The behavior of double bottom structures is studied through the model tests for two types of grounding. The one type is associated with the case where a ship runs on a rock which penetrates through the bottom plate. In the other type, a ship strikes a rock and suffers the intrusion of the rock into the double bottom from the forepart of the ship. The test results for the former type of grounding are compared with a nonlinear finite element program. It is demonstrated that the finite element method represents a useful tool for the analysis of load-rock penetration curves of double bottom structures. In addition, the height of double bottom required for the inner bottom plate intact against rock penetration is examined in a usual tide range, through a simplified analytical procedure.