Issue 50

O. Mouhat et alii, Frattura ed Integrità Strutturale, 50 (2019) 126-140; DOI: 10.3221/IGF-ESIS.50.12 131   0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 - 0 0 0 0 0 0 - i i i i i i N x N y N N y x N x N B y              0 0 0 0 - - 0 0 0 0 - 0 0 0 - 0 0 0 0 0 0 0 i i i i i i i N N y x N N y N N x N                                                              (11) Matrix required for the stability analysis The pre-buckling can be given by this precautionary measure:       0 0 0 = K q f (12) The second phase is the detection of critical states on the fundamental path reason, it is important to calculate the geometry of the stiffness matrix   K  this can be done as follows:        = d T K G G      (13) And matrix G, which is formed by:   =   i T N G x (14) Where    is the stress vector, stress reorganized in the form of a matrix according to Taylor [20].   0 0 0 0 0 0 0 0 0 0 y x x xy xy y N N N N N N                 (15) The linear Eigenvalue problem is: