Section 3 Analysis
Clasification Society 2024 - Version 9.40
Clasifications Register Rules and Regulations - Rules and Regulations for the Classification of Offshore Units, July 2022 - Part 9 Concrete Unit Structures - Chapter 3 Structural Design - Section 3 Analysis

Section 3 Analysis

Parent topic: Chapter 3 Structural Design

3.1 General

3.1.1 The methods of analysis used in assessing compliance with the requirements of the various limit states are to be based on as accurate a representation of the behaviour of the structure as is practicable. The analysis that is carried out to justify a design can be broken into two primary stages: analysis of the structure and analysis of the sections.

3.1.2 For analysis of the whole or part of the structure, and to determine force distributions within the structure, the properties of materials may be assumed to be those associated with their characteristic strengths, irrespective of which limit state is being considered. For section analysis of elements, the properties of the materials are to be those associated with their design strengths to the limit state being considered.

3.2 Analysis of structure

3.2.1 The analytical model may be based on non-linear or linear elastic theory. Where linear elastic analysis is used, the relative stiffnesses of members may be based on any of the following:
  • The concrete cross-section: this is the entire plain concrete cross-section, ignoring the reinforcement.
  • The homogenous or gross section: this is the entire concrete cross-section, including the reinforcement on the basis of modular ratio.

A consistent approach is to be used for all elements of the structure.

3.2.2 When cracking, creep or other causes lead to significant redistribution of loads, this should be considered. Alternatively, plastic methods of analysis such as yield line analysis may be used.

3.2.3 Values for elastic moduli, Poissons ratio, coefficient of temperature expansion, etc. used in the analysis may be based on the selected Code or Standard or knowledge of similar concretes. The values used in the analysis should be confirmed with tests on the concrete mixes used on site.

3.3 Analysis of sections

3.3.1 The element section analysis should consider the requirements of Pt 9, Ch 3, 2.1 Codes and Standards 2.1.2.

3.3.2 The following are to be addressed for the section analysis:
  • Appropriate stress strain relationship for materials.
  • Allowable compressive and tensile concrete strength limits.
  • Material factors.
  • Crack width formulae.
  • Watertightness criteria.
  • Fatigue strength relationships.

Detailed requirements for these items are to be covered in the recognised Codes or Standards, but further requirements are given in Section 4 for each of the limit states under consideration.

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