Abstract
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. 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. Thus, load-deflection curves were drawn up to the point in which a great number of longitudinal slab bars ruptured. Introducing 5 stages on each curve, finite element outputs on concrete cracking pattern and rebar stress state were presented. 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. Moreover, the findings indicated that the slab damaged zone could exceed the panels under uniform overloading.
Highlights
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 [1]. is event can be triggered in frames, space structures, and domes [2,3,4]
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 [9]. ese notional scenarios might represent the impact of a wide range of unusual loading conditions [10, 11]
The results of the separate analyses RP, RI, and reinforced concrete (RC) are compared from three aspects of load-deflection curves, the stress state of the bars up to slab near-collapse state, and concrete crack pattern at a moment corresponding to first bar yielding
Summary
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 [1]. is event can be triggered in frames, space structures, and domes [2,3,4]. 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 [5]. Vieira et al [12] with employing the special techniques conducted four quasistatic experiments on half-scaled specimens considering a central column loss scenario in a perimetral portal frame. Fascetti et al [15] proposed a new procedure derived from nonlinear static and dynamic analyses for comparing the relative robustness of RC frame buildings against progressive collapse. Genikomsou et al [16] conducted nonlinear finite element analyses of reinforced concrete slab-column connections under static and pseudodynamic loadings to investigate their failure modes in terms of ultimate load and cracking patterns. Du et al [17] investigated the performance of a RC spatial frame structure and found that short-
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