Experimental investigation on the ultimate strength of cracked unstiffened and stiffened plates under cyclic loading

The aim of this paper is to investigate the ultimate collapse behavior of ship structures under cyclic loading. To this end, experimental investigations were conducted to explore the ultimate strength reduction of hull unstiffened and stiffened plates considering the fatigue crack propagation and cumulative plasticity simultaneously. Twenty-one specimens including eleven unstiffened plate specimens and ten stiffened plate specimens were designed and fabricated with the same initial crack length, and a set of test devices was ingeniously designed for evaluating the ultimate strength under cyclic loading. Different loading conditions were applied by varying the cyclic loading magnitudes and crack propagation lengths to make clear the relationship between the crack lengths on the stiffener and on the plate. The prediction formulas were derived to estimate the ultimate strength values of cracked unstiffened and stiffened plates under cyclic loading; the accuracy of the prediction formulas was validated by comparing them with the experimental and numerical results. It helps to further explore the ultimate collapse behavior of cracked ship structures in harsh sea condition. • The ultimate strength of hull unstiffened and stiffened plates under cyclic loading is analyzed by experimental study. • A set of test devices is ingeniously designed for the ultimate strength evaluation under cyclic loading. • A functional relationship between the crack length on the stiffener and the crack length on the plate is established. • The ultimate strength reduction is studied considering the crack propagation and cumulative plasticity simultaneously. • Prediction formulas are derived to estimate the cyclic ultimate strength of cracked unstiffened and stiffened plates.