Stress and strain analysis that occurs in the structure of a section and in its lifting installation, during the lifting and turning maneuvers

"During the shipbuilding processes carried out in the shipyards, there is a need to transport the sections of ship structure, from the place where they are built to the assembly location. When the shape and structure of the sections allow, they are built in an inverted position, and after finishing all the works that can be performed in this type of placement, the section will have to be turned to continue the section building process and subsequent the assembly. Loads that appear in the structure during these maneuvers are different from those that appear during the operation and from those for which calculations were made at the stage of the initial project. Therefore, it is necessary to calculate them and design a lifting / turning installation, which should also contain stiffening elements where required, in order to prevent both accidents and deformations or detachments that could occur at the section level. From this necessity appears the plan generically called ""lifting plan"" and which contains the installations, the schemes, the necessary instructions to remove the units from the section building hall, turn it to the gantry cranes and brought into the mounting position."

Numerical and Experimental Investigation on Nonlinear Cyclic Collapse Response of Ship Model in Regular Waves

Large ocean waves with large wave height may destroy the ship’s structure, whereas it is difficult to predict the nonlinear dynamic strength in the large waves. In this study, we used a nonlinear simulation based on boundary element method (BEM)-finite element method (FEM) and a collapse experiment of ship model to study dynamic ultimate strength and dynamic course of collapse of ship structure, the collapse test was performed in regular tank wave. Besides, a simulation method for nonlinear dynamic ship strength was proposed to predict and compare the results of collapse test. A collapsed model consisting of a plastic hinge and two ship strips is designed. Subsequently, we performed the nonlinear simulation of the ultimate strength of ship model induced by tank wave. Wave loads were calculated following potential theory and BEM. Next, ship structural FEM model was modeled, the ship pressure was transferred to ship wet surface elements, and inertia force was exerted as well. Finally, the nonlinear dynamic strength calculation of ship model was performed in accordance with nonlinear FEM. A four-point-bending test adopted displacement controlling method was designed to obtain the hysteresis characteristic of the elastoplastic hinge. Hysteretic test and simulation analysis was performed to determine post-ultimate bending moment. Time-domain computational results including rotation angle history and vertical bending moment are close to collapse test results so that the two methods are verified. This study verifies that structural nonlinearities of ship structure induced by wave loads could be predicted.