Global Strength Assessment for Semi-Submersible Column After Supply Vessel Collision Accident

2009 ◽  
Author(s):  
Zhiqiang Hu ◽  
Jianmin Yang ◽  
Longfei Xiao ◽  
Xiaomei Yan
Keyword(s):  
Direct Calculation ◽  
Finite Element Models ◽  
Sea State ◽  
Distinctive Character ◽  
Strength Assessment ◽  
Structure Damage ◽  
Collision Zone ◽  
Global Strength ◽  
Collision Force ◽  
Numerical Simulation Technique

The researches of the anti-collision characters of a semi-submersible column and its capability of surviving in severe sea state after collision accident are completed in the paper. Three collision cases are designed. A 5000 ton vessel hits the semi-submersible column in transversal, longitudinal and oblique direction. Numerical simulation technique is used to do the analysis, and anti-collision characters of the semi-submersible column are summarized by the curves of collision force vs. penetration, the energy absorption proportion and structural damages. It can be pointed out that the column show a distinctive character when the contact surface is large at the beginning of the collision. There is no rupture of outer shell, which means the column can sustain such kind of collision. Taking advantage of the direct calculation method with finite element models, the global strength of the semi-submersible is verified to assess the influence of structure damage by the collision on the semi’s survival capability in severe sea state. The structure damage caused by the collision is taken into consideration in the FE models. The code SESAM is used to do the calculation through the design wave method. Several assumptions are made to realize the comparison between collision cases. It is found that the collision influence is restricted within the scope of structural components around the collision zone. The collision damage caused by the hitting of 5000 ton vessel will not bring a serious threat to the global strength capability of the semi-submersible.

Global Strength Assessment of Trimaran Structure

2012 ◽  
Vol 538-541 ◽  
pp. 2860-2863 ◽  
Author(s):  
Khurram Shehzad ◽  
Hui Long Ren ◽  
Chun Bo Zhen ◽  
Asifa Khurram
Keyword(s):  
Structural Strength ◽  
Direct Calculation ◽  
Fe Analysis ◽  
Strength Analysis ◽  
Stress Concentrations ◽  
Strength Assessment ◽  
Analysis Technique ◽  
Current Design ◽  
Design Loads ◽  
Global Strength

This paper presents structural strength assessment of trimaran by global FE-analysis. Global strength analysis using the finite-element method is a powerful tool extensively used to design well-balanced and reliable sea going vessels. This analysis technique is particularly recommended in unconventional and new ship designs. Lloyd’s Register rules (LR Rules) for classification of trimaran are used to compute design loads and load cases. Global FE analysis is performed as per direct calculation procedure of LR Rules. Maximum stress concentration locations or hot spots corresponding to each load case are identified. The stresses induced in trimaran structure for all load cases are less than the maximum allowable stress. Furthermore, some modifications in current design are suggested to reduce the stress concentrations and hence to improve the structural strength.

A Comparison of Direct Calculation Approaches Applied on the Fatigue Strength Assessment of a Panamax Container Ship

2012 ◽  
Author(s):  
Zhiyuan Li ◽  
Wengang Mao ◽  
Jonas W. Ringsberg
Keyword(s):  
Stress Response ◽  
Fatigue Strength ◽  
Fatigue Damage ◽  
Measurement Data ◽  
Direct Calculation ◽  
Container Ship ◽  
Calculation Methods ◽  
Strength Assessment ◽  
Strip Theory ◽  
Calculation Procedures

Today, it is common practice to carry out fatigue assessments of ship structures using direct calculation procedures. A direct calculation analysis of a ship’s fatigue strength involves hydrodynamic analysis, stress response evaluation followed by fatigue damage calculation. Many numerical codes are available for these types of analyses. They could yield different values in a fatigue life prediction because of the different degrees of complexity in the computation of the ship’s response. For example, hydrodynamic loads can be calculated using the strip theory or the panel method. The stress response to these loads can be computed using a beam theory or more advanced analyses, such as global and/or local finite element analyses. In a direct fatigue analysis for ship design, spectral methods have been dominating but there is a growing interest in time-domain fatigue damage calculation procedures. The objective of the current investigation is to compare four commonly used direct calculation methods against measurement data. The comparison is carried out by making a case study on a Panamax container ship on which full-scale measurements have been performed. The computational efforts involved in the application of the current direct calculation methods are compared and their applicability in ship fatigue design is discussed.

scholarly journals Predictions of Ship Extreme Hydroelastic Load Responses in Harsh Irregular Waves and Hull Girder Ultimate Strength Assessment

2019 ◽  
Vol 9 (2) ◽  
pp. 240 ◽  
Author(s):  
Jialong Jiao ◽  
Yong Jiang ◽  
Hao Zhang ◽  
Chengjun Li ◽  
Chaohe Chen
Keyword(s):  
Ultimate Strength ◽  
Time Domain ◽  
Three Dimensional ◽  
Direct Calculation ◽  
Wave Force ◽  
Irregular Waves ◽  
Restoring Force ◽  
Strength Assessment ◽  
Hull Girder ◽  
Rule Approach

In this paper, the hydroelastic motion and load responses of a large flexible ship sailing in irregular seaways are predicted and the hull girder ultimate strength is subsequently evaluated. A three-dimensional time-domain nonlinear hydroelasticity theory is developed where the included nonlinearities are those arising from incident wave force, hydrostatic restoring force and slamming loads. The hull girder structure is simplified as a slender Timoshenko beam and fully coupled with the hydrodynamic model in a time domain. Segmented model towing-tank tests are then conducted to validate the proposed hydroelasticity theory. In addition, short-term and long-term predictions of ship responses in irregular seaways are conducted with the help of the developed hydroelastic code in order to determine the extreme design loads. Finally, a simplified strength-check equation is proposed, which will provide significant reference and convenience for ship design and evaluation. The hull girder ultimate strength is assessed by both the improved Rule approach and direct calculation.

Auxiliary Turbine Generator Set Isolation System Design for US Naval Vessel

2012 ◽  
Author(s):  
Paul G. Jones ◽  
Steven L. Carmichael
Keyword(s):  
Finite Element Models ◽  
Component Level ◽  
Sea State ◽  
Turbine Generator ◽  
Full System ◽  
Naval Vessel ◽  
Isolation System ◽  
Actual Performance ◽  
Detail Design ◽  
Machinery Space

The RR4500 Auxiliary Turbine Generator (ATG) incorporates an isolation system addressing four main design requirement environments. These environments include high-impact shock, structureborne vibration, sea state motion, and installation/integration into the machinery space. Multiple design iterations were performed, beginning with a simplified system representation and expanding to full system finite element models. Specific resilient isolation mounts were selected to satisfy the competing criteria from the different requirement sets. Design resolutions passed specific requirements down to the component level and were addressed during detail design. Structures, system components, and flexible ship connections were adapted to meet the requirements needed by the isolation system. Testing of the system indicates good correlation between system predictions and actual performance.

scholarly journals STRUCTURAL ASPECTS DURING CONVERSION FROM GENERAL CARGO SHIPS TO CEMENT CARRIERS

Brodogradnja ◽  
2021 ◽  
Vol 72 (2) ◽  
pp. 37-55
Author(s):  
Paul Jurišić ◽  
◽  
Joško Parunov ◽  
Keyword(s):  
Finite Element ◽  
Case Studies ◽  
Thickness Measurement ◽  
Present Condition ◽  
Finite Element Models ◽  
3D Finite Element ◽  
Strength Assessment ◽  
Structural Modifications ◽  
General Cargo ◽  
Structural Aspects

An approach to converting general cargo ship to cement carrier is analysed in the present study, emphasising the structural aspects of the conversion. A comprehensive re-appraisal of the conditions of the ship hull, considering her history and present condition of the structure, is provided. Two case studies are presented where the strength assessment has been performed using 2D sectional and 3D finite element models, generated according to the available hull drawings and thickness measurement reports. The results of the two studies are interpreted with respect to the structural modifications carried out during the conversion process, and some general conclusions are drawn.

scholarly journals Fatigue Strength Assessment of Trimaran Cross-Deck Structure Based on Spectral and Simplified Fatigue Method

2019 ◽  
Vol 2019 ◽  
pp. 1-13
Author(s):  
Chunbo Zhen ◽  
Tianlin Wang ◽  
Pengyao Yu ◽  
Liang Feng
Keyword(s):  
Transfer Functions ◽  
Three Dimensional ◽  
Stress Transfer ◽  
Direct Calculation ◽  
Fatigue Behaviour ◽  
Fatigue Analysis ◽  
Fe Analysis ◽  
Linear Potential ◽  
Wave Loads ◽  
Strength Assessment

In order to investigate the fatigue behaviour of trimaran cross-deck structural details, the spectral and simplified fatigue analysis approaches are proposed. In spectral fatigue approach, three-dimensional (3D) linear potential flow theory and global FE analysis are used for wave loads and stress transfer functions calculation; the stochastic spectral fatigue analysis is carried out considering the weighted wave headings factors. In simplified fatigue approach, based on the direct calculation procedure of LR rules, the evaluation of simplified fatigue loads and loading conditions are presented, and the stress ranges are obtained by global finite element (FE) analysis. Then the fatigue lives of a few hot spots are computed to demonstrate the application of the proposed method. The result shows that the method given in this paper has a good applicability. This study offers methodology for the fatigue analysis of trimaran cross-deck structure, which may be regarded as helpful references for structural design of these types of ships.

Global Strength Assessment of a Trimaran Hull Multi-Purpose Frigate

2004 ◽  
Author(s):  
A Ungaro ◽  
◽  
E Pino ◽  
M Viviani ◽  
R Dattola ◽  
...  
Keyword(s):  
Strength Assessment ◽  
Global Strength

Fatigue Assessment of Trimaran Structure Based on Simplified Procedure

2012 ◽  
Vol 525-526 ◽  
pp. 333-336
Author(s):  
Hui Long Ren ◽  
Shehzad Khurram ◽  
Chun Bo Zhen ◽  
Khurram Asifa
Keyword(s):  
Fatigue Damage ◽  
High Speed ◽  
Hot Spot ◽  
Mathematical Formulation ◽  
Direct Calculation ◽  
Assessment Procedure ◽  
Hot Spot Stress ◽  
Fatigue Assessment ◽  
Strength Assessment ◽  
Simplified Procedure

In recent years, Trimaran platform design has got the attention of naval architects owing to its superior seagoing performance. Trimaran structure experiences severe loads due to its unique configuration and high speed, causing stress concentration, especially in cross deck region and accelerate fatigue damage. This paper presents fatigue strength assessment of Trimaran structure by simplified procedure. A methodology is proposed to evaluate fatigue loads and loading conditions by load combinations of direct calculation procedure of Lloyds Register Rules for Classification of Trimaran (LR Rules). Global FE analysis, in ANSYS, is performed to investigate the stress response. The stress range is computed by hot-spot stress approach, and its long term distribution is specified by Weibull distribution. Fatigue damage of selected critical details is calculated using mathematical formulation of simplified fatigue assessment procedure of Common Structure Rules (CSR).

Analysis of Nonlinear Modal Damping due to Friction at Blade Roots Using High-Fidelity Modelling

2018 ◽  
Author(s):  
Junjie Chen ◽  
Chaoping Zang ◽  
Biao Zhou ◽  
E. P. Petrov
Keyword(s):  
Finite Element ◽  
Direct Calculation ◽  
Surface Friction ◽  
Mode Shapes ◽  
Finite Element Models ◽  
High Fidelity ◽  
Three Dimension ◽  
Blade Vibration ◽  
Modal Damping ◽  
Energy Dissipated

In this paper, a methodology is developed for analysis of modal damping in root joints of bladed discs using large finite element models and detailed description of friction contacts at contact interfaces of the joints. The methods allows the analysis of: (i) a single blade vibration and (ii) a bladed-disc assembly for any family of modes (lower and higher modes) calculating the modal damping factors for different levels of vibrations. Three-dimension solid finite element models are used in the calculations. The analysis is performed in time domain through the transient dynamics analysis. The methodology allows the use of widely available finite element packages and based on the direct calculation of the energy dissipated at root joints due to micro-slip over the multitude of contact elements modelling the surface-to-surface friction contact interactions. The numerical studies of the dependency of modal damping factors on the vibration amplitudes are performed for simplified and realistic bladed disc models for different blade mode shapes, engine-order excitation numbers and nodal diameter numbers using high-fidelity models.

Strength Assessment of Membrane LNG Tank Structure Based on Direct Calculation of Structural Response

2009 ◽  
Author(s):  
Zoran Mravak ◽  
Je´roˆme de Lauzon ◽  
Yun-Suk Chung ◽  
Louis Diebold ◽  
Eric Baudin
Keyword(s):  
Structural Response ◽  
Direct Calculation ◽  
Elastic Interaction ◽  
Small Scale ◽  
Assessment Procedure ◽  
Strength Assessment ◽  
Stochastic Nature ◽  
Containment System ◽  
Recent Developments ◽  
Lng Tank

Expanding LNG market reinforces the demand for new concepts of LNG transportation. Membrane LNG vessel design widely applied until now, encounters new challenges due to requirement for larger vessel’s capacities and more flexible operation in partially filled conditions. Present assessment procedures of LNG tank structure usually combine small scale sloshing loads measurement and containment system structural strength assessment, on a comparative base for the reference and target vessels. For the new LNG design, more rational methods become essential in the assessment procedure. Some improvements in the strength assessment procedure of membrane LNG tank structure is presented in this paper, combining small scale sloshing load measurements with direct FEM calculation of structural response. The complexity of problem is the consequence of: stochastic nature of impulsive sloshing loads, material used for the cargo containment system at cryogenic temperature and strong hydro-elastic interaction during impacts. Disadvantages of small scale testing and limits of today’s numerical methods require that further in the future certain simplifications and assumptions should remain. In the paper, method for the design loads selection from the small scale sloshing measurements is described and discussed. The impulse, transferred over the corresponding impacted surface, is the base for the comparison of successive violent sloshing loads. The stochastic nature and statistics of measured loads are discussed. The structural analysis of LNG tank structure under selected design sloshing loads, using on-linear and time-dependant explicit FE calculations, is described. This paper presents Bureau Veritas recent developments and their applications in the field of sloshing assessment.

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