Section 1 Introduction
Clasification Society 2024 - Version 9.40
Clasifications Register Guidance Information - Guidance Notes for the Classification of Special Service Craft – Version 1.0 Design Details, July 2013 - Chapter 2 Guidance for Designers for Steel/Aluminium Construction - Section 1 Introduction

Section 1 Introduction

Parent topic: Chapter 2 Guidance for Designers for Steel/Aluminium Construction

1.1 Definition

1.1.1  Critical areas can be defined as locations that, by reason of stress concentration, alignment/discontinuity and corrosion will have a higher probability of failure during the life of the craft than the surrounding structures. Critical locations are defined as the specific locations within the critical area that can be prone to fatigue damage for which design improvements are provided.

1.2 General

1.2.1 In order to assist the designer to minimise fatigue failures, LR has developed an extensive database on structural detail design aspects.

1.2.2 Utilising the results from detailed finite element analyses for an extensive range of structural details it has been possible to examine a variety of configurations for each detail thereby enabling a grading to be made of their relative fatigue performance.

1.2.3 The outcome from some of this work has been condensed into these Guidance Notes. It is intended as a conservative approach to improving the fatigue life performance of structural details.

1.2.4 The designer may therefore, using these Guidance Notes, readily upgrade the detail design arrangements to provide a higher fatigue performance configuration.

1.2.5 It is intended that the detail design database given in Ch 4 Detail Design Improvement for Steel/Aluminium Construction will be extended to incorporate further detail arrangements, to reflect in-service experience of their fatigue performance, design and construction practice, as well as any significant data made available from research studies.

1.2.6 In addition, guidance is provided to the designer and Builder on other methods to improve the fatigue life performance of the structural detail such as detail geometry, construction tolerances, welding sequence, weld defect, weld dressing, etc.

1.3 Application

1.3.1 The detail design improvements provided in these Guidance Notes are applicable to all grades of steel, commonly used aluminium alloys and composite structures. This is because the fatigue life improvement will be achieved through the suggested change of geometry which will reduce the stress concentrations and the improved construction requirements which will improve the performance throughout the design lifetime of the structural detail under the expected stress variations.

1.3.2 In areas where mild steel and basic grade aluminium may be used a number of the suggested detail improvements may not be necessary due to the lower stress ranges that the details are designed to experience. However, in areas where higher tensile steel (HTS) or higher strength grade aluminium are used, the operating stresses will generally be higher. Therefore the detail improvements suggested may become necessary in order to meet the fatigue strength of the structure.

1.3.3  Alternative structural arrangements will, in general, be acceptable provided it can be demonstrated, that a satisfactory fatigue life performance will be maintained throughout the design life span. In addition the structural arrangements and scantlings are to satisfy Rules for Special Service Craft.

1.3.4 Where suggested values are indicated regarding geometries or scantlings, these are given as guidance.

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