Section 7 Stress Factors
Clasification Society 2024 - Version 9.40
Clasifications Register Guidance Information - Guidance Notes for the Certification of Masts, Spars and Standing Rigging, January 2017 - Chapter 1 Guidance notes for the certification of masts, spars and standing rigging - Section 7 Stress Factors

Section 7 Stress Factors

Parent topic: Chapter 1 Guidance notes for the certification of masts, spars and standing rigging

7.1 General

7.1.1 This Section details the permissible stress factors as referenced in the LR recommendation for the dimensions of masts, spars, spreaders and rigging as given in 3.2.

7.2 The basis for the stress factors

7.2.1 The stress factors given in this Section are related to the Characteristic Failure Stress, CFS. The characteristic failure stress is the stress at which, for the material loaded in the way it is loaded in the rig structure, the probability of breakage does not exceed 5 per cent.

Permissible stress = SF*CFS.

For test series with a normal stochastic distribution this level can be derived from tests of not less than 5 representative samples, as the average measured strength less two times the standard deviation.

The loads to which the stress factors are related are defined in 5.4.

Table 1.7.1 Stress factors, SF, regarding seagoing and survival conditions

Condition Metal Composite
Controlled condition during manufacture/stepping/maintenance 0,80 0,33
Masts and spars, seagoing, sailing 0,65 0,25
Masts and spars, seagoing, survival 0,80 0,33
Standing rigging, sailing 0,53

0,27 (carbon)

0,37 (PBO)
Standing rigging, survival 0,68

0,34 (carbon)

0,47 (PBO)
Note 1. If a significant part of the load under consideration is a personnel load, then the stress factor is not to exceed 0,4 for metal or 0,17 for a composite material.
Note 2. For masts and spars, the stress factors are valid for both tensile and compression load types. Proposals to use a separate factor for compression will be subject to special consideration.
Note 3. Where an element is subjected to a combined load, such as bending and compression, this combination is also to be considered. A detailed description of suitable methods can be found within LR’s Code for Lifting Appliances in a Marine Environment, July 2022 Ch 4, 2 Shipboard cranes.
Note 4. Stress factors for other sailing conditions are to be agreed with LR in the load case definition phase.
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