The Analysis of Ship Structures Subjected to Slamming Loads

1960 ◽  
Vol 4 (04) ◽  
pp. 11-27
Author(s):  
S. F. Borg
Keyword(s):  
Structural Design ◽  
Sudden Change ◽  
Time Effect ◽  
Ship Hull ◽  
Impact Loads ◽  
Fundamental Study ◽  
Ship Hulls ◽  
Ship Slamming ◽  
Slamming Load ◽  
Elastoplastic Range

This paper describes the results of a fundamental study of various phases of the ship structural design problem, as affected by slamming-type loads. By a slamming load, we mean a suddenly applied impact-type load such as is introduced for example, by: (a) The pitching and heaving motions induced by waves, which in turn cause the ship's bow to emerge and then reenter the seaway at a relatively high velocity. Upon reentering the sea, suddenly applied impact-type loads may be applied to the ship hull. These cause a sudden change in acceleration, generally felt as a shudder (or series of shudders or vibrations) which introduces the slam loading. (b) Berthing or docking of ships. If, for any reason the berthing introduces heavy impact loads due to sudden contact between the ship hull and the fender-dock system then we have a response very similar to that described in (a). The study[1]2 was concerned with several different facets of the over-all slam problem. Among the topics considered (and reported upon herein) are 1) time effect in ship-slamming problems; 2) damping of slam oscillations; 3) model scaling requirements for slam phenomena; 4) an approximate method of analysis for ship hulls (in the elastic range) subjected to slam loads; 5) comparisons between the method 4) and other methods; 6) extension of 4) to the elastoplastic range.

Brush Development for Ship Hull Grooming

2015 ◽  
Author(s):  
Melissa E. Tribou ◽  
Geoffrey Swain
Keyword(s):  
Normal Force ◽  
Environmentally Friendly ◽  
Ship Hull ◽  
Operational Parameters ◽  
Free Condition ◽  
Independent Variables ◽  
Ship Hulls ◽  
Normal Forces ◽  
Different Types ◽  
Environmentally Friendly Method

Ship hull grooming is proposed as an environmentally friendly method of controlling fouling on ship hulls. It is defined as the frequent and gentle cleaning of a coating when the ship is idle to prevent the Establishment of fouling. Prior research by Tribou and Swain has evaluated the effectiveness of different methods and the frequency of grooming on different types of ship hull coatings. It was found that vertical rotating cup style Brushes provided the best method to maintain the coatings in a smooth and fouling free condition. This study investigated brush design and operational parameters in relationship to normal forces imparted by the brushes to the surface. A brush stiffness factor was developed and the independent variables for brush design non-dimensionalized for the normal force. A load cell was used to measure the forces imparted by different brushes and the models were validated using these non-dimensional terms. The knowledge gained by these studies will be used to optimize brush design for the implementation of grooming.

Ultimate Longitudinal Strength of Ship Hulls of Composite Materials

2008 ◽  
Vol 52 (03) ◽  
pp. 184-193
Author(s):  
Nian-Zhong Chen ◽  
C. Guedes Soares
Keyword(s):  
Composite Materials ◽  
Cross Section ◽  
Reaction Force ◽  
Strain Curve ◽  
Ship Hull ◽  
Stiffened Panel ◽  
Average Strain ◽  
Ship Hulls ◽  
Longitudinal Strength ◽  
Load Average

A progressive collapse analysis method is proposed to predict the ultimate longitudinal strength of ship hulls of composite materials. The load-average strain curve derived from a progressive failure nonlinear finite element analysis is adopted for representing the behavior of each stiffened composite panel forming a hull cross section. The bending moment of the ship hull under a prescribed curvature is achieved by integrating the reaction force of each stiffened panel over a hull cross section based on the load-average strain curves. The ultimate longitudinal strength of a ship hull is obtained from the moment-curvature relationship of the ship hull, which is established by imposing progressively increasing curvatures of a hull cross section. An all-composite ship is analyzed as an application.

scholarly journals A Self-Organizing Fuzzy Logic Classifier for Benchmarking Robot-Aided Blasting of Ship Hulls

Sensors ◽  
2020 ◽  
Vol 20 (11) ◽  
pp. 3215 ◽  
Author(s):  
M. A. Viraj J. Muthugala ◽  
Anh Vu Le ◽  
Eduardo Sanchez Cruz ◽  
Mohan Rajesh Elara ◽  
Prabakaran Veerajagadheswar ◽  
...  
Keyword(s):  
Fuzzy Logic ◽  
Robotic System ◽  
Ship Hull ◽  
Integrated System ◽  
Ship Hulls ◽  
System Solution ◽  
Maintenance Work ◽  
Dry Dock ◽  
Self Organizing

Regular dry dock maintenance work on ship hulls is essential for maintaining the efficiency and sustainability of the shipping industry. Hydro blasting is one of the major processes of dry dock maintenance work, where human labor is extensively used. The conventional methods of maintenance work suffer from many shortcomings, and hence robotized solutions have been developed. This paper proposes a novel robotic system that can synthesize a benchmarking map for a previously blasted ship hull. A Self-Organizing Fuzzy logic (SOF) classifier has been developed to benchmark the blasting quality of a ship hull similar to blasting quality categorization done by human experts. Hornbill, a multipurpose inspection and maintenance robot intended for hydro blasting, benchmarking, and painting, has been developed by integrating the proposed SOF classifier. Moreover, an integrated system solution has been developed to improve dry dock maintenance of ship hulls. The proposed SOF classifier can achieve a mean accuracy of 0.9942 with an execution time of 8.42 µs. Realtime experimenting with the proposed robotic system has been conducted on a ship hull. This experiment confirms the ability of the proposed robotic system in synthesizing a benchmarking map that reveals the benchmarking quality of different areas of a previously blasted ship hull. This sort of a benchmarking map would be useful for ensuring the blasting quality as well as performing efficient spot wise reblasting before the painting. Therefore, the proposed robotic system could be utilized for improving the efficiency and quality of hydro blasting work on the ship hull maintenance industry.

scholarly journals Combined Close Range Photogrammetry and Terrestrial Laser Scanning for Ship Hull Modelling

Geosciences ◽  
2019 ◽  
Vol 9 (5) ◽  
pp. 242 ◽  
Author(s):  
Pawel Burdziakowski ◽  
Pawel Tysiac
Keyword(s):  
Laser Scanning ◽  
Measurement Accuracy ◽  
Terrestrial Laser Scanning ◽  
Ship Hull ◽  
Ship Hulls ◽  
Advantages And Disadvantages ◽  
Close Range Photogrammetry ◽  
Market Requirements ◽  
Close Range ◽  
Result Analysis

The paper addresses the fields of combined close-range photogrammetry and terrestrial laser scanning in the light of ship modelling. The authors pointed out precision and measurement accuracy due to their possible complex application for ship hulls inventories. Due to prescribed vitality of every ship structure, it is crucial to prepare documentation to support the vessel processes. The presented methods are directed, combined photogrammetric techniques in ship hull inventory due to submarines. The class of photogrammetry techniques based on high quality photos are supposed to be relevant techniques of the inventories’ purpose. An innovative approach combines these methods with Terrestrial Laser Scanning. The process stages of data acquisition, post-processing, and result analysis are presented and discussed due to market requirements. Advantages and disadvantages of the applied methods are presented.

Cross-Deck Slamming Load Calculation of Trimaran Based on Modified Plate Slamming Theory

2013 ◽  
Vol 477-478 ◽  
pp. 325-329 ◽  
Author(s):  
Hui Long Ren ◽  
Liang Liang Chen ◽  
Guo Qing Feng ◽  
Fang Duan ◽  
Peng Yao Yu
Keyword(s):  
Spatial Distribution ◽  
Calculation Method ◽  
Structural Design ◽  
Peak Pressure ◽  
Added Mass ◽  
Preliminary Design ◽  
Statistical Process ◽  
Load Calculation ◽  
Slamming Load ◽  
Air Cushion

Since slamming loads on connecting bridges of trimaran is very important for the structural design. In this paper, trimaran slamming load calculation method is studied. First added mass caused by typical hull section and wet-deck slamming are investigated, then wet-deck slamming peak pressure are gotten by modified flat slamming theory with considered of the effect of air cushion, the regression equation of which is given by statistical process. Finally, the time-spatial distribution of slamming pressure along the wet-deck is given. This method can provide a reference for the preliminary design and operation of trimaran.

Assessment of LNG Pump Tower Loads

2019 ◽  
Author(s):  
Michael Thome ◽  
Jens Neugebauer ◽  
Ould el Moctar
Keyword(s):  
Structural Design ◽  
Numerical Study ◽  
Three Dimensional ◽  
Navier Stokes ◽  
Impact Loads ◽  
Detached Eddy Simulation ◽  
Morison Equation ◽  
Field Methods ◽  
Delayed Detached Eddy Simulation ◽  
Tower Structure

Abstract The assessment of design loads acting on Liquefied Natural Gas (LNG) pump tower are widely based on Morison equation. However, the Morison equation lacks consideration of transverse flow, impact loads and the interaction between fluid and structure. Studies dealing with a direct simulation of LNG pump tower loads by means of Computational Fluid Dynamics (CFD), which can cover the aforementioned effects, are currently not available. A comparative numerical study on LNG pump tower loads is presented in this paper focusing on the following two questions: Are impact loads relevant for the structural design of LNG pump towers? In which way does the fluid-structure interaction influence the loads? Numerical simulations of the multiphase problem were conducted using field methods. Firstly, Unsteady Reynolds-Averaged Navier-Stokes (URANS) equations, extended by the Volume of Fluid (VoF) approach were used to simulate the flow inside a three-dimensional LNG tank in model scale without tower structure. The results were used to validate the numerical model against model tests. Motion periods and amplitudes were systematically varied. Velocities and accelerations along the positions of the main structural members of the pump tower were extracted and used as input data for load approximations with the Morison equation. Morison equation, URANS and Delayed Detached Eddy Simulation (DDES) computed tower loads were compared. Time histories as well as statistically processed data were used. Global loads acting on the full (with tower structure) and simplified structure (no tower structure, but using Morison equation) are in the same order of magnitude. However, their time evolution is different, especially at peaks, which is considered significant for the structural design.

A Fundamental Study on the Dynamic Response of Hull Girder of Container Ships due to Slamming Load

2017 ◽  
Author(s):  
Yasuhira Yamada ◽  
Kyoko Kameya
Keyword(s):  
Plastic Material ◽  
Bending Moment ◽  
Beam Model ◽  
Time Duration ◽  
Fundamental Study ◽  
Natural Period ◽  
Hull Girder ◽  
Slamming Load ◽  
Explicit Analysis ◽  
Vertical Bending Moment

The purpose of the present study is to fundamentally investigate dynamic hull girder response due to slamming load. A series of time domain FE-simulation is carried out using a non-uniform finite element beam model of a 8000 TEU container ship where slamming load is applied at the bottom of the bow. The ship is modeled by elaso-plastic material with equivalent ultimate strength and strain rate effect is considered. Hull-girder vertical bending moment as well as deformation modes, bending stress are investigated by varying the time duration of the slamming load which is modeled by sinusoidal impulse. In order to obtain post vibration after the first slamming load explicit analysis is adopted instead of implicit analysis with considering gravity and buoyancy. Buoyancy is modeled by inelastic spring elements. It is found from the present study hull girder vertical bending moment is dependent on time duration of slamming load. Especially if time duration is smaller than natural period response bending moment may become smaller than applied bending moment. Moreover effect of inertia at fore and aft is also investigated in detail.

scholarly journals A Numerical Model for Torsion Analysis of Composite Ship Hulls

2012 ◽  
Vol 2012 ◽  
pp. 1-17 ◽  
Author(s):  
Ionel Chirica ◽  
Elena-Felicia Beznea
Keyword(s):  
Composite Material ◽  
Composite Materials ◽  
Numerical Model ◽  
Computer Program ◽  
Ship Hull ◽  
Simplified Model ◽  
Container Ship ◽  
Elastic Analysis ◽  
Ship Hulls ◽  
Composite Ship

A new methodology based on a macroelement model proposed for torsional behaviour of the ship hull made of composite material is proposed in this paper. A computer program has been developed for the elastic analysis of linear torsion. The results are compared with the FEM-based licensed soft COSMOS/M results and measurements on the scale simplified model of a container ship, made of composite materials.

Collapse Analysis of Ship Hull Girder Using Hydro-Elastoplastic Beam Model: Part 2

2020 ◽  
Author(s):  
Han Htoo Htoo Ko ◽  
Akira Tatsumi ◽  
Kazuhiro Iijima ◽  
Masahiko Fujikubo
Keyword(s):  
Cross Sections ◽  
Ship Hull ◽  
Average Stress ◽  
Beam Model ◽  
Fundamental Study ◽  
Hull Girder ◽  
Softening Behavior ◽  
Smith Method ◽  
Collapse Analysis ◽  
Elastoplastic Beam

Abstract In Part 1 study, a time-domain collapse analysis method of ship hull girder was developed and named FE-Smith method. Hull girder was treated as elastoplastic beam model and Smith’s method was used for collapse analysis of cross sections. A concept of average stress-average plastic strain relationship was introduced so that nonlinear collapse behavior of members can be treated as pseudo strain-hardening/softening behavior. Fluid-structure interaction effects were considered. Uniform cross-section beam was assumed as a most fundamental study. In this Part 2, a container ship is taken as subject model. Not only FE-Smith analysis but also non-linear FE analyses using shell model for collapse parts are performed for comparison purpose. Two types of average stress-average strain curves are considered for FE-Smith analysis, i.e. obtained by Gordo-Soares formulae and by shell FEM. Applicability of FE-Smith method is examined comparing with more precise but time-consuming methods. Some parametric studies are also performed. Wave response will be reported in the next papers.

Static and Dynamic Comparisons for the Evaluation of Ship Hull Coatings

2017 ◽  
Vol 51 (2) ◽  
pp. 71-75 ◽  
Author(s):  
Kelli Z. Hunsucker ◽  
J. Travis Hunsucker ◽  
Harrison Gardner ◽  
Geoffrey Swain
Keyword(s):  
Dynamic Testing ◽  
Ship Hull ◽  
Green Macroalgae ◽  
Ship Hulls ◽  
Marine Coatings ◽  
Coating Type ◽  
Fouling Release ◽  
Hydrodynamic Stresses ◽  
Static Conditions ◽  
Static Immersion

AbstractStatic immersion tests are commonly used to evaluate the performance of marine coatings prior to use on ship hulls or for other applications. Although these tests provide valuable data, they do not expose the coatings to the hydrodynamic and fouling conditions that will be present when a ship is underway, thus making it difficult to extrapolate results to ship hull performance. The present study reports data for two commercially available ship hull coatings (one antifouling and one fouling release coating) exposed concurrently to static and dynamic ocean conditions for 4 months. Coatings that were exposed to static conditions developed macrofouling communities dominated by tubeworms, tunicates, and encrusting bryozoans. The coatings subjected to dynamic conditions were fouled only by biofilms and green macroalgae. The results show a difference in coating performance depending on immersion environment (static vs. dynamic) as well as coating type. This highlights the importance of utilizing dynamic testing concurrently with static immersion in coating evaluation to better understand how the system will respond to hydrodynamic stresses. Knowing how a coating performs under various real-world conditions can help drive ship hull management and determine which coating is appropriate for the ship's operational schedule.

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