Reliability and geotechnical safety applied to deep foundations in precast concrete piles - case study

Abstract

The Brazilian standard pertinent to the design and execution of foundations, NBR 6122/2019, establishes that the safety inspection of foundations of a given project must be conducted based on compliance with specified safety factors. Safety factor verification is imperative to meet regulatory requirements; however, it is not enough to guarantee the safety of a foundation. As there is variability in the resistance and solicitation of the piles that make up a foundation, each safety factor value reflects a failure probability. Therefore, it is fictitious that the use of an adequate safety factor value implies the absence of failure risk. Thus, a reliability analysis, applied to a real building with an access ramp whose foundations are composed of precast concrete piles, based on the probabilistic moments, mean, and coefficient of variation, associated with the variability of pile resistance and solicitation, is presented in this article. The values obtained for the safety factors (2.14 and 1.98 for the building and the ramp foundations, respectively) and failure probabilities (1:2,244 and 1:3,131 for the building and the ramp foundations, respectively) implies that the project in question has an acceptable safety level. This article allows us to conclude that a small variation in the reliability index results in a large variation in failure probability; that a greater global safety factor does not necessarily lead to a lower failure probability and it becomes evident that this reliability analysis is a practical way, to manage the uncertainties inherent in foundation design, allowing rational decision making regarding performance.

Análise comparativa das capacidades de carga de estacas pré-moldadas obtidas por métodos teóricos no software GEO5

“…Dada a diversidade de métodos propostos por diversos autores encontrados na literatura, alguns questionamentos surgem, como quais métodos apresentam resultados mais próximos dos valores reais obtidos em testes de carga. Vários pesquisadores buscam avaliar a qualidade das previsões de capacidade de carga para estacas, obtidas por meio de diferentes métodos (por exemplo, Shooshpasha et al 2013;Soares et al 2014;Monteiro et al 2017;Pereira et al 2020;Pereira et al 2021;Pessoa et al 2021ª;Pessoa et al 2021b;Silva & Araujo, 2021;Moreira & Araujo, 2022).…”