Page 394 - Marine Structural Design

370 Part III Fatigue and Fracture

A2 ~ [ ~ O

.......................... .

Figure 19.4 Definitions of Geometry Parameters (Ma et a1 2000)

19.7 Examples

Example 19.1: Fatigue Design of a Semi-submersible
Problem:
Calculate the maximum allowable stress range for a semi-submersible with a long-term stress
range distribution as:
[ : : : I t:

s=so l--

and the Weibull distribution parameter {=1.1. Total number of stress cycles No =108,
allowable damage ratio q=0.20, class F weld (m=3, K=lOEI 1.8).
Solution:
The maximum allowable stress range can be derived as:

J

If the maximum allowable stress range is scaled by a factor of # . For instance, for q=O.l,
the maximum allowable stress range becomes:
SOoIlmuoble= 93.6 .(O. 110.2)' = 74.2MPa