Curved panels are widely used in fore and aft side shells and circular bilge parts of container ships, which are subjected to complicated loads combination including axial compression, bending and lateral pressure, particularly in the most critical hull girder vertical bending conditions. In this paper, the nonlinear structural behaviors and ultimate strengths of bilge panels are investigated by performing a series of finite element analyses, and interactions between above loads are also addressed. Meanwhile, variations in geometric parameters and structural scantlings are considered according to practical structural designs in ship industry. Additionally, the effects of influencing factors such as initial deflections are investigated, and closed-form ultimate strength prediction formulae are proposed for curved stiffened plates. The results are representative and can be of reference values for structural evaluations and designs for similar structures.
Container ships are widely used today, and about 90% of non-bulk cargo worldwide is transported by container ships, and the largest modern container ships can carry over 21,000 TEU. Container ships now rival crude oil tankers and bulk carriers as the largest commercial seaborne vessels. The strength of container ships has been concern of both industry and academia in the past decades.
Hull girder bending ultimate strength of container ships is very important for structural evaluation, especially in the case of hogging. In hull girder hogging bending, the longitudinal members above neutral axis are under tension while those below are under compression, e.g. the double bottom structures are under longitudinal compression, which may fail due to buckling, so the associated ultimate strength problems are very important. Additionally, bottom plates are subjected to both longitudinal and transverse thrusts especially with increased ship depth in ultra-large container ships, i.e. bi-axial compression exists in the bottom structures. The ultimate strength in this respect is a critical problem in practical structural designs, and many researchers have investigated these problems, e.g. Fujikubo and Yao (1999) studied the elastic buckling strength by introducing torsional rigidity to simulate the interaction between stiffener and plate, and they also studied the influences of welding residual stress on the buckling strength; An extensive study was made on the ultimate strength of continuous plates and continuous stiffened panels under combined transverse thrust and lateral pressure ((Fujikubo, Harada, Yao, Reza Khedmati and Yanagihara, 2005, Fujikubo, Yao, Khedmati, Harada and Yanagihara, 2005)); Tanaka, Yanagihara, Yasuoka, Harada, Okazawa, Fujikubo and Yao (2014) studied 720 cases with different numbers, types and sizes of stiffeners by Nonlinear Finite Element Analysis (NFEA), and compared the results with predictions by several existing methods, such as CSR, PULS and FYH, and concluded that the PULS and FYH method can give good estimations.
