With the projected increase in the average and maximum temperatures in Canada owing to global warming, the deterioration rates of bridge infrastructure are expected to increase. Among the various deterioration issues in bridges, malfunctioning of the expansion joints is one of the most common. Although the cost of bridge expansion joints accounts for less than 1% of the total bridge construction costs, their maintenance costs can be as high as 8% of the overall bridge. Owing to the accumulation of debris and dirt in the joints, the axial movement of the bridge superstructure may be restrained, leading to axial forces at levels for which the structural members of the bridges were not originally designed. Consequently, it was anticipated that the presence of an axial force would reduce the moment capacity of the composite sections. In this paper, a literature review on the quantification of the moment resistance of concrete slab on steel girder (CSSG) systems subjected to the interactions of axial force and shear is provided. It was observed that moment–axial force–shear interaction relationships exist for sections with relatively shallow beams/girders. To test the applicability of positive moment-axial compression relationships to CSSG Bridges’ relatively deeper girders, a Finite Element Analysis (FEA)-based case study was conducted. The case study included a commonly used composite section in Canada with a 1200 mm deep web girder and a 225 mm thick concrete slab. The FEA model of the CSSG section was first subjected to pure positive bending to determine its composite moment capacity numerically. Subsequently, the change in positive moment capacity at different axial load levels was numerically investigated. The outcomes were compared with Canadian Highway Bridge Design Code (CHBDC) resistance models, as well as the positive moment-axial compression relationships found in the literature.