Use of Finite Element Methods in Geotechnical Limit State Design

Abstract

The finite element method (FEM) continues to gain importance as a tool for practical and economic design. Whereas many other calculation methods require the engineer to prescribe a mode of behaviour or incipient failure, the FEM has the major advantage that it can point out unexpected mechanisms. Unlike most other forms of calculation, it can be applied usefully to both working and failure states. The use of the FEM in limit state design raises a series of issues, some of which are equally relevant to non-FEM calculation, though they may be less clearly identified. This paper considers the following issues: • the relative merits of materials factor and load/resistance factor approaches • the merits of a dual calculation, as proposed by Eurocode 7 • for analyses of staged construction, at what stage to impose safety factors • procedures for checking both ultimate and serviceability limit states • complex soil models in which strength and stiffness are related • the significance of yield in structural elements The approach adopted has been to raise questions, offer solutions where possible, and provide some examples, either within the text or by reference to other recent work.