Why the observed motion history of World Trade Center towers is smooth

Jia Liang Le, Zdeněk P. Bažant*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

7 Scopus citations


The collapse of the World Trade Center towers was initiated by the impact of the upper falling part onto the underlying intact story. At the moment of impactthe velocity of the upper part must have decreased. The fact that no velocity decrease can be discerned in the videos of the early motion of the tower top has been recently exploited to claim that the collapse explanation generally accepted within the structural mechanics community was invalid. This claim is here shown to be groundless. Calculations show that the velocity drop is far too small to be perceptible in amateur video records and is much smaller than the inevitable error of such video records.

Original languageEnglish (US)
Article number005101QEM
JournalJournal of Engineering Mechanics
Issue number1
StatePublished - Jun 15 2010


  • Collapse
  • Damage
  • Impact
  • Structural dynamics
  • Structural monitoring

ASJC Scopus subject areas

  • Mechanics of Materials
  • Mechanical Engineering


Dive into the research topics of 'Why the observed motion history of World Trade Center towers is smooth'. Together they form a unique fingerprint.

Cite this