1、 Guidance Notes on Whipping Assessment for Container Carriers GUIDANCE NOTES ON WHIPPING ASSESSMENT FOR CONTAINER CARRIERS FEBRUARY 2014 American Bureau of Shipping Incorporated by Act of Legislature of the State of New York 1862 Copyright 2014 American Bureau of Shipping ABS Plaza 16855 Northchase
2、Drive Houston, TX 77060 USA ii ABSGUIDANCE NOTES ON WHIPPING ASSESSMENT FOR CONTAINER CARRIERS .2014 Foreword Foreword The main purpose of these Guidance Notes is to supplement the Rules and Guides that ABS has issued for the Classification for container carriers. ABS Rules for Building and Classing
3、 Steel Vessels (Steel Vessel Rules, or the Rules) and the ABS Guide for Application of Higher-Strength Hull Structural Thick Steel Plates in Container Carriers require the evaluation of whipping effect on hull structures. These Guidance Notes address how to carry out such evaluations. These Guidance
4、 Notes provide detailed procedures for the assessment of whipping loads and subsequent structure strength for container carriers. The technical background is based on the direct analysis of slamming load and structure dynamic response. These Guidance Notes are applicable to Container Carriers which
5、have hull forms that can be susceptible to whipping effects. The 2014 revision includes updated wave scatter diagram tables, details of closed form approach for whipping induced acceleration, and editorial changes. The effective date of these Guidance Notes is the first day of the month of publicati
6、on. Users are advised to check periodically on the ABS website www.eagle.org to verify that the version of these Guidance Notes is the most current. Comments or suggestions can be sent electronically to rsdeagle.org. ABSGUIDANCE NOTES ON WHIPPING ASSESSMENT FOR CONTAINER CARRIERS .2014 iii Table of
7、Contents GUIDANCE NOTES ON WHIPPING ASSESSMENT FOR CONTAINER CARRIERS CONTENTS SECTION 1 Introduction 1 1 General . 1 2 Whipping Phenomenon . 1 3 Whipping Assessment Procedure . 2 FIGURE 1 Whipping Stress due to Slamming 1 FIGURE 2 Whipping Strength Assessment Procedure 3 SECTION 2 Loading Condition
8、s, Speeds, and Headings . 4 1 General . 4 2 Critical Loading Conditions . 4 3 Standard Speed Profile . 4 4 Wave Heading 4 TABLE 1 Standard Speed Profile for Whipping Load Prediction . 4 SECTION 3 Wave Environments . 5 1 Wave Scatter Diagram 5 2 Wave Spectrum 6 TABLE 1 North Atlantic Wave Scatter Dia
9、gram for Strength Evaluation . 5 TABLE 2 North Atlantic Wave Scatter Diagram for Fatigue Evaluation . 6 SECTION 4 Vessel Motions . 8 1 General . 8 2 Closed-form Motion Calculation Approach . 8 2.1 Motions 8 2.2 Relative Motions 9 2.3 Short-term Statistics 10 3 Three-dimensional Seakeeping Analysis M
10、ethod 10 3.1 General Modeling Considerations . 10 3.2 Dominant Load Parameters . 11 3.3 Critical Wave Conditions . 12 3.4 Time Domain Analysis . 13 iv ABSGUIDANCE NOTES ON WHIPPING ASSESSMENT FOR CONTAINER CARRIERS .2014 SECTION 5 Whipping Response A Closed-form Method . 14 1 General . 14 2 Bowflare
11、 Impact Load . 14 3 Vertical Bending Moment and Shear Force due to Whipping . 17 3.1 Response of 2-Node Hull Girder Mode under Impact Loads . 17 3.2 Whipping Bending Moment 18 3.3 Whipping Shear Force . 23 TABLE 1 Sea States from IACS Recommendation 34 21 FIGURE 1 Bowflare Geometry Model 15 FIGURE 2
12、 Flare Angle and Local Breadth of Wedge Section 16 FIGURE 3 Calculation of Flare Angle and Local Breadth 16 FIGURE 4 1, 20, 40-Year Return Sea States from IACS Recommendation 34 . 21 FIGURE 5 Definition of Bow Flare Geometry for Bow Flare Shape Parameter . 22 FIGURE 6 Definition of Half Deck Width 2
13、2 SECTION 6 Whipping Response Time Domain Numerical Approach . 24 1 General . 24 2 Impact Load 24 3 Whipping Response 24 SECTION 7 Strength Assessment . 26 1 General . 26 2 Vertical Hull Girder Ultimate Limit State . 26 3 Hull Girder Ultimate Bending Moment Capacity . 26 3.1 General 26 3.2 Physical
14、Parameters 27 3.3 Calculation Procedure . 29 3.4 Assumptions and Modeling of the Hull Girder Cross-section . 30 3.5 Stress-strain Curves - (or Load-end Shortening Curves) 31 FIGURE 1 Bending Moment Curvature Curve M- . 27 FIGURE 2 Dimensions and Properties of Stiffeners 28 FIGURE 3 Example of Defini
15、ng Structural Elements . 30 FIGURE 4 Example of Stress Strain Curves - 32 SECTION 8 Fatigue Damage Assessment 36 1 General . 36 2 Fatigue Damage . 36 2.1 General 36 2.2 Wave-Frequency Response Fatigue Damage . 37 2.3 Combined Wave and Whipping Response Fatigue Damage . 37 2.4 Whipping Contribution t
16、o Fatigue Damage 38 ABSGUIDANCE NOTES ON WHIPPING ASSESSMENT FOR CONTAINER CARRIERS .2014 v 3 Fatigue Damage Assessment . 38 FIGURE 1 Combination of a LF Stationary and HF Transient Process . 37 SECTION 9 Whipping Induced Acceleration 39 1 General . 39 2 Closed Form Approach . 39 2.1 Whipping Induce
17、d Vertical Acceleration 39 2.2 Standard Deviation 39 2.3 Maximum Acceleration 40 APPENDIX 1 Wave-Induced Vertical Bending Moment A Closed-form Method 41 1 Wave Induced Bending Moment (Linear) . 41 2 Wave Induced Bending Moment (Non-Linear) . 42 APPENDIX 2 Fatigue Damage Assessment . 43 1 General . 4
18、3 1.1 Note . 43 1.2 Applicability . 43 1.3 Loadings 43 1.4 Effects of Corrosion . 43 1.5 Format of the Criteria 43 2 Connections to be Considered for the Fatigue Strength Assessment 44 2.1 General 44 2.2 Guidance on Locations 44 2.3 Fatigue Classification 44 3 Fatigue Damage Calculation 53 3.1 Assum
19、ptions 53 3.2 Criteria . 53 3.3 Long Term Stress Distribution Parameter, 53 3.4 Fatigue Damage 54 4 Fatigue Inducing Loads and Load Combination Cases 57 4.1 General 57 4.2 Wave-induced Loads . 57 4.3 Combinations of Load Cases for Fatigue Assessment 57 5 Determination of Wave-induced Stress Range 58
20、 5.1 General 58 5.2 Hatch Corners . 58 6 Hot Spot Stress Approach with Finite Element Analysis 66 6.1 Introduction 66 6.2 Calculation of Hot Spot Stress at a Weld Toe . 67 6.3 Calculation of Hot Spot Stress at the Edge of Cut-out or Bracket 69 vi ABSGUIDANCE NOTES ON WHIPPING ASSESSMENT FOR CONTAINE
21、R CARRIERS .2014 TABLE 1 Fatigue Classification for Structural Details 45 TABLE 2 Welded Joint with Two or More Load Carrying Members . 48 TABLE 3 Combined Load Cases for Fatigue Strength Formulation 57 FIGURE 1 Basic Design S-N Curves . 56 FIGURE 2 Hatch Corners at Decks and Coaming Top 64 FIGURE 3
22、 Circular Shape 65 FIGURE 4 Double Curvature Shape 65 FIGURE 5 Elliptical Shape 65 FIGURE 6 Hatch Corner for Longitudinal Deck Girder . 66 FIGURE 7 . 67 FIGURE 8 . 69 ABSGUIDANCE NOTES ON WHIPPING ASSESSMENT FOR CONTAINER CARRIERS .2014 1 Section 1: Introduction SECTION 1 Introduction 1 General The
23、design and construction of the hull, superstructure and deckhouses of container carriers are to be based on the applicable requirements of the ABS Rules and Guides. As a supplement to the ABS Rules and Guides, these Guidance Notes provide detailed procedures for whipping assessment for container car
24、riers. The procedure is easy to use and can be utilized to make quick estimates of the whipping effect on hull girder bending moment and on fatigue load. It could be utilized during the conceptual design phase and to perform a sensitivity study of its variation with main dimensions and operational p
25、rofiles. The technical background is based on the direct analysis of slamming load and structure dynamic response. The procedure has been calibrated using a number of existing designs. 2 Whipping Phenomenon In rough seas, the ships bow and stern may occasionally emerge from a wave and re-enter the w
26、ave with a heavy impact or slam as the hull structure comes in contact with the water. A ship with such excessive motions is subject to very rapidly developed hydrodynamic loads. The ship will experience impulse loads with high-pressure peaks during the impact between the ship hull and water. Of int
27、erest are the impact loads such as bowflare slamming, bottom slamming, stern slamming, green water, and bow impact loads. These impact loads are of a transient nature and can cause severe structural damages. Impact loads can cause local structural damage due to high impact pressure. They can also in
28、duce hull girder vibration mainly in the fundamental 2-node mode. This hull girder vibration is referred to as “whipping”, as shown in Section 1, Figure 1. The vibratory hull girder bending stress, or whipping stress, is of much higher frequency than the wave-induced stress, and is effectively super
29、imposed on it. The period of the fundamental mode of whipping is usually in the range from 0.5 to 2 sec. Whipping has been observed in full scale measurements and can result in an increase of the extreme value of the hull girder bending moment and fatigue damage to structures. FIGURE 1 Whipping Stre
30、ss due to Slamming 0.60.60.40.40.20.20Max. hogHog stressDeckten.Slam Max. sagBase lineTime“WHIPPING“Mean stress lineSag stressDeckcomp.2 secEnvelope of exp. stressStresskg/mm2Section 1 Introduction 2 ABSGUIDANCE NOTES ON WHIPPING ASSESSMENT FOR CONTAINER CARRIERS .2014 For vessels possessing signifi
31、cant bowflare or operating at shallow draft, the impact load and the structure response to the impact load need to be evaluated accordingly. The ABS Guide for Slamming Loads and Strength Assessment for Vessels provides procedures for the assessment of the impact load and the structure strength due t
32、o impact pressures. These Guidance Notes focus on the hull girder response to the impact load, namely whipping effects. 3 Whipping Assessment Procedure The recommended whipping assessment procedure includes the following: Determine the critical loading conditions, forward speed, and operational head
33、ings for whipping assessment. Select wave environmental data, such as wave scatter diagram and wave spectrum. Perform vessel motion analysis. Calculate impact load. Calculate impact load induced hull girder bending moment. Calculate wave load induced hull girder bending moment. Determine total hull
34、girder bending moment. Perform ultimate hull girder strength assessment. Determine whipping induced fatigue damage. Determine total fatigue damage. Calculate fatigue damage contribution from whipping. Calculate whipping induced acceleration The analysis flowchart is given in Section 1, Figure 2. Det
35、ailed descriptions for the analysis procedures are given in Section 2 though Section 8. Section 1 Introduction ABSGUIDANCE NOTES ON WHIPPING ASSESSMENT FOR CONTAINER CARRIERS .2014 3 FIGURE 2 Whipping Strength Assessment Procedure Linear SeakeepingAnalysisINPUT DATAHull Geometry, Light Weight,Load C
36、ondition, SpeedExtreme values of DLPSCritical wavesLocal Geometry(Hull Section Forms)Non-linear motion andimpact force calculationSectionalimpact forceSectionalstructureproperties1D beam responseanalysisSTRENGTHASSESSMENTFATIGUEASSESSMENTVBM with whippingVBM w/o whippingS-N CurveStress Coefficient4
37、ABSGUIDANCE NOTES ON WHIPPING ASSESSMENT FOR CONTAINER CARRIERS .2014 Section 2: Loading Conditions, Speeds, and Headings SECTION 2 Loading Conditions, Speeds, and Headings 1 General Impact loads are closely related to the relative motions between the vessel and the water surface. Loading condition,
38、 vessels transit speed, and wave direction affect motions of the vessel and should be selected to cover the critical conditions for impact load and whipping response. 2 Critical Loading Conditions In general, the critical loading conditions are to be identified based on the susceptibility of the hul
39、l structure to impact loads, giving consideration to the fore and aft hull forms, as well as the local drafts relative to the hull structure. Container carriers are, in general, susceptible to bowflare slamming due to large flare angles. For the strength and fatigue assessment against whipping, two
40、loading conditions are to be considered. One is the seagoing loading condition corresponding to the scantling draft, and the other is the seagoing condition with minimum draft. 3 Standard Speed Profile In high seas, the ship speed may be reduced voluntarily or involuntarily. If a specific operation
41、profile for the vessel is not available, a standard speed profile is to be applied based on the significant wave height as shown in Section 2, Table 1, where Vdis the design speed. 4 Wave Heading It is assumed that whipping mainly occurs in bow sea conditions. It is recommended that wave headings of
42、 head sea (180-degree), 165-degree and 150-degree bow seas are to be included in the whipping analysis. TABLE 1 Standard Speed Profile for Whipping Load Prediction (1 February 2014) Significant Wave Height, HsSpeed 0 14.5 1 5 13 19 19 13 7 77 Sum over All Heights 8 326 3127 12779 24880 26874 18442 8
43、949 3335 1014 266 100000 2 Wave Spectrum Sea wave conditions are to be modeled by the two-parameter Bretschneider spectrum, which is determined by the significant wave height and the zero-crossing wave period of a sea state. The wave spectrum is given by: S() = 4524)/(25.1exp165pspH where S= wave en
44、ergy density, m2-sec (ft2-sec) Hs= significant wave height, m (ft) = angular frequency of wave component, rad/sec p= peak frequency, rad/sec = 2/TpTp= peak period, sec = 1.408 TzTo consider short-crested waves, “cosine squared” spreading is to be utilized, which is defined as: f() = k cos2( 0) Secti
45、on 3 Wave Environments ABSGUIDANCE NOTES ON WHIPPING ASSESSMENT FOR CONTAINER CARRIERS .2014 7 where = wave heading, following sea is 0 degrees, and head sea is 180 degrees, in the range of 0 2 0+ 20= main wave heading of a short-crested wave k = factor determined such that the summation of f() is e
46、qual to 1.0, i.e.: = +=2/02/01)(f 8 ABSGUIDANCE NOTES ON WHIPPING ASSESSMENT FOR CONTAINER CARRIERS .2014 Section 4: Vessel Motions SECTION 4 Vessel Motions 1 General (1 February 2014) This Section describes prediction of vessel motions. The motions of interest for slamming load calculations are rel
47、ative velocity and relative motion in the vertical direction between waves and the part of the vessel subject to wave impact. Vessel motions may be obtained either by model testing or through seakeeping analysis. A three-dimensional seakeeping analysis code is to be used for the motion and whipping
48、analysis for final strength assessment. A closed-form motion calculation approach can also be utilized in the whipping assessment at an early design stage. The closed-form motion calculation will combine with the impact load and whipping analysis approach specified in Section 5. The closed-form anal
49、ysis approach is easy to use and requires only main particulars of the design. It could be used during conceptual design for sensitive analysis and be used to narrow down critical cases for further study. 2 Closed-form Motion Calculation Approach (1 February 2014) The closed-form expressions for the frequency response function for wave induced motions for monohull ships have been derived by Jensen and Mansour (2004). The closed-form expressions can be used to predict motions and relative motions at an
