We know that with the reliability structure, modeling is based on a deterministic physical system: the latter extract degradation mechanisms. Thus, mechanisms taken into account are crack propagations and are defects from thermal or vibratory fatigue, corrosion or erosion etc... The structure is submitted to some loadings in its environment; this, defines a finite number of modes of degradation. We can envision envisage two possible outcomes: failure or success. Therefore, we could consider the failure probability deterministic or probabilistic. According to the probabilistic approach, the risk will be evaluated without probability of failure. It is understood that this evaluation represents the entire problem of this work. In our study, we are going to be examining the development of two methods of structural reliability, which are the first order and second order: That is why we are going to use FORM and SORM method alongside with the Monte Carlo simulation, which are so effective that they are used to solve problems from the domain of the structure reliability. They allow approximating the limit state function, reliability index and the probability of failure.