The Dutch Concrete Act sets ambitious goals for sustainability, including significant CO2 reduction and high-quality reuse of concrete by 2030. Rijkswaterstaat, the Directorate-General for Public Works and Water Management, aims for circular practices by this time. Structural engineers play a crucial role in assessing existing structures. But too often it leads to the replacement of a structure because it is at the end of the designed service life. Concrete regulations influence engineering decisions, with changes increasing the use of reinforcement, although they may offer more flexibility than perceived. Structural engineers can influence sustainability by professionally assessing existing structures, potentially avoiding unnecessary replacements. However, there’s a tendency to prematurely classify structures as old, leading to conservative assumptions and modelling methods that may underestimate the structural safety. Despite limited technological advancements in concrete and reinforcement steel, existing structures often exceed strength requirements for new structures. Shear force requirements have evolved, yet structures without shear reinforcement are feasible under current regulations. The emphasis on reuse over new construction is proposed, urging a reconsideration of the necessity of shear reinforcement. Structural engineers can optimize material use by carefully considering modelling methods, structure dimensions and reinforcement amounts, aligning with the basic principles of reinforced concrete techniques while following the regulations.@en

This paper is about the assessment of masonry arch bridges in the Netherlands. A large part of the public road network in old city centres is still formed by masonry arch bridges. The general question of the local authorities is “can masonry arch bridges withstand motorised traffic including busses and occasionally heavy trucks?” Nonlinear finite element analysis in PLAXIS is applied for the assessment of the failure behaviour of the structure and its limits related to cracking and failure loading. A proof-loading of a real bridge increased the reliability of the calculation methodology. To assess a large group of single span masonry arch bridges, suggestions for a risk-based approach are made.

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Most bridges in the Dutch infrastructure are built before 1985 and have experienced increasing traffic intensities and loads. On the other hand, the structural (design) codes have changed over the years. A frequently faced problem in practice is that the original design calculations and technical drawings of a large percentage of the existing bridge stock are unknown or lost. Therefore, the current capacity of the bridge is unknown. The currently used method to map the reinforcement dimensions and amounts in an existing bridge is by (X-ray) scanning. As an alternative, this work proposes Reverse Engineering of the existing bridges, by redoing (a correct) former bridge design with a known design year and load class as a starting point. Consequently, the Reverse Engineered bridge design can be assessed according to the current Eurocodes. A parametric study reveals different capacity margins in former structural bridge design than expected beforehand. Bending moment seems to be the governing failure mode where the main focus in literature laid on shear failure.@en

Proof loading of bridges is an option to study existing bridges when crucial information is lacking. When proof loading is chosen, the question arises which maximum load should be attained during the test to demonstrate sufficient capacity, and which criteria, the “stop criteria”, based on the measurements during the test, would indicate that the test needs to be aborted before reaching the maximum desired load. A review of the literature identifies the stop criteria in currently used codes and guidelines. Beams sawn from the Ruytenschildt bridge were tested in a controlled way in the laboratory and analyzed with regard to the stop criteria from the literature. Recommendations are given for the future development of stop criteria for flexure and shear. These recommendations will form the basis for a guideline on proof loading of existing concrete bridges that is under development in The Netherlands. @en