1、 GUIDANCE NOTES ON ICE CLASS MARCH 2005 (Updated February 2014 see next page) American Bureau of Shipping Incorporated by Act of Legislature of the State of New York 1862 Copyright 2005 American Bureau of Shipping ABS Plaza 16855 Northchase Drive Houston, TX 77060 USA Updates February 2014 consolida
2、tion includes: October 2008 version plus Corrigenda/Editorials October 2008 consolidation includes: March 2005 version plus Corrigenda/Editorials ABSGUIDANCE NOTES ON ICE CLASS .2005 i Foreword Foreword The purpose of these Guidance Notes is to provide ship designers with clear guidance on alternati
3、ve design procedures for hull side structures, on alternative methods for determination of power requirements, and on procedures for propeller strength assessment based on the Finite Element Method for Baltic Ice Class Vessels. Chapter 1 provides a procedure on ice strengthening designs using direct
4、 calculation approaches. Chapter 2 provides a procedure for the calculation of power requirement for ice class vessels. Chapter 3 provides a procedure for the strength analysis of propellers for ice class vessels. This document is referred to herein as “these Guidance Notes” and its issue date is 31
5、 March 2005. Users of these Guidance Notes are encouraged to contact ABS with any questions or comments concerning these Guidance Notes. Users are advised to check with ABS to ensure that this version of these Guidance Notes is current. These Guidance Notes supersede the 2004 ABS Guidance Notes on N
6、onlinear Finite Element Analysis of Side Structures Subject to Ice Loads. This Page Intentionally Left Blank ABSGUIDANCE NOTES ON ICE CLASS .2005 iii Table of Contents GUIDANCE NOTES ON ICE CLASS CONTENTS CHAPTER 1 Ice Strengthening Using Direct Calculation Approaches 1 Section 1 Introduction .5 Sec
7、tion 2 Procedure for Ice Strengthening Side Structures Using Nonlinear FEM7 Section 3 References11 Appendix 1 Nonlinear FE Model 13 Appendix 2 Example of Nonlinear FEM Applications 21 Appendix 3 The Finnish Maritime Administration (FMA) “Tentative Note for Application of Direct Calculation Methods f
8、or Longitudinally Framed Hull Structure”, 30 June 2003 .29 CHAPTER 2 Power Requirement for Ice Class .33 Section 1 Introduction .35 Section 2 Alternative Methods to Calculate KC37 Section 3 Alternative Methods to Determine Rch(Resistance in Brash Ice)41 Section 4 References45 Appendix 1 Examples 47
9、CHAPTER 3 Propeller Strength Assessment49 Section 1 General Design Basis .51 Section 2 Ice Load Determination.53 Section 3 Blade Stress Analysis Procedure .61 Section 4 Summary of Propeller Strength Assessment Procedure .67 Section 5 References69 Appendix 1 Illustrative Example.71 This Page Intentio
10、nally Left Blank ABSGUIDANCE NOTES ON ICE CLASS .2005 1 Chapter 1: Ice Strengthening Using Direct Calculation Approaches CHAPTER 1 Ice Strengthening Using Direct Calculation Approaches CONTENTS SECTION 1 Introduction 5 1 Background5 2 Purpose5 3 Applications6 4 Key Components of these Guidance Notes
11、 6 5 Contents of this Chapter 6 SECTION 2 Procedure for Ice Strengthening Side Structures Using Nonlinear FEM7 1 Design of Side Structures 7 2 Step 1: FSICR Design7 3 Step 2: FMA Interim Design.8 4 Step 3: Alternative Design for Side Longitudinals .8 4.1 FEM Modeling.8 4.2 Ice Load on Side Longitudi
12、nals .8 4.3 Acceptance Criteria.8 5 Step 4: Alternative Design of Side Shell9 5.1 FEM Modeling.9 5.2 Ice Load on Side Shell 9 5.3 Acceptance Criteria.9 5.4 Abrasion/Corrosion .9 TABLE 1 Steps in Ice Strengthening of Side Structures.7 SECTION 3 References11 APPENDIX 1 Nonlinear FE Model13 1 Structura
13、l Idealization 13 1.1 Introduction .13 1.2 Extent of Structural Modeling 13 1.3 FEM Elements.13 1.4 Mesh Size .14 2 Material Model .15 2 ABSGUIDANCE NOTES ON ICE CLASS .2005 3 Boundary Conditions15 4 Line Load on Side Longitudinals16 5 Patch Load on Side Shell Plate .17 6 FEM Solution .18 6.1 Increm
14、ental Solution18 6.2 Convergence.18 7 Nonlinear FEM Theory and Software 18 7.1 Material Nonlinearity18 7.2 Geometrical Nonlinearity .19 7.3 Incremental Solutions19 7.4 Convergence Criteria 19 7.5 Commercial FEM package 19 TABLE 1 Boundary Conditions for FE Model16 FIGURE 1 FE Model Extent (Inner Ski
15、n Removed for Clarity)14 FIGURE 2 Mesh of Side Longitudinal and Bracket at Connection to Web Frame.15 FIGURE 3 Boundary Conditions for FE Model16 FIGURE 4 Ice Load as Line Load on Side Longitudinal17 FIGURE 5 Ice Patch Load Applied on Side Shell Plate 17 APPENDIX 2 Example of Nonlinear FEM Applicati
16、ons . 21 1 Problem Definition21 2 FEM Modeling21 3 Ice Load .23 4 Analysis Results.23 5 Alternative Design25 6 Example of Alternative Side Shell Design .26 FIGURE 1 FE Model22 FIGURE 2 Load Path (Loading and Unloading Phases).23 FIGURE 3 Von Mises Stress Contour .24 FIGURE 4 Pressure vs. Deflection
17、(Loading and Unloading Phases)25 FIGURE 5 Pressure vs. Deflection of Different Designs .25 FIGURE 6 Deformed Side Structure View from Outside26 FIGURE 7 Deformed Side Structure View from Inside.26 FIGURE 8 Pressure vs. Deflection of Side Shell Plate .27 ABSGUIDANCE NOTES ON ICE CLASS .2005 3 APPENDI
18、X 3 The Finnish Maritime Administration (FMA) “Tentative Note for Application of Direct Calculation Methods for Longitudinally Framed Hull Structure”, 30 June 200329 1 Introduction 29 2 Maximum frame spacing30 2.1 Plating thickness .30 2.2 Frame section modulus and shear area for longitudinal frames
19、 .30 3 Brackets on intersections between longitudinal frames and the web frames .31 This Page Intentionally Left Blank ABSGUIDANCE NOTES ON ICE CLASS .2005 5 Section 1: Introduction CHAPTER 1 Ice Strengthening Using Direct Calculation Approaches SECTION 1 Introduction 1 Background According to the F
20、innish-Swedish Ice Class Rules (abbreviated as “FSICR” in these Guidance Notes), it is stipulated that longitudinal frames shall be attached to all supporting web frames and bulkheads by brackets. In a subsequent paragraph, it is stated that “For the formulae and values given in this section for the
21、 determination of hull scantlings, more sophisticated methods may be substituted subject to approval by the administration or the classification society.” Ice load measurements conducted with vessels navigating in the Baltic show that loads several times higher than the design loads are often encoun
22、tered. It is deemed that designing up to the yield point with these high loads would be uneconomical, and so, some excess of the nominal design load is acceptable. In certain extreme cases, some plastic deformation will occur, leaving behind a permanent set. The design of the longitudinal frames can
23、 be checked by using a FEM program capable of nonlinear structural analysis. In such an analysis, the permanent set can be calculated and the ultimate load-carrying capacity of the frames predicted. The Finnish Maritime Administration (abbreviated as “FMA” in these Guidance Notes) released the “Tent
24、ative Note for Application of Direct Calculation Methods for Longitudinally Framed Hull Structure” (referred to as “FMA Guidelines” in these Guidance Notes) for alternative design of side structures using nonlinear FEM analysis. See Chapter 1, Appendix 3. In 2004, ABS released the Guidance Notes on
25、Nonlinear Finite Element Analysis of Side Structures Subject to Ice Loads to provide a procedure to design side longitudinals using a nonlinear FEM analysis. This publication incorporates the information in the 2004 Guidance Notes and supersedes that publication. 2 Purpose The purpose of this Chapte
26、r is to clearly define a procedure for ice strengthening of side structures using nonlinear FEM, including both side longitudinals and side shell plating. In accordance with Ice Class Rules, the results of such an analysis may be used to substitute for standard Rules formulae. Certain design require
27、ments, such as constraints on longitudinal frame spacing, the bracket attachment requirement between web frames and bulkheads and side shell thickness, may be relaxed. These Guidance Notes provide more technical details to supplement the FMA Guidelines. In addition, these Guidance Notes provide a pr
28、ocedure for alternative design of side shell plate using nonlinear FEM. This may lead to relaxation of side shell plating thickness requirements compared to the FMA Guidelines. Chapter 1 Ice Strengthening Using Direct Calculation Approaches Section 1 Introduction 1-1 6 ABSGUIDANCE NOTES ON ICE CLASS
29、 .2005 3 Applications The requirement that the maximum frame spacing of longitudinal frames “shall not exceed 0.35 meter for ice class IA Super and IA and shall in no case exceed 0.45 meter” stems from the fact that the ice loading is concentrated along a narrow horizontal strip, typically only 250
30、mm wide. In order to limit the possible catastrophic consequences of longitudinal frames collapsing, there is a Rule requirement to install brackets between longitudinal frames and transverse webs. These brackets increase the ultimate load-carrying capacity of the frames by effectively reducing thei
31、r span. However, the installation of such brackets may lead to higher production costs, and it is desirable to use nonlinear FEM to justify a decision to omit such brackets in order to optimize structural design. Nonlinear FEM is also used to optimize the design with a balanced strength between side
32、 shell plate and side longitudinals. 4 Key Components of these Guidance Notes The key components of applying a nonlinear FEM analysis of side structures subject to ice loads include: Design procedure Nonlinear FE model, including structural idealization, material modeling, loading, solution, converg
33、ence requirements etc. These analysis components can be expanded into additional topics, as follows, which become the subject of particular Sections in the remainder of this Chapter 5 Contents of this Chapter Chapter 1 of these Guidance Notes is divided into the following Sections and Appendices: Se
34、ction 1 Introduction Section 2 Procedure for Ice Strengthening Side Structures Using Nonlinear FEM Appendix 1 Nonlinear FE Model Appendix 2 Example of Nonlinear FEM Applications Appendix 3 The Finnish Maritime Administration (FMA) “Tentative Note for Application of Direct Calculation Methods for Lon
35、gitudinally Framed Hull Structure”, 30 June 2003 ABSGUIDANCE NOTES ON ICE CLASS .2005 7 Section 2: Procedure for Ice Strengthening Side Structures Using Nonlinear FEM CHAPTER 1 Ice Strengthening Using Direct Calculation Approaches SECTION 2 Procedure for Ice Strengthening Side Structures Using Nonli
36、near FEM 1 Design of Side Structures The ice strengthening procedure involves four steps for alternative design of the side structure under ice load. These four steps are summarized in 1-2/Table 1 and are described in detail below. TABLE 1 Steps in Ice Strengthening of Side Structures Step Design No
37、tes 1 FSICR design, baseline design Design fully complies with FSICR (Ice strengthened longitudinal spacing, less than 450 mm) 2 FMA interim design Design complies with the FMA Guidelines, item 2 (Longitudinal spacing is wider than that specified by FSICR) 3 Alternative design for side longitudinals
38、 Side longitudinals without brackets are determined using nonlinear FEM. 4 Alternative design for side shell Side shell thickness is determined using nonlinear FEM for extreme ice loads. 2 Step 1: FSICR Design The initial design of side structures should fully comply with FSICR. FSICR require that t
39、he maximum frame spacing of longitudinal frames “shall not exceed 0.35 meter for ice class IA Super and IA and shall in no case exceed 0.45 meter”. Brackets are required to connect longitudinals and webs. Chapter 1 Ice Strengthening Using Direct Calculation Approaches Section 2 Procedure for Ice Str
40、engthening Side Structures Using Nonlinear FEM 1-2 8 ABSGUIDANCE NOTES ON ICE CLASS .2005 3 Step 2: FMA Interim Design FMA interim design uses the FMA Guidelines to design side structure with longitudinal spacing about 800 millimeters. The ice pressure is higher than that of FSICR. Brackets are need
41、ed to connect longitudinals and webs. The side shell plating thickness is calculated following the FMA Guidelines (see Chapter 1, Appendix 3), as in the equation below: cYPLtfpst +=2667 mm where pPL is the ice pressure acting on the side shell plating. The details of this equation can be found in th
42、e FMA Guidelines (1-A3/2.1). 4 Step 3: Alternative Design for Side Longitudinals Alternative structures shall follow the FMA Guidelines to ensure equivalency in permanent deformation of the side longitudinals. Nonlinear FEM can be applied to evaluate this equivalency. Structural modeling is to follo
43、w the procedure in these Guidance Notes. The permanent deformation of the side longitudinals should be checked by the acceptance criteria in 1-2/4.3. The details of this step, including the FEM modeling, load applied and acceptance criteria, are described below. 4.1 FEM Modeling The FEM modeling pro
44、cedure and boundary condition requirements are described in Chapter 1, Appendix 1. Other details about FEM, including FEM solution and convergence requirements can also be found in Chapter 1, Appendix 1. 4.2 Ice Load on Side Longitudinals For the purpose of designing a side longitudinal and its end
45、connections to web frames, the ice loads may be represented as line loads acting on the longitudinal within the ice belt. The load applied to the FE model is described in detail in 1-A1/4. 4.3 Acceptance Criteria FMA recommends “ that the shell structure is modeled both for the rule requirements wit
46、h brackets and for the proposed structure without brackets. If the plastic deformation for the proposed structure is equal to or smaller than for the rule structure, the scantlings of the proposed structure may be considered acceptable.” (See Chapter 1, Appendix 3.) The proposed unbracketed design i
47、s to be compared with the FMA interim design. The Finite Element procedures outlined in these Guidance Notes should be used to perform the analysis of both bracketed and unbracketed designs. If an unbracketed longitudinal scantling can be shown to resist plastic deformation such that it results in p
48、ermanent deformation that is either equal to or less than the Rule bracket design, the unbracketed design can be accepted. The FSICR initial design and FMA interim design can be used as the benchmark for this comparison. Chapter 1 Ice Strengthening Using Direct Calculation Approaches Section 2 Proce
49、dure for Ice Strengthening Side Structures Using Nonlinear FEM 1-2 ABSGUIDANCE NOTES ON ICE CLASS .2005 9 5 Step 4: Alternative Design of Side Shell Alternative design of side shell plating thickness may also be accepted if the resulting permanent deformation of shell plating subject to extreme ice loads falls within an acceptable range. Nonlinear FEM analysis is to be performed to calculate the permanent deformation of the side shell plating. The side longitudinal is the same as the FMA alternative design as in Step 3. Permanent deformation of t
