On bounding the life of structures subjected to steady load and operating within the creep range

The paper offers a simplified life assessment for structures nominally subjected to constant load and operating within the creep range. It is shown that the life of any structure, subjected to conditions where creep occurs, may be bounded by two procedures.In the particular case where the plastic yield surface is similar to the isochronous creep failure surface, the upper bound on life is obtained from a knowledge of the plastic collapse load. The lower bound approach requires a knowledge of the stationary state stress distribution. The authors argue that the actual time of failure relative to these bounds is governed by a material property rather than the geometry of the structure.The bounds on life have been applied to some simple structures where a more complete analysis or experimental data are available. It is shown that the upper bound solution gives a close approximation to the life of these structures provided that there is adequate ductility.