Influence of punching shear reinforcement on the flexural response of flat slabs

Physical punching shear models such as the Critical Shear Crack Theory (CSCT), which is the basis of Model Code 2010 (MC 2010), describe generally the punching strength as a function of the slab deformation. Thus, the prediction of an accurate load-deformation curve is essential for the prediction of the punching strength as well as the deformation capacity of flat slabs. In the vicinity of columns, the flexural response of flat slabs depends not only on the flexural moments but also on the concentrated shear forces. In the case of slender slabs, slabs with low amounts of flexural reinforcement, or slabs without shear reinforcement, the shear forces are limited and thus their influence in the flexural response is low. However, in the case of thick slabs with shear reinforcement, large shear forces are carried influencing the flexural response of the flat slab. Despite the importance of an accurate prediction of the load-rotation response, little research has yet been performed on this subject. This paper presents an investigation on the flexural response of 6 full-scale flat slab specimens. The specimens presented herein belong to an extensive experimental campaign of 16 full-scale flat slab specimens performed at the Ecole Polytechnique Fédérale de Lausanne (Switzerland) with the aim to investigate the punching strength and the rotation capacity of flat slabs with and without shear reinforcement. The investigated parameters were the column size, the slab thickness, the amount of shear reinforcement, and the type of shear reinforcement system. The investigation of the flexural response consists of the comparison of the experimentally obtained load-rotation responses to the predictions by the CSCT, MC 2010, and a modified approach based on the CSCT.