Effect of soil–structure interaction and spatial variability of ground motion on seismic risk assessment of bridges - Seismic Risk Analysis and Management of Civil Infrastructure Systems - page 603

mate of the characteristics of incoming seismic motion is of paramount
importance. Along these lines, there are at least fi ve key factors in forming
a realistic excitation scenario for bridge design and assessment: (a) overall
seismotectonic features of the area, (b) quantitative criteria provided in
modern seismic codes and design guidelines (typically related to rules for
matching a prescribed spectrum), (c) modifi cation of seismic motion to
consider kinematic soil-structure interaction, (d) direction of excitation and
consideration of the rotational component of earthquake ground motion,
and (e) spatial variability of seismic motion. All these issues are discussed
below.
22.4.1 Selection and generation of earthquake ground
motion scenarios
Earthquake record selection tools
Numerous computational tools have been developed for selecting suites of
earthquake records from available strong ground motion record databases.
Most common earthquake record selection procedures involve spectral
matching of the average response spectrum of the records to be used, with
a target, code-prescribed or seismic hazard-defi ned elastic response spec-
trum (Beyer and Bommer, 2007), or a conditional mean spectrum (Baker
et al. , 2011). Recent work evolved to develop methods and computational
tools for quantifying and/or optimizing the spectrum compatibility (Naeim
et al. , 2004; Kottke and Rathje, 2008). In case of the performance-based
design approach, the selection of acceleration time series is considered with
the goal of accurate prediction of the structural response at a specifi ed
ground motion IM. Most commonly, the peak ground acceleration (PGA)
of the eligible records and some other characteristic parameters (i.e. the
spectral acceleration, S a ) have been used as suitable IMs. Nevertheless,
advanced intensity measures, including information about the spectral
shape and structural characteristics, are preferable for records selection and
scaling procedures as they result in a more accurate and reliable estimate
of the seismic demand (Baker et al. , 2011; Huang et al. , 2009).
Despite the aforementioned state-of-the-art evolution in the research
fi eld, a rather rough framework is prescribed by modern seismic codes and
guidelines (inclusive of Eurocode 8, CEN, 2004, and FEMA P-750, FEMA,
2009) concerning the motions to be used for time history analysis. In fact,
most of the aforementioned record selection methods proposed in the lit-
erature have not yet been incorporated in any seismic code worldwide,
despite the fact that evidence exists that this leads to large dispersions of
structural response (Katsanos et al. , 2010). Along these lines, numerous
computational tools have been developed to raise the limitations imposed