The relevant steps for reliability analysis are fast described referring to a generic system and then applied to typical maritime structures. A picture of the existing codes that suggest target reliability level is supplied to compare reliability estimate with the target value. Reliability methods were applied to a typical rubble mound breakwater and to a typical vertical breakwater. The results have shown that reliability level of maritime structures is low if compared with the target values suggested by codes.
In these last decades, a great development of probabilistic methods in Civil Engineering can be recognised, in particular Hydraulic. During the last few decades, in fact, the belief that absolute security could be provided has been recognised to be mistaken in many branches of engineering. This happens as the consequence of the imperfect predictability of load intensity, structural characteristics and structural behaviour, of the uncertainties of engineering models, as well as of gross human errors during the design and construction phases or during exploitation period In coastal engineering, in particular, conventional design practice for maritime structures is deterministic in nature, and is based on the concept of a design load, which should not exceed the resistance of the structure. Almost all the available design formulae only give the relationship between wave characteristics and structural response and are semiempirical, being based mainly on central fitting to model test results. The often considerable scatter in test results is not considered in general because the formulae normally express on the mean values. Consequently the applied characteristic value of the resistance is then the mean value and not a lower fractile as is usually the case in other civil engineering fields.
