Nonlinear finite element analysis for structural assessment of existing bridges: Network manager experiences

The Dutch Directorate-General for Public Works and Water Management (Rijkswaterstaat) is assessing its bridges as a part of the major renovation and replacement task of bridge-structures in the Netherlands. For assessments it appears that calculations show that an increasing number of existing bridges no longer comply with current assessment standards or are becoming restricted in their functionality. Complete renovation is costly, results in disruption of traffic, and is not sustainable. The Eurocode permits to demonstrate sufficient safety using a nonlinear finite element analysis (NLFEA). NLFEA offers a possibility to demonstrate additional structural safety of the existing bridge-structures. The challenge is to gain confidence that the approach gives reliable results for the structural safety of the considered bridge. Moreover, experience learns that NLFEA demands many choices to be made by Rijkswaterstaat as a client and will not always lead to unambiguous results. These choices concern modelling aspects, applied safety format, load positions, and the required sensitivity analyses. Another question is what conclusions, based on the obtained results of this analysis, can be drawn for similar structures. This paper shows how Rijkswaterstaat has dealt with these challenges with case 'Peddemors' and what lessons are learned, all from the viewpoint of a client.