Section 4 Method of non-linear analysis
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Clasifications Register Guidance Information - Guidance Notes for the Polar Class Vessel and Criteria for Non-Linear Analysis, January 2022 - Chapter 2 Non-Linear Analysis - Section 4 Method of non-linear analysis

Section 4 Method of non-linear analysis

Parent topic: Chapter 2 Non-Linear Analysis

4.1 Material model

4.1.1 Non-linear structural responses involve material nonlinearity in association with plasticity, among other factors. For non-linear finite element analysis, therefore, the characteristics of material behaviour should be defined adequately in terms of the stress versus strain relationship.

4.1.2 A bi-linear stress-strain curve with strain hardening parameter (E/1000), as shown in Ch 2, 4.1 Material model 4.1.2, is recommended for this non-linear analysis.

Figure 2.4.1 Bi-linear-hardening material

4.2 Responses of non-linear analysis

4.2.1 The deformation curve from the non-linear analysis is to be evaluated in accordance with the criteria described in Ch 4 Acceptance Criteria.

4.2.2 An idealised loading and unloading behaviour is reflected by a material with an initially linear stress-strain curve, followed by some nonlinearity which then becomes linear for a large portion of the curve. The loading and unloading cycle produces some strain hardening and permanent deformation, as shown in Ch 2, 4.2 Responses of non-linear analysis 4.2.2.

Figure 2.4.2 Loading and unloading behaviour

4.2.3 For the lateral deformation, the displacement for the load-deformation curve is measured perpendicular to the shell plating at the point on the member under consideration where deformation is the largest at the design load. For out-of-plane deformation, the displacement for the load-deformation curve is measured perpendicular to a reference point on the member under consideration where deformation is the largest at the design load.

4.2.4 When the structure is unloaded, the remaining permanent deformation is equal to the plastic displacement of the structure, as shown in Ch 2, 4.2 Responses of non-linear analysis 4.2.4.

Figure 2.4.3 Load-deformation curve

4.3 Ice patch load and class factors

4.3.1 The loading and unloading behaviour with an ice patch load up to is to be applied to the considered structure members to obtain the permanent local deflection of the member, .

Where,

= The average pressure in MPa, as defined in Ch 1, 3.1 Symbols 3.1.1

= Overload capacity factor, as listed in Ch 2, 4.3 Ice patch load and class factors 4.3.2

4.3.2 

Overload capacity factor, , is used to define a capacity margin that the primary structure has over the design pressure, .

Table 2.4.1 Overload capacity factors

Polar Class
PC 1 - PC 3 1,10
PC 4 - PC 5 1,15
PC 6 - PC 7 1,20
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