Abstract This work presents the validation of the Morgenstern-Price method implemented in the Risk Assessment applied to Slope Stability (RASS) computational program to carry out deterministic and probabilistic analyses of slope stability. Deterministic analyses, based on the factor of safety approach, are performed using limit equilibrium methods. The probabilistic ones, on the other hand, are carried out through the direct coupling of these methods to the First Order Reliability Method (FORM). Initially, two benchmark cases are presented for validation of the computational routine related to the Morgenstern-Price method. Next, two illustrative examples are presented, with the investigation of the critical surfaces defined by deterministic and probabilistic criteria, which correspond to the minimum factor of safety, the maximum probability of failure, and the maximum quantitative risk. In the set of stability analyses, it was verified that both the numerical responses and the geometry of the critical surfaces can vary depending on the choice of the limit equilibrium method and the criterion for identifying the critical surface. The different possibilities presented by the methodology used in this study define not only a critical surface, but a set of critical surfaces that can help in the engineering decision-making process and slope risk management, complementing the widely used purely deterministic analyses in geotechnics.

resumo: Lajes lisas de concreto armado são sistemas estruturais compostos por lajes diretamente apoiadas em pilares, sem o uso de vigas. Um fenômeno estrutural que merece atenção nesses sistemas é a punção, caracterizada pela ocorrência de tensões de cisalhamento nas proximidades da interface laje-pilar, que podem produzir ruptura frágil nessas regiões. Este estudo apresenta resultados do índice de confiabilidade β obtidos para ligações laje-pilar a partir de análises de confiabilidade utilizando o FORM, segundo o modelo da norma brasileira, considerando o erro de modelo. Os contornos críticos C e C’ sem armadura de punção são analisados. Os resultados mostraram que a falha no contorno C é muito improvável, enquanto que as probabilidades de ruptura no contorno C’ quando se considera a influência do erro de modelo são maiores que valores alvo recomendados na literatura para o ELU.

abstract: Reinforced concrete flat slabs are structural systems in which slabs are directly supported by columns, without the use of beams. A structural phenomenon that deserves attention in these systems is the punching shear, characterized by the occurrence of shear stresses close to the slab-column interface, which can produce fragile rupture in those regions. This study presents some results of reliability index β obtained for slab-column connections based on FORM, according to the Brazilian standard’s model, considering the model error. The critical contours C and C’ without shear reinforcement are analyzed. The results showed that failure in the C contour is very unlikely, while the probabilities of rupture in the C' contour when considering the influence of the model error are greater than the target values recommended in the literature for the ULS.

Abstract In this paper, a simplified numerical approach to study the influence of the confinement effect provided by transversal reinforcement on the ductility behavior of RC beams in bending is proposed. A unidimensional FEM mechanical model coupled to the Mazars’ damage model to simulate concrete behavior was adopted to assess ductility curvatures at the ultimate limit state. The confinement effect was incorporated to the numerical model through a calibration process of the damage internal parameters, based on the Least Square Method and an analytical law proposed by Kent and Park (1971). Several numerical analyses were carried out considering different designs of RC beams according to a parametric study varying the neutral axis position, concrete compressive strength and the volumetric transversal reinforcement ratio. The obtained results showed the importance of the amount of transversal reinforcement on the ductility behavior, increasing the ductility factor even for the cases with inappropriate neutral axis position.