Aging infrastructure in the Netherlands presents a significant challenge, particularly with precast girder bridges made continuous, which exhibit inadequate shear reinforcement per current design codes. To address shear capacity and accuracy of current assessment practices, a research program including full-scale shear tests is underway at Delft University of Technology. As a part of the research, a blind pre-diction contest with two specimens has been organized. The experiments showed that the loss of composite action at the interface is the primary failure mechanism, and generally an accurate model of the interface behaviour in such composite members is missing. In this paper, a further review of the available interface models and previous tests is conducted. This review leads to the challenges in the accurate evaluation of the interface behaviour, as well as the next steps to address them: a new set of full-scale specimens, and a small-scale test setup reflecting a realistic stress distribution.