Nonlinear behaviour of reinforced concrete flat slabs after a column loss event

Abstract

Previous studies have demonstrated that reinforced concrete flat slab structures could be vulnerable to progressive collapse. Although such events are highly dynamic, simplified static analyses using the sudden column loss scenario are often used to gain an indication into the robustness of the structure. In this study, finite element analysis is used to replicate column loss scenarios on a range of RC flat slab floor models. The model was firstly validated against the results of scaled slab experiments and then used to investigate the influence of different geometric and material variables, within standard design ranges, on the response of the structure. The results demonstrate that slab elements are able to effectively redistribute loading after a column loss event, and therefore prevent a progressive collapse. However, the shear forces to remaining columns were 159% of their fully supported condition and increased to 300% when a dynamic amplification factor of 2.0 was applied. It is shown that this can potentially lead to a punching shear failure in some of the slab elements.

Numerical Study on the Behavior and Bearing Mechanism of Flat Slabs in Column Loss Events

“…e FE model of this research was validated with the findings of an existing experimental program, where Russell et al [30] evaluated the behavior of a scaled two-panel flat slab supported by 5 columns (lacking a corner column). e slab was under a uniform downward increasing load on its entire top surface and the pattern of crack propagation on slab bottom surface at the end of the loading process was reported.…”

“…where η is the ratio of compressive strain to concrete cracking strain and σ c is a stress calculated as a function of compressive strain over relevant range. k is a numerical constant which is considered equal to 2.15 for grades C25 and C30 concrete [30]. e tensile concrete behavior was assumed to be linearly elastic up to the point of cracking, but was followed by a nonlinear softening stage in accordance with equation (3) [35].…”

“…Pham et al [29] also studied the behavior of beam and beam-slab subassemblages with different loadings and showed that removal of a penultimate column could be even more critical than a corner column loss. Russell et al [30] evaluated the effect of some design parameters on the nonlinear behavior of flat slabs considering different column removal locations. However, as the panels connected to the removed column were only overloaded up to initial uniform loading on the entire floor, no limit states such as extensive failure of slab bars were reported in that study.…”

Stress distribution and failures in partially overloaded support-removed flat slab floors

“…The assumed concrete stress-strain curves are presented in Fig. 3 (Russell et al, 2018 [15]; Okamoto and Maekawa, 1991 [6]). As can be seen in the compressive part, at first, the curve rises parabolically from the initial elastic area up to the point which corresponds to the concrete compressive strength (equal to 30 MPa).…”

A Novel Feature Selection Approach Based on Tree Models for Evaluating the Punching Shear Capacity of Steel Fiber-Reinforced Concrete Flat Slabs

“…Moreover, these structures can result in a reduced overall height of the story. The benefits of reinforced concrete flat slabs have attracted the attention of a large number of researchers working on the reactions of such structures in both theoretical and experimental studies [ 4 , 5 , 6 ]. According to the available literature, the punching shear capacity of the slab-column connections can be considered as the maximum strength of a reinforced concrete flat slab [ 1 ].…”