Seismic risk models for aging and deteriorating buildings and civil infrastructure - Seismic Risk Analysis and Management of Civil Infrastructure Systems - page 382

(including both accidents and terrorists attacks). Damage accumulation
after earthquakes has attracted a signifi cant amount of interest, especially
after the recent events in Chile and Japan. Frequently earthquake damage
is evaluated in terms of the variation (e.g., increment) of the inter-storey
drift, the loss of stiffness or the amount of energy dissipated. A large
number of papers and reports have been produced regarding damage accu-
mulation in structures in a single seismic shock due to repeated cyclic load-
ings (e.g., Jeong and Iwan, 1988; Ballio and Castiglioni, 1994). However, not
very many papers are available discussing the problem of damage accumu-
lation over time after the structure is subjected to successive earthquakes.
Earthquake damage accumulation is in general diffi cult to assess and quan-
tify. In other fi elds of engineering, and from a more mathematical perspec-
tive, extensive research has been carried out on models for shock
degradation; for more details see Barlow and Proschan (1965), Aven and
Jansen (1999), Nakagawa (1976), Feldman (1977) and Zuckerman (1977).
These models have been shown to have features which can be used for
better understanding of structural damage accumulation over the struc-
ture's lifetime.
The objective of this chapter is to present an overview of existing sto-
chastic models to manage structural deterioration as a result of the indi-
vidual or combined action of both progressive and extreme event
degradation. The chapter emphasizes the importance of including damage
accumulation when studying the life-cycle performance of structures and
infrastructure systems. This chapter has been prepared as assemble of previ-
ous works published by the authors on topics related to stochastic modeling
of damage accumulation. The reader can fi nd some additional details in the
following reference documents: Sánchez-Silva and Rackwitz (2004), Basti-
das et al. (2010, 2011), Sánchez-Silva et al. (2011), Gosh et al. (2012) and
Sánchez-Silva and Riascos-Ochoa (2012a,b). The chapter is structured as
follows: in Section 15.2 we present an overall description of the deteriora-
tion process and the main characteristics of both progressive and shock-
based mechanisms. In Sections 15.3 we focus primarily on shock-based
damage processes while in Section 15.4 there is a discussion on progressive
degradation models. Finally in Section 15.5 the combined effect of both
progressive and shock-based mechanisms is discussed.
15.2 Structuraldegradation
15.2.1 Defi nition of degradation
Structural deterioration (i.e., damage) is defi ned as any change to the mate-
rial or the geometric properties affecting the structural performance (e.g.,
capacity). The deterioration of the system is commonly measured with