Design Approaches

EN 1997 introduces design approaches into the analysis; they differ by application of partial factors.

According to EN 1997-1 the partial factors are generally applied to loading actions or their effect, to properties of foundation soil M, or to resistances R or both. The values of partial factors differ not only by the assumed design approach, but also by the type of geotechnical task (support structures, pile, etc.). The values of partial factors are in general specified by Eurocode in Annexes A; the national choice of values of partial factors specifies NA. The program automatically displays the required coefficients depending on the selected design approach (or possible according to National Annex).

Regarding the fact that individual Design approaches introduce the partial factors into the analysis in a different way, it is logical that the results attributed to these design approaches may also considerably differ. If National Annex does not recommend for a given geotechnical task a Design approach, it is up to the designer to select it (and therefore also to evaluate whether the results correspond to the analyzed situation). 

Design approach 1 – Verification is performed for two sets of coefficients (Combination 1 and Combination 2) used in two separate analyses. Coefficients are applied to loading actions and to material parameters.

Design approach 2 – Applies partial factors to loading actions and material resistance (bearing capacity)

Design approach 3 – Applies partial factors to loading actions and at the same type to material (material parameters of soil)

"Partial factors" dialog windows for analysis according to EN 1997 – Choice of design approach