Page 494 - Marine Structural Design

470 Pari IV Structural Reliability

where the characteristic strength, RC is

R, = 0.85.~~
and the characteristic load effect, SC, is
s, =PS
p~ and ps are mean values. The corresponding coefficients of variation are VR=O. 1
and Vs4.2. The standard deviation are given by OR = VR PR and os = Vs ps.
Assume that design check is fdfilled by the equality sign. What value should y have
so that the design check corresponds to a failure probability of 10” and lo4,
respectively?
Solution
Given
Rc = 0.85~~
sc = PS
Applies the equality condition in the design check formula
Rc = YSC
0.85PR=Y PS
PR/Ps = 1.18 y
The reliability index, p, is given by

Then,

To reach the failure probability of lo3
a(-p) = 10”
1.18~-1
= 3.09
p= JiiiiqXz

Hence,
y = 1.56
To reach the failure probability of 10“‘
CD(-P) = lo4