When the shear resistance of prestressed beams with stirrups is determined with the current Eurocode, no distinction is made between regions with and without flexural cracks. This while it may be expected that a region without flexural cracks will have a higher shear resistance. This is due to the lower longitudinal strains and the narrow crack widths, resulting in a higher contribution of aggregate interlock. Also, the Eurocode does not take into account that in regions without flexural cracks, a significant part of the shear force is transferred through the uncracked flanges. This article proposes therefore a shear resistance model, based on Modified Compression Field Theory (MCFT), that does consider the low longitudinal strains and shear transfer through the uncracked flanges. From a comparison it was found that the proposed model can determine shear resistance as accurately as the most comprehensive level III approach of the Model Code 2010. However, the proposed model was found to be much easier to use in engineering practice as no iterations are necessary.

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Diagonal tension cracking is the governing failure mode for bridge girders with a thin web that are highly prestressed and contain little shear reinforcement. When assessing existing bridge girders using the Eurocode 2 [1], it often turns out that it is not possible to demonstrate sufficient resistance to diagonal tension cracking. This paper evaluates the method to determine the maximum principal tensile stresses as used in the Eurocode 2 [1] and investigates how flexural cracks affect the principle tensile stresses in the regions without flexural cracks. This paper also investigates how the tensile strength of the web is affected by the presence of compressive stresses and by the size of the area subjected to high tensile stresses. Based on the results of these investigations, an improved model is proposed to determine the resistance to diagonal tension cracking.

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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.@en