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USE OF FINITE ELEMENT METHODS IN GEOTECHNICAL ULTIMATE LIMIT STATE DESIGN (2005)
The paper introduces to the use of FEM in Ultimate Limit State Design. The accuracy of FEM to predict failure load is briefly discussed. Procedures for FEM in MFA (Material Factoring Approach) and LRFA (Load and Resistance Factoring Approach) formatsare proposed. In MFA it is advised to simulate the stress and loading history using unfactored values of the material parameters and, at each stage where the ULS requirements have to be checked, to reduce stepwise the shear strength parameters to their design values(ϕ’-c’ reduction, usually performed using a simple elastic-purely plastic model). This allows to check for ULS in the ground and provides design values of forces in structural members. In LRFA, the design values of forces in structural members are obtained by multiplying their characteristic values by the load factor. Checking for geotechnical failure in LRFA is in some cases not always straight-forward. The links between the proposed procedures and the three Design Approaches introduced by Eurocode 7 for persistent andtransient design situations are explained. The advantages and limitations involved by the use of a simple elastic-purely plastic model for the ϕ’-c’ reduction are discussed.
16th International Conference on Soil Mechanics and Geotechnical Engineering, Osaka, 12-16/09/2005
V.U.B. University of Brussels
Belgium