W artykule omówiono zagadnienia modelowania struktur maszyn eksploatowanych w długich przedziałach czasu. Przedstawiono systemowe podejście do podjęcia struktury koncentrując się na strukturach obserwowanych w procesie projektowania i eksploatacji. Przedstawiono przykłady zmienności tych struktur i zwrócono uwagę na konieczność uwzględniania tego aspektu we wszystkich fazach życia obiektu.
In the paper, problems of structure modelling of the objects operated in long period is described. It is observed in long-term tests that some performance characteristics as well as structure in micro and macro scale change due to wear out, fatigue, corrosion and other ageing processes. Therefore, the current technical state of the object is only known if monitoring or diagnostic procedures are carried out. In case of operation within 50-100 years, much information is lost and decision process concerning prediction of rest lifetime is getting difficult. Ageing processes influence the most the object performance, reliability and safety. It is visible in the form of lower efficiency, shape deformation, lack of some less important components, or low attention to functionality of safety measures. Such events do not disturb the operation at the beginning, but its accumulation in long time would exclude the object from operation later. Systemic attempt to the structure concept is applied. Discussion is directed to structures observed in the process of design and operation. Functional structure is defined as a set of component functions creating main function and function relations are binary, probabilistic or fuzzy functions. Reliability function describes relation between reliability state of components and object state. Function of reliability structure depends on component configuration and on its reliability state, while both variable in time. Real process changes components and its structure through: various failure modes, ageing processes, human errors, and secondary failures due to design errors during modernisations and large repairs. Safety structure takes into account effects and consequences of undesirable events like object failure, human error and unexpected state of environment conditions. Man as an operator or maintenance crew member is one of the most important element in operation system. His erroneous activity is presented as an error tree. Cost structure represents operational cost of the object and may be a platform for assessing object variation due to its ageing. Examples taken from real operation systems of structure variation are shown.