Charter (30 April 02)

1. OBJECTIVES

The objectives of the Ad Hoc Panel on "Investigation of Head-Sea Parametric Rolling and Resulting Cargo Securing Loads" are to:

(a) Describe sea and vessel criteria necessary to initiate head-sea parametric rolling in ocean-going vessels based upon current data;

(b) Propose operational guidelines and procedures for existing vessels to avoid or to reduce the effects of head-sea parametric rolling;

(c) Evaluate classification society and international criteria for predicting cargo lashing and vessel loads and compare with loads imposed by head-sea parametric rolling;

(d) Develop a suitable amendment for MSC Circular 707, "Guidance to the Master for Avoiding Dangerous Situations in Following and Quartering Seas," to account for head-sea parametric rolling;

(e) Summarize current knowledge on head-sea parametric rolling;

(f) Define factors contributing to head-sea parametric rolling which require further investigation;

(g) Present findings and recommendations.

2. SCOPE OF WORK

The intended scope of work is as follows:

Literature Review

The extensive data underlying the paper "An Investigation of Head-Sea Parametric Rolling and its Influence on Container Lashing Systems," soon to appear in Marine Technology, should be fully reviewed and analyzed in accordance with the objectives set forth above. Furthermore, existing literature should be collected and reviewed for the purpose of identifying vessel characteristics and operational and sea conditions that do and do not give rise to a parametric rolling response. Particular emphasis should be given to reports of model testing and non-linear computer modeling results. As following sea parametric rolling is a reasonably well-documented phenomenon, the criteria utilized in assessing the likelihood of that response may serve as a guide for evaluating the head sea parametric rolling response.

Questionnaire to Operating Companies

Create a confidential questionnaire for distribution to owners/operators of container, ro-ro, cruise and other similarly and dissimilarly shaped ships for information on their experiences with extreme rolling responses within a preceding common period. Evaluate the results with a view to identifying head-sea parametric rolling responses and to determining vessel characteristics and operational and sea conditions that were necessary to cause a head-sea parametric rolling response. Assess frequency of occurrence of head-sea parametric rolling in terms of vessel type and characteristics, fleet size, geographic and seasonal operating areas, sea conditions, and at-sea hours or vessel life.

Technical Assessment of Literature and Questionnaire Responses

Establish quantitative vessel, operational, and sea conditions that increase the risk of head-sea parametric rolling. Establish quantitative criteria for accelerations acting on vessels and their cargoes while undergoing head-sea parametric rolling responses, with a view to correlation with the magnitudes of motion responses, especially roll, pitch and heave.

Climatological Analysis

Review the geographic areas of major shipping routes in standard climatological atlases for the frequency of occurrence of sea conditions likely to result in head-sea parametric rolling for a range of vessel characteristics and operational conditions.

Comparison of Current Standards for Estimating
Vessel Motions, Resulting Accelerations, and Forces

Compare major classification society and other international criteria for establishing extreme motion responses and resulting accelerations and forces for design and operational standards for vessels, lashing systems, and containers suitable for on-deck carriage.

Assess the sufficiency of such existing criteria with expectable motions, accelerations and forces resulting from head-sea parametric rolling. Develop necessary recommendations for unifying classification society and international criteria for predicting vessel motions and accelerations and resulting forces and for assessing risk levels associated with such criteria.

Recommendations for Vessel Operating Information

Develop methods for presentation of vessel characteristics, and operating and sea conditions in practical forms for utilization by vessel operators and mariners to avoid or minimize the risk of head-sea parametric rolling, including polar plots, diagrams or modifications to ship's motion monitoring and routing software. Recommend amendment of MSC/Circ.707, "Guidance to the Master for Avoiding Dangerous Situations in Following and Quartering Seas" to incorporate guidelines for vessels prone to head-sea parametric rolling.

Recommendations for Further Research

Propose further model testing and/or computer modeling to better identify the effects of vessel design and modifications to existing vessels (including bow and stern shapes, bilge keel size, anti-roll tanks and devices, ballast tank arrangements), and vessel operations on head-sea parametric rolling responses, and on cargo stowage and lashing criteria.

3. PANEL COMPOSITION

The panel shall have expertise in areas of: ship and lashing system design, operation, construction, and costing; climatological evaluation and sea state spectral analysis; risk analysis and regulatory development; ship motions; and time domain computer modeling of ship motions. Members shall include representatives from ship design firms, shipping companies, shipyards, regulatory agencies, and individuals with expertise in meteorology/oceanography, theoretical foundations of ship motions, and time domain/non-linear computer codes for predication of ship motions.

4. DELIVERABLES

The investigations, findings, and recommendations of the panel shall be disseminated through a paper at the SNAME annual meeting in San Francisco in 2003 and such other means as are appropriate.

In addition, there shall be delivered a document suitable for presentation as an information paper to the IMO Sub-Committee on Stability, and Load Lines, and on Fishing Vessels Safety (SLF).