In old Dutch inner cities like Amsterdam a large number of steel-concrete bridge decks built between 1880 and 1960 remain in service nowadays and currently need assessment of their bearing capacity. A significant number of these decks were designed without any mechanical connectors like shear studs in the interface between concrete and steel. Moreover, the concrete decks were designed with only shrinkage reinforcement in both directions on the top layer of concrete. No additional transverse reinforcement was placed that can ensure proper (re)distribution of loads after cracking. In order to study the bearing capacity of this deck typology, two specimens of an existing bridge were taken to the Stevin Lab of TU Delft and tested until failure. In this work, the experimental results of both tests are presented. Then, finite element models including nonlinear behaviour of the materials and the interface are presented and compared with the experimental observations. Experimental results show that the bearing capacity is achieved after yielding of the steel beams. Nevertheless, the ductility and transverse load distribution of the elements is affected by the interface behaviour and the poor detailing. The finite element simulation strategy used shows good agreement with the experiment and can be used for future assessments.
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A large number of bridges in the Netherlands have transversely post tensioned deck slabs cast in-situ between flanges of precast girders and were found to be critical in shear when evaluated by Eurocode 2. To investigate the bearing (punching shear) capacity of such bridges, a 1:2 scale bridge model was constructed in the laboratory and static tests were performed by varying the transverse prestressing level (TPL). A 3D solid, 1:2 scale model of the real bridge, similar to the experimental model, was developed in the finite element software DIANA and several nonlinear analyses were carried out. It was observed that the experimental and numerical ultimate load carrying capacity was much higher than predicted by the governing codes due to lack of consideration of compressive membrane action (CMA). In order to incorporate CMA in the Model Code 2010 (fib 2012) punching shear provisions for prestressed slabs, numerical and theoretical approaches were combined. As a result, sufficient factor of safety was observed when the real bridge design capacity was compared with the design wheel load of Eurocode 1. It was concluded that the existing bridges still had sufficient residual bearing capacity with no problems of serviceability and structural safety.

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A recent contest of shear tests modelling was carried out in 2019. Teams from universities and consultancies around Europe were invited to predict the shear capacity of two reinforced concrete beams. The basics of the numerical models were to be set up according the Dutch NLFEM Guideline RTD 1016–1:2017. In the contest, two reinforced concrete beams without stirrups but having large depth (1200 mm), tested at Delft University of Technology, were selected as the modelling target. Most participants in the contest did not obtain good agreement with the test results. This paper presents a postdiction study on one of the two tests: H123. Based on this study, some adaptations are made to the recommendations of RTD 1016–1:2017 in order to approach the test results better. The intention of this contribution is to improve the existing NLFEA Guideline for practical engineering structures with uncommon reinforcement layouts.

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The Netherlands has a large number of thin, transversely prestressed concrete bridge decks, cast in-situ between flanges of prestressed concrete girders dating back to the 1960s and 1970s. These bridges are critical in shear when analyzed using EN 1992-1-1:2005; however, in reality, they show no significant signs of distress, possibly because of residual bearing (punching shear) capacity arising from compressive membrane action. Since these bridges are old, it is an astute approach to check whether they can be used for a few more decades, provided they are safe and reliable against modern traffic loads. The results could then be applied to a wider range of structures, especially in developing countries facing economic constraints. A prototype bridge was selected and experimental, numerical and theoretical approaches were used to investigate its bearing capacity. Respective coefficients of variation of 11% and 9% were obtained when the experimental and the finite element analysis punching loads were compared with the theoretical results. This led to the conclusion that the existing transversely prestressed concrete bridge decks still have sufficient bearing capacity and considerable cost savings can be made if compressive membrane action is considered in the analysis.@en

The Dutch Ministry of Infrastructure and the Environment is concerned with the safety of exist-ing infrastructure and assessment thereof, which can be done with nonlinear finite element analysis. The 2017 updated version of the Dutch NLFEA Guidelines can be used for reinforced and prestressed beams and slabs. The purpose of the guidelines is twofold: 1) advice analysists on NLFEA of concrete structures, and 2) ex-plain choices and model uncertainty. This paper introduces the latest version of the guideline, and shows the application for a reinforced concrete slab on top of a concrete beam grid. An overheight vehicle caused dam-age to the concrete cover and the reinforcement of the beams. The analysis shows the results of modeling the bridge without and with damage. The outcome of the assessment is that the structure fulfils the code require-ments. This case study shows that the Dutch NLFEA Guidelines can be used for the assessment of damaged concrete bridges.@en

It is widely known that as the structure of the size increases, its nominal strength decreases. In this paper, the effect of size on punching shear has been quantified for transversely post-Tensioned deck slabs cast between flanges of precast concrete girders. A 1:2 scaled model of the bridge was constructed in the laboratory, and experimental and numerical analyses were carried out. However, in order to apply these results on a real bridge, simply using the geometrical scale factors is not sufficient and a structural size effect has to be taken into account. Since a full-scale experimental study was not possible due to the costs involved, a numerical approach using finite element analysis software package TNO DIANA was used to model both the prototype and the real bridge, and a comparison was made to estimate the effect of size on the bearing capacity. It was found that increasing the transverse prestressing level had a positive effect on the punching shear strength of the deck slab. Furthermore, a lower size effect was observed with higher transverse prestressing levels. It is concluded that if a suitable size factor is used, either numerical or small-scale experimental studies can be reasonably used to investigate existing structures.@en

Proof load testing of existing reinforced concrete bridges is becoming increasingly important as the current bridge stock is aging. In a proof load test, a load that corresponds to the factored live load is applied to a bridge structure, to directly demonstrate that a bridge fulfills the code requirements. To optimize the procedures used in proof load tests, it can be interesting to combine field testing and finite element modeling. Finite element models can for example be used to assess a tested structure after the test when the critical position could not be loaded. In this paper, the case of viaduct De Beek, a four-span reinforced concrete slab bridge, is studied. Upon assessment, it was found that the requirements for bending moment are not fulfilled for this structure. This viaduct was proof load tested in the end span. However, the middle spans are the critical spans of this structure. The initial assessment of this viaduct was carried out with increasingly refined linear finite element models. To further study the behavior of this bridge, a non-linear finite element model is used. The data from the field test (measured strains on the bottom of the concrete cross-section, as well as measured deflection profiles) are used to update the non-linear finite element model for the end span, and to improve the modeling and assessment of the critical middle spans of the structure. Similarly, an improved assessment based on a linear finite element model is carried out. The approaches shown for viaduct De Beek should be applied for other case studies before recommendations for practice can be formulated. Eventually, an optimized combination of field testing and finite element modeling will result in an approach that potentially reduces the cost of field testing.@en

The Dutch Ministry of Infrastructure and the Environment is concerned with the safety of existing infrastructure and expected re-analysis of a large number of bridges and viaducts. Nonlinear finite element analysis can provide a tool to assess safety; a more realistic estimation of the existing safety can be obtained.
Dutch Guidelines, based on scientific research, general consensus among peers, and a long-term experience with nonlinear analysis, allow for a reduction of model and user factors and improve the robustness of nonlinear finite element analyses.
The 2017 version of the guidelines can be used for the finite element analysis of basic concrete structural elements like beams, girders and slabs, reinforced or prestressed. Existing structures, like box-girder structures, culverts and bridge decks with prestressed girders in composite structures can be analysed.
The guidelines have been developed with a two-fold purpose. First, to advice analysts on nonlinear finite element analysis of reinforced and pre-stressed concrete structures. Second, to explain the choices made and to educate analysts, related to the responsibility of limiting model uncertainty.
This paper contains an overview of the latest version of the guideline and its latest validation extensions. Most important impact is the extended operational lifetime of an existing reinforced concrete slab structure. @en

In 1997, the Second Stichtse Bridge was built in the Netherlands using the balanced cantilever method. The use of high-strength concrete was proposed. At that time, the long-term behaviour of this material was not known, and no code provisions were applicable. Therefore, it was proposed to monitor the material behaviour and the deflections of the bridge. To evaluate the development of the
concrete compressive strength and the concrete splitting tensile strength over time, concrete cubes were cast at the same time as each of the cantilever segments, and stored inside the bridge. These samples have been tested at different points in time to study the development of the strength as a function of the elapsed time. Creep and shrinkage measurements were carried out on samples stored inside the bridge as well as in the laboratory. Temperature and moisture were monitored as well. The deflections of the bridge superstructure have been measured periodically. These measurements can be compared to predictions from finite element models. Based on the available data, it is found that the concrete compressive and splitting tensile strength remain constant. The deflections are small, and the advanced finite element models resulted in good predictions.@en

As the existing bridge stock is aging, improved assessment methods such as proof load testing become increasingly important. Proof load testing involves large loads, and as such the risk for the structure and personnel can be significant. To capture the structural response, extensive measurements are applied to proof load tests. Stop criteria, based on the measured quantities, are used to identify when further loading in a proof load test is not permitted. For proof load testing of buildings, stop criteria are available in existing codes. For bridges, recently stop criteria based on laboratory tests on beams reinforced with plain bars have been proposed. Subsequently, improved stop criteria were developed based on theoretical considerations for bending moment and shear. The stop criteria from the codes and the proposed stop criteria are compared to the results from field testing to collapse on the Ruytenschildt Bridge, and to the results from laboratory tests on beams sawn from the Ruytenschildt Bridge. This comparison shows that only a small change to the stop criteria derived from laboratory testing is necessary. The experimental evidence strengthens the recommendation for using the proposed stop criteria in proof load tests on bridges for bending moment, whereas further testing to confirm the stop criteria for shear is necessary.@en

The paper investigates the effect of various geometrical and material parameters on the bearing (punching shear) capacity of transversely prestressed concrete deck slabs by numerical methods. Experiments on a 1:2 scale model of such a bridge were carried out in the laboratory and a 3D nonlinear finite element (FE) model was developed in the finite element analysis software package TNO DIANA (2012) to study the structural behavior in punching shear. A comparison of the experimental and numerical ultimate loads show that the non-linear FE models can predict the load carrying capacity quite accurately with a standard deviation of 0.1 and the coefficient of variation of only 10%. The effect of varying the transverse prestressing level, the presence and size of the ducts, size of the loading plate and the concrete class is also described as part of the parametric study. It was observed that sufficient saving in cost could be made if calibrated numerical models are employed to investigate existing structures rather than doing expensive experimental studies.@en