Shell-Based Finite Element Analysis of Reinforced Concrete Slabs Subjected to Non-uniform Stress Distribution at Column Connection Regions

Abstract

RC flat plates design provisions and mechanical models have been developed in a highly-idealized manner and, as a result, loosely represent the performance of real-world RC flat plates. Part of this inadequacy is due to the insufficient amount of reliable data for typical RC flat plate constructions scenarios in comparison with the abundantly studied idealized test specimens, which generally consist of symmetric specimen geometries, uniform/regular loading conditions and reinforcement arrangements. In this regard, there is a need for reliable and cost-effective analysis procedures that may be used to estimate the performance and facilitate the design of atypical real-world RC flat plates. This thesis presents the application of a low-cost thick-shell nonlinear finite element analysis (NLFEA) procedure to estimate the punching shear resisting performance of RC slab-column connections under variable connection shear stress conditions. Variation of connection stress conditions stems from columns with different cross-section aspect ratios, different distributions of gravity loading conditions, slabs constructed with significantly different planar reinforcement conditions in the orthogonal directions, as well as a combination of gravity loading and unbalanced bending moments. In this regard, forty-eight isolated slab-column connection specimens that are presented in the literature and were constructed without out-of-plane shear reinforcement presented were modelled and analyzed using the shell-based finite element-based analysis procedure VecTor4. The results from these analyses were used to assess NLFEA model performance. All results were developed using a predefined set of material models and analysis parameters, defined on the basis of prior and unrelated validation studies, and were shown to provide good agreement with experimental findings without the need for extensive calibration studies or the adoption of case-specific failure criteria. From the findings obtained, it was determined that the thick-shell NLFEA employed is suitable for estimating the punching shear response for slabs subjected to varied and highly non-uniform shear stresses within the connection regions and provided similar levels of precisions as that previously obtained for isolated slab-column connections constructed with idealized geometries and reinforcing conditions, and subject to idealized loading conditions. For the forty-eight slabs considered, the mean computed-to-reported punching capacity ratio was 0.97, with a coefficient of variation (CoV) of 12%.