Load-resisting mechanism to mitigate progressive collapse of flat slab structures

Abstract

For reinforced concrete flat slab structures, column failure due to unexpected extreme loading may significantly increase the moment and shear force at adjacent slab-column connections, which can trigger punching shear failure at these connections and result in progressive collapse of flat slab structures. To determine the possible load-resisting mechanisms developed in flat slab structures in resisting progressive collapse, three multi-panel flat slab substructures are tested in this study. A flat slab substructure is tested as a control specimen. The remaining two specimens are strengthened by adding drop panels or post-installed shear bolts. Punching shear failure is observed in the control specimen and the specimen with post-installed shear bolts after reaching their yield loads. However, even the control specimen without any strengthening exhibited considerable post-failure resistance and deformation capacity mainly due to sufficient integrity reinforcement, which had been installed in the bottom of the slab. Test results indicated that drop panels not only increase the flexural resistance but also raise the punching shear resistance of the connections significantly. Thus, no obvious punching shear failure is observed in the specimen with drop panels.However, post-installed shear bolts can only increase the punching shear resistance. For post-failure behaviour, this is not very effective. The test results demonstrated that flexural failure dominates the performance of test specimens, as relatively low slab reinforcement ratio but high span/thickness ratio was designed.

Experimental study on the progressive collapse behaviour of RC flat plate substructures subjected to corner column removal scenarios

“…Imposing an increasing UDL either on the entire slab or on those bays adjacent to the removed column is being typically used to evaluate the collapse resistance of flat plates [18,19,22]. In this study, the UDL was applied to the slab in two different ways.…”

“…However, these studies have predominately focused on frame systems. Relevant investigations on RC flat plate structures, a commonly used structural system, are still scarce [18][19][20][21][22][23][24][25][26].…”

“…While studies on single slab-column connections pertinent to either lateral restraints [37,38] or post-punching performance [39][40][41] have been carried out, they cannot to some extent, account for the actual load redistribution paths of the RC flat plate system in a progressive collapse event. With respect to the progressive collapse research on multi-column flat plate substructures, experimental studies on scaled RC flat plate substructures under an interior column removal scenario were carried out by Yi et al [18], Qian and Li [19] and Xue et al [20]. A sudden edge column loss scenario was experimentally investigated by Russell et al [21] and Peng et al [22] to simulate the dynamic responses of RC flat plate structures.…”

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

“…He emphasized the important effect of the slab reinforcements in preventing progressive collapse. Also Qian and Lee, 2015 [13] evaluated the crack formation pattern after an interior column loss by testing a scaled flat slab consisting of 4 panels and showed that, due to the low percentage of reinforcement and large ratio of bay length to slab thickness, the flexural collapse mode dominates primarily on the punching shear mechanism. The findings of the mentioned study strongly confirmed that the pattern proposed by the yield-line theory for predicting the flexural collapse mechanism corresponds to reality.…”

Theoretical assessment of progressive collapse capacity of reinforced concrete structures

“…Investigating and quantifying these mechanisms has been conducted experimentally, and analytically through numerical work. Due to the expense of experimental work, a few limited experimental tests are available (Regan, 1975, Sasani et al, 2007, Orton, 2007, Yi et al, 2008, Su et al, 2009, Sadek et al, 2011, Yu and Tan, 2013a, Pour et al, 2015, Ahmadi et al, 2016, Hou et al, 2015, Qian and Li, 2015, Alogla et al, 2016b, Alogla et al, 2016a. Other researchers have examined the structural resistance against progressive collapse using finite element analysis performing non-linear static and dynamic analysis (Bao et al, 2008, Alashker et al, 2011, Kim and Yu, 2012, Yu and Tan, 2013a, Yu and Tan, 2013b.…”