The Design Value Method and Adjusted Partial Factor Approach for Existing Structures

Abstract

In contrast to the design of new structures, the assessment of existing structures often relies on the subjective judgement of the investigating engineer. An objective verification format for existing structures based on alternative partial factors is however feasible, enabling a rather simple and straightforward, but objective and coherent safety evaluation of existing concrete structures by practitioners. The proposed framework is compatible with the current Eurocodes for the design of new structures, but additionally enables incorporation of alternative values for the target reliability level, alternative values for the remaining working life and also updated information based on, for example, on-site inspection data and data from testing, as all these considerably influence the partial factors in the structural reliability assessment of existing structures. After introducing the framework for the derivation of partial factors, two suitable methods for developing alternative partial factors for existing structures are described and explained, i.e. the Design Value Method (DVM) and the Adjusted Partial Factor Method (APFM). The performance of both methods is investigated by first order reliability method (FORM) based reliability analyses.