![]() These notional scenarios might represent the impact of a wide range of unusual loading conditions. Concerns about the possible consequences of such disasters in very commonly used flat slab system led the researchers to evaluate their behavior after column loss events. Although the behavior and propagation pattern differs from one case to another, many structural collapse incidents, including the twin towers of the World Trade Center (WTC), Pipers Row Car Park, and Sampoong Department Store, were considered to mainly include pancake collapse mode. Progressive collapse can occur in a variety of forms such as domino (e.g., a series of adjacent buildings overturn on each other), pancake (for example, upper floors fall down on the ones below), instability (e.g., structural elements buckle consecutively), zipper-type (for example, suspension bridge cables tear away one after another), or combined collapse modes. This event can be triggered in frames, space structures, and domes. Progressive collapse is defined as gradual spread of local damage from one element to another until collapse of the whole or a part of a structure which is disproportionate to the initial damage. Moreover, the findings indicated that the slab damaged zone could exceed the panels under uniform overloading. A significant increase in the stresses along the diagonals of the slab panels accompanied by bar ruptures around columns adjacent to the removed column proved contribution of an important load-bearing mechanism in addition to the behavior called “quasiframe action.” Consecutive rupture of bars showed formation of a zipper-type collapse mode as well as a great tendency to transfer load share of missing column mainly along shorter direction of slab panels. Introducing 5 stages on each curve, finite element outputs on concrete cracking pattern and rebar stress state were presented. Thus, load-deflection curves were drawn up to the point in which a great number of longitudinal slab bars ruptured. ![]() ![]() The scenarios are rather similar to those used in the conventional evaluation of the progressive collapse potential however, application of the uniformly distributed loading over panels adjacent to the removed columns was not limited to twice the value of the initial load. This study investigates the behavior and the load-bearing mechanism of a typical flat slab with rectangular panels in several scenarios including the removal of a corner, penultimate, and internal columns. ![]()
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