Pitting corrosion is a great concern when the integrity of ship's hull structures is considered. Corrosion pits with a conical shape are typically observed on coated hold frames in way of cargo holds of bulk carriers which exclusively carry coal and iron ore. Therefore, it is important to investigate the effect of pitting corrosion on local strength of hold frames of bulk carriers. In the present study, a series of 3-point bend tests with structural models which consist of web, shell and face plates has been conducted. In these tests, a concentrated load has been vertically applied at the center of simply supported models so that shear load would act on the web plate with artificial pits. In this testing condition, load increased even after shear buckling occurred. When there is artificial pitting, fracture of web plates occurs due to strain concentration at the pits. It has been revealed that the empirical formula, which was developed based on non-linear FE-analyses, overestimates the equivalent thickness for the shear ultimate strength obtained in the present experiment, because the effect of web fracture is not taken into account in the analyses.