Design of spread foundations according to the EC7 and the reliability evaluation

This paper presents the philosophy and the concepts of Eurocode (EC7) applied to spread foundations. The five ultimate limit states presented in the EC7 are defined. More emphasis is devoted to the ultimate limit state GEO. It is presented an overview of the reliabity methods and the levels corresponding te the probabilistic methods are defined. It is analysed a spread foundation submitted to vertical loading using all the design approaches of the EC7, the traditional Portuguese approach based on global safety factor and the Spanish codes. The results obtained are compared. Using the Excel solver it is calculated the Hasofer-Lind second moment reliabity index ß for three foundation dimensions obtained in the EC7 design and with the other approaches. Several coefficients of the variation for soil parameters are used to evaluate reliabilty index ß.Fundação para a Ciência e a Tecnologia (FCT) - Projecto POCI/ECM/57495/2004 - Geotechnical risk for tunnels in high-speed trains