Double Hull Research Articles

Deformation process of web girders in small-scale tanker double hull structures subjected to lateral impact

Experimental drop weight impact tests are performed to examine the dynamic response of web girders in a one-tenth scaled tanker double hull structure struck laterally by a knife edge indenter. The small stiffeners of the full-scale prototype are smeared in the small-scale specimen by increasing the thicknesses of the corresponding plates. The plastic response is evaluated at two impact velocities and the impact location is chosen between two web frames to assure damage to the outer shell plating and the stringers. The laboratory results are compared with numerical simulations performed by the LS-DYNA finite element solver. In the simulations, the strain hardening of the material is defined using experimental data of quasi-static tension tests and the strain rate sensitivity is evaluated using standard coefficients of the Cowper–Symonds constitutive model. The experimental permanent deflection and shape of the deformation show a good agreement with the collision simulations. It is found that the crushing resistance of the specimens is determined by the deformation mechanism of the stringers. Thus, the deformation process is described and compared with theoretical deformation modes for web girders subjected to large in-plane quasi-static loads. Additionally, the influence of the stiffeners on the shape of the deformation of the stringers is illustrated through simulations of stiffened structural elements.

Structural analysis of a steel double hull underwater tank, intended for oil recovery from shipwrecks

In the present work, the survivability of a submerged structure against loads, imposed by the operational environment, such as hydrostatic pressure is presented. The structure under consideration is a component (buffer bell) of a system called DIFIS that recovers fuel from shipwrecks. It consists of two parts: the reservoir and the floater. The floater is the part that produces the buoyancy force that holds the whole system in place and therefore its structural integrity is crucial for the safety of the structure. The floater is designed as a double hull structure made of steel plates and stiffeners. The task of the structural analysis is to ensure that the floaters’ double hulls are able to withstand the hydrostatic pressure due to the depth and maintain the needed buoyancy forces. In the present analysis, the strength of the hulls is evaluated for three different scenarios (operational, worst case and accident scenarios).

Lateral pressure effect on average compressive strength of stiffened panels for in-service vessels

This paper presents the estimation of the average compressive strengths of three types of stiffened panels under axial compression and lateral pressure based on simplified formulae in the CSR for tankers (common structural rules for double hull oil tankers) and nonlinear finite element analyses (FEAs). Basic scenarios are determined based on the slenderness ratios of the stiffened panels used for in-service ships. Secondary scenarios are subdivided by external pressures that are applied to finite element model by increasing 1 bar, assuming 30 m water height. The total number of FEAs for flat bar (FB)-, angle bar (AB)- and tee bar (TB)-stiffened panels is 189. FEA results show that the existence of pressure can cause a significant reduction of ultimate strength, while CSR formulae do not take into account the effect of lateral pressure. The lateral pressure is more detrimental to the ultimate strength of stiffened panels with a higher column slenderness ratio than those with a smaller column slenderness ratio. A new concept of the relative average compressive strain energy, instead of the ultimate strength, is introduced in order to rationally compare the average compressive strength through a complete compressive straining history. The differences in the ultimate strengths between CSR formulae and FEA results are relatively small for FB- and AB-stiffened panels, but larger discrepancies of relative average compressive strain energies are obtained.

Spectral fatigue damage assessment of tanker deck structural detail subjected to time-dependent corrosion

The paper presents a spectral fatigue damage analysis of a double hull tanker structural detail accounting for corrosion wastage over time. The cyclic load of the wave-induced vertical bending moment, analysis using a strip theory on the frequency domain, is considered for two loading conditions. The influence of sea environment parameters and operational profiles including the use of different scatter diagrams, and wave variance spectra have been analyzed. The effect on the time-dependent cumulative fatigue damage as a function of corrosion deterioration is calculated.

Heuristic Solution Strategy for the Sequential Ballast Water Exchange Problem

The sequential ballast water exchange problem is characterized by its combinatorial and computational complexity that must be resolved in transoceanic ship design and involves key technologies. Solving the problem is subjected to many safety criteria including ships’ intact stability, hull girder strength, fore and aft drafts, and bridge visibility, et cetera. The combinatorial and computational complexity of the problem grows exponentially with the growth of the problem’s scale. It has been verified that current existing approaches are not adequate in solving the problem for ships with small design margins of the sequential exchange performances. This paper presents a heuristic solution strategy for the problem that has been tested to be applicable to double hull tankers and bulk carriers with small sequential exchange design margins. A simplified algorithm is developed and presented in this paper. Numerical simulations are conducted using a 50,000 deadweight (DWT) double-hull product tanker. The results show that, compared with existing approaches, the proposed approach is superior in flexibility and capability of automatically obtaining improved solutions with better key performances of the ship.

Intra-Industry Market Response to the Tae-an Oil Spill Accident and the Corporate Environmental Disclosure

This paper researched market responses for listed companies in several industries affected by the major oil spill accident off the coast of Taean, in December 7, 2007. The Taean accident triggered considerable concerns in people over the possibility of potential future regulation in shipbuilding and petroleum industries. However, the accident also provided an unexpected business opportunity for environmental clean-up industry and shipbuilding industry. The oil spill triggered the acceleration of the enactment of policies that require all new oil tankers to be constructed with double hull, which is interpreted as a good news for shipbuilding industry. Increased public pressure coupled with the prospect of tightened regulation is expected to decrease the market values of firms in the affected 태안만 원유유출사건에 대한 시장반응과 환경공시 최종서1)*・임형주2)** Intra-Industry Market Response to the Tae-an Oil Spill Accident and the Corporate Environmental Disclosure Jong-Seo Choi and Hyoung-Joo Lim 1) 제1저자: 부산대학교 경영대학 교수(Professor of Accounting, School of Business, Pusan National University) 2) 교신저자: 부산대학교 경영대학 박사과정(Ph. D student, School of Business, Pusan National University) 제출: 2012년 3월 6일 수정: 2012년 5월 15일 승인: 2012년 6월 12일 * 제1저자: jschoi@pusan.ac.kr ** 교신저자: Limhj@pusan.ac.kr

Effect of corrosion on the ultimate strength of double hull oil tankers - Part I: stiffened panels

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.

Effect of corrosion on the ultimate strength of double hull oil tankers - Part II: hull girders

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.

The necessity of applying the common corrosion addition rule to container ships in terms of ultimate longitudinal strength

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.

Fatigue damage assessment of corroded oil tanker details based on global and local stress approaches

Fatigue damage assessment of double hull oil tanker structural details is performed, based on global and local structural finite element models. The wave-induced vertical and horizontal bending moments, as well as local pressure loads are accounted for in the fatigue damage calculations. Local stress analyses are considered based on the notch stress approach. Time-dependent stresses as a function of corrosion deterioration are analyzed based on nonlinear corrosion wastage during the design life of ship. The effective notch stress approach is applied for analyzing the stress distributions and the fatigue damage of the welded joint at two hotspots. The hotspots are located between the flat bar stiffener of a transverse web frame and the flange of a longitudinal stiffener at the side shell of a tanker ship hull. The details under consideration are modeled separately in a fine mesh employing the sub model techniques. Finally the fatigue damage assessment accounting for corrosion deterioration of the considered hotspots is analyzed.

Models for estimating grounding frequency by using ship trajectories and seabed geometry

Because a lot of ships involved in grounding accidents have caused severe environmental damages of sea areas, the prevention of groundings has been so important that several counter measures such as double hull or Electronic Chart Display and Information System (ECDIS) were developed and equipped to ships. To develop effective measures against grounding, the assessment of risks associated with groundings of ships is required. For the risk assessment, an accurate estimation of grounding frequency is important. This paper presents new models for the estimation of grounding frequency using ship trajectories and seabed geometry in a considered sea area. There are some existing models for the estimation of grounding frequency based on traffic density or position distribution of ships in the lateral direction of a traffic lane. However, these models do not fully consider the rationale behind grounding. The rationale is that unlike collision, most of the grounding accidents occurred by deviation from the planned route and grounding can be prevented by keeping it. The new models introduced here are based on it. The models are called Model A and Model B. Model A is based on the view that grounding occurs by deviation from a planned route. Model B is based on the view that grounding occurs by deviation from trajectories without groundings, the cause of which is an omission error in the process of following a modified route to cope with a deviation from the planned route. For verification of the models, a number of grounding candidates and a number of groundings were estimated using ship trajectories in Akashi Channel and seabed geometry of the channel by use of them. Moreover by comparing the results with statistics of groundings in the channel, probability of failing to avoid grounding and annual frequency of grounding were estimated by varying some parameters. These estimated values indicate the rationality of the models, even though there still remain some problems to be solved.

Smith법에 의한 손상 유조선의 잔류강도 평가 연구

2016년 7월부터 강제 적용 예정인 목표기반 선박건조 기준(GBS)의 설계단계의 기능요건 중 잔류강도 평가 부분은 현재의 유조선설계, 건조 규칙인 공통구조규칙에는 아직 포함되어 있지 않은 실정이다. 기능요건에 포함된 잔류강도 부분은 충돌이나 좌초와 같은 해상사고시 발생가능한 선체손상을 고려하여 강도측면의 제한조건을 규정함으로써 사고시에도 일정부분 선박의 안전을 확보하려는 것이다. GBS에서 주로 다루고 있는 위험도에 근거하여 잔류강도를 평가하기 위해서는 다양한 손상에 대한 광범위한 평가 작업이 필요하다. 이때, 매번 비선형 유한요소해석을 수행하기보다 선체구조를 보강판 요소의 집합으로 보는 간이화된 강도 해석법의 하나인 Smith법이 유용할 것이다. 본 연구에서는 좌초사고로 인해 선저가 손상된 경우를 대상으로 Smith법을 적용하여 최종강도 평가를 수행하였으며, 3개의 화물창 구역을 모델링하여 수행한 비선형 구조해석 결과와의 비교를 통해 Smith법을 적용한 결과의 정도를 확인하였다. The present Common Structural Rules for double hull oil tanker is not included the residual strength, which is one of the functional requirements in design part of Goal-based new ship construction standards (GBS). The GBS will be enforced after July 1, 2016. The requirement related residual strength has the goal to build safe ship even if she has the specified damages due to marine accidents including collision and grounding. In order to assess the residual strength based on risk for structural damages according to GBS, tons of nonlinear FE analysis work taking into account various types of damage will be needed. The Smith's method, a kind of simplified method for the strength analysis is very useful for this purpose. In this paper, the residual strength assessments based on ultimate strength using Smith's method were carried out. The objected ship is VLCC with stranding damage in bottom structures. Also, the results were compared with that of nonlinear FE analysis using three cargo hold model.

The effectiveness of double hulls in reducing vessel-accident oil spillage

While much work has been done in investigating determinants of oil spillage attributed to vessel accidents, little research has been conducted on the effectiveness of ship hull design in reducing marine pollution. This paper addresses whether the double-hull requirement reduces vessel-accident oil spillage. The volume of oil spillage due to oil-cargo vessel accidents was investigated using tobit regressions and an empirical data set of individual vessel accident pollution incidents investigated by the US Coast Guard from 2001 to 2008. The results indicate that the double hull design on average reduces the size of oil spills by 20% and 62% in tank barge and tanker ship accidents, respectively.

Influence of Acoustic Coating on the Underwater Sound Radiation of a Double Hull Cylindrical Shell Structure

This paper studies the influence of acoustic coating to the underwater sound radiation characteristic of a double hull cylindrical shell by the Statistical Energy Analysis (SEA) method. Influence of covering density and laying location of acoustic coating to the underwater sound radiation characteristic of the double hull cylindrical shell structure are discussed. Study shows that low covering density of acoustic coating will cause “sound leaking” phenomena, sound will leak out from the uncovered area of the double hull cylindrical hull structure and radiate into the surrounding water, which harms the underwater noise reduction performance of the acoustic coating; however, the noise reduction capacity of the acoustic coating improves gradually as the covering density increases. Besides, laying location of acoustic coating also impact the underwater sound radiation performance of the double hull cylindrical shell structure; inner hull covered with acoustic coating is better than the outer hull covered from the noise treatment point of view

Modeling and analysis of panel hull block assembly system through timed colored Petri net

To implement efficient production control, this paper provides a timed colored Petri net (timed CPN) approach to performance modeling, real-timed dispatching and simulation of Panel hull block assembly system (PHBAS). The definition of Petri net is extended to accord with the real-world PHBAS’s organization, and the modeling method for hull flow production is provided in order to simplify modeling program. Using modeling and analyzing method, the dynamic characteristics of the system can be emulated and quantitatively calculated and work control tactics can be optimized. For the double bottom hull block shipbuilding system in a recently built shipyard in China, the simulation model with timed CPN was described and the system parameters and optimal task sequence which has the minimum operation time were obtained for a scheduling case.

Assessment of IACS-CSR implicit safety levels for buckling strength of stiffened panels for double hull tankers

The present study aims at applying structural reliability methods to assess the implicit safety levels of the buckling strength requirements for longitudinal stiffened panels implemented in the IACS Common Structural Rules (CSR) for double hull oil tankers. The buckling strength requirements considered are used in the initial stage of the hull girder scantlings’ design to control the buckling capacity of longitudinal stiffened panels subjected to the compressive loads induced by the hull girder vertical bending. The following buckling collapse failure modes are explicitly considered in the design formulation: uniaxial buckling of the plating between stiffeners, column buckling of stiffeners with attached plating and lateral-torsional buckling or tripping of stiffeners. The paper presents the procedure used to assess the implicit safety levels of the strength requirements for the three buckling collapse failure modes above mentioned, which includes the optimization of the scantlings of the plate panels and longitudinal stiffeners in order to reflect the minimum strength required by the formulation. A first order reliability formulation is adopted, and stochastic models proposed in the literature are used to quantify the uncertainty in the relevant design variables. A sample of five oil tankers representative of the range of application of the IACS-CSR design rules is considered. The effect of corrosion in the implicit safety levels is quantified based on the three corrosion levels of the Net Thickness Approach (NTA) adopted in the design rules. Sensitivity analyses are also performed to quantify the relative contribution or importance of each design random variable to the implicit safety levels.

Probabilistic Approach to Predicting Residual Longitudinal Strength of Damaged Double HullVLCC

This paper estimates the residual longitudinal strength of a damaged double hull VLCC (Very Large Crude Carrier) under combined vertical and horizontal bending moments using Smith's method. The damage estimated in this study occurred due to collision or grounding accidents. The effects of the randomness of the yield stress, plate thickness, extent of damage, and the combination of these three parameters on the ultimate hull girder strength were investigated. Random variables were generated by a Monte Carlo simulation and applied to the double hull VLCC described by the ISSC (International Ship and Offshore Structures Congress) 2000 report.

Balancing Response Operations with Safety, the Environment and Commerce

ABSTRACT On January 23, 2010, a double hull tank vessel spilled nearly 9,500 barrels of high sulfur crude oil into the Sabine-Neches River (SBR) in Port Arthur, Texas. An ensuing evacuation of surrounding areas, coupled with the potential environmental impact and closure of the Intracoastal Waterway, elevated public, political and environmental concerns. Through an effective multi-agency Incident Command, rapid call up of abundant response resources to properly implement pre-identified response protocols, and the development of innovative response tactics, response managers successfully balanced environmental, commercial and safety concerns to execute a highly effective spill response in one of the busiest shipping thoroughfares in the United States. Collectively, the support of a cohesive Unified Command to execute operational strategies, and the RP's diligence in ensuring all needed response resources were quickly made available, enabled the command post to be stood down and the majority of the cleanup ...

Modelling the impact of double hull technology on oil spill numbers

This article presents the results of modelling the behaviour of oil spill numbers published by the International Tanker Owners Pollution Federation over the period 1970 to 2005. Poisson count or negative binomial models are estimated to identify the major determinants of oil spill numbers over this period. The results are used to estimate the number of oil spills that would have occurred in the absence of the adoption of double hull technology. Other potential factors, such as changes in the regulatory regimes regarding oil transportation, were found to be insignificant.

Optimization of ship’s subdivision arrangement for offshore sequential ballast water exchange using a non-dominated sorting genetic algorithm

Ship’s subdivision arrangement is a multi-objective combinatorial optimization problem with multiple nonlinear constraints. This study focuses on finding a methodology for ship’s subdivision arrangement that can guarantee ship’s offshore sequential ballast water exchanging (SBWE) performances in the preliminary design stage. A mathematical model is built using minimizing trims and hull girder longitudinal bending moments and shearing forces occurred in the SBWE as the objectives, and the multiple safety criteria of the SBWE as the constraints. The longitudinal lengths of the ballast water tanks (BWTs) are taken as design variables that will alter within a reasonable length range. An elitist nondominated sorting genetic algorithm (NSGA-II) is utilized to perform the optimization, in which the nondominated sorting mechanism is employed to handle the multiple objectives, and the constraint-domination principle is utilized to handle the multiple constraints. A special crossover operator called the dispersion apportioned allelic (DAA) crossover is introduced to perform the reproduction of the special problem. A real case study of the subdivision arrangement based on the SBWE of a 50,000DWT double hull product tanker is conducted to demonstrate the feasibility and effectiveness of the proposed approach.