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Mineral wool is an insulation material commonly used in passive fire protection (PFP) systems on offshore installations. Insulation materials have only been considered functional materials for thermal analysis in the conventional offshore PFP system design method. Hence, the structural performance of insulation has yet to be considered in the design of PFP systems. However, the structural elements of offshore PFP systems are often designed with excessive dimensions to satisfy structural requirements under external loads such as wind, fire and explosive pressure. To verify the structural contribution of insulation material, it was considered a structural material in this study. A series of material tensile tests was undertaken with two types of mineral wool at room temperature and at elevated temperatures for fire conditions. The mechanical properties were then verified with modified methods, and a database was constructed for application in a series of nonlinear structural and thermal finite-element analyses of an offshore bulkhead-type PFP system. Numerical analyses were performed with a conventional model without insulation and with a new suggested model with insulation. These analyses showed the structural contribution of the insulation in the structural behaviour of the PFP panel. The results suggest the need to consider the structural strength of the insulation material in PFP systems during the structural design step for offshore installations.

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 and/or local structural members do not reach the ultimate strength during cyclic axial-compressive loading. Details of the test database are documented, which will be useful to validate computational models for the ultimate strength analysis.

The aim of the paper was to develop a test database of the ultimate strength characteristics of full-scale steel stiffened plate structures under axial compressive loading at a temperature of −80°C...

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, https://doi.org/10.1016/j.istruc.2020.05.026). The aim of the paper was to present a test data on the ultimate compressive strength characteristics of a full-scale steel stiffened plate structure at cryogenic condition which may be due to unwanted release of liquefied gases. Steel plate panels of an as-built containership carrying 1,900 TEU were referenced for this purpose. The test structure was fabricated in a shipyard using exactly the same welding technology as used in today’s shipbuilding industry. It is observed that the test structure reaches the ultimate limit states triggered by brittle fracture, which is totally different from typical collapse modes at room temperature. Details of the test database are documented as they can be used to validate computational models for the structural crashworthiness analysis involving brittle fracture at cryogenic condition.

The Integrated Offshore Standard Specification (IOSS) involves Korean shipyards, classification societies, research institutes, the Korean industrial society, engineering companies, and oil companies with the objective of reducing costs and risks without compromising safety in international offshore engineering procurement construction (EPC) projects using new standardized bulk components and qualification procedures. The activities of the IOSS include the analysis of the existing rules and regulations to achieve the best standardization, which is reflected in the best practices, and minimize the variables in regulations and rules. In addition, a standard inventory of shapes and dimensions, referred to as specifications, is proposed in the IOSS. In this paper, the aluminum tertiary standardization part (IOSS S102-1/2 S104: Specification for Structural Tertiary Design) is presented with the details of the procedures, background reviews, and cost-benefit analyses of the design and verification methods for standard designs in the IOSS standardization items. Based on the cost-benefit analysis, the application of standardized aluminum tertiary items to offshore projects has significant advantages in terms of maintenance and repair compared to the carbon steel tertiary items utilized in current industrial practices.

The aim of this paper is to present a fire test database on the collapse of a full-scale steel stiffened plate structure without passive fire protection under lateral patch loading. Steel plate pan...

Helidecks are used to access offshore installations for support and transport operations. The helideck and its supporting structure are critical safety elements due to their essential role ...

The structural engineering problem associated with a ship colliding with an ice-ridge involves highly nonlinear mechanisms including buckling, collapse, crushing, plasticity and fracture together with environmental and operational factors, such as the loading speed (strain rate), temperature and salinity. The objective of this paper is to develop an advanced technology for numerical computations of structural crashworthiness in the event of a ship colliding with an ice-ridge. The nonlinear finite element method is used for modelling the problem, in which the ship structures are modelled by plate-shell finite elements and the ice-ridge structures are modelled by solid elements together with the KOSORI ice material models. Two sets of experiments are performed to validate the numerical computations. In the first set of experiments, ice is dropped on a steel plate from a height of 2 m, and in the second, a steel solid (rigid) body is dropped on a steel plate under the same conditions. The results of the two experiments are compared to determine the differences between the ice responses and solid (rigid) body responses on the steel plate. It is concluded that the developed technology is very useful for computing the structural crashworthiness of a ship when colliding with an ice-ridge. Details of the test results are documented.

Helicopters are essential for supporting offshore oil and gas activities around the world. To ensure accessibility for helicopters, helideck structures must satisfy the safety requirements associated with various environmental and accidental loads. Recently, offshore helideck structures have used aluminium because of its light weight, low maintenance requirements, cost effectiveness and easy installation. However, section designs of aluminum pancakes tend to modify and/or change from the steel pancakes. Therefore, it is necessary to optimize section design and evaluate the safety requirements for aluminium helideck. In this study, a design procedure was developed based on section optimization techniques with experimental studies, industrial regulations and nonlinear finite element analyses. To validate and verify the procedure, a new aluminium section was developed and compared strength capacity with the existing helideck section profiles.

Ships and offshore platforms that operate in Arctic regions at low temperatures are likely subjected to impact loads that arise from collisions with icebergs. The aim of this paper was to examine the nonlinear impact response of steel-plated structures in an Arctic environment. In addition to material tensile tests for characterisation of the mechanical properties of polar-class high-tensile steel of grade DH36, an experimental study was undertaken in a dropped-object test facility on steel-plated structure models under impact loads and at low temperatures equivalent to those in Arctic regions. LS-DYNA nonlinear finite element computations were also performed for the corresponding test models. We conclude that nonlinear finite element analyses are useful in the analysis of the nonlinear impact structural responses involving yielding, crushing and brittle fracture at low temperatures as long as the modelling techniques are adequate. The conclusions and insights developed in this paper should be useful in the safety design of ships and offshore platforms intended for operation in Arctic regions.

Accidental limit state-based ship collision analysis was undertaken to identify the operability of aged non-ice class ships in the Arctic Ocean. Internal collision mechanics analysis of the struck vessel structures was carried out at a right angle with an initial velocity. The striking ship and struck ship were the same ship, a 157,500 DWT Suezmax class double hull oil tanker. Various Arctic ambient temperature conditions, room temperature to −80 °C, were applied to the ambient exposed plating of the struck ship. Time-variant corrosion wastage was employed in the case of age-related damage. Nonlinear finite element software, LS-DYNA, was conducted to apply the nonlinear constitutive curves of the materials from a series of tensile tests at low temperatures. The operability of aged ships in the Arctic condition was estimated based on the results.

In the early design stage of ships, the two most important structural analyses are performed to identify the structural capacity and safety. The first step is called global strength analysis (longitudinal strength analysis or hull girder strength analysis) and the second step is local buckling analysis (stiffened panel strength analysis). This paper deals with the ultimate strength performance of Arctic sea route-going commercial ships considering the effect of low temperature. In this study, two types of structural analyses are performed in Arctic sea conditions. Three types of ship namely oil tanker, bulk carrier and container ship with four different sizes (in total 12 vessels) are tested in four low temperatures (−20, −40, −60 and −80oC), which are based on the Arctic environment and room temperature (20oC). The ultimate strength performance is analysed with ALPS/HULL progressive hull collapse analysis code for ship hulls, then ALPS/ULSAP supersize finite element method for stiffened panels. The obtained results are summarised in terms of temperature, vessel type, vessel size, loading type and other effects. The important insights and outcomes are documented.

This study explores the ultimate longitudinal strength of five different sizes of container ships to investigate the impact of considering aged corrosion effects throughout a ship's life. The typical design life of double oil tankers and bulk carriers, according to the CSR (Common Structural Rule), is 25 years and approximately 20 years for other commercial ships. In case of container ships, whether corrosion addition is required differs according to classification society with some not stipulating any such requirements. To conveniently define aged corrosion additions for container ships, the corrosion addition requirements for a double hull oil tanker, which has a relatively similar mid-ship the section configuration, were applied in this study as an initial guideline. The ultimate strength of the selected container ship, including their longitudinal strength behavior, is investigated in this study to show the necessity of corrosion addition application to container ships and the relevant predictions regarding decreases in the longitudinal strength of new-building container ships after corrosion. The investigation results regarding longitudinal strength reduction and other findings from this analysis of five container ships will be useful in enforcing corrosion addition as a general guideline.

Numerous oil tanker losses have been reported and one of the possible causes of such casualties is caused by the structural failure of aging ship hulls in rough weather. In aging ships, corrosion and fatigue cracks are the two most important factors affecting structural safety and integrity. This research is about effect on hull girder ultimate strength behavior of double hull oil tanker according to corrosion after Part I: stiffened panel. Based on corrosion data of Part I (time-dependent corrosion wastage model and CSR corrosion model), when progressing corrosion of fourtypes of double hull oil tankers (VLCC, Suezmax, Aframax, and Panamax), the ultimate strength behavior of hull girder is compared and analyzed. In case of the ultimate strength behavior of hull girder, when occurring corrosion, the result under vertical and horizontal bending moment is analyzed. The effect of time-dependent corrosion wastage on the ultimate hull girder strength as well as the area, section modulus, and moment of inertia are also studied. The result of this research will be useful data to evaluate ultimate hull girder strength of corroded double hull oil tanker.

Age-related problems especially corrosion and fatigue are normally suffered by weatherworn ships and aging offshore structures. The effect of corrosion is one of the important factors in the Common Structural Rule (CSR) guideline of the ship design based on a 20 or 25 years design life. The aim of this research is the clarification of the corrosion effect on ultimate strength of stiffened panels on various types of double hull oil tankers. In the case of ships, corrosion is a phenomenon caused by the ambient environment and it has different characteristics depending on the parts involved. Extensive research considering these characteristic have already done by previous researchers. Based on this data, the ultimate strength behavior of stiffened panels for four double hull oil tankers such as VLCC, Suezmax, Aframax, and Panamax classes are compared and analyzed. By considering hogging and sagging bending moments, the stiffened panels of the deck, inner bottom and outer bottom located far away from neutral axis of ship are assessed. The results of this paper will be useful in evaluating the ultimate strength of an oil tanker subjected to corrosion. These results will be an informative example to check the effect of ultimate strength of a stiffened panel according to corrosion addition from CSR for a given type of ship.

The aim of the study reported herein was to investigate the effects of low temperatures on the crushing characteristics of steel plated structures. The motivation of this study is for the analysis of ship collisions in Arctic waters. A series of tensile coupon tests were performed to examine their material behaviour at low temperatures, and then quasi-static axial crushing tests were carried out on thin-walled square tubes. The test tubes were made of ASTM A500-type carbon steel, and both the tensile coupon tests of the material and the crushing tests of the tubes were performed in a liquid nitrogen cooled chamber. To reflect the conditions of the Arctic environment more realistically, the tensile coupon tests of the material were also carried out in a dry-ice cooled chamber. LS-DYNA nonlinear finite element method simulations applying a practical approach of modelling techniques were performed to investigate the structural crashworthiness of the thin-walled steel tubes numerically. The tests in the liquid nitrogen cooled chamber showed that the fracture strain of the material was not affected (reduced) by temperatures as low as −80 °C, although fracture strain was significantly reduced below −100 °C. The fracture strain results obtained in the dry-ice cooled chamber, however, show this strain to be affected (reduced) by low temperatures even between 0 °C and −80 °C, which is equivalent to the Arctic environment. It was also observed that fracture occurs in thin-walled tubes under crushing loads at low temperatures. The LS-DYNA computations also detected the fracture behaviour of test tubes in cold temperatures in a relevant way.

Structural crashworthiness with regard to crushing and fracture is a key element in the strength performance assessment of ship collisions in the Arctic. The aim of this study is to investigate the crashworthiness characteristics of steel-plated structures subject to low temperatures that are equivalent to the Arctic environment. The effect of low temperatures on the material properties is examined on the basis of tensile tests. Crushing tests are undertaken on steel-square tubes subject to a quasi-static crushing load at both room and low temperatures. The crushing behavior of the square tubes in this test is compared with ls-dyna computations. It is found that low temperatures have a significant effect on not only the material properties but also the crashworthiness of steel-plated structures in terms of mean crushing loads and brittle fracture. It is suggested that the collision-accidental limit state design of ships intended to operate in the Arctic region should be carried out by taking the effect of low temperatures into account.

The aim of the study reported herein was to investigate the effects of low temperatures on the crashworthiness of steel-plated structures. A series of material tensile tests were performed to examine the material behaviors at low temperatures. Then, unstiffened steel-plated structure and stiffened steel-plated structure were collided with a cone-shaped drop object to estimate the crashworthiness of steel-plated structures. The material tensile test specimens and test structures were made of Polar class steel for ships and offshore structures which is a sufficient condition of the IACS requirements concerning Polar Class and Strength of Ships. The tests considered room and low temperatures relevant to an Arctic environment and a cryogenic condition. LS-DYNA nonlinear finite element simulations applying a practical approach of modeling techniques were performed to investigate the structural crashworthiness of the steel-plated structures numerically with results of material tensile tests.Copyright © 2015 by ASME

In this study, the safety of floating liquefied natural gas (FLNG) hull structures in collisions with icebergs in an Arctic environment is examined through experimentation and LS-DYNA numerical computations in association with normal and accidental conditions in operation of LNG cargo containment system. The material properties of Polar-class high-tensile steel at the low temperatures associated with an Arctic environment and liquefied natural gas-induced cryogenic conditions are characterized by tensile coupon tests under quasi-static and dynamic conditions. The structural crashworthiness of plate panels subject to impact loads is studied through an experiment and numerical computations at low temperatures. The technologies and insights provided by this study at the material and structural member levels are then applied to FLNG hull structure collisions with icebergs in an Arctic environment.

The aim of this study was to investigate the effects of low temperatures on the material properties and crashworthiness of ASTM A131-type carbon steel. A series of tensile coupon tests and crushing tests on square tubes were performed in a liquid nitrogen cooled chamber to examine their material behavior and crashing behavior at a series of low temperatures under quasistatic conditions. The temperature conditions cover a cryogenic condition, the typical Arctic temperatures and room temperature. In the previous study, ASTM A500-type carbon steel is considered [13] and in present study the different grades of ASTM A131-type carbon steel for ships and offshore structures are considered, including Grades A, B and D of mild steel and Grades AH and DH of high tensile steel. The results of the tensile coupon tests showed an increase in the strength and in non-uniform fracture strain behavior in different grades and temperatures. Unstable crushing behavior and fractures were observed in the crushing tests. LS-DYNA nonlinear finite element method analyses were performed using reliable nonlinear finite element method modeling techniques to assess the structural crashworthiness of the materials at low temperatures.