American Bureau of Shipping Introduction To ABS Rules

1
American Bureau of ShippingIntroduction To ABS
Rules

• Presentation to the Naval Academy
• 6 April 2005

2
What is Classification?
Classification is third party certification in
the marine industry
Classification is a process which certifies
adherence to a recognized set of technical
standards, representing that a ship or other
type of marine structure is structurally sound
and mechanically fit for its intended purpose.
3
The Classification Process
Develop Technical Standards (Rules) Developed
through industry-based technical committee
structure Embraces recognized external
standards Updated annually Customized when
necessary (new technology/new
application) Implement Technical Standards
Design Plan review and engineering
analysis Survey during construction Periodic
survey throughout vessel life
4
The Classification Process
Rules and Guides
Rules are the foundation of the process Over 60
sets of Rules and Guides Developed with industry
Naval Vessel Rules
Industry Committee Based Peer review from all
relevant parties Continual feedback and
update Calibrated to proven experience
5
ABS - a Snapshot
world leader in ship safety and environmental
protection since 1862 1500 people 225
offices 81 countries
ISO 9000 certified 60 Rules and
Guides 10,000 ships in class (250
Government) totaling over 100 million gross
tons 20,000 manhours engineering review per
month 708 new construction ships under survey (15
million gross tons) A Industry and Government
Involved in Management and Operations
6
Engineering Group

• OED - Offshore Engineering Department
• AA - Advanced Analysis Department
• SED - Ship Engineering Department
• Materials Welding Department
• Naval Engineering Department

7
Ship Engineering Department

• Tanker / Bulk Carrier / Ship Safety Group
• General Cargo Ship Group
• Tonnage
• Load Line Stability Group

8
ABS Rules

• Steel Vessel Rules
• Steel Barges - Ocean Service Barges of any Length
• Steel Vessels Under 90 m - Crewboats, Tugs
• High Speed Naval Craft- Patrol Boats HSVs
• Steel Vessels for Service on Rivers, ICW - River
  Barges, Towboats
• Bulk Carriers for Service on the Great Lakes -
  Freshwater Operations
• Reinforced Plastic Vessels - F. R. P. Vessels
• Aluminum Vessels - Aluminum Commercial Vessels
  100 - 500
• Naval Vessel Rules
• MODU - Mobile Offshore Drilling Units

9
ABS Guides

• Motor Pleasure Yachts - Steel, Aluminum, or FRP
• High Speed Craft, - Commercial/Government Service
  Planing vessels
• Fishing Vessels - Steel Fishing Vessels Under 90
  m (200)
• Offshore Racing Yachts - Steel, Aluminum, or FRP
  Sailing Vessels
• Fire Fighting Vessels - Steel Fireboats
• Crew Accommodations Guide
• Oil Recovery Vessels - Oil Spill Cleanup Vessels
• Floating Production Storage and Offloading
  Vessels - (FPSO)
• Small Waterplane Area Twin Hulled Vessels -
  (SWATH)

10
Ship Acquisition Process
MNS
ORD
A-Spec
Requirement Derivation RULES
B-Spec
Optional Step
C-Spec
Build-to- Print
Owner
Contractor
Technical Validation CLASSIFICATION
11
Function - Fitness - Safety
Owners Requirements not addressed
elsewhere mission related owner unique

Detailed Component and Performance Standards
Statutory Compliance safety of life
issues environmental protection
Classification Rules structural and mechanical
fitness physical attributes of ship
Baseline Technical Standards
12
Hull Classification Considerations

• Intact and Damaged Stability
• Specialized Vessel Criteria
• Freeboard Assignment
• Strength of Hull Structure
• Longitudinal Strength Requirements
• Local Strength Requirements
• Condition Assessment
• Surveys During Construction
• Surveys In-Service

13
Structural Analysis

• 1. Load Determination - What are the Loads?
• 2. Response Determination - How do these loads
  affect the Structure?
• 3. Strength Evaluation - Are the structural
  arrangements and materials adequate for the
  determined response?

14
Ship Structure

• Longitudinal Strength (Continuous Members)
• Local Plating/Stiffener Requirements
• Main Supporting Members
• Longitudinal/Transverse Bulkheads
• Web Frames
• Appendages
• Rudder/Skeg
• Bilge Keel
• Materials
• Grade ( Strength Toughness )
• Castings / Forgings
• Welding

15
Longitudinal StrengthUnified IACS Requirement

• Still Water Bending Moment
• Wave Bending Moment
• Hogging Condition
• Sagging Condition
• Total Bending Moment

16

17

18

19

20
Strength Evaluations

• Material Selection
• Grade (Strength vs. Toughness)
• Castings/Forgings
• Welding
• Service Temperature
• Thickness
• Failure Modes
• Yielding
• Buckling
• Fatigue
• Fracture

21
Fatigue Assessment

• Description of the Environment
• Calculations of Ship Motions, Sealoads, and Local
  Hydrodynamic Pressures
• Calculations of Structural Response and Stress
  Transfer Function
• Selection of Appropriate S-N Curves and Stress
  Concentration Factors
• Estimation of Fatigue Life and Comparison with
  Acceptance Criteria

22

23

SemiEmpirical
Approach to Hull Classification
Longitudinal Strength
Yielding (Explicit)
P
Buckling (Both)
Analysis
Local Strength
Response
Determination

Fatigue (Implicit)
Fracture (Implicit)
Main Supporting
Members
Material Requirements
Strength vs.
Toughness
24
Semi-Empirical RulesDerived from First Principles

• Stiffeners (beams)
• Assume Fixed End Beams where M
  wl2 / 12
• w s h SM M / Fb
• Allowable Stress Fb 15.68 KSI or 20.16KSI for
  Ordinary Steel Fy 34KSI
• ABS Rule
• SM ,0041 c h s l2

25

26
Safehull Project Objective A Completely
Restated Set of Hull Design and Evaluation
Criteria

• Establish Loads and Combinations Acting on the
  Global and Local Structure
• Specify the Extent and Types of Analyses Required
  to Determine Loads
• Establish the Required Strength of the Structure
  to Resist Load Effects

27
Traditional Approach

• Nominal Loading - Prescribed
• Simple Design Equations in Rules
• Calibrated by Satisfactory Service Experience

28
Modern Approach

• Expected Loading - Calculated
• Analysis Methods to Establish Load Effects
• Strength Performance Criteria Under Demands of
  Loads

29
Net Ship Approach

• Design Strength is Evaluated with Expected
  Corrosion Values Removed
• Nominal Strength can be Preserved for the Entire
  Life of the Vessel
• Appropriate Corrosion Margins can be added to
  Accommodate Longer Design Lives
• Allows Explicit Means to Assess Sensitivity of
  Structural Strength to Corrosion

30
Net Ship Concept

• Corrosion
• Fatigue
• Corrosion/Fatigue Interaction

31

32
Corrosion Margins
Recommended Corrosion
Location/Structural Element
Margin for Class (mm)
Cargo Tank
Ballast Tank
Effectively Coated
Deck Plating
1.0
2.0
Side Shell Plating
N.A
1.5
Bottom Plating
N.A
1.0
Innerbottom Plating
1.5
1.5
Longitudinal Bulkhead Plating
1.0
1.5
Transverse Bulkhead Plating
1.0
1.5
Transverse Longitudinal Deck
Supporting Members
1.5
2.0
Double Bottom Tank Internals (Stiffeners,
Floors and Girders)
N.A
2.0
Vertical Stiffeners and Supporting
Members Elsewhere
1.0
1.0
Non-vertical Longitudinals/Stiffeners and
Supporting Members Elsewhere
1.5
2.0
33
(No Transcript)
34
(No Transcript)
35
(No Transcript)
36
Load ComponentsDetermined Through Parametric
Seakeeping Analysis

• Hull Girder Loads
• Still Water and Wave Induced Bending Moment and
  Shear Force
• Vertical, Horizontal and Torsional
• Internal Tank Pressure
• Added Pressure Head due to Roll and Pitch
• Internal Forces due to Accelerations
• Sloshing
• External Pressure
• Hydrostatic Pressure Distribution
• Wave Induced Dynamic Pressure Distribution

37

38

39
Load Determination

• North Atlantic Route
• Strip Theory for Response
• Probabilistic Approach
• Long Term Values Incorporating
• Wave Spectra
• Ship Headings
• Service Speed

40
(No Transcript)
41
(No Transcript)
42
(No Transcript)
43
Summary of Criteria Features

• Format
• Loads
• Net-Ship Concept
• Strength Criteria
• Fatigue Criteria
• Analysis to Obtain Load Effects

44
Finite Element Analysis(Phase B)

• 3-Dimensional - Determine Global Loads and
  Boundary Conditions
• 2-Dimensional - Determine Local Stress and
  Deflections
• Yielding
• Buckling
• Fatigue

45
(No Transcript)
46
(No Transcript)
47
Naval Vessel Rules

• Derived from Gen Specs and Design Data Sheets
• Requires Analysis of Longitudinal Strength using
  DDS 100 and SPECTRA Program
• Requires a FEM Analysis
• Uses Prescribed Loads from Traditional Navy
  Criteria and Specific Design Loads
• Concern over Shock Load Ship Weight

48
High Speed Naval Craft

• Based on Design Criteria from NSWC- CD Combat
  Craft Department and NAVSEA
• Determines Loads from Vessel Response to Sea
  State, Speed and Heading
• Calculate local Slam pressures and Slam Moments
• Combines Slam Moment with Hull Girder Bending
  Moments