This paper is the first of two companion papers dealing with ultimate longitudinal strength analysis of a container ship considering local loads effects. The purpose of this paper is to clarify the effect of bottom local loads on the longitudinal bending collapse behavior of a large container ship. An important problem is a bending deformation of the double bottom due to upward bottom local loads that may reduce the hull girder ultimate strength.

A 1/2+1+1/2 hold model of a container ship is analyzed using nonlinear implicit finite element method. The analysis shows two major effects of the bottom local loads on the ultimate hull girder strength; i.e. the buckling of the outer bottom plating is accelerated due to the increased longitudinal compressive strain, while the effectiveness of the inner bottom plating that is in the tension side of local bottom bending is significantly decreased.