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An Overview of Progressive Collapse
Aut hors Ketul Ruparelia Student, CEPT Univ ersity Dr. P V Patel Professor, Nirm a Univ ersity Bhairav Patel Structural Engineer, VMS Engineering Abst ract Progressiv e collapse is spread of an initial local structural dam age …show more content…
The collapse of WTC towers of New York in Sept. 2 001 is exam ple of this ty pe of collapse where collapse is said to be initiated by weakening of the floor joists due to fire that resulted from the aircraft im pact. The loss of structural m em ber was lim ited to the few stories but it progressiv ely extended throughout the height of tower. The potential energy of upper part of collapsed m em bers conv erted in to kinetic energy which turned in to im pact force which was far bey ond the resisting capacity of the lower floors and ultim ately resulted in to total collapse of the tower. 2) Zipper-ty pe collapse: this ty pe of collapse is initiated by rupture of one cable and propagating by ov erloading & rupture of adjacent cables. Exam ple of this ty pe of collapse is collapse of original Tacom a Narrows Bridge. After the first hangers of that suspension bridge snapped due to wind induced v ibrations of the bridge girder, the entire girder peeled off and fell. Im pact force does not ty pically occur in this ty pe of collapse, which is the case in pancake-ty pe collapse. 3) Dom ino-ty pe collapse: m echanism behind this ty pe of collapse is, initial ov erturning of one elem ent, fall off that elem ent in angular rigid-body m otion around a bottom edge, transform ation of potential energy into kinetic energy , lateral im pact of the upper edge of that elem ent on the side face of an adjacent elem ent where the horizontal pushing force