1、 Guidance Notes on Springing Assessment for Container Carriers GUIDANCE NOTES ON SPRINGING 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 Northchas
2、e Drive Houston, TX 77060 USA ii ABSGUIDANCE NOTES ON SPRINGING 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 recently published the Guide
3、 for Application of Higher-Strength Hull Structural Thick Steel Plates in Container Carriers, which requires the evaluation of the springing effect on fatigue damage of hull structures. These Guidance Notes address how to carry out such evaluations. These Guidance Notes provide detailed procedures f
4、or the assessment of springing loads and the subsequent structural fatigue damage for container carriers. The technical background is based on direct analysis of hydrodynamic load and structure dynamic response. The 2014 revision includes an updated wave scatter diagram table and editorial changes.
5、The effective date of these Guidance Notes is the first day of the month of publication. Users are advised to check periodically on the ABS website www.eagle.org to verify that this version of these Guidance Notes is the most current. Comments or suggestions can be sent electronically to rsdeagle.or
6、g ABSGUIDANCE NOTES ON SPRINGING ASSESSMENT FOR CONTAINER CARRIERS .2014 iii Table of Contents GUIDANCE NOTES ON SPRINGING ASSESSMENT FOR CONTAINER CARRIERS CONTENTS SECTION 1 Introduction 1 1 General . 1 2 Springing Phenomenon 1 3 Springing Assessment Procedure 2 FIGURE 1 Time History of Measured V
7、ertical Bending Moment . 1 FIGURE 2 Springing Assessment Procedure. 3 SECTION 2 Loading Conditions, Speeds, and Headings . 4 1 General . 4 2 Loading Conditions . 4 3 Standard Speed Profile . 4 4 Wave Heading 4 TABLE 1 Standard Speed Profile for Springing Load Prediction . 4 SECTION 3 Wave Environmen
8、ts . 5 1 Wave Scatter Diagram 5 2 Wave Spectrum 5 TABLE 1 ABS Wave Scatter Diagram for Unrestricted Service Classification . 5 SECTION 4 Springing Susceptibility Assessment 7 1 General . 7 2 Hull Girder Natural Frequency 7 3 Wave Characteristics 7 4 Springing Susceptibility . 8 FIGURE 1 Probability
9、Distribution of Tz8 FIGURE 2 Typical Dynamic Amplification Factor . 9 FIGURE 3 Springing Susceptibility Indicator 9 iv ABSGUIDANCE NOTES ON SPRINGING ASSESSMENT FOR CONTAINER CARRIERS .2014 SECTION 5 Calculation of Response Amplitude Operator . 10 1 General . 10 2 Vertical Bending Moment RAOs of Rig
10、id Body . 10 2.1 General Modeling Consideration . 11 2.2 Hydrostatic Balance . 11 2.3 Roll Damping . 11 3 Vertical Bending Moment RAO of Flexible Body 12 3.1 Calculation of 2-Node Vibration Mode . 12 3.2 Hydroelasticity . 13 3.3 Large Range of Wave Frequency 13 4 Springing Damping . 14 5 Stress RAO
11、Calculation 14 FIGURE 1 Definition of Ship Motion . 10 FIGURE 2 Vertical Bending Moment RAO (rigid body) 12 FIGURE 3 2-Node Vertical Vibration Mode 12 FIGURE 4 Bending Stiffness Distribution . 13 FIGURE 5 Vertical Bending RAO Distribution 13 SECTION 6 Response Statistics . 15 1 General . 15 2 Short
12、Term Statistics . 15 FIGURE 1 Vertical Bending Moment Response Spectra . 16 SECTION 7 Fatigue Assessment . 17 1 General . 17 2 Fatigue Damage . 17 2.1 General 17 2.2 Wave-Frequency Response Fatigue Damage . 18 2.3 Combined Wave and Springing Response Fatigue Damage . 18 2.4 Springing Contribution to
13、 Fatigue Damage 19 3 Fatigue Damage Assessment . 20 APPENDIX 1 Fatigue Strength Assessment . 21 1 General . 21 1.1 Note . 21 1.2 Applicability 21 1.3 Loadings 21 1.4 Effects of Corrosion . 21 1.5 Format of the Criteria . 21 2 Connections to be Considered for the Fatigue Strength Assessment. 22 2.1 G
14、eneral 22 2.2 Guidance on Locations 22 2.3 Fatigue Classification . 22 ABSGUIDANCE NOTES ON SPRINGING ASSESSMENT FOR CONTAINER CARRIERS .2014 v 3 Fatigue Damage Calculation 32 3.1 Assumptions 32 3.2 Criteria . 32 3.3 Long Term Stress Distribution Parameter, 32 3.4 Fatigue Damage 33 4 Fatigue Inducin
15、g Loads and Load Combination Cases 36 4.1 General 36 4.2 Wave-induced Loads . 36 4.3 Combinations of Load Cases for Fatigue Assessment 36 5 Determination of Wave-induced Stress Range 37 5.1 General 37 5.2 Hatch Corners . 37 6 Hot Spot Stress Approach with Finite Element Analysis 45 6.1 Introduction
16、45 6.2 Calculation of Hot Spot Stress at a Weld Toe . 46 6.3 Calculation of Hot Spot Stress at the Edge of Cut-out or Bracket 48 TABLE 1 Fatigue Classification for Structural Details 23 TABLE 2 Welded Joint with Two or More Load Carrying Members . 26 TABLE 3 Combined Load Cases for Fatigue Strength
17、Formulation 36 FIGURE 1 Basic Design S-N Curves . 35 FIGURE 2 Hatch Corners at Decks and Coaming Top 43 FIGURE 3 Circular Shape 44 FIGURE 4 Double Curvature Shape 44 FIGURE 5 Elliptical Shape 44 FIGURE 6 Hatch Corner for Longitudinal Deck Girder . 45 FIGURE 7 . 46 FIGURE 8 . 48 This Page Intentional
18、ly Left Blank ABSGUIDANCE NOTES ON SPRINGING ASSESSMENT FOR CONTAINER CARRIERS .2014 1 Section 1: Introduction SECTION 1 Introduction 1 General The design and construction of the hull, superstructure, and deckhouses of container carriers are to be based on the applicable requirements of the ABS Rule
19、s and Guides. As a supplement to the ABS Rules and Guides, these Guidance Notes provide detailed procedures for assessment of springing and the subsequent structural fatigue damage for container carriers. The procedure is easy to use and can be utilized to make quick estimates of the fatigue damage
20、due to springing at the conceptual design phase and to perform a sensitivity study of its variation with main dimensions and operational profiles. The technical background is based on the direct analysis of hydrodynamic load and structure dynamic response. 2 Springing Phenomenon Springing is wave-in
21、duced hull girder vibration, and it is mainly excited by waves with an encounter frequency coinciding with the springing frequency. For a hull girder vibration, the most important springing frequency is its 2-node vertical natural vibration frequency. Springing can also be excited by waves with an e
22、ncounter frequency of half of the springing frequency due to the second order contribution to the response. Springing could increase the fatigue load of the vessel, although its contribution to the extreme hull girder load may not be significant. Springing is not a new topic. Early springing researc
23、h has mainly focused on inland water ships. These ships, with large length/depth ratios, are flexible operating at low draft. Springing was not considered important for oceangoing ships due to the general observation that oceangoing vessels were relatively more rigid and their hull girder natural fr
24、equencies of vibration are farther away from the encountered wave frequencies. However, wave-induced hull girder vibration has been observed from full-scale measurements in oceangoing ships (see Section 1, Figure 1). Also, with the rapid growth in ship size, especially container carriers, the new an
25、d next generations of post-Panamax container carriers are relatively flexible. These Guidance Notes provide procedures on the assessment of springing contribution to the structural fatigue damage and focus on the application to container carriers. FIGURE 1 Time History of Measured Vertical Bending M
26、oment Measured VBM Filtered VBM 2-node vibration Section 1 Introduction 2 ABSGUIDANCE NOTES ON SPRINGING ASSESSMENT FOR CONTAINER CARRIERS .2014 3 Springing Assessment Procedure The recommended springing assessment procedure includes the following: i) Determine the critical loading conditions, forwa
27、rd speed, and operational headings. ii) Select wave environmental data, such as wave scatter diagram and wave spectrum. iii) Perform springing susceptibility assessment. iv) Perform detailed springing assessment: Calculate vertical bending moment/stress RAOs including only rigid body motions. Calcul
28、ate vertical bending moment/stress RAOs including rigid body motions and 2-node vibration. Calculate stress response statistics and fatigue damage including only rigid body motions. Calculate stress response statistics and fatigue damage including rigid body motions and 2-node vibration. Calculate t
29、otal fatigue damage including only rigid body motions. Calculate total fatigue damage including rigid body motions and 2-node vibration. Calculate springing contribution to fatigue damage. The analysis flowchart is given in Section 1, Figure 2. Detailed descriptions for the analysis procedures are g
30、iven in Sections 2 through 7. Section 1 Introduction ABSGUIDANCE NOTES ON SPRINGING ASSESSMENT FOR CONTAINER CARRIERS .2014 3 FIGURE 2 Springing Assessment Procedure Assemble OperationalConditionsObtain Wave EnvironmentalConditionsPerform SpringingSusceptibility AssessmentIf not satisfiedPerform Det
31、ailed Springing AnalysisFor each heading, frequency, and speedCalculate BM/stress RAOs including only rigid body motionsCalculate BM/stress RAOs including rigid body motions and 2-node vibration modeFor each sea state (Hs, Tz) and headingCalculate stress response statistics and damage including only
32、 rigid body motionsCalculate stress response statistics and damage including rigid body motions and2-node vibration modeFor an operational condition (speed, heading, loading condition) and wave scatter diagramAdd up the damage contributions including only rigid body motionsAdd up the damage contribu
33、tions including rigid body and 2-node vibrationCalculate damage contributions due to 2-node vibration4 ABSGUIDANCE NOTES ON SPRINGING ASSESSMENT FOR CONTAINER CARRIERS .2014 Section 2: Loading Conditions, Speeds, and Headings SECTION 2 Loading Conditions, Speeds, and Headings 1 General For a given v
34、essel, springing is influenced by, among other factors, loading conditions, encountered waves, and vessel speed. These conditions need to be considered in the springing assessment. 2 Loading Conditions (1 February 2014) For the fatigue assessment of a container carrier, a minimum of two loading cond
35、itions is recommended: Homogeneous loading condition at design draft Homogeneous loading condition at lowest draft 3 Standard Speed Profile In high seas, the ship speed may be reduced voluntarily or involuntarily. If a specific operational profile for the vessel is not available, a standard speed pr
36、ofile 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 springing mainly occurs in bow sea conditions. It is recommended that wave headings of head sea (180-degree), 165-degree, and 150-degree bow seas
37、 are to be included in the springing analysis. TABLE 1 Standard Speed Profile for Springing 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 8949 3335 1014 266 100000 2 Wave Spectrum Sea wave condit
38、ions 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 Section 3 Wave Environments 6 ABSGUIDANCE NOTES ON SPRINGING ASSESSMENT
39、FOR CONTAINER CARRIERS .2014 where S= wave energy 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
40、, which is defined as: f() = k cos2( 0) 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 equal to 1.0, i.e.: = +=2/02/01)(f ABSGUIDANCE NOTES ON
41、SPRINGING ASSESSMENT FOR CONTAINER CARRIERS .2014 7 Section 4: Springing Susceptibility Assessment SECTION 4 Springing Susceptibility Assessment 1 General Springing is wave-induced vibration. Its effect on the operation and the structure of vessels can become important when the natural frequency of
42、the vessel is close to the encountered wave frequency. If the natural frequency of the vessel is far from that of encountered waves, springing effect may be considered as insignificant. The first step in the springing assessment is to evaluate the springing susceptibility of the vessel. This Section
43、 describes the recommended springing susceptibility criteria. 2 Hull Girder Natural Frequency (1 February 2014) The hull girder natural frequency can be obtained through finite element method, beam method, or full-scale measurement. If they are not available, the following formula can be used to est
44、imate hull girder natural frequency: n= Iv/(i3BPL )1/2, rad/sec where: = 321500 (176118) Iv= moment of inertia, m4(ft4) i= virtual displacement, including added mass of water, t (Lt) = 1.2 + B/(3dm) B = breadth of vessel, m (ft) dm= mean draft of vessel, m (ft) = vessel displacement, t (Lt) LBP= ves
45、sels length between perpendiculars, m (ft) 3 Wave Characteristics (1 February 2014) Waves are normally generated by winds and they are random in nature. Waves can be characterized by zero up-crossing periods, peak periods, wave energy spectrum, and other parameters. For a sea state (or storm), the p
46、eak period is defined as the wave period at which the wave energy spectrum reaches its peak. It means that the greatest wave energy of the storm is associated with that wave period. For a fully developed sea, the relationship of peak period and zero up-crossing period can be written as: Tp= 1.408Tzs
47、ec where Tpis peak period and Tzis zero up-crossing period in second. The peak frequency is the inverse of the peak period. The vessel encountered wave frequency can be written as: e= 2V/g cos() rad/sec Section 4 Springing Susceptibility Assessment 8 ABSGUIDANCE NOTES ON SPRINGING ASSESSMENT FOR CON
48、TAINER CARRIERS .2014 where = wave frequency, rad/sec V = vessel forward speed, m/sec (ft/sec) g = acceleration of gravity, m/sec2(ft/sec2) = wave heading For head sea conditions, the peak frequency can be written as: p= pT2+ 22pTV/g rad/sec For North Atlantic waves, Section 4, Figure 1 depicts the
49、probability distribution of zero crossing wave periods according to Section 3, Table 1. FIGURE 1 Probability Distribution of Tz(1 February 2014) 0.000.050.100.150.200.250.303.5 4.5 5.5 6.5 7.5 8.5 9.5 10.5 11.5 12.5 13.5Tz(s)4 Springing Susceptibility (1 February 2014) Springing is a dynamic response of the hull girder to the wave load. As for any dynamic problem, the dynamic response amplification factor can range from near zero to a very high value at the resonance frequency. Section
