Civil Engineering Reference
In-Depth Information
Earthquake
Structure
Phase 1
Seismic hazard curves
Phase 2
Structural performance
Phase 3
Vulnerability evaluation
Fragility curve
Seismic loss function
Phase 4
Seismic risk assessment
Expected loss evaluation
Seismic risk curve
27.3
Seismic risk analysis procedure for railway viaduct (Yoshikawa
et al
., 2007).
Provisions for Railway Structures (Seismic Design) by Railway Technical
Research Institute (RTRI) are considered. The current version has been
revised based on the careful review after the Kobe Earthquake in 1995. The
objective of this investigation is to quantify the seismic risk of railway via-
ducts with different seismic capacities, and to assess the benefi t gained from
improved seismic design provisions for such structures.
The numerical procedure of seismic risk analysis is shown in Fig. 27.3,
which consists of four phases (Yoshikawa
et al.
, 2007): (1) seismic hazard
analysis at a construction site, (2) evaluation of structural performance of
a viaduct by pushover analysis, (3) vulnerability and loss evaluation of the
structure, and (4) seismic risk assessment by taking into account seismic
hazard and vulnerability characteristics. The fi nal output from the analysis
is the seismic risk curve and other seismic loss quantities.
The fi rst case study is focused on seismic risk analysis of reinforced con-
crete viaducts. In this case study, two viaducts are considered: viaduct 1 was
designed by the old provisions (RTRI, 1992), while viaduct 2 is based on
the current design code (RTRI, 2004). The structures are supposed to be
located in Tokyo, Shibuya ward, and then seismic hazard analysis is carried
out. The foundations of the viaduct 1 are spread-footings isolated each
other and have no piles, while the columns of the viaduct 2 are connected
rigidly with underground beams and have piles from the column base
straight down into the ground.
Probabilistic seismic risk analysis of two railway viaducts was carried out.
For nonlinear pushover analysis (as part of vulnerability assessment), the
viaducts were modeled as two-dimensional frames in transverse and longi-
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