Photoelasticity method along with the numerical methods of equilibrium equation integration or with any other experimental methods makes it possible to determine stresses in structural members. To assess structural strength, it is necessary to apply the corresponding structural strength theories. If material properties are time dependent, then it is necessary to possess complete information on material behavior in time. But such a procedure for the solution of problems on structural strength and durability seems to be too complicated and not expedient from an engineering point of view. The paper in question suggests a direct method for structural strength and durability modeling by using the analogies of dimensions.