[en] High temperature nuclear components of Class I which are subject to cyclic thermal and mechanical loading must be verified according to Code-defined procedures, which take into account the operational cycles the component might experience during its design lifetime. This paper describes a framework for the analysis of such a component starting from its operating diagram, which defines the permanent state conditions and the interconnecting transients associated to their occurrences. The main part of this framework is a procedure which generates, starting from the operating diagram, a set of possible cases of combinations of operational cycles, each exhausting the life of the component. This procedure embodies a heuristic section aimed to eliminate, from the set of possible cases, loading histories not likely to lead to the highest damage. Therefore, in order to satisfy the requirements of the Code, a limited number of creep-fatigue verifications performed, even in the case the loading histories of the component are not definable in a simple manner and are not univocally determined. The framework is completed by two algorithmic procedures to interface the cycle-recognizing procedure to the verification program and to build the loading histograms of the retained cases. (orig./GL)

[en] While analyzing heavy concrete structures the thermal problem has a huge importance due to the large stiffness of the structure themselves. However cracking occurs and a large reduction in the stiffness of the structures and consequently on the loads takes place. This characteristic (already taken into consideration by ASME code for steel structures) needs some more care for the case of concrete due to its relatively brittle nature (however this benefit has been recognized by ACI codes). Following the same line of research presented by some of the authors some experience has been made in the field of the analysis of concrete structures under cracking due to thermal loads. (orig.)