Load Transfer and Collapse Resistance of RC Flat Plates under Interior Column Removal Scenario

Abstract

Reinforced concrete (RC) flat-plate structures are vulnerable to punching shear failure at their slab-column connections, potentially leading to a catastrophic progressive collapse. In practice, the slab-column connection above an interior column, removed due to abnormal loads, may be subjected to a concentrated downward force due to the absence of the supporting column and further being pushed due to different live load intensities on individual stories. This force is different to the full design load that the column withstands in normal situation and, combined to the gravity load acting on the slab, may cause punching shear failure at the interior slabcolumn connection. This will further trigger failure propagation to the surrounding slab-column connections. This paper presents the experimental tests performed on two identical large scale 2×2-bay RC flat-plate specimens under an interior column removal scenario. A 5 kPa uniformly distributed load was applied first to the slab followed by an incremental concentrated force imposed on the slab-column connection above the removed interior column. The complete collapse resistant behavior and load redistribution pattern of the specimens were investigated and are reported herein. Results show that more than 90% of the applied concentrated force is solely distributed to the four nearest adjacent columns. Three load carrying mechanism phases, in form of flexural, tensile membrane, and a combination of one-way catenary and dowel actions can be distinguished in resisting the applied concentrated load.

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

“…The tension and compression axial forces and bending moments resisted at the column bases were measured by the load cells throughout T1 and T2. Further details of the design of the custom-made load cells can be found in Xue et al [20].…”

“…Note that T2 was conducted 12 days after T1 due to installation and connection of required experimental instruments, and cutting of column C9. The tests were not repeated as the results were shown to be repeatable in Xue et al [20].…”

“…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.…”

Experimental investigation of asymmetrical reinforced concrete spatial frame substructures against progressive collapse under different column removal scenarios

“…In real RC frame structures, slabs play an important role in the redistribution of unbalanced loads because slabs are cast in situ together with beams to transfer the unbalanced gravity load induced by an initial local failure. Published experiments on RC slabs under interior, exterior, corner, and penultimate column removal scenarios indicated that a slab will exhibit a two‐dimensional “compressive membrane action” in the primary mechanism stage and a two‐dimensional “tensile membrane action” in the secondary mechanism stage, thereby providing structural resistance. Russell et al conducted dynamic column loss analysis of RC flat slabs and compared with equivalent static cases in order to determine the dynamic amplification factor.…”