1            2

[1]                                                       [2]

3

[3]

Progressive Collapse is “the collapse of multiple bays or floors of a structure resulting from an isolated structural failure due to a chain reaction or domino effect” [a]. The engineering profession started to investigate such behavior worldwide since it was the main mechanism that completely destructed the World Trade Center Towers in the New York City. Any extreme loading that damages structural components such as support beams and columns are subjected to potential cause for progressive collapse. In the case of 9/11 attacks, airplanes crashed into the buildings and blew out the upper floors which took down the layers below to complete ground level. The mechanics of Progressive Collapse has two phases: “Crush-down, whereby gravity and the immense downward kinetic thrust of floors upon mashed floors successively crushes everything below, gives way to crush-up, the free-falling top floors now piling on top of the wreckage. This second phase further pulverizes the rubble” [b].

The nature of the Progressive Collapse which contains impulsive and dynamic external loads make it difficult to fully predict its random occurrence. As a result, although number of researches have been conducted over the past, there are only few standardized structural designs for resisting collapse.   However, steel reinforcement technology can reduce the pancaking effect by enhancing the ductility and structural integrity. Reinforced concrete structures that close the space of beams and columns, connect top and bottom reinforcement, and limit span lengths provide uniform layout to the structural system [c].

Advertisements