1、 Guidance Notes on the Structural Direct Analysis for High-Speed Craft GUIDANCE NOTES ON STRUCTURAL DIRECT ANALYSIS FOR HIGH-SPEED CRAFT APRIL 2011 (Updated February 2014 see next page) American Bureau of Shipping Incorporated by Act of Legislature of the State of New York 1862 Copyright 2011 Americ
2、an Bureau of Shipping ABS Plaza 16855 Northchase Drive Houston, TX 77060 USA Updates February 2014 consolidation includes: April 2011 version plus Corrigenda/Editorials ABSGUIDANCE NOTES ON STRUCTURAL DIRECT ANALYSIS FOR HIGH-SPEED CRAFT .2011 iii Foreword Foreword These Guidance Notes are an extens
3、ive revision of and supersede the ABS Guidance Notes on Dynamic Load Approach and Direct Analysis for High Speed Craft (February 2003). This revision is effective 1 April 2011. These Guidance Notes provide information about the analysis procedure for Structural Direct Analysis, which is available to
4、 assess the strength of high-speed craft and high-speed naval craft. In addition, they provide guidance to be followed when submitting required direct analyses or such analyses submitted in place of standard calculations. In the text herein, this document is referred to as “these Guidance Notes”. Se
5、ctions 1-1-3 and 1-2-2 of the ABS Rules for Conditions of Classification High-Speed Craft (Part 1) contains descriptions of the various basic and optional classification notations available for high-speed craft. The requirements for Direct Analyses are specified in Section 3-1-3 of the ABS Rules for
6、 Building and Classing High-Speed Craft (HSC Rules). Sections 1-1-3 and 1-3-2 of the ABS Rules for Conditions of Classification High-Speed Craft (Part 1) contains descriptions of the various basic and optional classification notations available for high-speed naval craft. The requirements for Direct
7、 Analyses are specified in Section 3-1-3 of the ABS Guide for Building and Classing High-Speed Naval Craft (HSNC Guide). Users of these Guidance Notes are welcomed to contact ABS with any questions or comments concerning these Guidance Notes. Users are advised to check periodically with ABS or by vi
8、siting the Rules and Guides section of the ABS website (www.eagle.org) that their version of these Guidance Notes is current. iv ABSGUIDANCE NOTES ON STRUCTURAL DIRECT ANALYSIS FOR HIGH-SPEED CRAFT .2011 Table of Contents GUIDANCE NOTES ON STRUCTURAL DIRECT ANALYSIS FOR HIGH-SPEED CRAFT CONTENTS SEC
9、TION 1 Introduction 1 1 Background . 1 1.1 Types of High-Speed Craft 1 1.3 Current Regulations on High-Speed Craft . 1 1.5 Naval Requirements 1 3 The Concept and Benefits of Structural Direct Analysis (SDA) 2 5 Types of Structural Assessments . 2 5.1 Strength . 2 5.3 Fatigue . 3 5.5 Vibration 3 5.7
10、Hydroelastic Considerations 3 7 Scope and Overview . 3 FIGURE 1 Overview of the Structural Direct Analysis for High-Speed Craft 5 FIGURE 2 Schematic of the Structural Direct Analysis Procedure 6 SECTION 2 Loading Conditions and Load Cases . 7 1 Loading Conditions . 7 3 Dominant Load Parameters (DLPs
11、) 7 3.1 Mono-hull High-Speed Craft 7 3.3 Multi-hull High-Speed Craft 7 5 Load Cases . 8 5.1 Basic Considerations . 8 5.3 Selection of Load Cases 8 7 Other Accompanying Load Components 9 9 Miscellaneous Loads 9 SECTION 3 Environmental Conditions . 10 1 Basic Considerations 10 3 Environmental Data 10
12、3.1 General 10 3.3 Special Wave Data Needs . 10 ABSGUIDANCE NOTES ON STRUCTURAL DIRECT ANALYSIS FOR HIGH-SPEED CRAFT .2011 v SECTION 4 Analysis of Ship Motions, Wave Loads, and Extreme Values 11 1 Overview . 11 3 Still-water Loads . 11 5 Essential Features of Spectral-based Analysis of Motions and L
13、oads 11 5.1 General Modeling Considerations . 11 5.3 Diffraction-Radiation Methods . 11 5.5 Panel Model Development 11 5.7 Ship Motion and Wave Load Response Amplitude Operators . 12 7 Extreme Values Analysis 12 SECTION 5 Equivalent Design Waves 13 1 General . 13 3 Equivalent Wave Amplitude 13 5 Wav
14、e Frequency and Heading . 13 FIGURE 1 Equivalent Wave Amplitude 14 SECTION 6 Nonlinear Seakeeping Analysis 15 1 General . 15 3 Nonlinear Seakeeping Analysis 15 5 Modeling Consideration 15 5.1 Mathematical Model 15 5.3 Numerical Course-keeping Model . 16 7 Nonlinear Instantaneous Load Components 16 S
15、ECTION 7 External Pressure . 17 1 General . 17 3 External Pressure Components 17 5 Pressures Accompanying the Dominant Load Component and Their Distribution . 17 7 Pressure Loading on the FE Model 17 FIGURE 1 Instantaneous Pressure Distribution on FE Model of Multi-hull 17 SECTION 8 Slamming Loads 1
16、8 1 General . 18 3 Slamming Analysis 18 5 Whipping Analysis . 19 FIGURE 1 Instantaneous Bottom Slamming Pressure on a High-Speed Mono-hull 19 FIGURE 2 Instantaneous Wet-Deck Slamming Pressure on a High-Speed Multi-hull 19 FIGURE 3 Sample Mode Shapes in Vertical Mode 20 vi ABSGUIDANCE NOTES ON STRUCT
17、URAL DIRECT ANALYSIS FOR HIGH-SPEED CRAFT .2011 SECTION 9 Internal Tank Pressure . 21 1 General . 21 3 Pressure Components 21 5 Local Acceleration at the CG of Tank Content . 22 7 Simultaneously-acting Tank Pressure 22 SECTION 10 Acceleration and Motion-induced Loads . 23 1 General . 23 3 Local Acce
18、leration . 23 5 Inertial Loads in the Structural FE Model 23 5.1 Static Load . 23 5.3 Dynamic Load 23 7 Simultaneously-acting Loads on Lightship Structure and Equipment . 24 SECTION 11 Loading for Global Finite Element Model . 25 1 General . 25 3 Equilibrium Check . 25 5 General Modeling Considerati
19、ons 25 SECTION 12 Analysis of the Hull Structure . 26 1 General . 26 3 Structural Members . 26 5 3-D Global Modeling . 26 7 Analyses of Local Structure 27 SECTION 13 Acceptance Criteria 29 1 General . 29 3 Yielding . 29 5 Design Global Hull Girder Stresses 30 7 Buckling and Ultimate Strength . 31 SE
20、CTION 14 Additional Considerations . 32 1 General Considerations 32 3 Global Springing Response 32 5 Local Hydroelastic Response . 32 7 Scale Model Testing Using Segmented Flexible Model . 32 ABSGUIDANCE NOTES ON STRUCTURAL DIRECT ANALYSIS FOR HIGH-SPEED CRAFT .2011 1 Section 1: Introduction SECTION
21、 1 Introduction 1 Background 1.1 Types of High-Speed Craft The size, speed, and installed power of high-speed craft and/or high-speed naval craft have steadily increased. Most of the craft built during the last decade may be categorized into the following three groups: Mono-hulls Catamarans Trimaran
22、s A clear trend in the above types of high-speed craft is a continual increase in the length and complexity of craft that are being built. Most early high-speed craft were of the planing and semi-planing type, while the later and most recent builds have been shifting into the domain of the semi-disp
23、lacement type. Although this has given rise to new technological challenges, it has also made it possible to apply well-established methods developed for conventional vessels to the design and analysis of these high-speed craft. Distinct from the design criteria used for planing or dynamically-suppo
24、rted craft, where hydrodynamic impact governs the structural loads, these changes have brought about a shift of emphasis in load types and combinations, with global hull girder loads playing a more significant role than before. The trend towards larger craft sizes has also seen an increase in the ra
25、nge of different concepts such as multi-hulls and other novel designs. 1.3 Current Regulations on High-Speed Craft The International Code of Safety for High-Speed Craft (IMO, 2000) is the only IMO document addressing high-speed craft. It applies to all types of craft operating internationally, but C
26、hapter 3 of the IMO document deals with structures only in a basic manner. The requirements for direct analyses to be performed, based on craft length, speed and other special features, however, are stipulated in the following documents: i) ABS Rules for Building and Classing High-Speed Craft (HSC R
27、ules) ii) ABS Rules for Building and Classing High-Speed Naval Craft (HSNC Rules) 1.5 Naval Requirements ABS, with the assistance of the U.S. Navy, has developed the HSNC Rules for high-speed craft for a range of operations. Naval requirements specify that high-speed craft are to be designed to tech
28、nical standards that will provide the safety and operational effectiveness required for the intended mission. Currently, most high-speed craft are designed, built or classed for restricted service. Use of any high-speed craft with a mission that requires unrestricted open-ocean operations should be
29、evaluated for safety using the requirements of the HSNC Rules, especially if initially designed or classed for restricted service. This safety evaluation will invariably require a structural assessment that involves direct analysis designed to identify the operational limits. Section 1 Introduction
30、2 ABSGUIDANCE NOTES ON STRUCTURAL DIRECT ANALYSIS FOR HIGH-SPEED CRAFT .2011 3 The Concept and Benefits of Structural Direct Analysis (SDA) Direct analysis for high-speed craft provides enhanced structural evaluation capabilities to assess the adequacy of a structural design. In principle, a minimum
31、 requirement of direct analysis is that the preliminary design of the structure be in accordance with the HSNC Rules criteria. Should the direct analysis results indicate the need to increase basic scantlings, this increase is to be accomplished to meet the acceptance criteria of the direct analysis
32、. If, however, these Guidance Notes are being used for alternative structural design in consultation with ABS and Naval Administration, scantling reductions justified by the results of the analysis may be considered. The structural design portions of the HSNC Rules (i.e., especially Part 3, Chapter
33、2) are intended to provide the basis for a preliminary step-by-step design procedure of the structure of a high-speed craft. On the other hand, direct analysis is a process that emphasizes completeness and realism in both the extent of the structure modeled and the crafts loading conditions consider
34、ed. The modeling and analysis process utilizes multiple levels that start with a global model of the structure. Results of each previous level of analysis are used to establish: i) Areas of the structure requiring finer (more detailed) modeling and analysis ii) The local loading to be re-imposed and
35、 the boundary conditions to be imposed on the finer model Central to this direct analysis method is the use of an advanced computational tool based upon linear and/or nonlinear seakeeping theory for calculating ship motions and wave-induced load effects in design wave conditions that best characteri
36、ze the environmental and operating conditions of the craft. The enhanced realism provided by the direct analysis approach has benefits that are of added value to the overall structural safety evaluation based on the attributes mentioned above. Additionally, the knowledge of structural behavior gaine
37、d through this analysis is very useful in realistically evaluating and developing inspection and maintenance plans especially for aluminum and FRP hulls. Another potentially valuable benefit of direct analysis is that it provides access to a comprehensive structural evaluation model, which may be re
38、adily employed in the event of emergency situations that might arise during the service life of the craft, such as structural damage, repairs or modifications; ocean transit to a repair facility, or redeployment to another operating route. 5 Types of Structural Assessments 5.1 Strength In general, s
39、tructural assessments of high-speed craft will require the application of direct analysis methods, as their preliminary designs will invariably be based on craft service records or previous experience. This is discussed in detail in these Guidance Notes. Global wave-induced load effects on high-spee
40、d craft are not significantly affected by elastic deformations in most cases because the rigid body motions are dominant. In this case, the external impact loads (generally called slamming loads), such as those due to bottom slamming, are determined through motion analysis. The slamming loads can th
41、en be applied to the structure to obtain the elastic hull girder responses, (generally called whipping responses). For the enhanced structural assessments of modern high-speed craft, the slamming and whipping loads, in addition to the traditional wave-induced loads, are to be considered in the deriv
42、ation of structural responses. An addition to direct analysis would be to derive structural load effects from physically scaled model tests. Brief guidance on models used for this task is discussed in Subsection 14/7. Rigid models may be adequate for direct measurements of wave-induced ship motions
43、and slamming pressures, which are not significantly affected by elastic deformations. For direct measurement of wave induced springing and whipping loads, where flexibility and dynamics of the hull structure are important, use of a flexible model, dynamically scaled to represent hull girder structur
44、al characteristics, is recommended. This can be realized using either a continuous elastic model or a segmented model with elastic backbones. Section 1 Introduction ABSGUIDANCE NOTES ON STRUCTURAL DIRECT ANALYSIS FOR HIGH-SPEED CRAFT .2011 3 5.3 Fatigue The main factors that contribute to general fa
45、tigue problems are material used for construction, welding methods, and connection details, along with the stress range and the number of stress cycles. High-speed craft are usually designed for optimized structural weight, which results in increased flexibility of the hull. The combination of the i
46、ncreased hull flexibility and the higher encounter frequency due to high operational speed would tend to accelerate fatigue damage. While fatigue analysis is not a condition for classing high-speed craft, a fatigue assessment is recommended, especially for craft with novel hull forms. 5.5 Vibration
47、Generally, vibration analysis is not a requirement for classing high-speed craft. However, in some high-speed craft designs subject to increased flexibility of structures, especially those involving water-jet propulsion, flow-induced vibrations could significantly contribute to structural responses
48、that result in accelerated fatigue damage. The methods for dynamic response analysis developed for conventional vessels can be applied to vibration problems on high-speed craft. However, when applicable, the flexible stiffness and significantly different structural damping characteristics of FRP hul
49、ls (relative to steel hulls) must be taken into account. It is recommended that these methods be utilized to investigate vibration-induced fatigue of high-speed craft fitted with water-jet propulsion. 5.7 Hydroelastic Considerations In some cases, especially in multi-hull craft made of lightweight structural materials such as aluminum, there is true interaction of loads and responses, in which case they cannot be treated separately. This is particularly the case when the craft operates at high speeds which are associated with high encounter frequencies resulting in larg
