Discussion on “The logarithmic strain measure applied to the nonlinear positional formulation for space truss analysis” [Finite Element in Analysis and Design 45 (2009) 632–639] and “Nonlinear positional formulation for space truss analysis” [Finite Eleme

This discussion presents the application of the classical strain measures, and their energy conjugated stress pairs, to obtain a consistent geometrically nonlinear formulation based on the Finite Elements Method (FEM), particularly applied to the numerical analysis of space trusses. The development is performed using a numerical formulation based on a kinematical description that takes as reference only the global coordinates of the finite elements. This numerical approach is interesting because it is not necessary to use local systems of reference in the finite elements to describe the kinematics of the problem. The invariance on the formulation for the different strain measures is proved here.