The paper presents original approaches based on numeric solutions, which replace the analytic methods used in the solvers of the structural problems, in this way being accessed a higher level of generality and being reached an improved accuracy of the results. Firstly, in the materials’ fatigue evaluation, the safety domain is redefined in an original way, in order to avoid the imprecision due to the linearization of their frontiers, which would lead to smaller coefficients of safety. Another original aspect consists of the spline interpolation of the diagrams that store the information regarding the factors, which influence the fatigue limit, in this way the materials’ fatigue calculi being automatically performed. The application is used to evaluate several materials and to provide the safety coefficients that become, together with other materials’ constants, input data in a multi-criteria-decision-making (MCDM) software. In this way, the resulted hierarchy of materials assist the structural analyst to select an optimal material. Several original software instruments for research are developed in Python and GNU Octave.