Bridges are among the most important infrastructure assets, especially reinforced concrete slab bridges. Many were built with a skew angle instead of straight due to the limited space available. The skewness affects the internal shear force distribution of the slabs and causes shear stress concentration at the obtuse corner. Most of the shear design methods are developed based on straight slabs. Whether these methods apply to skewed slabs is unclear. On the other hand, experiments on skewed slabs are quite limited. Therefore, an experimental programme of skewed slabs was conducted at Delft University of Technology. The slabs have a height of 300 mm, representing a half-scale model of representative solid slab bridges in the Netherlands. A concentrated load was applied close to the edge of the slabs to induce a one-way shear failure. Both the top and bottom surfaces of the slabs were measured using stereo Digital Image Correlation (DIC). This paper presents the design and the results of the experiment. By using the stereo DIC from both surfaces, the internal shear crack propagation is captured. All specimens failed in shear and the results demonstrate that the shear capacity of the slabs decreases as the skewness increases. Moreover, the experiment confirmed that the shear stress concentration is more significant in the obtuse corner than in the acute corner. An evaluation method is proposed to calculate the shear capacity of the skewed slab combined with the Linear Finite Element Analysis. The calculated shear capacity given by the proposed method shows a good alignment with the experimental results.

As the existing bridge stock is aging, assessment of existing bridges becomes increasingly important. In the Netherlands, the shear capacity of reinforced concrete slab bridges is found to be insufficient. In particular, the shear and punching shear capacity of reinforced concrete slab bridges subjected to concentrated loads from the design tandem or truck is subject to discussion, as the shear behavior is situated in between oneway and two-way shear. Currently, an experimental program is being conducted at Delft University of Technology to determine the shear capacity of straight and skewed reinforced concrete slabs under point loads near to the support. This paper presents the results of the 25 tests conducted on six straight slabs of 5m × 2.5 m × 0.3 m subjected to a proof load testing loading protocol. The failure load and modes of the slabs are described in detail. Reinforced concrete slabs under concentrated loads can fail in shear, punching, and flexure, as well as a combination of these failure modes. The results of the experiments are compared to strength predictions obtained by using current design models and current methods for assessment. These experiments demonstrated that the Dutch guidelines, which are based on previous slab experiments, are an improvement as compared to the Eurocode for the assessment of existing reinforced concrete slab bridges. Ultimately, this work provides recommendations for bridge engineers tasked to assess reinforced concrete skewed slab bridges.

This paper proposes a new mechanical model to describe the dowel action with the aim of using the model to gain a deeper understanding of the unstable dowel splitting cracking observed in shear experiments of beams without shear reinforcement. The model was developed by combining beam on elastic foundation (BEF) theory and fracture mechanics. The proposed model is able to predict the whole evolution process of dowel action until the propagation of the dowel splitting crack becomes unstable. The model theoretically proves that the development of a dowel splitting crack can become unstable under certain conditions, therefore leading to the unstable shear failure of the whole member. In addition to the derivation of the analytical model, the paper also validates the model using data from the literature. Finally, an analytical solution of the critical shear displacement that triggers the unstable dowel splitting crack is derived. It can be used to improve the failure criterion initially proposed in the Critical Shear Displacement Theory (CSDT).