scope:

This NES defines the structural strength standards that are to be achieved in the design, construction and modification of all surface warships. It is also applicable to the military requirements of Royal Fleet Auxiliaries and other non-military craft owned by the MOD where these requirements are in addition to the Rules of Lloyd's or another Classification Society to which the ships are designed. The provisions of this NES apply only to conventional monohull vessels and not to multi-hulled or high-speed planing craft.

The requirements of this NES also apply to alterations and modifications to the structure of existing vessels where such changes have invalidated the original design calculations or where additional structure is being fitted. Where repairs to structure are being undertaken without change of material or configuration the requirements of NES 155 Part 2 are to be met.

When the suitability for purchase or long term charter into MOD service of ships designed to other standards or rules is being considered, the requirements of Section 1. on Material Quality are to be taken account of.

There are a number of aspects pertaining to structural design which are not absolute but which have to be defined specifically for each ship or class and are laid down in a Statement of Technical Requirements for that class as defined in Clause B.4. Many of these aspects are mentioned in the text of this NES and a list of the principal ones is given in Section 12.

The requirements of this NES cannot of necessity cover all possible structures and it remains incumbent on the designer always to use good practice and best engineering judgement, especially in areas of detail. The designer remains responsible for ensuring that the whole structure is fit for purpose.