ABS-127-2004.pdf
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1、 GUIDANCE NOTES ON NONLINEAR FINITE ELEMENT ANALYSIS OF SIDE STRUCTURES SUBJECT TO ICE LOADS APRIL 2004 American Bureau of Shipping Incorporated by Act of Legislature of the State of New York 1862 Copyright 2004 American Bureau of Shipping ABS Plaza 16855 Northchase Drive Houston, TX 77060 USA Copyr
2、ight American Bureau of Shipping Provided by IHS under license with ABS Licensee=Boeing Co/5910770001 Not for Resale, 08/07/2008 20:09:50 MDTNo reproduction or networking permitted without license from IHS -,-,- This Page Intentionally Left Blank Copyright American Bureau of Shipping Provided by IHS
3、 under license with ABS Licensee=Boeing Co/5910770001 Not for Resale, 08/07/2008 20:09:50 MDTNo reproduction or networking permitted without license from IHS -,-,- ABS GUIDANCE NOTES ON NONLINEAR FINITE ELEMENT ANALYSIS OF SIDE STRUCTURES SUBJECT TO ICE LOADS . 2004 iii Foreword These Guidance Notes
4、 provide a procedure for performing nonlinear finite element analysis of side structures subject to ice loads. This document is referred to herein as “these Guidance Notes” and its issue date is 15 April 2004. Users of these Guidance Notes are encouraged to contact ABS with any questions or comments
5、 concerning these Guidance Notes. Users are advised to check with ABS to ensure that this version of these Guidance Notes is current. Copyright American Bureau of Shipping Provided by IHS under license with ABS Licensee=Boeing Co/5910770001 Not for Resale, 08/07/2008 20:09:50 MDTNo reproduction or n
6、etworking permitted without license from IHS -,-,- This Page Intentionally Left Blank Copyright American Bureau of Shipping Provided by IHS under license with ABS Licensee=Boeing Co/5910770001 Not for Resale, 08/07/2008 20:09:50 MDTNo reproduction or networking permitted without license from IHS -,-
7、,- ABS GUIDANCE NOTES ON NONLINEAR FINITE ELEMENT ANALYSIS OF SIDE STRUCTURES SUBJECT TO ICE LOADS . 2004 v GUIDANCE NOTES ON NONLINEAR FINITE ELEMENT ANALYSIS OF SIDE STRUCTURES SUBJECT TO ICE LOADS CONTENTS SECTION 1 Introduction1 1 Background1 3 Purpose1 5 Applications1 7 Key Components of these
8、Guidance Notes 2 9 Contents of these Guidance Notes2 SECTION 2 Structural Idealization3 1 Introduction3 3 Extent of Structural Modeling.3 5 FEM Elements .3 7 Mesh Size4 FIGURE 1 FE Model Extent (Inner Skin Removed for Clarity)5 FIGURE 2 Mesh of Side Longitudinal and Bracket at Connection to Web Fram
9、e.5 SECTION 3 Material Model7 SECTION 4 Load Model.9 FIGURE 1 Ice Load as Line Load on Side Longitudinal9 SECTION 5 Boundary Conditions.11 TABLE 1 Boundary Conditions for FEM Model.12 FIGURE 1 Boundary Conditions for FEM Model.11 SECTION 6 FEM Solution13 1 Incremental Solution13 3 Convergence13 Copy
10、right American Bureau of Shipping Provided by IHS under license with ABS Licensee=Boeing Co/5910770001 Not for Resale, 08/07/2008 20:09:50 MDTNo reproduction or networking permitted without license from IHS -,-,- vi ABS GUIDANCE NOTES ON NONLINEAR FINITE ELEMENT ANALYSIS OF SIDE STRUCTURES SUBJECT T
11、O ICE LOADS . 2004 SECTION 7 Acceptance Criteria.15 1 General 15 3 FMA Approach: Comparative Study15 5 Permanent Deformation.15 APPENDIX 1 Nonlinear FEM Theory and Software.17 1 Material Nonlinearity17 3 Geometrical Nonlinearity17 5 Incremental Solutions 17 7 Convergence Criteria.18 9 Commercial FEM
12、 Packages 18 APPENDIX 2 Example of Nonlinear FEM Applications.19 1 Problem Definition19 3 FEM Modeling19 5 Ice Load .21 7 Analysis Results.21 9 Alternative Design23 FIGURE 1 FEM Model.20 FIGURE 2 Load Path (Loading and Unloading Phases).21 FIGURE 3 Von Mises Stress Contour.22 FIGURE 4 Pressure vs. D
13、eflection (Loading and Unloading Phases)23 FIGURE 5 Pressure vs. Deflection of Different Designs.23 APPENDIX 3 The Finnish Maritime Administration (FMA) “Tentative Note for Application of Direct Calculation Methods for Longitudinally Framed Hull Structure”, 30 June 2003 .25 Copyright American Bureau
14、 of Shipping Provided by IHS under license with ABS Licensee=Boeing Co/5910770001 Not for Resale, 08/07/2008 20:09:50 MDTNo reproduction or networking permitted without license from IHS -,-,- ABS GUIDANCE NOTES ON NONLINEAR FINITE ELEMENT ANALYSIS OF SIDE STRUCTURES SUBJECT TO ICE LOADS . 2004 1 S E
15、 C T I O N 1 Introduction 1 Background According to the Finnish-Swedish Ice Class Rules, 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
16、 for the 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 ships navigating in the Baltic show that loads several times higher than the design loads are often
17、encountered. 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 fram
18、es can 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 can be predicted. These Guidance Notes expound upon the ideas and notions introduced in the Finnish Mariti
19、me Administration (abbreviated as “FMA” in these Guidance Notes) “Tentative Note for Application of Direct Calculation Methods for Longitudinally Framed Hull Structure”, 30 June 2003. 3 Purpose The purpose of these Guidance Notes is to clearly define a procedure to conduct a nonlinear FEM analysis o
20、f side structures subject to ice loads. In accordance with Ice Class Rules, the results of such an analysis may be used to substitute for standard Rules formulae and values. Certain design requirements, such as constraints on longitudinal frame spacing and the bracket attachment requirement between
21、web frames and bulkheads, may be relaxed. These Guidance Notes provide more technical details to supplement the Finnish Maritime Administration “Tentative Note for Application of Direct Calculation Methods for Longitudinally Framed Hull Structure”, 30 June 2003. 5 Applications The requirement that t
22、he maximum frame spacing of longitudinal frames “shall not exceed 0.35 metre for ice class IA Super and IA and shall in no case exceed 0.45 metre” stems from the fact that the ice loading is concentrated along a narrow horizontal strip, typically only 250 mm wide. In order to limit the possible cata
23、strophic 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 capability of the frames by effectively reducing their span. However, the installation of such
24、brackets may lead to higher production costs, and it is desirable to use nonlinear FEM to justify a design decision to omit such brackets in order to optimize structural design. Copyright American Bureau of Shipping Provided by IHS under license with ABS Licensee=Boeing Co/5910770001 Not for Resale,
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