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Common Structural Rules

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The questions and answers you find below are provided with the purpose to clarify issues related to the implementation of CSR BC & OT

Bulk carriers and tankers are different vessel types, so why make a common rule set ?

Tankers and Bulk carriers are different ship types, but also have much in common. For example, both ship types are constructed of stiffened steel plate panels with similar yielding, buckling and fatigue properties, both ship types have to withstand the same wave loads, etc. The common requirements are given in Part 1 of the rules, while the ship type specific requirements are given in Part 2.


What should be the biggest concerns in the industry for application of CSR BC & OT?

Due to the extended scope, more resources and time will be required in the design phase unless better tools are available. However in case of good/smart tools, repetitiveness of design and approval will be improved.


Will ship designed to the new rules be heavier than the existing CSR-BC or CSR-OT designs?

The new rules shall ensure that vessels designed according to these rules will be at least as safe The questions and answers you find below are provided with the purpose to clarify issues related to the implementation of CSR BC & OT. and robust as the existing vessels. It is introduced new hull girder ultimate limit state criteria, and the FE-analysis scope has been extended. Based on this we expect a 1–3 % increase in steel weight if CSR BC & OT is applied on top of an existing CSR-BC or CSR-OT compliant design. However, if a vessel is designed from scratch applying CSR BC & OT criteria, the impact might be minimised.


Will it be possible for an existing CSR approved vessel to comply with the new CSR BC & OT criteria?

Yes, but an existing design would most likely require some modifications of the existing scantlings.


What is the rationale behind increasing the analysis scope?

With respect to extending the FE scope to cover the entire cargo area, IACS has recognized that the existing method of extrapolating results from mid-ship to fore and aft hold do not provide the transparency and consistency in results as IMO GBS requires. In addition the computerization capabilities have developed significantly, meaning with today’s tools it is feasible to do these analyses within a reasonable timeframe.


What measures are taken to ensure consistent interpretation of the rules amongst the IACS societies?

A Rule Maintenance Team has been established in IACS, consisting of 5 technical experts from the Classification societies with the assistance from the staff in IACS permanent secretariat. This project teams will answer questions and conduct the technical assessment of potential inconsistent interpretations, which may eventually draw up recommended Rule changes for approval by the IACS Hull Panel.


Will DNV GL do approval of a vessel if she is already approved according to CSR BC & OT by another IACS society?

If a Memorandum of Understanding (MoU agreement) is signed between shipowner, yard and DNV GL accepting another IACS society’s approval, there will be a limited review and comparison. In this case no comments with respect to CSR BC & OT are expected. If there is no MoU in place, DNV GL is obliged to do a full plan approval. However, we do not anticipate significant changes in scantlings.


How to handle a contract signed prior to 1st of July 2015 where construction will not commence until 2016?

The general rule is that ships or series of ships signed for construction prior to 1st of July 2015 are not subject to CSR BC & OT even if the construction is taking place later than 1st of July 2015. However, if the delivery is on or after 1st July 2020, SOLAS II-1 Regulation 3-10 “Goal-based ship construction standards for bulk carriers and oil tankers” (GBS) applies. CSR BC & OT is the only set of rules that complies with GBS; hence CSR BC & OT have to be applied for vessels with delivery on or after 1st July 2020, no matter when the building contract is signed.


A ship building contract signed prior to 1st of July 2015 includes options for additional ships. To which rules should the optional ships be constructed?

Options included in contracts signed prior to 1st of July 2015 are not subject to CSR BC & OT if the option is exercised within a year of the initial contract signing, except if delivery is on or after 1st July 2020.


A ship building contract signed before 1st of July 2015 is amended. To which rules should the additional ships be constructed?

Amendments are subject to the Rules in force at the date of signing the amendment. If the amendment is signed on or after 1st of July 2015, the ships are subject to CSR BC & OT.

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