摘要：This paper discusses the influence of the rotation of the neutral axis on the residual hull girder strength of asymmetrically damaged ships under longitudinal bending. Progressive collapse analysis of the damaged cross section is performed applying the Smith's method for the biaxial bending problem. An explicit expression of the location of the neutral axis including its rotation is given as a function of biaxial curvatures. The procedures of the progressive collapse analysis of the cross section under biaxial bending are presented for several loading and constraining conditions. A series of progressive collapse analysis of bulk carriers and double-hull tankers having collision damages at the side structures is performed. The residual hull girder strength of damaged ships considering the rotation of the neutral axis is found to be reduced from that obtained by constraining the rotation. The reduction rate of the ultimate strength is investigated for different damage location and extent. For a sagging condition, simple formulae to estimate the residual strength and the reduction rate due to the rotation of the neutral axis are proposed using the elastic cross-sectional properties and critical member strength. The effectiveness of the formulae is examined through a comparison with the progressive collapse analysis. The proposed analysis method and formulae can be utilized for the rational assessment of the residual hull girder strength of damaged ships.
