# Damage and Failure of a Column-Supported RC Flat Slab Subjected to Impulsive Loading
###### Abstract  
RC flat slabs supported by an array of columns subjected to the action of impulsive pressure were investigated. The slabs were designed for static loads according to current standards. The dynamic responses of 4 \(\times\) 4- and 8 \(\times\) 8-column-supported slabs were similar, as were damage and failure. A simplified model consisting of a tributary area and a central column yielded similar results, demonstrating the accuracy of the simplified model and its reliability. These analyses exhibited modes of damage and failure characterized by large shear distortions in the slab-column connection zone. The rest of the span remained undamaged and in a horizontal position. In all analyses, the slab concrete around the column was fully damaged. The rebars failed within a limited zone at the slab-column connections. The early failure of integrity reinforcement indicated that it could not fulfill its duty; thus, a subsequent progressive collapse scenario was inevitable. All bent-up rebars failed, and their contribution to shear resistance was doubtful. The static analysis was entirely different from the dynamic failure mode. Impulsive loading damage and failure were similar to those in the case of slab-on-slab impact; in both cases, the slab underwent large displacement and severe damage in the narrow slab-column zone, whereas the rest of the slab remained almost completely flat and undamaged. RC flat slabs; multi-span structure; impulsive loading; dynamic response; dynamic punching; slab-column connection +
Footnote †: journal: Applied Sciences  
a progressive collapse scenario and turn into global failure [8]. To avoid this catastrophic event, research has expanded to deal with the post-punching shear behavior of flat slabs, aiming at providing an alternative support to the detached slab to arrest the detached slab and prevent its fall, thus preventing failure propagation [1; 2; 9; 10; 11]. This is mainly performed by including special integrity reinforcement, which has shown its efficiency in static load tests [1; 3; 12; 13; 14; 15]. The mechanism of static punching shear failure has been studied widely, both experimentally and analytically [4; 5; 16; 17; 18; 19; 20; 21; 22], and the results of these investigations are implemented in design codes [12; 13; 14; 15; 23]. The static design of flat slabs is commonly performed using FE linear elastic analysis or, alternatively, simplified hand calculations of continuous beams in both slab directions for representative (column and field) strips of the slab. The analysis results provide the sagging bending moments within the slab span between the columns and the hogging bending moment in the slab-column connection zone and above the columns. Typically, maximum deflections are calculated at midspan. These results are implemented in the design process to assure proper reinforcement design and satisfy the slab performance criteria. Despite the attention given by different standards to the proper static design of RC flat slabs in general and to avoid punching shear failure in particular, punching shear failure occurs from time to time. There are numerous reasons for the occurrence of such failure under static conditions, such as excessive or unexpected loads; foundation settlement; faulty construction and material properties; material deterioration; combinations of the above; and dynamic loads such as impacts, blasts, and accidental gas explosions. Relatively to the static behavior of flat slabs, their dynamic behavior and especially their behavior under impact have received only a little attention. Vibration response is commonly solved using similar approaches and tools as in the static loading case. The response of RC flat slabs to extreme dynamic loads has hardly been investigated, although it occurs even in the case described above, where the detached falling slab impacts the slab underneath [24; 25].