Page 516 - Marine Structural Design

492 Part IVStructural Reliability

I m (BS8118) logC=a+bm LnC

R=O, a=6.74 3.25 -10.12 -23.30
b=- 1.04 3.5 -10.38 -23.90
R=0.3 a=-7.09 3.25 -9.8525 -22.69
b-0.85 3.5 -10.065 -23.18

~~ ~
Variable Distribution Mean cov
Initial crack size, a. Exponential 0.02 1 .o
Crack initial time ratio, 6 Fixed 0.10 ---
Detectable crack size, aD Exponential 1 .o 1 .O
Geometry bias factor, cy Normal 1 .o 0.1
Stress model error, cS Lognormal 1 .O 0.1
Material parameter, In C Normal -23.30 0.022
Stress scale parameter, InA Normal 1.019 0.10
Crack aspect ratio, ah Fixed 0.5 _---
Random bias of ah, Normal 1 .O 0.1
Miner’s sum at failure, A Lognormal 1 .O 0.3
S-N fatigue parameter, InK Normal 27.065 0.019
Stress shape parameter, 5 Fixed 0.95 _--
Material parameter, m Normal 3.25 0.06
Plate thickness, TH Fixed 30 I--
Plate width, wp Fixed 100 ----
Stress ratio, R Fixed 0.0 ---
Stress cycles per year, vo Fixed 2.5E+6 ----
Fraction of a ship at sea, r Fixed 0.765 _---
Note: Correlation between m and InC is p(m, lnC)=-0.95; is calibrated by S-N approach;
InA is estimated based on BS8118 code with D=0.1, K=2.09E+ll, m=3.25.