In-plane deformability of RC floors: assessment of the main parameters and influence on dynamic behaviour

In-plane floor deformability is an important issue for the correct assessment of the behaviour of Reinforced Concrete (RC) structures subjected to seismic loads. Several studies have demonstrated that in-plane floor deformability is often not negligible in structures with RC walls as vertical resistant elements, since it mainly depends on the relative stiffness of floor and vertical elements. In this paper, approximately 700 simple buildings constructed with RC walls were simulated in finite element models considering both two-dimensional and one-dimensional modelling strategies. First, the reliability of the simplified modelling strategy was evaluated. Then, the simplified model was used to assess the effects of building shape and number of walls on the in-plane floor deformability. The differences between the behaviour of the buildings under the assumption of deformable and rigid floors were examined in terms of both floor displacements, based on static analyses, and the main vibration periods of the building, based on linear dynamic analyses. Finally, based on the collected numerical results, reliable regression curves for both the maximum displacements and the periods evaluated under the assumption of deformable and rigid floors were obtained as function of a parameter significant of floor and walls stiffness. The curves may provide a tool for evaluating the error related to an incorrect assumption about the in-plane floor deformability.