Vertical and horizontal plate stiffeners are designed for the steel infill plate of the steel plate wall (SPW) systems to improve buckling stability and to prevent early elastic buckling of infill plates. Nevertheless, a lack of analytical model exists that are capable of replicating stiffened plates’ load-displacement behavior. In this paper, an analytical method is proposed that is capable of modeling the load-displacement behavior of stiffened infill plates for steel plate wall (SPW) systems. The analytical model is an addendum to the previously proposed plate frame interaction (PFI) method used for determining the shear load-displacement of unstiffened steel infill plates of SPW systems. To evaluate the proposed model, the predictions of this model are compared to results obtained from tests previously conducted, as well as those gained from finite element (FE) analyses performed for this study. Considering the simplicity of the analytical mode, the result of the evaluation indicates that the model is providing the stiffness and strength of stiffened infill plates with an average error of -7% and 15% respectively.
