1、 GUIDANCE NOTES ON THE STRENGTH ASSESSMENT OF CARGO TANK STRUCTURES BEYOND 0.4L AMIDSHIPS IN OIL CARRIERS 150 METERS OR MORE IN LENGTH MAY 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 Nort
2、hchase Drive Houston, TX 77060 USA This Page Intentionally Left Blank ABSGUIDANCE NOTES ON THE STRENGTH ASSESSMENT OF CARGO TANK STRUCTURES BEYOND 0.4L AMIDSHIPS IN OIL CARRIERS 150 METERS OR MORE IN LENGTH .2004 iii Foreword These Guidance Notes were developed as a direct response to requests from
3、our clients to develop an analysis procedure for the forward and aft tank structure beyond 0.4L. This procedure is based on existing ABS SafeHull procedures included in the ABS Rules. It should be noted that ABS is currently working within IACS on the Joint Tanker Project (JTP) and some components o
4、f these Guidance Notes have been developed using JTP procedures. It is understood that this process will continue and once the JTP Rules mature, these Guidance Notes will be unified with respect to components such as the net thickness, loads, acceptance criteria, etc. These Guidance Notes describe a
5、 strength assessment procedure for cargo tank structures beyond 0.4L amidships in oil carriers having L greater than 150 meters. In addition to the Rule scantlings as required by Section 5-1-6 “Hull Structure Beyond 0.4L Amidships” of the ABS Rules for Building and Classing Steel Vessels (SVR), thes
6、e Guidance Notes may be optionally applied to verify the strength adequacy of main supporting members using a set of standard design load cases. Application of the procedure is required for novel structural configurations or scantlings/details. This Page Intentionally Left Blank ABSGUIDANCE NOTES ON
7、 THE STRENGTH ASSESSMENT OF CARGO TANK STRUCTURES BEYOND 0.4L AMIDSHIPS IN OIL CARRIERS 150 METERS OR MORE IN LENGTH .2004 v GUIDANCE NOTES ON THE STRENGTH ASSESSMENT OF CARGO TANK STRUCTURES BEYOND 0.4L AMIDSHIPS IN OIL CARRIERS 150 METERS OR MORE IN LENGTH CONTENTS SECTION 1 Introduction 1 1 Scope
8、 of Application 1 3 Overview of Strength Assessment.1 5 Coordinate Systems.2 5.1 Ship Coordinate System for Ship Motion and External Pressure (Right Hand) 2 5.3 Tank Coordinate System for Internal Pressure (Left Hand) 2 5.5 Finite Element Coordinate System (Right Hand).3 7 Nomenclature.3 FIGURE 1 Ou
9、tline of the Strength Assessment Procedure.5 FIGURE 2 Tank Coordinate System for Internal Pressure6 SECTION 2 SafeHull Dynamic Load Criteria7 1 General 7 3 Vertical Wave-induced Bending Moment.7 5 Horizontal Wave-induced Bending Moment 8 7 External Pressure 8 9 Internal Pressure9 9.1 Effective Pitch
10、 Amplitude 9 9.3 Effective Roll Amplitude 9 9.5 Effective Accelerations10 9.7 Internal Pressure.11 11 Bottom Slamming Pressure .11 TABLE 1 kloCoefficient .8 TABLE 2 Coefficient.12 TABLE 3 Aiand BiCoefficients12 FIGURE 1 Distribution Factor for Vertical Wave-induced Bending Moment mv.13 ABSGUIDANCE N
11、OTES ON THE STRENGTH ASSESSMENT OF CARGO TANK STRUCTURES BEYOND 0.4L AMIDSHIPS IN OIL vi CARRIERS 150 METERS OR MORE IN LENGTH .2004 FIGURE 2 Distribution Factor for Horizontal Wave-induced Bending Moment mh.13 FIGURE 3 Pressure Distribution Function klo14 FIGURE 4 External Pressure Calculation Poin
12、ts 14 SECTION 3 Standard Design Load Cases . 15 TABLE 1 Standard Design Load Cases15 FIGURE 1 Standard Design Load Cases for Oil Carrier with Two Outer Longitudinal Bulkheads Only .16 FIGURE 2 Standard Design Load Cases for Oil Carrier with Two Outer Longitudinal Bulkheads and One Centerline Longitu
13、dinal Bulkhead 18 FIGURE 3 Standard Design Load Cases for Oil Carrier with Two Outer Longitudinal Bulkheads and Two Inner Longitudinal Bulkheads.22 SECTION 4 Structural Modeling and Analysis 27 1 Net Ship Approach.27 3 Structural Idealization 27 3.1 Extent of Finite Element Model27 3.3 Finite Elemen
14、t Modeling28 5 Boundary Constraints for Local and Hull Girder Sub Load Cases.29 5.1 Local Sub Load Case 29 5.3 Hull Girder Sub Load Case30 7 Overall Check of Finite Element Results .30 TABLE 1 Nominal Design Corrosion Values (NDCV) .31 FIGURE 1 Nominal Design Corrosion Values (NDCV) .32 FIGURE 2 Typ
15、ical Finite Element Model for Foremost Cargo Tank Structure32 FIGURE 3 Typical Finite Element Model for Aftmost Cargo Tank Structure33 FIGURE 4 Modeling of Bracket Toe and Tapered Face Plate 33 FIGURE 5 Boundary Constraints for Local Sub Load Cases34 FIGURE 6 Loads and Boundary Constraints for Hull
16、Girder Sub Load Cases.35 SECTION 5 Acceptance Criteria . 37 1 General 37 3 Yielding Failure Mode 37 3.1 Field Stress .37 3.3 Local Stress.37 3.5 Hot-Spot Stress.38 ABSGUIDANCE NOTES ON THE STRENGTH ASSESSMENT OF CARGO TANK STRUCTURES BEYOND 0.4L AMIDSHIPS IN OIL CARRIERS 150 METERS OR MORE IN LENGTH
17、 .2004 vii 3.7 Allowable Stresses for Various Finite Element Mesh Sizes .38 5 Buckling Failure Mode .38 5.1 Buckling Control Concepts39 5.3 Buckling Criteria40 TABLE 1 Allowable Stresses (kgf/cm2) for Various Finite Element Mesh Sizes 38 FIGURE 1 Coordinate System for Buckling Strength Evaluation 40
18、 SECTION 6 Documentation of Strength Assessment for Classification Review 41 APPENDIX 1 Calculation of Critical Buckling Stresses 43 1 General 43 3 Rectangular Plates.43 5 Deep Girders, Webs and Stiffened Brackets.44 5.1 Critical Buckling Stresses of Web Plates and Large Brackets 44 5.3 Effects of C
19、ut-outs.44 5.5 Tripping .44 7 Stiffness and Proportions.45 7.1 Stiffness of Web Stiffeners45 7.3 Stiffness of Supporting Members 45 7.5 Proportions of Flanges and Face Plates .46 TABLE 1 Buckling Coefficient Ki.47 This Page Intentionally Left Blank ABSGUIDANCE NOTES ON THE STRENGTH ASSESSMENT OF CAR
20、GO TANK STRUCTURES BEYOND 0.4L AMIDSHIPS IN OIL CARRIERS 150 METERS OR MORE IN LENGTH .2004 1 SECTION 1 Introduction 1 Scope of Application These Guidance Notes describe a strength assessment procedure for cargo tank structures beyond 0.4L amidships in oil carriers 150 meters or more in length. In a
21、ddition to the Rule scantlings as required by Section 5-1-6 “Hull Structure Beyond 0.4L Amidships” of the ABS Rules for Building and Classing Steel Vessels (Steel Vessel Rules), these Guidance Notes may be optionally applied to verify the strength adequacy of main supporting members using a set of s
22、tandard design load cases. For designs with satisfactory service experience or designs that have been subjected to other forms of engineering analysis, these Guidance Notes need not be applied. However, application of these Guidance Notes is required for novel structural configurations or scantlings
23、/details. The primary concern for main supporting members is the strength adequacy against external sea and internal liquid pressures while the hull girder load effects in these members tend to be less significant. Cargo tank structures within 0.4L amidships are to comply with the requirements of Se
24、ction 5-1-4 “Initial Scantling Criteria” of the Steel Vessel Rules and Section 5-1-5 “Total Strength Assessment” of the Steel Vessel Rules and are to be directly evaluated by using the ABS SafeHull System. The strength assessment procedure in these Guidance Notes is not applicable to cargo tank stru
25、ctures within 0.4L amidships. The description of the procedure in these Guidance Notes is aided by figures for forward cargo tank structures only, but the same procedure is also applicable to aft cargo tank structures (excluding bottom slamming and green water pressures). The parameters in these Gui
26、dance Notes are defined in ABS SafeHull units and coordinate systems. If the measurement units and/or coordinate systems are different from these specifications, conversion is to be done appropriately. 3 Overview of Strength Assessment The core of the strength assessment procedure is the SafeHull dy
27、namic loading concept. It is generally expected that local dynamic loads experienced by cargo tank structures beyond 0.4L amidships can be more severe than those within 0.4L amidships. Section 1, Figure 1 shows the outline of the procedure. In these Guidance Notes, the strength assessment procedure
28、is described in five Sections: Section 2 SafeHull Dynamic Load Criteria Section 3 Standard Design Load Cases Section 4 Structural Modeling and Analysis Section 5 Acceptance Criteria Section 6 Documentation of Strength Assessment for Classification Review Section 1 Introduction ABSGUIDANCE NOTES ON T
29、HE STRENGTH ASSESSMENT OF CARGO TANK STRUCTURES BEYOND 0.4L AMIDSHIPS IN OIL 2 CARRIERS 150 METERS OR MORE IN LENGTH .2004 The dynamic load criteria given in Section 2 of these Guidance Notes are consistent with those given in Section 5-1-3 “Load Criteria” of the Steel Vessel Rules for oil carriers.
30、 Simplifications to the dynamic load formulae are introduced with special emphasis to application of the strength assessment procedure using recognized finite element modeling/analysis/post-processing software tools such as FEMAP, PATRAN, NASTRAN and ANSYS. The standard design load cases given in Se
31、ction 3 of these Guidance Notes represent combinations of individual design load components defined in Section 2 of these Guidance Notes for cargo tank structures beyond 0.4L amidships. When warranted, additional design load cases are also to be analyzed to verify the strength of main supporting mem
32、bers against wave impact on bow, bow flare slamming and sloshing. Section 4 of these Guidance Notes describes the finite element modeling and analysis techniques generally used for cargo tank structures beyond 0.4L amidships. These techniques may be substituted by alternative techniques. It is recom
33、mended that consultation with ABS on the alternative techniques be made before commencing structural idealization. The acceptance criteria for the strength assessment procedure are consistent with those in Section 5-1-5 of the Steel Vessel Rules and also given in Section 5 of these Guidance Notes fo
34、r ready reference. Appropriate documentation of the strength assessment described in Section 6 of these Guidance Notes is essential for ABS plan approval. A complete technical report is to be prepared as supporting data of design and submitted together with the relevant plans for ABS review. 5 Coord
35、inate Systems Three sets of Cartesian coordinate systems are used to describe SafeHull load criteria and finite element modeling in these Guidance Notes. When alternative coordinate systems are used, attention should be paid to the default coordinate systems used in the dynamic load formulae in Sect
36、ion 2 of these Guidance Notes. 5.1 Ship Coordinate System for Ship Motion and External Pressure (Right Hand) Origin Intersection of the AP section, waterline and centerline planes. xTLongitudinal distance from the AP to the center of the tank, in m, positive toward bow. yTVertical distance from the
37、waterline to the center of the tank, in m, positive above and negative below the waterline. zTTransverse distance from the centerline to the center of the tank, in m, positive toward starboard. x Longitudinal distance from the AP to the external pressure point considered, in m. xoLongitudinal distan
38、ce from the AP to the reference station, in m. The reference station is the point along the vessels length where the wave trough or crest is located and may be taken at the mid-length of the considered tank. 5.3 Tank Coordinate System for Internal Pressure (Left Hand) Origin Intersection of the vert
39、ical, horizontal and transverse planes that are tangential to the envelope of the tank. This origin is also referred to as the zero dynamic pressure point. For example, the zero dynamic pressure point in Section 1, Figure 2 is located at the upper corner of the aft transverse bulkhead on the port si
40、de, and the forward portion of the tank on the starboard side is under high dynamic pressure and is targeted for strength assessment. Section 1 Introduction ABSGUIDANCE NOTES ON THE STRENGTH ASSESSMENT OF CARGO TANK STRUCTURES BEYOND 0.4L AMIDSHIPS IN OIL CARRIERS 150 METERS OR MORE IN LENGTH .2004
41、3 xlLongitudinal distance from the zero dynamic pressure point of the tank to the pressure point, in m, positive toward bow for a fore cargo tank structure. ylVertical distance from the zero dynamic pressure point of the tank to the pressure point, in m, positive downward. zlTransverse distance from
42、 the zero dynamic pressure point of the tank to the pressure point, in m, positive toward starboard. 5.5 Finite Element Coordinate System (Right Hand) Origin Intersection of the baseline, centerline and aftmost transverse planes. X Longitudinal distance from the origin, in cm, positive from aft to f
43、ore. Y Vertical distance from the origin, in cm, positive upward. Z Transverse (athwartship) distance, in cm, positive toward starboard. 7 Nomenclature Ascross sectional area of the spring bar, in cm2Asheareffective shear area of a hull girder cross section, in cm2and can be taken as the sectional a
44、rea of each side shell, longitudinal bulkhead, deck, inner bottom or bottom in question aleeffective longitudinal acceleration, in m/sec2, positive forward ateeffective transverse acceleration, in m/sec2, positive starboard aveeffective vertical acceleration, in m/sec2, positive downward B molded br
45、eadth, in m bihalf breadth at the 1/10draft of the i-th section in the heavy ballast condition, in m bi*half width of flat of bottom at the i-th section, in m Cbblock coefficient at the scantling draft dbdraft amidships in the heavy ballast condition, in m dfscantling draft, in m didraft at the i-th
46、 section in the heavy ballast condition, in m dmdraft amidships for a specific loading condition, in m doi 1/10of the section draft of the i-th section in the heavy ballast condition, in m fyminimum specified yield point of the material, in kgf/cm2fuminimum specified tensile strength of the material
47、, in kgf/cm2Fbifreeboard from the highest deck at side to the load waterline (LWL) at the i-th section GM metacentric height, in m hshydrostatic pressure head in still water, in m kceload combination factor for external pressure Section 1 Introduction ABSGUIDANCE NOTES ON THE STRENGTH ASSESSMENT OF
48、CARGO TANK STRUCTURES BEYOND 0.4L AMIDSHIPS IN OIL 4 CARRIERS 150 METERS OR MORE IN LENGTH .2004 kclload combination factor for effective longitudinal acceleration kcmhload combination factor for design horizontal wave-induced bending moment kcmvload combination factor for design vertical wave-induc
49、ed bending moment kctload combination factor for effective transverse acceleration kcvload combination factor for effective vertical acceleration kcload combination factor for effective pitch amplitude kcload combination factor for effective roll amplitude krroll radius of gyration, in m ksload factor for internal pressure L scantling length, in m LBPlength between perpendiculars, in m lslength of the spring bar, in cm ltcargo tank length between transverse bulkheads, in cm Mwsvertical sagging wave-induced bending moment, in tf-m Mwhvertical hogging wave-induced bending moment, in
