Web Frame Research Articles

공액경사법을 이용한 LPG 운반선 화물창 내부구조물 중량최소화 설계

Since the cargo tank of LPG carriers is made of expensive low-temperature steel that can maintain its function even at -50oC, the reduction of cargo tank materials has been a major concern for shipyards to improve price competitiveness. The purpose of this study is to minimize the weight of the web frames and stringers that form the interior of the cargo tank of the LPG carriers. A total of 92 design variables including 6 shape-related design variables were selected for the minimum weight design. In order to reduce the time required for the optimization process, the conjugate gradient method, which is a gradient-based optimization technique, was adopted. In addition, for the structural analysis, the cargo tank located at the second position in the bow was selected as the structural analysis target, and in order to improve the reliability of the analysis, a boundary condition considering the deformation of the entire ship for each loading condition was applied to the partial model. As a result of the study, it was confirmed that the error rate did not exceed the maximum 3% by comparing the maximum stress value generated in all internal structures for the entire model structure analysis and the partial model one. A total of 92 dimensions with the minimum objective function were determined, and the weight was reduced by about 39 tons per cargo tank.

A Two-Stage Optimisation of Ship Hull Structure Combining Fractional Factorial Design Technique and NSGA-II Algorithm

The intricate nature of ships and floating structures presents a significant challenge for ship designers when determining suitable structural dimensions for maritime applications. This study addresses a critical research gap by focusing on a three-cargo hold model for a multipurpose cargo ship. The complex composition of these structures, including stiffening plates, deck plates, bottom plates, frames, and bulkheads, necessitates thorough structural analysis to facilitate effective and cost-efficient design evaluation. To address this challenge, the research utilises FEMAP-integrated NX NASTRAN software (2021.2) to assess hull girder stress. Furthermore, a novel approach is introduced, integrating the Design of Experiments (DOE) principles within Minitab 21.4.1 software to identify critical parameters affecting hull girder stress and production costs. This method determined the top five key parameters influencing hull girder stress: Hatch coaming plate, Hatch coaming top plate, Main deck plate, Shear strake plate, and Bottom plate, while also highlighting key parameters that impact production costs: the inner bottom plate, Inner side shell plate, Bottom plate, Web frame spacing, and Side shell plate. Ship design optimisation is then carried out by incorporating regression equations from Minitab software into the Non-dominated Sorting Genetic Algorithm II (NSGA-II), which is managed using Python software (PyCharm Community Editon 2020.3.1). This optimisation process yields a significant 10% reduction in both ship weight and production costs compared to the previous design, achieved through prudent adjustments in plate thickness, web frame positioning, and stiffener arrangement. The optimally designed midship section undergoes rigorous validation to ensure conformity with industry standards and classification society regulations. Necessary adjustments to inner bottom plates and double bottom side girders are made to meet these stringent requirements. This research offers a comprehensive framework for the structural optimisation of ship hulls, potentially enhancing safety, sustainability, and competitiveness within the maritime engineering industry.

Study on flexural behaviour of printed concrete wide beams using polypropylene fibres

Sustainability in building construction is an inevitable aspect of future construction projects. The justification of sustainability is highly appreciated by comparing 3D concrete printing technology with conventional construction. However, the 3D printing concrete system has limitations and challenges in industrial applications. The reason is that this process was initially used in small non-structural applications and is now being adopted for large-scale structures. Thanks to concrete printing machines, a wide variety of web frames are also available - something completely impossible to achieve using traditional formwork for pouring concrete. In this study, the girder web is designed in the style of truss beams. Three wide beams with different amounts of polypropylene (PP) fibre were printed, and 3-point loading tests were conducted. The failure mode, load-bearing capacity, and deflection were reported in this study. According to the results, applying concrete printing technology in civil and industrial construction is entirely feasible. The printing process successfully produced models with a nozzle diameter of 22 mm and layer height of 10 mm, ensuring sufficient adhesion force between the printing layers. Using a PP fibre content of about 0.25% yielded the best results in terms of concrete compressive strength and beams’ flexural strength, while a PP fibre content of about 1.00% tended to increase the ductility of the member. Although the failure mode is brittle, the beams exhibited deflection before fracture far beyond the allowable deflection value of a flexural member. Therefore, the application of printed components to construction is feasible.

Enhanced ship cross-section design methodology using peridynamics topology optimization

In this study, peridynamics topology optimization (PD-TO) framework is implemented to reduce the total weight of ship structures and increase their structural endurance against cracks. PD-TO is a general nonlocal optimization strategy that performs the minimization of strain energy density as the objective function and uses pre-defined volume fractions as optimization constraints. To analyze ship structures herein, both the optimality criteria (OC) algorithm and the proportional (PROP) approach are implemented into the PD-TO solver. As the initial design domain, a reference bulkhead geometry of trailing suction hopper dredger (ship) is modeled. This web frame is optimized according to critical wave/loading conditions such as hogging and sagging. Different volume fractions are investigated to obtain lighter designs based on OC and PROP methods. In addition, different cracked scenarios are created by locating the cracks into various positions on the reference ship cross-section. Optimized results for cracked cases shows that the proposed method can create alternative web frames for specific definitions of the possible damaged regions on the board. To prove the efficiency of the proposed method, maximum displacements and compliance of the reference and optimized structures are compared. The results proves that topologically optimized designs offered stiffer structures as compared to conventional designs under the same loading conditions. Finally, some of the optimized results are smoothed to demonstrate the practical utility of the PD-TO for manufacturing. Overall, it is revealed that the PD-TO can be effectively utilized to design marine structures to achieve a higher strength/weight ratio while considering critical operation conditions and possible damaged regions.

Complete gene sequence and mechanical property of the fourth type of major ampullate silk protein.

Spiders spin a great diversity of silk types for daily survival and reproduction. Of the six orb-weaver silk types, the dragline silk forming orb web frame attracts the most attention because of its extremely high tensile strength and toughness. So far, four types of major ampullate silk proteins (MaSp1-4) that make up dragline silk have been identified. These MaSp types have diversified amino acid motifs that underlie the impressive mechanical property of dragline silk by forming particular structures. Existing knowledge of MaSp4 proteins is fragmented, making it difficult to illuminate the structure and function of MaSp4. Here, we report the full-length MaSp4 gene with 11,334 bp from the orb-weaving spider Araneus ventricosus. Removing the only intron, the spliced complete transcript of MaSp4 gene is 6897 bp and encodes 2298 amino acids. Analysis of the primary structure of A. ventricosus MaSp4 protein reveals the repetitive region lacks poly-A and GGX motifs but has the unique GPGPQ motifs. Quantitative real-time PCR analyses show high levels of MaSp4 mRNA were detected in major ampullate gland. Structural characterization using CD- and FTIR sepctroscopy reveals a mainly α-helical solution conformation and a very high β-turn content within fibers. Collectively, our new findings provide complete template for recombinant silk protein with specific properties and support that the GPGPQ motif found in MaSp4 could increase flexibility in dragline silk by packing in more β-turns, expanding the repertoire of sequences known to form β-turn that is available for artificial chimeric silk fibers. STATEMENT OF SIGNIFICANCE: Dragline silk forming orb web frame attracts the most attention because of its extremely high tensile strength and toughness. So far, four types of major ampullate silk proteins (MaSp1-4) that make up dragline silk have been identified. Existing knowledge of MaSp4 proteins is fragmented, making it difficult to illuminate the structure and function of MaSp4. Here, we report the full-length MaSp4 gene from the orb-weaving spider Araneus ventricosus. We further identify the sequence, structure, and mechanical property of MaSp4 protein, providing a new insight into the structure-funtion relationships associated with MaSp4. Collectively, our new findings provide complete template for recombinant silk protein with specific properties and support that the GPGPQ motif found in MaSp4 could increase flexibility in dragline silk by packing in more β-turns, expanding the repertoire of sequences known to form β-turn that is available for artificial chimeric silk fibers.

Effect of local cut-out on fatigue strength assessment in ship structures

The aim of the work is to evaluate different design alternatives to obtain criteria for the selection of the most effective design by fatigue strength assessment of the local cut-out as a result of the connection between the longitudinal or ordinary stiffener and the transverse web frame (longi-web) in the side hull structure (upper wing torsional box), very important area due to its high stress concentration, of a container vessel, one of the most important ships in terms of its influence on the world economy. Structural solutions and design guidelines are established, by means of numerical models validated by experimental tests, which allow alternative designs to be obtained that improve their fatigue behaviour. Standard cut-out geometries are studied under the presence of different variables (radius of curvature, longitudinal spacing, longitudinal stiffener cross-section, and flange arrangement) that are evaluated to determine their effect in the structural assessment (fatigue damage, stress concentration, and fracture mechanics) and the weight comparison between alternatives.

Designing the internal reinforcements of a sailing boat using a topology optimization approach

In naval design it is common practice to define an internal regular web frame made of longitudinal elements and transversal sections with the purpose of giving stiffness to the whole structure and, at the same time, promoting lightness. In this work, FEM simulation and Topology Optimization (TO) tools are implemented to present a different approach in placing the reinforcements inside the hull of a sailing dinghy. The methodology proposed in this paper considers as a starting point the volume inside the hull and the deck completely filled with material and the result after the simulations is a free form shape of the sailboat reinforcements. The TO procedure is based on two different input FEM solutions: one is the result of a structural analysis on the boat loaded with real forces acting during navigation and the other one is the result of a modal analysis aimed to extract natural frequencies of the structure. The result must fulfil several requirements such as weight, stiffness and stress. TO models have been compared with a traditionally designed sailboat with the same total mass and relevant improvements have been obtained in terms of local stiffness and reduction of moments of inertia.

Effect of bow hull form on the buckling strength assessment of the corner bracket connection

The aim of the paper is to study the influence on the structural strength assessment, in terms of fore end weight, in the conversion process from a conventional to an inverted bow hull of a platform supply vessel under bow flare impact loads. Linear and elastic buckling analyses of the corner bracket connection (deck beam with web frame) located in the fore body are obtained from modifications to its geometry and the inclusion of different stiffening methods. A series of numerical and experimental analyses are undertaken with the design and construction of a new auxiliary structure. The most effective combination (bracket geometry and stiffening method) is established and alternative geometries that optimize the local weight of the corner bracket are proposed by means of topology optimization, obtaining an innovative bracket geometry (omega bracket) that minimises weight while maintaining constant buckling strength. The results obtained establish useful and valuable design criteria that save material and weight to the ship's structure.

Effect of the Torsion Box Dimensions on Local Stress Distribution and Fatigue Strength Assessment of a Container Ship

The aim of this paper is to estimate the influence of the dimensions of the torsion box (height and width), of a 2400 TEU feeder-class container ship, on local stress distribution and assessment of local fatigue strength by using a numerical approach based on the fatigue limit-state and ultimate limit-state in the midship region. In terms of the fatigue limit-state, the effect of the dimensions of the torsion box is obtained by geometrical modifications, in the connection between the side shell longitudinal stiffeners with the transverse web frame for nine structural details, referring to different arrangements of strengthening elements (brackets and flat bars). The process of comparing the different elements determines the most effective combination. This structural influence on the local stress distribution is assessed, along the longitudinal plates between ordinary stiffeners bounding the perimeter of the torsion box, by calculating the hull girder stresses, local buckling stresses and shear stress distribution induced by vertical and horizontal shear forces, Saint Venant and warping torques, and finally the shear stresses induced by a warping moment. Scantling criteria are obtained allowing for a better design of this very important region in container ships.

Exploration of the protein conformation and mechanical properties of different spider silks

To analyze the protein conformation and mechanical properties of what types of spider silks, web frame silks from spiders of five different families, Parawixia dehaani (P. dehaani), Herennia ornatissima (H. ornatissima), Nephilengys malabarensis (N. malabarensis), Hippasa lycosina (H. lycosina) and Macrothele bannaensis (M. bannaensis), were investigated by tensile testing, Raman spectroscopy and X-ray diffraction. The order of the fracture strength or breaking force (H. ornatissima > N. malabarensis > P. dehaani, H. lycosina > M. bannaensis) is in accordance with the order of the Raman intensity ratios or crystallinity, the order of the extensibility (H. ornatissima < N. malabarensis < P. dehaani) is inversely proportional to the order of the degree of orientation of the β-sheets, which verify the theory that mechanical properties of silk mainly depends on protein conformation. Meanwhile, the Raman spectra of the web frame silks from four Araneidae spiders (Gasteracantha diadesmia, Gasteracantha kuhli, Macracantha arcuata and P. dehaani) and two Tetragnathidae spiders (Leucauge tessellata and H. ornatissima) show that the slight spectral differences might enable preliminary identification and classification of spiders. We believe that researching either the relationship between or individual performance of the mechanical properties and structures of various types of spider silks would benefit the utilization of silks as biomaterials and the classification of spider silks.

Концептуальные проблемы организации рентабельной разработки и добычи железомарганцевых конкреций со дна Мирового океана

Object and purpose of research. The study is focused on problems of extraction of ferromanganese nodules from the bottom of the World Ocean. This extraction is still insignificant and amounts to no more than 2% of the value of ores mined on land, but its potential is disproportionately large. Of great interest is the deep-water zone of the Clarion- Clipperton faults, where one of the largest deposits of ferromanganese nodules has been registered. For many years, the development of deep-sea deposits of such nodules was considered a low-profit and complex process, but recently the position of researchers has been changing. To increase profitability, it is required to minimize the number of dives and, consequently, to have large-sized hull structures. Main results. To solve this problem, the design of the hull of the underwater vehicle according to the type of the so-called polyhull is proposed. Its main idea is related to the fact that for reinforced cylindrical shells of large diameter, the cylindrical shape of the body is not effective due to technological (in thickness) and strength limitations. The polyhull, whose diameter is not less than 20 m, contains at least 12 modules with a diameter of 2–4 m. The modules are connected by double stringers, web frames and transitional airlocks. The modules are intended to serve as an energy module, a high-pressure tank, an accommodation module, floats, a preparation and processing plant, a warehouse and a repair base for mining robotics, a rescue module, etc. The proposed design solutions can also be used to lift large-sized sunken objects. Conclusion. Research in this area is increasingly becoming the prerogative of governments, because, on the one hand, they require a large amount of capital investment, and, on the other hand, metals found in nodules are constantly becoming more expensive. The development of new technologies stimulates the technological development of the entire industry and opens up new prospects for the economic system.

Application of a BEM model with dipole elements

A potential flow code is extended to include dipole elements to handle potential flow problems for offshore structures consist of thin shell geometry with both sides exposed to ocean waves. The solution on dipole elements can be represented by the drop of fluid potential across the thin shell surface. By adjusting the porous effect parameter, such a dipole element model can be applied for the solid impervious thin shell structures, porous surfaces and even the imaginary sheets attached to the sharp edges where the local flow dissipation occurs. Special attention is paid on different approaches to evaluate the drift forces on floating bodies with porous surface, including the traditional far field and pressure integration methods as well as the control surface integration approach. The solutions from the BEM model on excitation forces, off-body kinematics and drift forces are verified against the analytical solutions for a concentric porous cylinder system fixed at the seabed. The numerical performance of a two-layer source/sink model with very small gaps is investigated, taking the results from the corresponding dipole element model as the baseline. It is suggested that the mesh size requirement from DNV-RP-C205 is too strict for the two-layer panel model in the case that the exact fluid velocity on both sides of the wall is not needed. The proposed model is demonstrated in two case studies which involve the internal fluid dynamics inside tanks with interior web frame structures of a floating barge for one case and the damping effects from the sharp edge of a box barge model for the other case.

Design recommendations for container ship side-shell structure under fatigue strength assessment

The aim of the work is to evaluate various designs in order to arrive at some guidelines for choosing a good standard design by means of a fatigue damage analysis in the connection between longitudinal stiffener and transverse web frame on container ship side-shell structure located in the upper wing torsional box. Design proposals and recommendations are developed, based on numerical and experimental analysis, which allow, from different structural configurations formed by combinations between cut-outs and collar plates, to establish more and less adequate structural designs in one of the ships with the greatest future projection. In the first phase, the cut-out without influence of the longitudinal stiffener is studied and the stress state and fatigue assessment are determined. In the second phase, the longitudinal stiffener is taken into account under the presence of the collar plate in the model and different geometrical alternatives (thickness, ducktail, overlap and radius of curvature) and their influence on the determination of stress and fatigue life are studied. From the different configurations, the most appropriate combination is established and structural solutions are proposed in order to improve the design.

Постановка и решение задачи проектирования рамного набора поперечной водонепроницаемой переборки крупнотоннажного контейнеровоза с использованием оптимизационно - поисковых процедур и нормативных требований правил DNV-GL

Поперечные переборки крупнотоннажных контейнерных судов представляют собой сложные конструкции, при проектировании которых обычно используется методология проверочного расчета на основе метода конечных элементов (МКЭ). Для создания конечно-элементной модели необходимо знать размеры всех элементов конструкций, входящих в состав переборки. Поэтому такой подход к проектированию является итерационным, что обуславливает высокую трудоемкость процесса проектирования. На ранних стадиях проектирования размеры конструкций поперечных переборок контейнеровоза могут быть быстро и достаточно точно оценены на основе аппарата нелинейного программирования, относительно простой модели составной (конструктивно-ортотропной) пластины и нормативных требований Правил классификационных обществ. Такой подход применяется в Российской практике при проектировании двойных конструкций типа двойное дно или понтон плавучего дока. В статье предложено решение задачи проектирования рамного набора поперечной переборки крупнотоннажного контейнеровоза на нагрузки от контейнеров, действующие на переборку при качке судна. Конструкция переборки приводится к условной модели «коффердамного» типа. Затем используется методика приведения составной «конструктивно-ортотропной» пластины к изотропной пластине с несколько иным соотношением сторон, но с такими же параметрами изгиба. Это позволяет применить существующие табличные данные для определения расчетных изгибающих моментов и перерезывающих сил, которые после аппроксимации представляются в виде полиномов – аналитических зависимостей. Показана постановка оптимизационно-поисковой задачи математического программирования. Целевая функция – характеристика массы рамного набора. Ограничения задачи формируются на основе нормативных требований DNV-GL и математических зависимостей модели составной пластины. Для решения задачи используется инструмент MS Excel «Поиск решения» Представлены результаты тестового проектного расчета применительно к конструкции крупнотоннажного контейнеровоз с контейнерной вместимостью 18 тыс. TEU. Сопоставление результатов проектирования с оригинальными расчетами фирмы – проектанта показали удовлетворительное соответствие. The transverse bulkheads of the large container vessels are complex structures that are commonly designed using the finite element method (FEM) verification methodology. To create a finite element model, it is necessary to know the dimensions of all structural elements of the bulkhead. Therefore, this approach to design is iterative, which leads to a high complexity of the design process. At the early stages of design, the dimensions of the structures of the transverse bulkheads of a container vessel can be quickly and accurately estimated based on the nonlinear programming technique, a relatively simple model of a composite (structural-orthotropic) plate, and the regulatory requirements of the Rules of Classification Societies. This approach is used in practice in Russia when designing double structures such as a double bottom or pontoon of a floating dock. The article proposes a solution to the problem of the transverse bulkhead web frames designing in application to a large-tonnage container vessel for loads of containers acting on the bulkhead when the vessel is moving on the waves. The bulkhead structure is reduced to the conditional "cofferdam" type model. The technique is used to reduce a composite "structurally-orthotropic" plate to an isotropic one with a slightly different aspect ratio, but with the same bending parameters. This allows applying the existing tabular data to determine the design bending moments and shear forces, which, after approximation, are represented as polynomial analytical dependencies. The statement the optimization-search problem of mathematical programming is shown. The goal function is the characteristic of the bulkhead's webs mass. The constraints of the problem are formed on the DNV-GL regulatory requirements and mathematical relationships of the composite plate model. MS Excel tool "Solver" is used to solve the problem. The results of a test calculation are presented as applied to a large-capacity container ship with container capacity of 18000 TEU. Comparison of the design results with the original calculations of the designer’s company showed satisfactory agreement.

Coarse mesh finite element model for cruise ship global and local vibration analysis

This paper presents a practical procedure for creating finite element (FE) model for vibration analysis of cruise ships. The most preferable FE modelling approaches are studied and discussed through case studies of common ship structures, which cover the range from low to high frequencies. The application of homogenized equivalent single layer (ESL) theory based equivalent element for stiffened panel is extended to local forced vibration analysis, where inertia induced interaction between plate and stiffener occurs. Modal method is used with an energy-based correction for accounting the plate-stiffener interaction into modal properties. Case study results reveal that mesh density of one 4-node element per web frame spacing is suitable for global FE-model when vibration analysis is limited to global hull girder modes. For such modes it is sufficient to only include the membrane stiffness of stiffened panels. For investigating the response at higher frequencies, bending properties of stiffened panel should be included and mesh density should be at least two elements per web frame spacing. Then forced vibration analysis can be performed with an excellent accuracy up to frequencies about one third of the local plate natural frequencies between the stiffeners. Beyond that, the influence of the local plate vibration becomes more significant in panel vibration, making the ESL-theory based element limited. With the applied correction method, the validity of the ESL-model can be extended to approximately two thirds of the local plate natural frequency.

Experimental numerical and analytical analysis of the penetration of a scaled double-hull tanker side structure

The paper presents experimental, numerical and analytical analyses of a small-scale double-hull structure quasi-statically punched at the mid-span by a rigid flat edge indenter, to examine its energy-absorbing mechanism and fracture. The present study aims to further validate the numerical analysis procedure and the analytical method of individual stiffened panels and web girders against the experiment of the double-hull structure. The specimen, scaled from a tanker's double side structure, includes three spans between the web frames and two spans between the stringers. The paper provides practical information to estimate the extent of structural damage within ship sides during collision accidents. The experimentally obtained force-displacement response and deformation shape show a good agreement with the simulations performed by the explicit LS-DYNA finite element solver. The analysis of the double-hull structure demonstrates the accuracy of the procedure for identifying standard inputs used in numerical codes, in particular the definition of material plastic hardening and the calibration of the critical failure strain by tensile test simulation. The experimental and numerical results are used to validate the analytical method proposed in previous investigations at the plastic deformation stage and a revised semi-analytical method is proposed in the present study for the large penetration stage.

Oil Tanker Simplified Fatigue Assessment with Inspection and Repair Approach and Parameters

The occurrence of cracks in the hull structure of oil tankers is an important concern for the maritime industry because crack propagation will reduce collapse strength of deck-stiffened panels and, consequently, decrease the ultimate hull girder capacity of ship’s structures. Fatigue is an important design criteria for ships to ensure a sufficiently high safety level. Fatigue life predictions of ship’s structural details have traditionally been carried out using S-N approach and the Palmgren-Miner’s rule. The principal objective of such approach is to estimate the time to failure in order to ensure a satisfactory design lifetime of ship’s structural components. Potential cracks are considered to occur in the side shell, in the connections between longitudinal stiffeners and transverse web frame. The main objectives of the present study are to evaluate the fatigue life of vessel’s amidships using the simplified fatigue method, which is based on DNVGL-CG-0129 “Fatigue Assessment of Ship Structures” in order to determine the main cause of the observed cracks on the single skin oil tanker. Fatigue assessment was based on worldwide trade. Longitudinal stiffeners at transverse frames amidships are considered. The results show that fatigue life is generally above 20 years; however, analysis has revealed that the fatigue life of typical stiffener transitions in the side shell is below 20 years. The fatigue lives of side shell longitudinals are regarded as normal for ships built in the period between 1980 and 1990 with extensive use of high tensile steel in the side shell. Inspection and repair proposals of details with fatigue lives below 20 years are advised accordingly. Findings of fatigue analyses provide remaining life assessment, inspection plan definition, determination of repair and modification solutions, and avoiding integrity issues resulting in production downtime and hot work or dry dock.

Ultimate strength analysis of typical perforated high web frame structure in cruise ships

Objectives The perforate high web structure is a special structure widely used in the superstructures of large cruise ships. In order to establish the design method of this kind of structure, it is necessary to fully grasp the mechanical characteristics of typical perforated high web structures used in the superstructures of large cruise ships. Methods Using the nonlinear finite element theory and classical stiffened plate theory, an analysis is made of the influence law of initial deck defects, longitudinal girder specifications and web openings on the ultimate bearing capacity of the plate frame under longitudinal compression. Results The thin plate frame is more sensitive to initial defects, and the initial deformation mode is different from that of the thick plate frame. The longitudinal girder ultimate capacity contribution is bigger and the sensitivity of longitudinal pressure limit capacity to the proportion and shape of holes is low. The locations of the collapse failure buckling zones are determined by the locations of the holes. The failure modes of perforated high web frame structures are revealed. Conclusions The results of the influence law of key factors such as initial deck defects, geometrical dimensions of longitudinal girders and web openings on the ultimate strength of perforated high web frame structures provide guidance for the lightweight design and safety assessment of cruise ship superstructures.

Fatigue assessment of FPSO hull side shell longitudinals using component stochastic and full spectral method

The emphasis of this work is on comparison of fatigue damage capacity at the bulkhead and web frame connections of side shell longitudinals under the effect of vertical and horizontal bending in combination. Fatigue analysis methods adopted such as component stochastic and full spectral consider an FPSO of 325 m length, selecting side shell longitudinal structural elements connected to the typical transverse bulkhead and web frame at mid ship area. The analyses are being performed in accordance with three loading conditions such as fully loaded, intermediate and ballast condition. This research uses spectral fatigue analysis to create a function of stress transfer that in turn helps generate the power spectral density function by the bending moment transfer function. The combination of spectral moments with the Palmgren-Miner law results in the FPSO's accumulated fatigue damage. The findings provide insight into the changes in fatigue damage of the structural component under the effect of vertical and horizontal bending moments. Not only acting global loads and local pressure are important on the side shell longitudinal elements, but also relative deflections of webs influence the stress response due to additional stiffener bending are required. Due to the large amount of intersection details of side shell longitudinals at transverse web frame and bulkhead and due to high repair costs in case of damage, a sound structural design is thus necessary. The findings and insights developed from the present work are discussed in detail.

Minimum Weight Design for Web Frames of Cargo Tanks in the LPG Carrier

Minimum Weight Design for Web Frames of Cargo Tanks in the LPG Carrier