Abstract
In this paper a modification of the reliability-based robust geotechnical design (RGD) method is proposed. The intention of the proposed modifications is to simplify the method, make it less computationally expensive, and harmonise of the results with Eurocode 7. The complexity of the RGD method mainly stems from the calculation of the design’s robustness measure, which is the feasibility robustness index (ββ). Due to this fact, the replacing of the existing robustness measure with a generalised reliability index (β) is considered. It was demonstrated that β fits into the robustness concept, and is traditionally used as a construction reliability measure, making it intuitive and “user friendly”. It is proposed to conduct a sensitivity analysis using Soboli indices, with the aim of freezing the variables whose contribution to the system response variance is negligible, which will further simplify the method. By changing the robustness measure, the number of the required reliability analyses is significantly decreased. Further reduction is achieved by conducting analyses only for the designs chosen in the scope of the genetic algorithm. The original RGD method is used as an extension of traditional reliability-based design. By applying the proposed modifications, the RGD method can be used as an alternative to the classic and reliability-based design method.
Highlights
Since the aim of this paper is to present the procedure of the modified robust geotechnical design method” (RGD) method whose results have been harmonised with EC7, the bearing capacity of a shallow foundation is determined according to the recommendations from this technical standard
We suggest calculating objectives only for the designs chosen in the procedures included in the Non-Dominated Sorting Genetic Algorithm II (NSGA-II) algorithm
The problem of optimising a shallow foundation on non-coherent soil was considered, similar to the one presented by Juang et al [1], from which we took the characteristics of the used variables
Summary
A new geotechnical design approach, called “reliability-based robust geotechnical design method” (RGD) was suggested by Juang et al [1] in 2012. The term “reliabilitybased” stems from the fact that the aim of the method is “to ensure robustness of reliabilitybased design even if uncertainties exist in the estimated statistical moments of noise factors”. They prescribed the methodology of defining non-dominated and robust designs of shallow foundations in cohesionless soil. The aim of the RGD method is to calculate a set of non-dominated designs (Pareto front) through multi-objective optimisation, which is conducted using the genetic algorithm NSGA-II. The final design is chosen from this set, and it is a trade-off between the cost and the robustness of the foundation
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