In the Netherlands, most of the bridges were built more than 50 years ago and it is essential for bridge authorities to find out if these bridges are still safe for modern traffic loads for which they were not designed initially. Experiments on a 1:2 scale were carried out in the laboratory of the Delft University of Technology (TU Delft) to investigate the bearing capacity of bridge decks with varying levels of transverse prestressing subjected to concentrated wheel loads. All the tests showed failure in punching shear. It was found that, as a result of compressive membrane action (CMA) by virtue of lateral restraint effects, in combination with the transverse prestressing, the punching shear resistance of the decks was much larger than predicted by most international codes that do not consider the effect of CMA. It appears to be worthwhile to regard CMA when assessing the bearing resistance of existing bridges to avoid unnecessary strengthening measures.@en

For the assessment of existing structures and the design of new structures, it is important to have a good understanding of the flow of forces, here applied to reinforced concrete solid slabs. Two analytical methods are used: finite element models with 3D solid elements and a plasticity-based model that is suitable for hand calculations, the Modified Bond Model. The slabs that are modeled are half-scale models of reinforced concrete solid slab bridges. As the Eurocode live load model prescribes more heavily loaded trucks in the first lane, the load model is asymmetric. For the finite element models, limited use is made of the redistribution capacity of the slab. For the Modified Bond Model, the influence of torsion and the edge effect need to be taken into account. The results of these studies improve the current state-of-the-art for analysis and design of reinforced concrete slabs. @en

A large number of existing reinforced concrete solid slab bridges in the Netherlands are found to be insufficient for shear upon assessment. However, research has shown additional sources of capacity in slab bridges, increasing their total capacity and possibly changing their failure mode. Previous testing was limited to half-scale slab specimens cast in the laboratory. To study the full structural behaviour of slab bridges, testing to failure of a bridge is necessary. Research on load testing is carried out in order to develop load testing guidelines. In August 2014, a bridge was tested in two spans. The bridge was load tested, and additional cycles until yielding occurred in the reinforcement were added to the experiment. Though calculations with current design provisions showed that the bridge could fail in shear, the field test showed failure in flexure before shear. The unity check for flexure was determined. The experiment shows that the methods for rating of existing reinforced concrete slab bridges are conservative.@en

In August 2014, the Ruytenschildt Bridge, a reinforced concrete solid slab bridge, in Friesland, the Netherlands was tested until failure. One of the goals of the experiment is to analyze the failure mode of the slab bridge under a tandem of 4 wheel loads and to compare the capacity of the full bridge structure to the predicted results, to have an idea of the residual strength of existing bridges. The methods used are experi-mental (testing of the bridge to failure in two of its five spans) and analytical. The analytical work involved predicting the bending moment capacity, the shear capacity and the punching capacity of the bridge. In both spans, the bridge failed in flexure. The total capacity during the experiment was significantly higher than pre-dicted. The results indicate that the traditional rating procedures for shear are very conservative when applied to slab bridges that benefit from transverse load redistribution.@en