GDP 59451 SFr
l 80.4 yearsw (^) 0.112
(^) 0.722
g (^) 35931 SFr
q (^) 0.175
Table 13.2: Demographical constants for Switzerland, (BFS, 2004).
Based on Equation (13.11) the relationships between dg and which lead to increases in
the LQI may be determined which in turn can be utilized for assessing the acceptable
probability of different types of failures of relevance for a considered system.
d
The Societal Willingness To Pay (SWTP) as basis for acceptability criteria
Considering structural reliability applications the relative change in life expectancy
d
may
be exchanged by a change in mortality das (Rackwitz, 2005):
7
xx
d
Cd Ckdm (13.13)
where is the dm failure rate and Cx is a demographical economical constant corresponding
to a given scheme x for mortality reduction and is the probability of dying given a failure.
The constant
k
Cx can be set to 19.0, see Rackwitz et al. (2007). k should be assessed on the
basis of statistical analysis of failures or by specific risk analysis, see Lentz (2007). Rather
conservative, considering structural failures k can be set equal to 1.
Finally there is:
yxPE
g
dC C N kdm
q
(13.14)
where dCy are the annual investments which should be invested into life safety and NPE is
the number of persons exposed to the failure.
Based on Equation (13.14) and Equation (13.11) an acceptance criterion may now be defined
as:
yxPE* ()g
dC C N kdm p
q(13.15)
where the failure rate dm(p) is now introduced as a function of p, the possible decision
alternatives for risk reduction. Equation (13.15) should now be interpreted such that risk
reduction measures must be undertaken as long as the corresponding marginal risk reduction
exceeds the marginal costs of risk reduction. The principle is illustrated in Figure 13.9.