A method for determining a mechanical performance parameter of a structure in which damage has caused a wall of the structure to change from an initial shape to a damaged shape. The method comprising for geometrically characterizing an external surface of the damaged shape; modeling a test body comprising a surface substantially identical to the external surface of the damaged shape; modeling a test wall having a portion of a shape substantially identical to the initial shape; calculating a deformed test wall and a stress state related to the deformation, the deformation of the test wall being caused by a relative displacement of the test body and the test wall, the relative displacement being configured to give the deformed test wall an external surface substantially identical to the external surface of the damaged shape; and evaluating mechanical performance of the deformed test wall.