THE CRUSHING MECHANICS OF BOW STRUCTURE IN HEAD-ON COLLISION (2ND REPORT: A SIMPLE CALCULATION FORMULA)

The purpose of this paper is to derive an approximation method, which is both simple in mathematics and reasonable in mechanics, for predicting the crushing strength of ship bow structures. The first emphasis of this paper is on the analysis of the crushing strength of a parallel structure whose axis direction is the same as the direction of the compressing load. It is found that the dimensionless crushing strength is not sensitive to the slenderness ratio of its plate flanges. The energy absorption factor α E is then introduced to represent the energy absorption ability of a parallel element. The second part is an analysis of energy absorption reduction which is caused by inclination of element with respect to external compressing load. This reduction effect is represented by an inclination correction factor α I . It is found that the energy absorption ability of an element depends strongly on the angle of its initial axial inclination. The third part is the proposition of a simple formula for approximating the crushing strength of ship bow structures, using the two factors α E , α I introduced above. During collision, the crushing strength of a ship bow can be derived by multiplying the flow stress of the material, the cross-sectional area, the energy absorption factor α E and the inclination correction factor α I . The effectiveness of this one -term formula is validated by the fact that calculation results show good agreement with model test data. Because of its simplicity, this formula is sure to be able to find its usages in practical designs.