Specifying the target reliability levels is one of the key issues in the assessment of existing structures. For a majority of existing buildings and infrastructures, the design life has been reached or will be reached in the near future. These structures need to be reassessed in order to verify their safety. Eurocodes provide a general basis primarily intended for the design of new structures, but the basic principles can be used for assessing existing buildings, too. Reliability levels are generally based on both economic optimization and criteria for human safety. In this study, both methods are elaborated for existing structures. It appears that the requirement for the same target reliability for existing and new structures is uneconomical. Further, cost optimization seems to yield rather low reliability levels and human safety criteria often become the critical factor. The study concludes with practical guidelines for establishing reliability indices for existing structures linked to Eurocode principles

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Within short time, the Eurocodes will be accepted as the official rules for design of new structures in most European countries. Also for the existing stock Eurocodes will be a suitable starting point for the assessment as these codes are expected to be based on the best and most recent knowledge available. However, it would be uneconomical to require all existing buildings and civil engineering works like bridges to comply fully with these new codes. Already without the introduction of a set of new codes, the assessment of existing structures differs from the design situation. This paper describes the main differences with respect to the relevant reliability requirements and develops a set of partial factors that could be used in those cases.

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