Aplicação da probabilidade de ruína em de fundação com estacas pré-moldadas de concreto utilizando o princípio de Hamilton

Abstract

The great challenge of Civil Engineering in the design phase of a project is to establish a model that is technically possible and economically feasible. One aspect that has a direct relationship with both quality and safety issues is the safety factor. However, Cintra and Aoki (2010) present substantial considerations regarding the use of this parameter, since the uncertainties that involve a project are not considered, so the authors defend the use of the analysis of ruin probability. Another parameter with crucial role in the process of choosing the use of a foundation type is the load capacity of the soil, which in high demands in general is used the pile foundations. The Aoki-Velloso method (1975) is widely practiced to estimate loads supported by a soil-pile assembly. Another proposal to estimate the resistance of a soilpile system is to apply the Hamilton Principle, which relates the energy of the punch blow and the displacements at the pile that consequently occur (Aoki et al., 2007). Based on these two methods, the load of the soil-pile interaction was estimated for six precast concrete piles, although in Aoki-Velloso method (1975)) the data did not behave according to normal distribution. The statistical analysis showed that there is no significant difference between the mathematical models and experimental to estimate the load capacity. Relating to the load capacity estimated by the Energy Conservation Principle and the Aoki-Velloso method (1975), four of six piles presented substantial values, three with results equal to 1. These same loads, when compared with the load determined in a dynamic test, allowed the determination of average value of 0.90 ± 0.17. It was also evaluated the ruin probability with load estimated by the principle of conservation of energy, which was determined a safety factor of 2.15, being above 1.6 that is recommended by the standard 6122 (ABNT, 2010). It was also revealed a possibility of remote ruin, then recalculated the safety factor for the acceptable reliability index advocated by Pereira Jr. (2003), β = 3.0. The new safety factor of 1.62 is a very closer number compared to that found for the load test of 1.52. Finally, it is noticed that the probability analysis is an important tool because it is possible to detect errors and make corrections in the execution phase of the project, avoiding expenses with future pathologies, as well as avoiding waste.