When two ships collide, strength of the struck ship will reduce due to damage. The strength reduction depends on the size and shape of the damage. Therefore, structural behavior of a scaled box beam with damage is numerically investigated with three-dimensional finite element (FE) model simulations and incremental-iterative approach. Intact and damaged box beams are simulated under four-point bending. The effect on bending response is analyzed with respect to the variability in damage shape and size in the box beam. Although the relatively simple box beam analysis do not sample all the relevant deformation pathways, this apparent drawback limits the number of modelling approximations, idealizations, and assumptions rendering the analysis insightful to the response of damaged ship structures.