Assessing Seismic
Collapse Risk of Buildings
Olive View Hospital,
San Fernando Earthquake, 1971
courtesy: V. Bertero
PEER’s performance-based earthquake engineering methodology has been
applied to assess the risk of earthquake-induced collapse of reinforced concrete
frame
buildings.
This
process
entails
…
EQ: 11121, Sa: 2.86g
EQ: 11122, Sa: 2.32g
n-stories at H
the development of analytical models and simulation tools …
PEER has developed an open-source nonlinear
analysis platform (opensees.berkeley.edu), which
includes advanced material models and geometric
transformations, and robust convergence algorithms
that are capable of predicting structural behavior up
to collapse.
Wlean
Wtrib
M
beam
column
H1st-story
beamcolumn joint
leaning
(P-D)
column
foundation
bay size
Illustration of dynamic analysis results
Idealized model for nonlinear
analysis of RC building frame
that are validated by experimental results …
The PEER column performance database
contains cyclic test data from over 400
reinforced concrete columns. PEER
researchers have tested additional
structural components, and calibrated
nonlinear models for response simulation.
300
Experimental Results
Model Prediction
Shear Force (kN)
200
100
Comparison of cyclic
test data with
model predictions
0
-100
-200
and incorporate key sources of
Column Drift (displacement/height)
uncertainty …
to predict the structural collapse risk.
-300
-0.1
0.2
0.5
1
1.5
2
2.5
Ground Motion Intensity, Sa(T1) [g]
3
Effect of modeling uncertainties
on collapse fragility curve
Quantification and propagation of
uncertainties in both ground motions
and structural modeling are essential
aspects of risk assessment.
Applications
0.8
Older non-ductile:
perimeter frames
space frames
0.5
0.1
0.7
0.6
0.4
0.5
0.3
0.4
Modern:
perimeter frames
space frames
0.2
0.3
0.2
0.1
0.4
0.3
EQ: 121231, Sag.m.(T=0.87sec): 2.26g
EQ: 121232, Sag.m.(T=0.87sec): 1.66g
EQ: 121321, Sag.m.(T=0.87sec): 3.06g
EQ: 121322, Sag.m.(T=0.87sec): 2.99g
0.2
0.1
ASCE 7-2002
Space Frames
Perimeter Frames
0.1
00
00
ASCE 7-2005: Reduced
minimum base shear
requirement
0.5
]
ground motion
variability only
0.4
0
0
0.05
0.9
2/50
0.6
0
P[Collapse|Sa
P[collapse]
0.8
ground motion
& modeling
uncertainties
P[Collapse|Sa ]
P[Collapse|2 in 50 2/50
yr. gm]
1
-0.05
2
5
4
10
6
8
15
Number
of Stories
Number
of Stories
10
20
12
Space Frames
Perimeter Frames
14
0
0
5
10
15
20
Number of Stories
Conditional probabilities of collapse, given an extreme ground motion (2% in 50 year).
Above left, the collapse risk of older (1967 UBC) and modern (2003 IBC)
reinforced concrete frame buildings of different heights and configurations
are compared. The older non-ductile buildings are significantly more likely to
collapse under large ground motions. Above right, reducing the minimum
required base shear for taller long-period structures increases their risk.
These studies can be used to assess and improve current building code provisions. In the ATC-63 project, probabilistic collapse
methods are used to assess building system performance factors, such as R-factors. Analytical studies of collapse risk are also
useful for identifying vulnerable buildings for retrofit.
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Poster By: Abbie Liel and Greg Deierlein (Stanford), and Curt Haselton (CSU, Chico)