Description
The calculation, verification and assessment of structures in Europe shall follow Eurocode 0, which employs a semi-probabilistic safety concept with partial safety factors to account for scattering uncertainties in materials and actions. However, in the case of existing structures, the features like materials and actions are already determined and can be in many cases measured. Hence, a rigorous application of this safety concept for existing structures may yield conservative results and potentially lead to unnecessary rehabilitation, strengthening and replacements procedures. To address this issue, the fib Bulletin 80 provides two approaches to modify partial safety factors for materials and actions: the design value method (DVM) and the adjusted partial factor method (APFM). This paper investigates how DVM and APFM can be used to specify the partial safety factors for the dead load of existing structures based on precise geometry measurements. For this purpose, the Nibelungen Bridge in Worms, which serves as the validation structure of the German Research Foundation-funded priority programme SPP 100+, is used as an example. As a part of this programme, an as-designed 3D-geometry model based on inventory technical drawing as well as an as-built 3D-geometry model based on point clouds, which was generated using laser scanning technology, of the bridge are developed. As a result, the deviations between these two models are determined and analyzed. Subsequently, object-based partial safety factors are derived. In the end, new safety factors are proposed for the German recalculation guideline.
