Plate panels of ships and floating offshore structures are likely subjected to cyclic loads arising from waves at sea. Depending on sea states, e.g., whipping in harsh sea states, the maximum amplitude of the cyclic loads may reach over 70% of ultimate loads. Of concerns is how the cyclic loads will affect the ultimate strength compared to a case of monotonically increasing loads. The aim of this paper is to experimentally investigate the ultimate strength characteristics of a steel stiffened plate structure under cyclic axial-compressive loading. A full-scale collapse testing in association with bottom structures of an as-built 1,900 TEU containership was conducted. It is concluded that the effects of cyclic loading on the ultimate compressive strength of steel stiffened plate structures are small as far as fatigue damages are not suffered due to the small number of load cycles. Details of the test database are documented, which will be useful to validate computational models for the ultimate strength analysis.
The aim of the present study is to experimentally examine the corrosion progress characteristics of steel associated with fresh and sea water immersion at low temperatures. Three types of steel, namely mild steel (Grade A) and high tensile steel (Grades A and D) are tested under various corrosive conditions in the fresh water, in the sea water and in the air at a temperature of 18°C, 0°C and-10°C. Mass loss of test specimen due to corrosion is measured at a monthly interval and it is converted to a loss of steel plate thickness. Based on the test database, the effects of parameters affecting the corrosion progress are discussed. Test database obtained in the present study are documented.
The primary objective of the present study is to develop a rapid method for calculating hull collapse strength of double hull oil tankers after collisions. For this purpose, the statistical characteristics of hull girder collapse after collision are studied. Four double hull oil tankers with different size are considered: Panamax, Aframax, Suezmax and VLCC. A set of 50 credible collision scenarios are selected by a sampling technique associated with the collision hazard identification based on the historical ship collision database. Four parameters, namely vertical collision location, damage penetration, striking ship's bulbous bow height, and striking ship's bulbous bow length are determined as a consequence of the corresponding collision scenario. The intelligent supersize finite element method is used to compute the progressive collapse behaviour of hull girder structures with the collision damages so determined. The residual hull girder strength indices can then be determined and formulated in a closed expression associated with collision damages and ship length. The developed formulations will be useful to quickly calculate the hull collapse strength of double hull oil tankers immediately after collisions.
This paper is a sequel to the authors' earlier article (Paik et al. 2020a, Full-scale collapse testing of a steel stiffened plate structure under cyclic axial-compressive loading, Structures,
As a sequel to another paper of the authors on welding-induced initial deformations [1], this paper aims to obtain a direct measurement database of welding-induced residual stresses in a full-scale steel stiffened plate structure and also to study the applicability of computational models to predict them. A full-scale steel stiffened plate structure in association with plate panels in bottom structures of an as-built containership carrying 1,900 TEU was fabricated using exactly the same welding technology as used in today's shipbuilding industry. The X-ray diffraction method was employed to measure the residual stress distributions in the plating. In addition to simple formula estimations, computational models using the three-dimensional thermo-elastic-plastic finite element method were applied to predict the residual stress distributions. A comparison between full-scale measurements, numerical predictions and simple formula estimations was made. Details of the full-scale measurements are documented as they can be useful to validate the computational models formulated by other researchers.
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