Download or read book Linear Structural Stress Analysis of a Hull Girder Penetration and a Short Longitudinal Bulkhead Using Finite Element Modeling written by Gregg W. Baumann and published by . This book was released on 1997 with total page 49 pages. Available in PDF, EPUB and Kindle. Book excerpt: The objective of this study is to investigate structural shadow zones encountered in shipbuilding design using the I-DEAS (Integrated Design Engineering Analysis Software) software. The term 'shadow zone' refers to areas of low stress concentrations that are caused by lines of stress bending around structural discontinuities. Two ship design situations frequently encountered that result in shadow zones are hull girder penetrations and short structural longitudinal bulkheads. In both of these situations, a long-used rule of thumb is to construct a line with a slope of 1:4 originating from the. discontinuity that encompasses the area of low stress. The material within this line is then considered ineffective when computing the section modulus. This can prove to be expensive. However, powerful finite element analysis software is readily available that can analyze the shadow zones in greater detail and possibly minimize the area considered ineffective. This study uses the I-DEAS software to develop finite element models of the cited design situations for a U.S. Navy Frigate, FFG-7 class of ship. It conducts a static structural linear analysis of the ship balanced on a trochoidal wave of height 1.1 VL. The results generated in this study validate the rule of thumb in both situations.

Download or read book Torsion and Shear Stresses in Ships written by Mohamed Shama and published by Springer Science & Business Media. This book was released on 2010-09-27 with total page 288 pages. Available in PDF, EPUB and Kindle. Book excerpt: In the last few decades, much research work was conducted to improve ship structure analysis and design. Most of the efforts were directed to improve the strength of hull girder and to use the method of finite element analysis more efficiently and effectively. Because of the high degree of complexity of ship structures the interaction between hull girder strength and local strength require special attention. The complex system of stresses could produce unacceptable deformations and high values of equivalent stresses. This book covers an area of ship structure analysis and design that has not been exhaustively covered by other books on ship structures in a simple form. It presents the basic concepts of the methods and procedures required to calculate torsion and shear stresses in ship structures. Moreover, it is enhanced with a set of some solved and unsolved problems, very useful for students of naval and marine engineering.

Download or read book Practical Design of Ships and Other Floating Structures written by You-Sheng Wu and published by Elsevier. This book was released on 2001-08-22 with total page 721 pages. Available in PDF, EPUB and Kindle. Book excerpt: This proceedings contains the papers presented at The 8th International Symposium on Practical Design of Ships and Other Floating Structures held in China in September 2001 - the first PRADS of the 21st Century. The overall aim of PRADS symposia is to advance the design of ships and other floating structures as a professional discipline and science by exchanging knowledge and promoting discussion of relevant topics in the fields of naval architecture and marine and offshore engineering. In line with the aim, in welcoming the new era, this Symposium is intended to increase international co-operation and give a momentum for the new development of design and production technology of ships and other floating structures for efficiency, economy, safety, and environmental production. The main themes of this Symposium are Design Synthesis, Production, Hydrodynamics, Structures and Materials of Ships and Floating Systems. Proposals for over 270 papers from 26 countries and regions within the themes were received for PRADS 2001, and about 170 papers were accepted for presentation at the symposium. With the high quality of the proposed papers the Local Organising Committee had a difficult task to make a balanced selection and to control the total number of papers for fitting into the allocated time schedule approved by the Standing Committee of PRADS. Volume I covers design synthesis, production and part of hydrodynamics. Volume II contains the rest of hydrodynamics, and structures and materials.

Download or read book Long Term Properties and Combinations of Stochastic Hull Girder Loads on Ships written by Martin Petricic and published by . This book was released on 2012 with total page 380 pages. Available in PDF, EPUB and Kindle. Book excerpt: This dissertation presents a novel simulation-based method which provides a consistent and rational framework for long-term hull girder load combination analysis. During its lifetime, which is typically a period of 20 to 25 years (long-term), a ship structure will be subjected to many different dynamic loads. Most of them are caused by very harsh and constantly changing ocean environment and they are random. Therefore, methods of classical statistics and time series analysis have to be applied in order to analyze the structural response to these loads. Many of currently available methods rely on the assumption of weak stationarity of the wave elevation process. This assumption usually holds for a period of up to three hours (short-term) and these methods cannot be used to analyze long-term statistical properties of the loads and their combinations. Long-term methods that can handle the non-stationarity of the wave elevation process often involve many assumptions and require the knowledge of short-term probability density functions of loads or their linear and nonlinear combinations as well as the joint probability density functions of multiple random variables having an impact on these loads. The method presented in this dissertation is based on efficient multi-voyage simulations of properly correlated hull-girder loads. It relies on a comprehensive statistical model from which nine relevant variables that have an impact on the hull-girder load spectral densities can be simulated or sampled using the rejection sampling technique. These nine variables are: significant wave height, zero crossing wave period, prevailing wind and wave direction, ship's relative heading with respect to waves, ship's location, season of the year, ship's speed, voluntary and involuntary speed reductions in severe sea states and the ship's loading condition. The rejection sampling can significantly decrease the number of sea state and operational profile combinations that have to be considered in the long-term analysis. Non-stationary wave elevations during the ship's entire life are treated as a sequence of different short-term weakly stationary Gaussian stochastic processes, each of which is two hours long. Hull girder sectional loads during each short-term period are efficiently simulated from the load spectral densities taking into account their relative phase differences. Multi-voyage long time series of various load combinations, including the nonlinear ones, are obtained and their correlation structure and other statistical properties are examined. Nonlinearities in the vertical bending moment (VBM) and the hydroelastic response of the ship in the form of springing and whipping are also included in the simulation. Slamming events are determined from the linear motion analysis and the subsequent whipping response of the structure is simulated in time domain using a combination of trapezoidal and finite element methods to numerically solve dynamic Timoshenko beam problem. Nonlinearities have a significant effect on the simulation time. However, neglecting the super and subharmonics of small amplitudes significantly reduces simulation time while retaining reasonable accuracy. This makes it possible to use simulation even at the initial stages of ship design process. Although some assumptions are necessary when calculating the loads on a ship structure, the main advantages of the simulation method are that it doesn't make assumptions about the statistical nature of these loads, and it enables nonlinear combinations of linear and nonlinear loads even when their theoretical short-term probability distributions don't exist. Three different ship types; container ship, tanker and bulk carrier, navigating in the North Atlantic, North Pacific, and between Europe and Asia are used to demonstrate the capabilities of the simulation method in three different areas of hull-girder structural analysis: load combinations, extreme value, and fatigue analysis. Correlation structure between all six sectional loads is examined as well as some linear and nonlinear load combinations. The effect of ship route, damping ratio, slamming extent, hydroelasticity, and nonlinearities on the long-term exceedance probabilities of the VBM are also examined. Finally, the fatigue behavior of a selected container ship is studied on all three routes. The total fatigue damage caused by the vertical bending stresses is separated into damage caused by low- and high-frequency VBM components. The high-frequency part is further divided into the damage caused by linear springing, nonlinearities (including nonlinear springing), and whipping. Linear springing does not have a significant effect on the long-term exceedance probabilities of the VBM, but has a significant effect on the fatigue life of the structure. Nonlinearities, on the other hand, have a significant effect on the exceedance probabilities of the VBM and its extreme values as well as on the fatigue life of the structure. Damping ratio has a relatively significant effect on the nonlinear component of the VBM, but does not significantly affect the long-term exceedance probabilities of the total VBM since the damping effects are only pronounced in moderate sea states with steep waves. Nonlinearities are also largest in these sea states. Whipping alone has a relatively small effect on the exceedance probabilities of the VBM and also on the fatigue life of the post-Panamax container ship analyzed in this work. This is attributed to the lack of strong positive correlation in time between whipping peaks and the peaks of the global VBM. More research is needed on studying the phase relationship between these peaks for different ship types, sizes and routes. Simulation method results agree very well with the full-scale measurements taken on board ships in service in terms of linear and nonlinear VBM exceedance probabilities and fatigue life predictions. For ships studied in this work, the simulation outperforms some existing and commonly used long-term methods in terms of accuracy.

Download or read book Application of the Finite Element Method to Multihull Ship Structural Analysis written by Paris Genalis and published by . This book was released on 1972 with total page 38 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Effect of Welding Residual Stress and Distortion on Ship Hull Structural Performance written by Liam Gannon and published by . This book was released on 2011 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Finite Element Stress Analysis of Midlife Refit Penetrations in QUEST Bottom Structures written by and published by . This book was released on 1997 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: This technical memorandum describes the finite element stress analysis of proposed major penetrations in the midship bottom structure of CFAV QUEST. This work was undertaken for two purposes. The first objective was to determine if the proposed modifications would have any detrimental effect on the structural integrity of QUEST's hull structure. The second objective was to demonstrate and validate the new capabilities in the global-detail finite element analysis code VAST DSA (Vibration And STrength, Detail Stress Analysis) developed as part of DREA's Ship Structures project. The results indicated that the penetrations will cause significant increases in stress but these values are still well within acceptable design limits. VAST DSA proved to be an efficient process for undertaking the complex global-detail top/down finite element analysis. This complex analysis was undertaken within a reasonable time frame which will be further decreased in future with improvements in data management and model generation.

Download or read book A Ship Structural Research Survey and Program written by R. Glasfeld and published by . This book was released on 1962 with total page 90 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Structural Analysis of SLICE Hulls written by Martin Rodriguez and published by . This book was released on 1995 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: The overall objective of this work is to investigate the structural aspects of a novel hull design called SLICE, developed by Lockheed under contract to Office of Naval Research. The program MAESTRO (The Method for Analysis, Evaluation, and Structural Optimization), which is a finite element-PC based analysis tool designed to facilitate the modeling of ocean engineering structures was used for the investigation. A three dimensional model of the SLICE structure was exposed to six different load cases. Each load case represents a different wave to hull angle interaction. Three cases were subjected to sea state 5, and the last three cases were exposed to sea state 8. Since the SLICE lacks the continuous underwater hull that offers the large longitudinally rigidity for the SWATH, its longitudinal structure is of concern and the transverse structure becomes a concern with the possibility of severe torsional loads midships on the box. The following concerns are addressed in this work: (1). Compare and verify the SLICE structure's reactions to the different load cases with known SWATH reactions. (2). Verify if the beam seas which provide the maximum prying side force in the SWATH also affect the SLICE structure similarly. (3). Validate the program MAESTRO by varying structural parameter for the "box" of the SLICE structure and then exposing it to the same load cases and comparing to the baseline model.

Download or read book Structural Analysis of SLICE Hulls written by Martin Rodriguez and published by . This book was released on 1995 with total page 107 pages. Available in PDF, EPUB and Kindle. Book excerpt: The overall objective of this work is to investigate the structural aspects of a novel hull design called SLICE, developed by Lockheed under contract to Office of Naval Research. The program MAESTRO (The Method for Analysis, Evaluation, and Structural Optimization), which is a finite element-PC based analysis tool designed to facilitate the modeling of ocean engineering structures was used for the investigation. A three dimensional model of the SLICE structure was exposed to six different load cases. Each load case represents a different wave to hull angle interaction. Three cases were subjected to sea state 5, and the last three cases were exposed to sea state 8. Since the SLICE lacks the continuous underwater hull that offers the large longitudinally rigidity for the SWATH, its longitudinal structure is of concern and the transverse structure becomes a concern with the possibility of severe torsional loads midships on the box. The following concerns are addressed in this work: (1). Compare and verify the SLICE structure's reactions to the different load cases with known SWATH reactions. (2). Verify if the beam seas which provide the maximum prying side force in the SWATH also affect the SLICE structure similarly. (3). Validate the program MAESTRO by varying structural parameter for the "box" of the SLICE structure and then exposing it to the same load cases and comparing to the baseline model.

Download or read book Hull Girder Ultimate Strength and Fracture Toughness of Damaged Marine Structures written by Özgür Özgüç and published by . This book was released on 2006 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: This thesis addresses the structural performance of the hull structure of a vessel in extreme response state of a combined loading consisting of vertical and horizontal moments for intact and damaged conditions, where fracture mechanics of ships with large damage openings are investigated in great detail. The motivation for conducting this research task is the importance of the ultimate and post-ultimate strength in relation to the reliability of intact as well as damaged vessels. Moreover, in an emergency situation, knowledge of the structural capacity of the vessel in whatever damaged or intact condition it may be in, is crucial to allow for a rational decision to be made regarding possible salvage, or at worst disembarkation of the crew, in the interest of safety for human life, environmental protection, and capital investment. To facilitate these requirements, the overall objective of the present research therefore becomes to build a rapid computer based analysis tool for calculation of the ultimate and post-ultimate capacity of the hull girder in intact and damaged states of combined bending moment loading. Then, to verify the accuracy of the procedure developed against available experimental results and by comparison with other theoretical results. To meet this objective essentially requires five sub-tasks to be completed. Hence, the scope of the work to be carried out becomes - A study of literature for the available methods usable to evaluate the ultimate and post-ultimate capacity of the stiffened plates - Developing the new simple design equations for predicting the ultimate strength of stiffened plates with imperfections in the form of imperfections, where a non-linear finite element method is employed on a wide range of typical ship panel geometries. The new simplified analytical method must be generalized to deal with such combined load cases. The performance of the proposed equations must be also verified by experimental results. - Establishing a rapid computer code based on simplified formulas developed for calculation of the ultimate capacity of the hull girder. This program must be capable of considering initial imperfections and must be compared with other theoretical approaches developed. - The influence of the coupled bending moment on the intact & damaged ship structures must be extensively investigated. The rational interaction equations must be developed, which based on the extensive ship types. - Accidents such as collision, grounding and explosions occur and can have major consequences to the ship structure. The effect of such large damages on the hull girder must be assessed under time pressure. The recent accident with the PRESTIGE shows the importance of being able to reliably assess the longitudinal strength of damaged vessels. The procedures for this must be developed. A major drawback is lack of knowledge of the failure mechanism that may play a role in such circumstances. Therefore, the fracture mechanism of damaged ships is essential. Key effects must be identified and if possible, included in the procedure. When these five points have been addressed, and the objectives solved, all that is needed for the development of a computer code for the ultimate strength. The remaining final task will thus to be benchmark the code against available experimental results and other theoretical methods.

Download or read book The Maritime Engineering Reference Book written by Anthony F. Molland and published by Elsevier. This book was released on 2011-10-13 with total page 921 pages. Available in PDF, EPUB and Kindle. Book excerpt: The Maritime Engineering Reference Book is a one-stop source for engineers involved in marine engineering and naval architecture. In this essential reference, Anthony F. Molland has brought together the work of a number of the world's leading writers in the field to create an inclusive volume for a wide audience of marine engineers, naval architects and those involved in marine operations, insurance and other related fields. Coverage ranges from the basics to more advanced topics in ship design, construction and operation. All the key areas are covered, including ship flotation and stability, ship structures, propulsion, seakeeping and maneuvering. The marine environment and maritime safety are explored as well as new technologies, such as computer aided ship design and remotely operated vehicles (ROVs).Facts, figures and data from world-leading experts makes this an invaluable ready-reference for those involved in the field of maritime engineering.Professor A.F. Molland, BSc, MSc, PhD, CEng, FRINA. is Emeritus Professor of Ship Design at the University of Southampton, UK. He has lectured ship design and operation for many years. He has carried out extensive research and published widely on ship design and various aspects of ship hydrodynamics. * A comprehensive overview from best-selling authors including Bryan Barrass, Rawson and Tupper, and David Eyres* Covers basic and advanced material on marine engineering and Naval Architecture topics* Have key facts, figures and data to hand in one complete reference book

Download or read book Stress and Vibration Analysis of the SWATH Vessel Frederick G Creed written by and published by . This book was released on 1992 with total page 60 pages. Available in PDF, EPUB and Kindle. Book excerpt: This report describes the work performed in application of finite element methods to a structural evaluation of a small waterplane area twin hull (SWATH) vessel, the Frederick G. Creed. The evaluation consisted of a stress analysis of a major bulkhead and determination of the global natural frequencies of the vessel. The analysis was performed by the finite element codes MAESTRO and VAST, using the prescribed displacement method (top down approach). The vibration analysis also used both MAESTRO and VAST. The results presented in the report include the maximum von Mises stress and maximum first principal stress at the bulkhead, the frequencies of the lower hull due to lateral vibration, and the vibration frequencies of the main deck and the cabins.

Download or read book Finite Element Analysis of Anchored Bulkhead Behavior written by Robert Lund Sogge and published by . This book was released on 1974 with total page 246 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Advanced finite element modelling for hull structure analysis written by Alla Geiro and published by . This book was released on 1999 with total page 260 pages. Available in PDF, EPUB and Kindle. Book excerpt: Includes bibliographical references.

Download or read book Finite Element Analysis of Longitudinal Glulam Timber Deck and Glulam Timber Girder Bridges written by Anil Varughese Kurian and published by . This book was released on 2001 with total page 354 pages. Available in PDF, EPUB and Kindle. Book excerpt: This report presents finite element models of longitudinal glulam timber deck and glulam timber girder bridges. Programs were developed using the ANSYS Parametric Design Language (APDL) that is available in ANSYS finite element commercial software, to be used as analytical tools in the assessment of these timber bridges. Six case studies were undertaken to validate the models developed and corroborate the results, obtained using the programs, with experimental observations.

Download or read book Ship Structural Analysis and Design written by Owen F. Hughes and published by . This book was released on 2010 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: For a structure as large ans as complex as a ship there are three levels of structural design, the second and most central of which is the subject of this book. Rationally-based design is design from first principles using the tools of modern engineering science: computer and the methods of structural analysis and optimization which computers have made possible. Thus, the rationally-based approach is ideally suited for preliminary structural design, and it is this approach and this level of design that is the subject of this book.