Estimation of Ultimate Longitudinal Bending Moment of Ships and Box Girders

The paper describes a methodology of computing the ultimate value of the longitudinal bending moment at any cross section of a ship or box girder. The cross section has been discretized into stiffened panels (one stiffener with its associated effective plating). The limit states for these panels, both tensile and compressive, are modeled in an appropriate manner. Since the ultimate strength of the girder section is largely governed by the behavior of the panels under compression, the authors have paid special attention in modeling the collapse as well as post-collapse behavior of these panels. A new stress-strain relationship is also introduced. The complete procedure has been coded into a FORTRAN program and tested against a number of box girder models and an actual ship for which the true behavior was known. The results obtained from the proposed program appear to be quite satisfactory. Good correlation was also found when compared with the results obtained by more complex and rigorous analytical methods.