Reliability aspects of assessment and upgrading

In decision making related to assessment and upgrading of building structures many and large uncertainties have to be taken care of. The basic questions are: how safe is the structure, how safe should it be and, where relevant, which measure should be taken? In all these cases the answers may differ from those in the design situation. Another typical aspect of existing structures is that uncertainties can be reduced by incorporating results of inspection and monitoring. This, however, raises new questions about when, where, what and how to inspect. Authorities and politicians may be interested in long term costs related to inspection, maintenance and replacement. To deal with these matters, a risk based decision approach offers a perfect theoretical framework. Application in practice, however, is another thing and turns out to be far from trivial. There is a need for guidance and where possible simplification. This should lead to codes of practice in a similar way as for the design of new structures where historical pragmatic design rules are merged with a risk and reliability background.