In the Netherlands, approximately 70 prestressed slab-between-girder bridges are present, built between the 1950s and 1970s. These bridges typically do not fulfil the requirements for shear in an assessment, but show no signs of distress upon inspection. Additional load-carrying mechanisms and effects of global bridge behaviour, such as compressive membrane action, compressive arch action, load (re)distribution, and the influence of the crossbeams, which could significantly enhance the structural capacity, are typically not considered in the assessment calculations. This paper studies the global structural behaviour experimentally of the full slab-between-girder bridge system as compared to the isolated T-girder. For this purpose, two spans of an existing multi-span T-girder bridge, the Vecht Bridge, built in 1962 were tested. In total, three experiments were carried out in span 4 (full system), and four experiments in span 2 (after applying saw cuts in the deck to create isolated girders). This paper reviews the state-of-the-art regarding collapse testing, global bridge behaviour, and slab-between-girder bridges in the Netherlands. Then, the results of the experiments are presented and analysed. It is expected that these experimental results will form the basis of improved assessment methods for slab-between-girder bridges in the Netherlands and beyond.

In the Netherlands, there are about 70 prestressed T-girder bridges with cast-inbetween decks, constructed post-WorldWar II.While they have low ratings upon assessment, inspections reveal no distress. This research aims to understand the structural behavior of the full system compared to isolated T-girders. Experiments were conducted on the original structure, as well as on the structure with the deck sawn to test individual girder behavior. The main insight is that the system behavior at the ultimate limit state is driven by compressive membrane action in the deck as well as compressive arching action in the girders, and that simplified distribution factors for shear derived from linear elastic behavior do not properly reflect the distribution and load path at the ultimate. These results can be used for a better assessment of the existing pre- stressed T-girder bridges.

About 70 prestressed concrete T-beam bridges, constructed in the Netherlands between 1953–1977, are still in use today with many located in the main highway network. This type of bridge consists of prefabricated and prestressed T-shaped beams, with an integrated deck slab, cross-beams and transverse prestressing. Even if these bridges are well maintained, two important factors demand the current need for assessment: (1) increased traffic loading and (2) potential lack of shear resistance. Using traditional assessment methods it was concluded that about 50% of these bridges do not fulfil the current design code requirements. However, this does not automatically imply that these bridges are structurally unsafe, since some potentially significant additional load-transfer mechanisms are not taken into account in a traditional assessment. This is strengthened by the observation that, in general, these bridges do not show any signs of distress....

In the Netherlands many concrete bridges that were built in the sixties and seventies are still in service. One subset of these bridges consists of prestressed concrete T-beams with cast-in-between slabs, cross-beams and transverse prestressing. Upon (re)assessment, the strength of these bridges is often too low. However, for this type of bridge several mechanism, that could possibly contribute to a higher load bearing capacity, are usually not taken into account. One of these mechanism is compressive membrane action (CMA), in transverse direction, in the concrete deck slab. Another potential mechanism is arch action, in longitudinal direction, in the T-beam. To investigate these mechanism or the so called ‘system behaviour’, and the ultimate load capacity, a T-beam bridge from 1962 was tested in seven full size collapse tests. In four tests the deck was sawn in longitudinal direction so that it became possible to test the load capacity of the individual beams. The individual beam tests are analyzed using a 3D non-linear finite element model. In the experiments, the load was placed at two different positions from the support. It was found that the nonlinear analysis shows good agreement with the load placed at 2.25 m from the support. However, with the load at 4.00 m from the support, the non-linear analysis shows an overestimation of ∼15%. Ultimately, this research aims to improve the calculation methods for the existing T-beam bridges in the Netherlands.

In the Netherlands, approximately 150 prestressed T-beam bridges with cast-in-between decks and mainly built in the sixties are still in service. Upon assessment, the prestressed beams often do not fulfil the design codes requirements, whereas upon inspection, they show no signs of distress. For the assessment, additional load transfer mechanisms, which could significantly enhance their structural capacity, such as compressive membrane action and transverse redistribution, are not considered. The presented research aims at quantifying these effects. Therefore, an existing simply supported multi-span T-beam bridge was tested. In total seven experiments were carried out using a single point load placed on the T-beam. Three experiments were carried out with the original structural system unchanged. In four experiments, the castin- between deck was sawn in longitudinal direction, so that the individual behaviour of the beams could be tested. In both cases two load positions, i.e. a distance of 2.25 m and 4.00 m from the support were used. By analysing both the single beam and the connected beam tests a better understanding of the load carrying capacity of this type of bridge is achieved.