Análise da probabilidade de ruína em elementos de fundação da obra do hospital do alto sertão em Delmiro Gouveia – AL

Abstract

In the scope of Civil Engineering, the great challenge is to design foundations in a safe and technically viable way. Although the Brazilian Technical Standard (ABNT) defines parameters for foundations to meet safety criteria, there are considerations in them that bring uncertainty and, therefore, some authors already use the analysis of the probability of ruin. Cintra and Aoki (2010) determine the probability of ruin through a probabilistic analysis, which seeks to assess the risks and uncertainties of foundations in a different way. An important step in making this analysis is to define the type of foundation and, consequently, its resistance, or load capacity for the proposed application. In this sense, the present work analyzes the probability of ruin for the foundation executed in Block A of the work of the Hospital do Alto Sertão, located in Delmiro Gouveia / Alagoas, and an alternative foundation of the spread footing type. In the project, Block A has 72 open-air pipes with 60 cm bore diameters, and varied base diameters, with just a simple recognition probe (SPT). The proposed methodology presents the technical comparison between the probability of ruin for the executed foundation and the dimensioned alternative foundation. As for the alternative foundation, the theoretical method of Terzaghi with Vésic's proposition (1943) was used. The results showed great variability between the load capacities obtained between the methods, however, there was no normal distribution for Aoki and Velloso (1975) and Décourt-Quaresma (1978), so both foundations used the Terzaghi theoretical method with a proposition of Vésic (1943). With the calculated capacities, the normal distribution curves for both foundations are projected, showing the incidence of probability of ruin, through the area where the curves intersect. Despite the low probability of ruin for the foundations, the spread footing have a higher reliability index, and a safety factor of 3.85, which meets NBR 6122/2019. Meanwhile, the executed foundation has a safety factor of 9.59, which implies the revision of the project, for a choice of foundation with lower load capacity. Finally, it is noted that the probability of ruin is an indispensable analysis to point out risks and possible uncertainties, adapting the best choice of the foundation and its geometry, reducing costs and increasing the reliability of the project.