discrete element framework for modeling tertiary creep of concrete in tension and compression.” Eng. Frac. Mech. 200 (Sep): 263–282.
Charles, R. J. 1957. “Energy-size reduction relationships in comminution.” Min. Eng. 9 (14): 80–88.
Di Luzio, G. 2009. “Numerical model for time-dependent fracturing of concrete.” J. Eng. Mech. 135 (7): 632–640. https://doi.org/10.1061/(ASCE)0733-9399(2009)135:7(632).
DOD (Department of Defense). 2016. Design of buildings to resist progressive collapse, with change 3. Washington, DC: DOD.
Ellingwood, B. R. 2006. “Mitigating risk from abnormal loads and progressive collapse.” J. Perform. Constr. Facil. 20 (4): 315–323. https://doi.org/10.1061/(ASCE)0887-3828(2006)20:4(315).
Ellingwood, B. R., R. Smilowitz, D. O. Dusenberry, D. Duthinh, H. S. Lew, and N. J. Carino. 2007. Best practices for reducing the potential for progressive collapse in buildings. Gaithersburg, MD: National Institute of Standards and Technology.
El-Tawil, S., H. Li, and S. Kunnath. 2014. “Computational simulation of gravity-induced progressive collapse of steel-frame buildings: Current trends and future research needs.” J. Struct. Eng. 140 (8): A2513001. https://doi.org/10.1061/(ASCE)ST.1943-541X.0000897.
GSA (General Services Administration). 2003. Progressive collapse analysis and design guidelines for new federal office buildings and major modernization projects. Washington, DC: GSA.
Izzuddin, B. A., A. G. Vlassis, A. Y. Elghazouli, and D. A. Nethercot. 2008. “Progressive collapse of multi-storey buildings due to sudden column loss—Part I: Simplified assessment framework.” Eng. Struct. 30 (5): 1308–1318. https://doi.org/10.1016/j.engstruct.2007.07.011.
Kaewkulchai, G., and E. B. Williamson. 2004. “Beam element formulation and solution procedure for dynamic progressive collapse analysis.” Comput. Struct. 82 (7–8): 639–651. https://doi.org/10.1016/j.compstruc.2003.12.001.
Kausel, E. 2001. “Inferno at the World Trade Center.” In The towers lost and beyond, edited by E. Kausel. Cambridge, MA: MIT Press.
Khandelwal, K., and S. El-Tawil. 2008. “Pushdown resistance as a measure of robustness in progressive collapse analysis.” Eng. Struct. 33 (9): 2653–2661. https://doi.org/10.1016/j.engstruct.2011.05.013.
Kiakojouri, F., V. D. Biagi, B. Chiaia, and M. R. Sheidaii. 2020. “Progressive collapse of framed building structures: Current knowledge and future prospects.” Eng. Struct. 206 (Jan): 110061.
Le, J.-L., and Z. P. Bažant. 2011. “Why the observed motion history of World Trade Center towers is smooth.” J. Eng. Mech. 137 (1): 82–84. https://doi.org/10.1061/(ASCE)EM.1943-7889.0000198.
Le, J.-L., and Z. P. Bažant. 2017a. “Mechanics-based mathematical studies proving spontaneity of post-impact WTC towers collapse.” Europhys. News 48 (1): 18–23. https://doi.org/10.1051/epn/2017102.
Le, J.-L., and Z. P. Bažant. 2017b. “Mechanics of collapse of WTC towers clarified by recent column buckling tests of Korol and Sivakumaran.” Int. J. Struct. Stab. Dyn. 17 (9): 1771011. https://doi.org/10.1142/S0219455417710110.
Le, J.-L., and B. Xue. 2014. “Probabilistic analysis of reinforced concrete frame structures against progressive collapse.” Eng. Struct. 76 (2): 313–323. https://doi.org/10.1016/j.engstruct.2014.07.016.
Lew, H. S., Y. Bao, F. Sadek, and J. A. Main. 2011. An experimental and computational study of reinforced concrete assemblies under a column removal scenario. Gaithersburg, MD: National Institute of Standards and Technology.
Masoero, E., F. K. Wittel, H. J. Herrmann, and B. M. Chiaia. 2010. “Progressive collapse mechanisms of brittle and ductile framed structures.” J. Eng. Mech. 136 (8): 987–995. https://doi.org/10.1061/(ASCE)EM.1943-7889.0000143.
McKay, A., K. Marchand, and M. Diaz. 2012. “Alternate path method in progressive collapse analysis: Variation of dynamic and nonlinear load increase factors.” Prac. Period. Struct. Des. Constr. 17 (4): 152–160. https://doi.org/10.1061/(ASCE)SC.1943-5576.0000126.
Mello, L., J.-L. Le, and R. Ballarini. 2020. “Numerical modeling of delayed progressive collapse of reinforced concrete structures.” J. Eng. Mech. 146 (10): 04020113. https://doi.org/10.1061/(ASCE)EM.1943-7889.0001843.
NIST. 2005. Final report on the collapse of the World Trade Center towers. Gaithersburg, MD: NIST.
Panagiotou, M., J. Restrepo, M. Schoettler, and G. Kim. 2012. “Nonlinear cyclic truss model for reinforced concrete walls.” ACI Struct. J. 109 (2): 205–214.
Pesce, C. P., L. Casetta, and F. M. dos Santos. 2012. “Equation of motion governing the dynamics of vertically collapsing buildings.” J. Eng. Mech. 138 (12): 1420–1431. https://doi.org/10.1061/(ASCE)EM.1943-7889.0000453.
Quintiere, J. G., M. di Marzio, and R. Becker. 2002. “A suggested cause of the fire-induced collapse of the World Trade Towers.” Fire Saf. J. 37 (7): 707–716. https://doi.org/10.1016/S0379-7112(02)00034-6.
Sadek, F., J. M. Main, H. S. Lew, and Y. Bao. 2011. “Testing and analysis of steel and concrete beam-column assemblies under a column removal scenario.” J. Struct. Eng. 137 (9): 881–892. https://doi.org/10.1061/(ASCE)ST.1943-541X.0000422.
Sasani, M., A. Kazemi, S. Sagiroglu, and S. Forest. 2011. “Progressive collapse resistance of an actual 11-story structure subjected to severe initial damage.” J. Struct. Eng. 137 (9): 893–902. https://doi.org/10.1061/(ASCE)ST.1943-541X.0000418.
Sasani, M., and S. Sagiroglu. 2008. “Progressive collapse resistance of Hotel San Diego.” J. Struct. Eng. 134 (3): 478–488. https://doi.org/10.1061/(ASCE)0733-9445(2008)134:3(478).
Schuhmann, R. 1940. Principles of comminution. I: Size distribution and surface calculation. New York: American Institute of Mining, Metallurgical, and Petroleum Engineers.
Song, B. I., and H. Sezen. 2013. “Experimental and analytical progressive collapse assessment of a steel frame building.” Eng. Struct. 56 (Apr): 664–672. https://doi.org/10.1016/j.engstruct.2013.05.050.
Wierzbicki, T., and X. Teng. 2003. “How the airplane wing cut through the exterior columns of the world trade center.” Int. J. Impact Eng. 28 (Sep): 601–625. https://doi.org/10.1016/S0734-743X(02)00106-9.
Xiao, Y., S. Kunnath, F. W. Li, Y. B. Zhao, H. S. Lew, and Y. Bao. 2015. “Collapse test of a 3-story half-scale RC frame building.” ACI Struct. J. 112 (4): 429–438.
Xu, G., and B. R. Ellingwood. 2011. “Probabilistic robustness assessment of pre-Northridge steel moment resisting frames.” J. Struct. Eng. 137 (9): 925–934. https://doi.org/10.1061/(ASCE)ST.1943-541X.0000403.
Xue, B., and J.-L. Le. 2016a. Risk assessment of reinforced concrete buildings against progressive collapse. Montreal: ACI.
Xue, B., and J.-L. Le. 2016b. “Simplified energy-based analysis of collapse risk of reinforced concrete buildings.” Struct. Saf. 63 (Apr): 47–58. https://doi.org/10.1016/j.strusafe.2016.07.003.
Xue, B., and J.-L. Le. 2016c. “Stochastic computational model for progressive collapse of reinforced concrete buildings.” J. Struct. Eng. 142 (7): 04016031. https://doi.org/10.1061/(ASCE)ST.1943-541X.0001485.
Information & Authors
Information
Published In
Journal of Structural Engineering
Volume 148 • Issue 6 • June 2022
Copyright
© 2022 American Society of Civil Engineers.
History
Received: Sep 28, 2021
Accepted: Jan 24, 2022
Published online: Apr 8, 2022
Published in print: Jun 1, 2022
Discussion open until: Sep 8, 2022
Authors
Metrics & Citations
Metrics
Citations
Download citation
If you have the appropriate software installed, you can download article citation data to the citation manager of your choice. Simply select your manager software from the list below and click Download.
Cited by
- Cosimo Pellecchia, Alessandro Cardoni, Gian Paolo Cimellaro, Marco Domaneschi, Farhad Ansari, Ahmed Amir Khalil, Progressive Collapse Analysis of the Champlain Towers South in Surfside, Florida, Journal of Structural Engineering, 10.1061/JSENDH.STENG-12485, 150, 1, (2024).
- Simos Gerasimidis, Bruce Ellingwood, Twenty Years of Advances in Disproportionate Collapse Research and Best Practices since 9/11/2001, Journal of Structural Engineering, 10.1061/JSENDH.STENG-12056, 149, 2, (2023).