This study aims to explore nonlinear similarity criteria for box girders under pure bending load, improve the prediction accuracy of the model on the response of prototype structures and provide a theoretical basis for establishing a distortional similarity model design method for actual ship structures.

First, based on the stability and nonlinear criteria of axially compressed reinforced slabs, a nonlinear similarity criterion for box girders under pure bending load is established using the theoretical analysis method. Second, the ultimate load-carrying capacity and buckling response of scaled-down prototype box girder models are then analyzed using the numerical calculation method to verify the validity of the similarity criterion.

The numerical calculation results show that different scale designs based on the proposed method have high similarities in their flexural failure modes, and the ultimate strength of the scaled-down prototype models can be accurately predicted. Under a specific flexural mode, an increase in the initial deformation reduces the ultimate load-carrying capacity of the box girder. In contrast, the initial deformation factor has less influence on the prediction accuracy of the scaled-down model.

This paper provides an effective nonlinear similarity model design method for the ultimate strength testing of hull beams under pure bending load, which has value for the study of the structural safety of ships.