Section 5 Design and Analysis of Other Major Hull Structural Features

501. General

The design and analysis criteria to be applied to the other pertinent features of the hull structural de- sign are to conform to this Guidance or Rules for the Classification of Steel Ships. For ship-type unit, the hull design will need to consider the interface between the position mooring system and the hull structure or the effects of structural support reactions from deck-mounted (or above-deck) equip- ment modules, or both. The interface structure is defined as the attachment zone of load transmission between the main hull structure and hull mounted equipment, such as topside module stools, crane pedestals and foundations, riser porches, flare boom foundation, gantry foundation, mooring and off- loading, etc. The zone includes components of the hull underdeck structures in way of module support stools and foundations, such as deck transverse web frames, deck longitudinals and upper parts of lon- gitudinal and transverse bulkhead structures, as well as foundations of the hull-mounted equipment. These components of the interface structure should comply with the criteria indicated in 504..

502. Hull interface structure

The basic scantlings in way of the hull interface structure is to be designed based on the first princi- ple approach and meet the requirements of strength criteria in Rules for Classification of Mobile Offshore Drilling Units or equivalent national industry standards recognized and accepted, such as API Standards. Welding design of hull interface structure connections is to be developed based on Pt

12, Ch 6, Sec 5 of Rules for the Classification of Steel Ships or

a direct calculation approach.

Material grades for the above deck interface structure are to be

Classification of Mobile Offshore Drilling Units. The material grades

selected as for the hull

per Rules for

structure compo-

nents, such as deck and frame structures, are to be selected as per Pt 3 of

Rules for the

Classification of Steel Ships. The verification of the hull interface structure as defined above is to

be performed using direct calculation of local 3-D hull interface finite element models, developed using gross scantlings and analyzed with load conditions and load cases described in the following sections.

1. Position mooring/hull interface modeling

A FEM analysis is to be performed and submitted for review.

(1) Turret or SPM Type Mooring System, External to the Installation’s Hull

(2) Mooring system internal to the Installation Hull (Turret Moored)

(3) Spread Moored Installations

2. Hull mounted equipment interface modeling

(1) Topside Module Support Stools and Hull Underdeck Structures

(2) Other Hull Mounted Equipment Foundation Structures

503. Loads

For all conditions, the primary hull girder load effects are to be considered, where applicable.

The DLP values are to be selected for the most unfavorable structural response. Maximum accel- erations are to be calculated at the center of gravity of the most forward and aft and midship topside production facility modules.

The load cases are to be selected to maximize each of the following DLPs together with other asso- ciated DLP values.

• Max. Vertical Bending Moment

• Max. Shear Force

• Max. Vertical Acceleration

• Max. Lateral Acceleration

• Max Roll

Alternatively, the number of load cases can be reduced by assuming that all maximum DLP values occur simultaneously, which is a conservative assumption.

As a minimum, the following two hull girder load cases are to be analyzed:

• Maximum hull girder sagging moment (i.e., generally full load condition)

• Maximum hull girder hogging moment (i.e.,

condition)

generally ballast, tank inspection or partial loading

504. Additional Application

Other various matters on the Design and Analysis of Other Major Hull Structural Features are to be as specified in Pt 5, Ch5, of Rules for the Guidance for Floating Production Units.