member of society such as the risk of death due to disease is often used as a measure of
comparison. Many people, however, accept voluntary risks several orders of magnitude
higher, but, as will be discussed in a later chapter, this should not be taken into account when
considering the safety of civil engineering facilities such as infrastructure and nuclear power
plants.
The Role of Human Errors
One of the most important roles of the engineer is to understand the hazard potentially
associated with a given activity and to appreciate the corresponding risks. This means that the
engineer in an informed and conscious way shall be able to implement adequate means of risk
treatment so that the risks associated with the activity are reduced and controlled to an
acceptable level.
In Figure 1.6 it is illustrated that in practice only part of the hazard potential associated with
an activity is objectively known. Furthermore, only part of this is subjectively realized.
Therefore, only a certain part of the total hazard potential may be considered in the
implementation of risk treatment measures. The risk treatment measures are implemented in
order to deal with the risks, which are not accepted.
For structural design risk treatment measures could be to design the structure in such a way
that the probability of failure is adequately low. However, only part of the risk treatment
measures will be adequate and again only part of these will be implemented correctly.
Therefore, eventually only part of the risk, which is not acceptable, will be circumvented by
the risk treatment measures and the remaining part may be considered risks due to human
errors.
It should be mentioned that human errors do not necessarily lead to increased risks. Even
though this might be the normal case, a number of human errors could actually lead to a
reduction of risks. However, human errors are more visible when they have severe
consequences and otherwise they are seldom discovered.
It is important to realize that when dealing with the design, execution, operation, maintenance
and decommissioning of technical installations such as e.g. structures decisions can only be
based on the available knowledge. Thus, on the basis of this knowledge, the decision problem
is to use the resources of society on a smaller scale. The resources of the owner and/or
operator of the installation cost shall be used optimally taking due account of the requirements
for safety to third parties and the environment. The hazard potential, which in effect remains
unknown, can only be reduced by means of research, education and learning from experience.
The treatment and/or acceptance of risks, which are realized, are essentially the core issue of
this course. According to Lind (2001) 10-20 per cent of the GDP produced in the developed
countries is in one way or the other reinvested in risk treatment such as safety, risk reduction
and public health. The decisions on how to allocate these resources should be justifiable. A
responsible way to ensure this is by quantifying the risks and the acceptable risks.