Combining finite element analyses and mechanical models for the assessment of reinforced concrete slabs
The influence of the level of deformation of the flexural reinforcement on the punching strength is well-established and mechanically founded since the pioneer works of Kinnunen and Nylander in the 1960’s. In code provisions, this influence is sometimes reflected by means of indirect parameters such as the flexural reinforcement ratio (as in many empirical formulae) or by means of mechanical approaches accounting for the ratio between the applied load and the flexural resistance of the specimen (as in fib’s MC2010). An accurate estimate of this parameter (level of deformation of the flexural reinforcement) is nevertheless complex in many situations, due to the determination of the moment field and the po-tential redistributions of bending moments. In order to provide a consistent approach to determine the punching strength, it has been recently proposed to couple refined finite element (FE) models describing accurately the flexural behavior of slabs (accounting for the influence of cracking, yielding and moment redistributions) with a robust strain-based failure criterion in shear. In this framework, the goal of this paper is to review specific case studies in which redistributions after cracking in bending and shear may be governing on the overall behavior of reinforced concrete slabs. Load–displacement responses of the investigated case studies are evaluated by means of FE analyses using a multi-layered shell formulation. Eventually, the numerical global response is combined with the failure criterion of the Critical Shear Crack Theory, that can directly consider the influence of the flexural response on the punching or shear capacity.
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