• inspection
• maintenance
• monitoring
• Structural Health Monitoring
• structural reliability
• updating

Assessment of existing structures is getting more and more important due to the increasing number of structures and infrastructures close to the end of their service life in conjunction with severe economic constraints. The aim of this thesis is to investigate on how Inspection and monitoring can be effectively used to this purpose.
To date, an obstacle to the spread of their use is represented by the existing fragmentation of guidelines and standards on structural monitoring and the lack of an international standard universally recognised. In spite of this, main characteristics and classifications of inspection and monitoring systems, together with maintenance topics, are carefully investigated. The idea to regularly inspect most structures and monitor the behaviour of critical parts or of the whole structure to get early warnings may lead to immediate interventions and cost minimisation assuring an acceptable reliability level.
A crucial step of the process is the use of newly obtained measurements together with prior information to evaluate the actual structural reliability. This can be done using probabilistic methods or updating partial safety factors on the base of probabilistic considerations.
The application of theoretical principles is illustrated by the case study of a stadium roof subjected to high snow load and of the change in use of an office building with an increase of loads. In the first example the results coming from the continuous monitoring of the snow depth on the roof are used to decide about the closure of the stadium whilst, in the second, the influence of destructive tests on specimens and proof load tests on the updating of the resistance of the considered steel beam is investigated.