Hull Deformation Effect on Membrane-Type LNG Containment Systems

2016 ◽  
Author(s):  
Bo Wang ◽  
Yung-Sup Shin ◽  
Eric Norris
Keyword(s):  
Structural Integrity ◽  
Water Pressure ◽  
Local Deformation ◽  
Fatigue Tests ◽  
Wave Loads ◽  
Insulation System ◽  
Structural Fatigue ◽  
Hull Structure ◽  
Membrane Type ◽  
Global Deformation

The objective of this study is to investigate the relationship between the maximum allowable hull deformation, which includes global elongation and local deflection, and the capacity of the CCS in membrane-type LNG vessels. The LNG CCS mainly consists of the primary barrier (e.g. a corrugated membrane for GTT MK III system and an invar membrane for GTT NO 96 system) and the insulation panel which is attached to the inner hull through mastics or couplers. The excessive hull elongation due to dynamic wave loads may cause fatigue damage of the primary barrier. Thus, the maximum allowable hull elongation (global deformation) can be determined based on the fatigue strength of the primary barrier. On the other hand, the excessive hull deflection due to cargo or ballast water pressure may cause failure of the insulation panel and the mastic. Therefore, the maximum allowable hull deflection (local deformation) in the hull design can be determined based on the strength of the insulation panel and the mastic. In the present paper, the determination of fatigue life vs. strain curves of materials has been summarized for the primary barrier. Fatigue curves based on either structural fatigue tests or standard specimen tests can be applied in fatigue assessment of a primary barrier. As an example, the finite element (FE) analysis has been conducted on the MK III CCS with the hull structure under pressure loads. Two different load cases including full load and ballast load conditions have been considered to evaluate the structural integrity of the insulation system in numerical simulations. FE results show that the mechanical behavior of the insulation system and the mastic under the maximum allowable hull deflection has been examined based on the yielding strength of each individual component. Finally, the complete procedure to determine the maximum allowable hull elongation and the maximum allowable hull deflection has been developed for meeting the requirements of containment system design for membrane-type LNG carriers.

scholarly journals Sloshing Impact Response in LNG Membrane Carriers: A Response Analysis of the Hull Structure Supporting the Membrane Tanks

2016 ◽  
Author(s):  
Jonas W. Ringsberg ◽  
André Liljegren ◽  
Ola Lindahl
Keyword(s):  
Structural Response ◽  
Response Analysis ◽  
Impact Loads ◽  
Dynamic Amplification Factor ◽  
Insulation System ◽  
Load Duration ◽  
Hull Structure ◽  
Load Characteristics ◽  
Membrane Type ◽  
Dynamic Amplification

This study presents the determination of structural response due to sloshing impact loads in LNG carriers with membrane type cargo tanks. These loads are characterized by very short durations and are thus likely to inflict a dynamic amplification in the response of the hull. Finite element analyses are presented using a model representing parts of an LNG membrane tank. The objective was to find and quantify the dynamic amplification factor (DAF) for the structural response towards sloshing impact pressures. The influence of variations in the load characteristics such as load duration, extent of the loaded area, load location as well as the influence of the insulation system was evaluated. The study shows that the response in the studied region of the hull structure experiences significant levels of dynamic amplification during impact loads with specific durations. The response sensitivity analysis also shows that the insulation system (MARK III type) has a large effect on the dynamic behaviour of the hull structure. It has been found to alter the magnitude of the stress and deflection response for key structural members. It also changes the load time durations for which the maximum dynamic amplification occurs and increases the magnitude of the corresponding response DAF. Finally, it has been found that dynamic response gives DAF values of up to 2. The effects have been found to be present for temporal load characteristics commonly occurring in sloshing model tests and full-scale measurements and are therefore likely to occur for a vessel in operation.

Springing Responses Analysis and Segmented Model Testing on a 550,000 DWT Ore Carrier

2016 ◽  
Author(s):  
Hui Li ◽  
Di Wang ◽  
Cheng Ming Zhou ◽  
Kaihong Zhang ◽  
Huilong Ren
Keyword(s):  
Natural Frequency ◽  
Design Stage ◽  
Resonant Vibration ◽  
Bending Moments ◽  
Wave Loads ◽  
Regular Waves ◽  
Segmented Model ◽  
Ship Model ◽  
Hull Structure ◽  
Stiffness Distribution

For ultra large ore carriers, springing response should be analyzed in the design stage since springing is the steady-state resonant vibration and has an important effect on the fatigue strength of hull structure. The springing response of a 550,000 DWT ultra large ore carrier has been studied by using experimental and numerical methods. A flexible ship model composed of nine segments was used in the experiment. The model segments were connected by a backbone with varying section, which can satisfy the request of natural frequency and stiffness distribution. The experiments in regular waves were performed and the motions and wave loads of the ship were measured. The experimental results showed that springing could be excited when the wave encounter frequency coincides with half or one-third the flexural natural frequency of the ship. In this paper, the analysis of the hydroelastic responses of the ultra large ore carrier was also carried out using a 3-D hydroelastic method. Comparisons between experimental and numerical results showed that the 3-D hydroelastic method could predict the motions and the vertical bending moments quite well. Based on this numerical method, the fatigue damage was estimated and the contribution of springing was analyzed.

scholarly journals Modal and Vibration Analysis of Filter System in Petrochemical Plant

2017 ◽  
Vol 2017 ◽  
pp. 1-13
Author(s):  
Zhongchi Liu ◽  
Ji Wang ◽  
Wie Min Gho ◽  
Xiao Liu ◽  
Xuebing Yu
Keyword(s):  
Structural Integrity ◽  
Natural Frequencies ◽  
Resonance Effect ◽  
Petrochemical Plant ◽  
Structural Fatigue ◽  
Filter System ◽  
Vibration Data ◽  
Finite Element Software ◽  
Vibration Problem ◽  
System A

Filter systems are widely used in petrochemical plants for removing solid impurities from hydrocarbon oils. The backwash is the cleaning process used to remove the impurities on the sieves of the filters without a need to interrupt the operation of the entire system. This paper presents a case study based on the actual project of a filter system in a petrochemical plant, to demonstrate the significant effect of vibration on the structural integrity of piping. The induced vibration had led to the structural fatigue failure of the pipes connecting the filter system. A preliminary assessment suggested that the vibrations are caused by the operation of backwashing of the filter system. A process for solving the vibration problem based on the modal analysis of the filter system using the commercial finite element software for simulation is therefore proposed. The computed natural frequencies of the system and the vibration data measured on site are assessed based on the resonance effect of the complete system including the piping connected to the filters. Several approaches are proposed to adjust the natural frequencies of the system in such a way that an optimal and a reasonable solution for solving the vibration problem is obtained.

Development of Methods for Temperature Calculation of LNG Carrier Hull

2021 ◽  
Author(s):  
MD Shafiqul Islam ◽  
Tae-Soon Choi ◽  
Tae-Hyun An ◽  
Kang-Hyun Song
Keyword(s):  
Thermal Analysis ◽  
Analytical Solution ◽  
Low Temperatures ◽  
Liquefied Natural Gas ◽  
Liquid Form ◽  
Temperature Calculation ◽  
Hull Structure ◽  
The World ◽  
Membrane Type ◽  
The Impact

Abstract LNG carriers are vessels used to store and transport liquefied natural gas. LNG, in its liquid form has the temperature of minus 163 degrees Celsius. Therefore, the types of steel used to build the hull structure must withstand the impact of low temperatures. Cargo Containment System (CCS) is used to reduce the transfer of heat from the outside environment into the cargo tank and to keep the LNG in liquid state. Presently, the most popular types of CCS are designed by GTT (Gaztransport & Technigaz). However, Korean shipyards, KOGAS (Korea Gas Corporation) and many other companies around the world are developing their own CCS systems. The thermal analysis of LNG carrier hull is generally performed by the CCS developer and therefore, in order to assist the new CCS developers and LNG carrier designers, KR has developed a guideline for temperature calculation of Membrane type LNG carrier’s hull. This study is a part of the guidelines and focuses on numerical and analytical solution procedures for accurate hull temperature calculation. For verification and accuracy of these methods, temperature calculation of a Membrane type LNG carrier hull is carried out and the results are compared with each other. Both methods, thoroughly analyzed in this study, could be applied in the design of membrane type LNG carrier hulls.

Structural Analysis for a Panamax Bulk Carrier

2008 ◽  
Author(s):  
Sandita Pacuraru-Popoiu ◽  
Paulina Iancu ◽  
Liviu I. Crudu
Keyword(s):  
Structural Analysis ◽  
Stress Distribution ◽  
Structural Integrity ◽  
Dynamic Pressure ◽  
Uniform Structure ◽  
Bulk Carrier ◽  
Element Analysis ◽  
Hull Girder ◽  
Fine Mesh ◽  
Hull Structure

This paper is devoted to the development of a structural analysis for a bulk carrier vessel. According to the CSR requirements for bulk carriers, an assessment of the hull structure using FEA (Finite Element Analysis) on a model extended over 3 cargo holds is presented. This method is used in order to assess the structural integrity of the cargo holds under the considered loads. The selected vessel is a PANAMAX bulk carrier with double hull and longitudinal uniform structure. There are three main priorities for the FE-analysis: one is to perform a fine mesh necessary to capture the stressed induced by the considered loads. The second priority is to apply the right boundary conditions in order to approach the hull girder bending and stress distribution on the cargo holds. The stress distribution is induced by the cargo weight, the hydrostatic pressure and the external water considered as dynamic pressure. The dynamic pressure was computed using an in-house code, neglecting the inertia forces induced by the ship motions and the horizontal accelerations. Also shear forces and bending moments were obtained for head angles of 0, 45 and 180 degrees.

Large-Scale Resonant Fatigue Testing of Welded Tubular X-Joints for Offshore Jacket Foundations

2019 ◽  
Author(s):  
Jeroen Van Wittenberghe ◽  
Philippe Thibaux ◽  
Maarten Van Poucke
Keyword(s):  
Large Scale ◽  
Fatigue Testing ◽  
Water Pressure ◽  
Limit State ◽  
Fatigue Tests ◽  
Offshore Wind ◽  
Design Standards ◽  
Initiation Phase ◽  
Out Of Plane ◽  
Jacket Structures

Abstract Offshore wind turbines are being installed in deeper water and with more powerful generators resulting in more severe loading conditions on its foundations such as jacket structures. Because the main loading is due to wind and currents, the dominant design limit state is fatigue. The fatigue performance of the tubular joints used in jacket structures has been assessed several decades ago based on test results with limited component dimensions (diameter and wall thickness). In addition, improvements of welding methods and evolution of steel grades are not considered in the current design standards. To provide experimental fatigue-life data on large-scale structures a test program has been carried out on 4 welded tubular X-joints. Each X-joint consists of two horizontal braces with a diameter of 711 mm welded to a central vertical tubular member with 806 mm diameter. The X-joint has a total length of 7.5 m and has two identical welds that are fatigue tested. The fatigue tests are carried out on an innovative resonant bending fatigue test rig that allows to load the specimen in in- and out-of-plane direction at a different amplitude to obtain an even stress distribution over the circumference of the welds. The tests are carried out at a speed close to the resonance frequency of the X-joint. During the test, hotspot strains are measured using strain gauges and a limited amount of water pressure is used to detect through-thickness cracks. The tests are carried out in two phases. During the crack initiation phase, the sample is loaded in both the in- and out-of-plane mode. Once cracks are detected, the test is continued in the crack propagation phase with loading in the plane where cracks had been initiated until through-thickness cracking appeared. During this phase the beach marking technique has been used to mark the shape of the fracture surface at different moments during the fatigue tests. The testing program is part of the RFCS project JABACO that aims to reduce offshore wind cost by incrementing prefabrication of the jacket substructure.

Hull Structure Integrity Management in Floating Structures–FSO Puteri Dulang Case

2014 ◽  
Vol 69 (7) ◽  
Author(s):  
Ajith Kumar Thankappan ◽  
M. Fazli B. M. Yusof
Keyword(s):  
Fatigue Life ◽  
Structural Integrity ◽  
Structural Response ◽  
Offshore Structures ◽  
Design Phase ◽  
Floating Structures ◽  
Offshore Installations ◽  
Hull Structure ◽  
Integrity Management ◽  
New Buildings

This paper highlights the key differences in practices employed in managing hull structure integrity of permanently moored floating offshore structures as against sailing vessels which are subject to periodic dry docking. During the design phase, the structural integrity management over the life of a sailing vessel is primarily taken into account by means of Class prescribed Nominal Design Corrosion Values which are added to minimum scantling requirements calculated based on strength and fatigue criteria. In contrast, for permanently moored offshore installations like FPSOs, FSOs etc. the hull structure integrity over the entire design life of the asset is a key design consideration both for new buildings and conversions. Analytic methods and tools (primarily those developed by Class Societies) are available to evaluate the strength requirements (based on yielding, buckling and ultimate strength criteria) and fatigue life of the hull structure. Typically three levels of analysis with increasing degree of complexity and analysis time are used to predict the structural response and fatigue life of the Hull during design phase. The degree of detailed analysis required needs to be determined in light of the expected optimization in terms of savings in scantlings for new building or for steel renewal requirements in case of conversions.

scholarly journals Mechanical Failure Mode of Metal Nanowires: Global Deformation versus Local Deformation

2015 ◽  
Vol 5 (1) ◽  
Author(s):  
Duc Tam Ho ◽  
Youngtae Im ◽  
Soon-Yong Kwon ◽  
Youn Young Earmme ◽  
Sung Youb Kim
Keyword(s):  
Failure Mode ◽  
Local Deformation ◽  
Mechanical Failure ◽  
Metal Nanowires ◽  
Global Deformation

Concepts and Techniques for Helicopter Airframe Fatigue Tests

1966 ◽  
Vol 11 (3) ◽  
pp. 45-57 ◽  
Author(s):  
Walter A. Lane
Keyword(s):  
Experimental Design ◽  
Fatigue Test ◽  
Structural Integrity ◽  
Fatigue Cracking ◽  
Fatigue Tests ◽  
Test Facility ◽  
Test Results ◽  
Fail Safe ◽  
Inspection Techniques ◽  
Automatic Simulation

Between February 1961 and June 1963, Sikorsky Aircraft, under the sponsorship of the U. S. Navy Bureau of Naval Weapons, performed the first laboratory fatigue test of a full scale helicopter airframe. This paper presents the concepts and techniques developed by Sikorsky for such tests. Airframe fatigue test concepts are directed toward defining modes of fatigue cracking, measuring rates of crack propagation, and demonstrating the adequacy of recommended inspection techniques and intervals to provide “fail safe” structural integrity. The experimental design includes consideration of the test article configuration, acceleration of test loads, loading spectra, and evaluation of test fractures. The design of the SH‐3A airframe fatigue test facility to provide automatic simulation of flight and landing loads, and the development problems encountered in achieving this capability are described. The facility and techniques to be used for CH‐53A airframe fatigue tests reflect improvements resulting from SH‐3A test experience. Correlation of airframe fatigue test results and service experience demonstrates the validity of the test concepts and techniques as well as the “fail safe” characteristics of the SH‐3A airframe.

scholarly journals Universal poroelastic mechanism for hydraulic signals in biomimetic and natural branches

2017 ◽  
Vol 114 (42) ◽  
pp. 11034-11039 ◽  
Author(s):  
J.-F. Louf ◽  
G. Guéna ◽  
E. Badel ◽  
Y. Forterre
Keyword(s):  
Growth Response ◽  
Pressure Pulse ◽  
Vascular System ◽  
Water Pressure ◽  
Local Deformation ◽  
Physical Parameters ◽  
Hydromechanical Coupling ◽  
Long Distance ◽  
Whole Plant ◽  
Basic Features

Plants constantly undergo external mechanical loads such as wind or touch and respond to these stimuli by acclimating their growth processes. A fascinating feature of this mechanical-induced growth response is that it can occur rapidly and at long distance from the initial site of stimulation, suggesting the existence of a fast signal that propagates across the whole plant. The nature and origin of the signal is still not understood, but it has been recently suggested that it could be purely mechanical and originate from the coupling between the local deformation of the tissues (bending) and the water pressure in the plant vascular system. Here, we address the physical origin of this hydromechanical coupling using a biomimetic strategy. We designed soft artificial branches perforated with longitudinal liquid-filled channels that mimic the basic features of natural stems and branches. In response to bending, a strong overpressure is generated in the channels that varies quadratically with the bending curvature. A model based on a mechanism analogous to the ovalization of hollow tubes enables us to predict quantitatively this nonlinear poroelastic response and identify the key physical parameters that control the generation of the pressure pulse. Further experiments conducted on natural tree branches reveal the same phenomenology. Once rescaled by the model prediction, both the biomimetic and natural branches fall on the same master curve, enlightening the universality of our poroelastic mechanism for the generation of hydraulic signals in plants.

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