A semi-Markov approach in the reliability of existing buildings affected by wearing

The structure is, here, assumed to be a system composed of elements. The structural reliability is dealt with dependent on wearing processes of the components also due to the environmental attacks. One of the critical effects connected with this process is the birth of particular stress states (fatigue states) in building materials; as a consequence the structural elements can suffer changes in their geometrical or mechanical features. When the change reaches a given level of damage the structural capacity of the element decreases and its reliability could be endangered. Therefore, the material degradation process can be numbered between the causes of wearing for the elements and the structure. To define the reliability degradation process due to this type of wearing, modelling the material degradation process is important. For example the degradation process of masonry materials attacked by salt crystallization has been dealt with. It seems to be a transition process with the characteristics of a renewal process. To model it the semi-Markov processes (s-MP) and the renewal theory are proposed. It is important to control, over time, the degradation process connected with the wearing. It is necessary to plan satisfactory strategies of prevention, maintenance and repair, so that the reliability level of the structural system can be maintained higher than a certain threshold over time. To make some hypotheses on the possible strategies to use, a probabilistic approach to the problem is needed. The s-M approach shown here moves in this direction.