Risk assessment and management of civil infrastructure networks: a systems approach - Seismic Risk Analysis and Management of Civil Infrastructure Systems - page 429

A network is a representation of a set of interacting elements. The last
decades of the twentieth century brought signifi cant development in the
fi eld of network modelling; the modelling and analysis of biological, physi-
cal, and social systems, as well as the availability of computational resources
facilitated the formalization of network research (Watts, 2004). Many prob-
lems are treated from a network perspective, e.g., the Internet network,
transportation, and communication (Gómez et al. , 2011a,b,c,d), as well as
less evident ones, such as protein chains (Barzel and Biham, 2009) and
percolation theory (Stauffer and Aharony, 1992). Network theory con-
denses models, measures, and algorithms that are useful to describe and
quantify the form (topology) and performance (fl ow and dynamics) of
networks.
Section 17.2 provides basic notions of systems thinking and network
modelling upon which the proposed framework is constructed. It describes
how systems can be described as the recursive embedding of subsystems in
a hierarchical fashion and offers a basic theoretical background, such as
network representation and computation of network performance indices.
Section 17.3 provides an introduction into network clustering as a pattern
recognition technique that facilitates the hierarchical decomposition of
infrastructure networks into sub-networks. Section 17.4 deals with risk
assessment of infrastructure networks, focusing on strategies to exploit
benefi ts of the proposed hierarchical model for the assessment of reliability,
vulnerability, and damage propagation. Finally, Section 17.5 discusses
relevant decision-making aspects in infrastructure systems and proposes
optimization strategies for resource allocation, based on the proposed
hierarchical model.

17.2 Systems and networks

17.2.1 Systems thinking

The rise of cybernetics (Wiener, 1948; Ashby, 1964) contributed to the
efforts towards a unifi ed theory of systems through the analysis of shared
properties of systems across several disciplines and domains. Further
theories and applications were developed based on such knowledge, includ-
ing organizational cybernetics and applied systems thinking (Beer, 1967;
Checkland, 1981; Blockley and Godfrey, 2000; Senge, 2006; Mingers and
White, 2009). Systems thinking (Ackoff, 1962; Churchman, 1963) emerged
as an oppositional paradigm to reductionist tendencies (Looijen, 1999) in
the fi rst half of the twentieth century. Systems thinking not only studies the
parts of a system but also the relationships between them, thus incorpor-
ating concepts such as wholes, parts, hierarchy of subsystems, and emergent
properties.