In Amsterdam, more than 30 steel-concrete composite bridges were constructed from 1880-1960 without mechanical connectors and transverse reinforcement. Currently, there are no simplified analytical methods to determine the bearing capacity of these bridges. Thus, the bearing capacity is verified using NLFEM or oversimplified analytical calculations. This research proposes an analytical method to determine the bearing capacity of historic steel-concrete-composite bridges without mechanical connectors to avoid time-consuming FEM calculations and offers reasonable results.

An experimental and numerical study is performed on data from in situ and laboratory testing of samples from two different bridge decks from these Amsterdam bridges. The tests are accompanied by a numerical model that has been studied and adjusted to a more generalized loading case. This study determined that the exterior composite girders are critical due to their lower lateral stiffness.

An analytical model is proposed to examine the behaviour of the exterior composite girder. The model considers a 3-point bending load at midspan between the exterior composite and adjacent girder. The force distribution is described through a compatibility-based strut and tie model (C-STM). The concrete in compression is considered elastic compression struts, only limited by the ultimate load of the model. The concrete in tension is interpreted as a tensile tie, which fails when it exceeds the concrete tensile resistance. Following the failure of the tensile tie, it is assumed that a longitudinal crack propagates between the exterior composite girder and the adjacent girder. Additionally, vertical and lateral stiffness components are included in the model. These account for the flexural stiffness of the exterior and interior composite girder. The vertical stiffness is accounted for as elastic springs, and the lateral stiffness as spring beams. The interior lateral spring beam summarises all the interior composite girders' stiffness, whereas the exterior lateral spring beam only considers the exterior composite girder. Therefore, the configuration assumes that the interior spring beam is significantly stiffer than the exterior. Moreover, the stiffness of the exterior spring beam reduces when the longitudinal cracking occurs, assuming a part of the concrete fails. The C-STM is linked to the cross-section verification of longitudinal shear, biaxial bending and vertical shear resistance in two stages. Stage 1, at the load at longitudinal cracking, determines if the specimen fails at this moment, indicating that there possibly is a brittle failure. Stage 2 is after longitudinal cracking, where the steel-concrete contact perimeters have reduced, and the corresponding resistances accordingly reduce.

The failure modes obtained by the analytical model are comparable to the ones observed during the experimental testing. The analytical model showed that the bridges failed due to biaxial bending limited by partial shear interaction. One of the specimens from the testing yielded due to bending but with limited ductility. The other specimen also yielded due to bending with concrete crushing at the top concrete fibre. Further, the bearing capacities obtained from the analytical model are comparable to the failure loads from the experimental and numerical results.

The model predicts the failure modes and the bearing capacity and can therefore contribute to the assessment of the historic Amsterdam bridges, helping to reduce the assessment time of the bridges and understand their load-bearing behaviour better. Future work should focus on verifying the method by examining more bridges using FEM.

Nowadays, most of the historical bridges (Amsterdam, 2019) of Amsterdam do not meet the load-bearing criteria of the current design code (Eurocode: 2012). This has several reasons. It comes partly because of the overdue of the maintenance (Amsterdam, 2019) but also because the traffic load for which the bridge has been designed, is lower than the present traffic load (Amsterdam, 2019). The current Eurocode 4 does not guarantee the safety of this type of bridge decks. To guarantee the safety and the remaining service life of the historical bridges in Amsterdam, the municipality has started an investigation on historical steel-concrete-composite-bridge-decks. The focus in this thesis is on historical steel-concrete-composite-bridge-decks (a.k.a. Verbundträger brücken in German) because this type of bridges does not contain shear connectors in their configuration. This leads to the fact that the capacity of the bridge deck is almost not determined in the longitudinal and completely not determined in the transversal direction. The bridge deck in the longitudinal direction satisfies the unity check based on the protocol of the municipality of Amsterdam to check this type of bridges on safety, where they only consider the steel profile to define the capacity of the bridge in this direction. This is very conservative because the concrete is not taken into account during the calculation of the cross-section. In the transverse direction, the bridge deck does not fulfil the necessary unit check limit, because the municipality takes only the shrinkage reinforcement into consideration during their calculations. In addition to this, the state of the bridge decks and relevant research about how the bridge deck is build-up, is investigated. The main conclusion that can be taken from the cross-section of these type of bridge decks is that there is a lot of variation in all the components of the bridge decks.

Furthermore, during the investigation of the bridge decks it is decided to choose three typical bridge decks (A, B, C), which will be simulated to gain more insights about the cross-section of these historical bridge decks. The current Eurocode 4, which is implemented to guarantee the safety of the type of cross-section containing steel and concrete, does not provide an answer to calculate the load-bearing capacity of historical steel-concrete-composite-bridge-decks, because of a significant difference between the designed current Eurocode 4 model and the designed cross section of the historical model.

The behaviour of the bridge is studied in two directions based on the available literature. In the longitudinal direction, the focus is on the interaction between steel and concrete and how this interaction can be described. In the transverse direction, the aim is to find the relevant failure mechanism and corresponding modelling approach to define the behaviour of the bridge deck in the transverse direction of these bridge decks. The failure mechanisms that were evaluated are: Punching shear failure, compressive membrane action, and failure of concrete strut.

The assessment of the aforementioned failure mechanisms is carried out and the most logical model which can be used to validate during the FEA-simulation is the failure of concrete strut which can be modelled by strut and tie model. This model will also be carried out on the other two chosen bridges, next to bridge A on which the in-situ-load-test is done, to validate this model on more than one bridge deck. There was made use of an analytical model based on Eurocode 2, which has been compared the values of the numerical simulations…