The design parameters are primarily determined empirically for the concrete overlay of steel-concrete composite bridge decks, as the lack of a clear stress analysis mechanism can lead to structural cracking or inefficiency. The transverse performance of the concrete overlay was simulated as a infinitely long beam on an elastic foundation based on the characteristics of orthotropic composite bridge deck. A theoretical analysis model was first established for the transverse behavior of the concrete overlay under wheel load, and the formulas were derived for the deformation, load, and effective range of the wheel load. A full-scale model static load test was then designed and conducted according to the practical orthotropic composite bridge deck. A corresponding spatial finite element model was also established, and the theoretical, experimental, and finite element results were compared to validate the accuracy of the proposed mechanical model. Due to the constraints imposed by the diaphragm and the rigid concrete layer, the torsional deformation of the U-rib under eccentric loading can be neglected. The effective range of the wheel load is limited to the span of 5 U-ribs. Parameter analysis indicated that both the arrangement of studs and transverse diaphragms have a significant influence on the transverse deflection of the concrete overlay. Within the range of commonly used design parameters, the proposed calculation formula is applicable to the design of steel-concrete composite bridge decks.