Mass and stiffness matrices Mass and stiffness matrices enguth (Mechanical) (OP) 29 Dec 17 03:32 Any way one can extract the mass and stiffness matrices from ETABS? Perhaps using an API? Thank you RE: Mass and stiffness matrices JasonMcKee71 (Structural) 19 Feb 18 18:49 You can do that using the API. Alternatively, you can choose the Standard solver and locate the corresponding text file produced during the analysis which contains mass/stiffness matrix elements. Jason McKee proud R&D Manager of Cross Section Analysis & Design Software for the structural design of cross sections Moment Curvature Analysis Interaction Diagrams Reinforcement Design etc.