ABS TECHNICAL PAPERS COMMITTEE V.1 Collision and Grounding

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1 16 th INTERNATIONAL SHIP AND OFFSHORE STRUCTURES CONGRESS AUGUST 2006 SOUTHAMPTON, UK VOLUME 2 Presented at the 16 th ISSC 2006 conference held in Southampton, UK, August 20-25, 2006 and reprinted with the kind permission of the International Ship and Offshore Structures Congress. You may find the entire report from "Proceedings of the 16th International Ship and Offshore Structures Congress, Vol. 2, edited by P.A. Frieze and R.A. Sheno. COMMITTEE V.1 Collision and Grounding COMMITTEE MANDATE Concern for structural arrangements on ships and floating structures with regard to their integrity and adequacy in the events of collision and grounding, with the view towards risk assessment and management. Consideration shall be given to the frequency of occurrence, the probabilistic and physical nature of such accidents, and consequences on watertight integrity, structural integrity and environment. COMMITTEE MEMBERS Chairman: Ge (George) Wang Chunyan Ji Pentti Kujala Sang-Gab Lee Alberto Marino Jaideep Sirkar Katsuyuki Suzuki Preben Terndrup Pedersen Alex W. Vredeveldt Vorobyov Yuriy KEYWORDS Collision, grounding, risk assessment, limit state design, accident scenarios, incident probability, acceptance criteria, internal mechanics, external mechanics. Collision and Grounding 161

2 CONTENTS 1. INTRODUCTION PRINCIPLES AND METHODOLOGY OF COLLISION AND GROUNDING DESIGN STANDARDS Accidental limit state design Existing design standards Current trends in design standard development related to accident limits Recent national and international projects Recommendations APPLICATION OF RISK ASSESSMENT METHODOLOGY Risk assessment methodology Application to collision and grounding problems Application to waterway designs Safety measures and risk control options Recommendations LIKELIHOOD OF INCIDENTS, PROBABILISTIC ENERGY DISTRIBUTION Available approaches Statistics of incidents Predictive calculations and energy reference values Recommendations MECHANICS OF COLLISION AND GROUNDING General Internal mechanisms Rupture criteria External mechanics Influences of fluid in tanks Coupled internal and external mechanics Recommendations CONSEQUENCES OF COLLISION AND GROUNDING Oil outflow Damage stability Ship evacuation Residual strength Post-accidental loads Other consequences Recommendations ESTABLISHMENT OF ACCEPTANCE CRITERIA Principles Comparative risk assessment Absolute risk assessment Recommendations Collision and Grounding

3 8. DESIGNS AGAINST COLLISION AND GROUNDING Buffer bow Innovative double hull designs and steel sandwich panels Double hulls Composite and sandwich panels Aluminum panels Economic considerations Recommendations OFFSHORE STRUCTURE COLLISION Existing criteria in offshore design codes FPSO collision FPSO collision scenarios Design events for FPSO collision Ship - Bridge collision Recommendations CONCLUSIONS AND RECOMMENDATIONS ACKNOWLEDGEMENT REFERENCES Collision and Grounding 163

4 INTRODUCTION This is the fourth time since 1990 that the ISSC has established a special committee to address the issue of ships collisions and groundings. The current 2006 Committee V.1 on Collision and Grounding is sequential to the 2003 Committee V.3 on Collision and Grounding, 1997 Committee V.4 on Structural Design against Collision and Grounding, and 1994 Committee V.6 on Structural Design for Pollution Control. This report intends to be both a handbook, which covers past and current research achievements, and a compass, directing us towards further research and development. Research and development in 1990s were characterized by: Several national and international large model testing projects and pilot simulation studies using nonlinear analysis tools, Theoretical development of the structural crashworthiness concept and methodology, and Development of environmentally friendly tank arrangements and structural designs. As of the late 1990s, the foci have been: The integration of key research achievements into risk-based methodology, Improved application of advanced simulation tools (FEM), Concepts to develop relevant rules and regulations, and Continued development of innovative crashworthy structures. These latest developments are the main topic of the current committee report. This report also provides an overview of the latest research, aiming at key risk assessment components for collisions and groundings. In addition to the traditional focus on oil tankers, this report also addresses collisions that occur with offshore structures, high speed crafts, and innovative double hull designs. Finally, the report looks at the crushing behavior of composite and aluminum panels. CONCLUSIONS AND RECOMMENDATIONS Crashworthiness: The concept and methodology of structural crashworthiness are maturing and have reached a level where they can be applied in analyses and evaluations of a wide range of collision and groundings. The committee advocates more studies and application, and recommends continued tools refinement to apply to structural crashworthiness. Probability of collision and grounding events: Future research on procedures that reduce collision and grounding probabilities should focus on developing risk-based software. The software should be capable of rationally modeling the cost and risk reduction features of each risk control option. The calculated cost of these risk reducing measures must then be compared with savings from calculated reductions in expenses. When such tools have been developed, we can balance risk control option investments and related safety improvements against the benefits. Risk assessment: Risk assessment approaches are well suited to collision and grounding issues, and are expected to continuously stand in the center of future development. The committee recommends focusing on integrating predictive calculation tools, including the development of streamlined software/programs. The committee knows that collision speeds in damage reports are not certain, and 164 Collision and Grounding

5 are of questionable credibility. We therefore recommend that the global community move towards unifying procedures to more precisely record incidents and damages. Rule and regulation development: Future rules and regulations on collisions and groundings need to address: Design incident/accident scenarios, Responses (of ships, offshore installations, bridges, etc) to an incident/accident, and Consequences and acceptance criteria. Risk assessment approaches are now viable tools to use for developing rules and regulations. Experiences of offshore industry and other industries provide a wealth of useful information, and may be good references for the shipping industry. The committee identifies some key development directions, which include framework for rule and regulation development, formalized accident scenarios, and definition of damage extents, among others. Predictive calculation approaches: The latest research and development since the early 1990s has produced many useful tools that can predict various aspects of a collision or grounding. Topics that will further refine these methods include: Rupture strain, Post-accident loads (both still-water and dynamic loads), Grounding, and Influences of ballast water or cargo oil in tanks. The number of these advanced predictive calculation approaches will reply on the development of useful software. Applications: The committee highly recommends more active application of the latest research and development achievements to offshore industry and high-speed crafts. We need further in-depth studies to investigate the behavior of aluminum and sandwich panels. We also need further studies to look into innovative designs that maximize the crashworthiness in an accidental impact. Collision and Grounding 165

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