Objectives  Blast loads differ according to whether the blast takes place in a free field or cabin.

  Methods  Dynamic software is used to simulate different explosive charge blasts in a free field, closed cabin and open cabin. The numerical results are then compared with the Henrych formula results, and the load characteristics of the open cabin and closed cabin are analyzed.

  Results  The research shows that the shockwave gathers in the corner of the closed cabin. The total impulse of the shockwave in the corner is about 1.45 times greater than the total impulse at the center of the plate, while the pressure in the corner of an open cabin is not obvious. The peak values of the reflected pressure and quasi-static pressure in a closed cabin are smaller than those in an open cabin. The total impulse of the shockwave in the open cabin is about 20% that of the closed cabin. The pattern of plate damage in the closed cabin is mainly the plastic deformation of the plate frame along the stiffeners and the plate tearing along the corner; the tear does not occur in the closed cabin corner, but valgus deformation occurs at the edge of the open cabin; the maximum deformation value of the plate center obtained by the numerical simulation method is close to that obtained by the simplified method when only the impact of the shockwave is considered. When both the impact of the shockwave and quasi-static pressure are considered at the same time, the error margin is larger.

  Conclusions  The results of this paper can be used to predict the characteristics of blast loading and stiffened plate damage.