Building Collapse Fragilities Considering
Mainshock-Aftershock Sequences Using
Publicly Available NEEShub Data
Yue Li and Ruiqaing Song
Michigan Technological University
John W. van de Lindt
The University of Alabama
Nicolas Luco
United States Geological Survey
1
Integration of Mainshock-Aftershock Sequences Into Performance-Based
Engineering Using Publicly Available NEEShub Data
Yue Li (PI)
Michigan Technological University
John van de Lindt (Co-PI)
University of Alabama
Nicolas Luco (Co-PI)
United States Geological Survey
Graduate Students:
Ruiqiang Song
Negar Nazari
NSF CMMI -1000567
Introduction
•
During earthquake events, it’s very common to observe many
aftershocks following the mainshock (588 aftershock with magnitude
5 and greater recorded after the Earthquake in Japan 2011).
Tohoku Aftershock
•
Although smaller in magnitude, aftershocks may have a large
ground motion intensity, longer duration and different frequency
content
3
Motivation
•
Potential to cause
severe damage to
buildings and threaten
life safety even when
only minor damage is
present from the
mainshock
•
However, most of
current seismic risk
assessment focus on
risk due to a mainshock
event only
February 2011 Christchurch Earthquake
4
Research Challenges
• Significant uncertainty in collapse capacity
of damaged buildings after the mainshock
• Characteristics of aftershocks are quite
complex
• Lack of system fragility models to evaluate
building performance
PBE objectives
Design/retrofit
options
Task 1
Design portfolio
Building
No.
1
Building Type
Brief Description
Steel
2
Steel
3
Steel
4
Light-frame
Wood
Light-frame
Wood
Three-story steel building
with ordinary moment frame
Four-story steel building with
special moment frame
Eight-story steel building
with special moment frame
Two-story light commercial
building
Three-story
apartment
building
5
Pcollapse =
Numerical model
selection
Task 2
Global-level hysteresis
damage model
Consider
aftershock?
Mainshock-aftershock
sequence simulation
PBE framework
mainshock only
Task 3
Fragility generation for
degrading systems
Task 4
Integration of
aftershock hazard
with PBE
 P[Collapse | S
a
 x] | dH ( x) |
Satisfied
performance
expectation?
Task 5
Illustration and Integration
into Existing
Methodologies
Seismic Rehabilitation of Existing Building
Tested Steel Structure at NEES @ Buffalo
• A typical 4-story 2-bay steel moment frame
(1/8 scale) is selected
(Lignos and Krawinkler 2011)
7
Calibration of Prototype and Test model
Natural period in the EW direction
Pushover analysis in EW direction
Results
T1
T2
T3
Peak based shear/weight
Maximum roof drift
Lignos Thesis
1.32
0.39
0.19
0.2
8.2%
Centerline model
1.32
0.44
0.24
0.2
8.2%
Based Shear/Weight
Lignos Result: Figure
8.1
Simulation Model
0.2
0.15
0.1
0.05
0
0.00
•
0.05
Roof Drift
0.10
Probability of Exceedence
Pushover Curves
0.25
Fragility Curve
1
0.8
0.6
0.4
Simulated model
0.2
Lignos's result
0
0
1
2 Sa (g) 3
4
5
The first three modal periods, pushover curve, fragility curves and
time history response of prototype and test model are calibrated
8
2010 - 2011 Canterbury Earthquake
Records at Resthaven, New Zealand
9
Structural Collapse Capacity
•
•
22 Far-Field records and 28 Near-Field records from
FEMA P695
Preform incremental dynamic analysis (IDA) to determine
structural collapse capacity
10
Damaged Building from Mainshock
•
In order to obtain the specific structural damage condition
sustained from mainshock, the intensity level of mainshock is
scaled to cause the following drift defined in ASCE/SEI 41-06
Damage Level
Drift
Immediate occupancy
0.7% transient
life safety
2.5% transient
collapse prevention
5% transient
11
Structural Collapse Capacity
Difference Damage Level from Mainshock + Aftershock
Spectral acceleration (g)
IDA for different damage state from MS
2
1.8
1.6
1.4
1.2
1
0.8
0.6
0.4
0.2
0
Only Mainshock
I.O.(0.7% from MS, Unchanged) + AS
L.S.(2.5% from MS, Unchanged) + AS
C.P.(5.0% from MS, Unchanged) + AS
0
0.05
0.1
0.15
Drift
0.2
0.25
12
Structural Collapse Capacity
Difference Damage Level from Mainshock + Aftershock
Spectral acceleration (g)
IDA for different damage state from MS
2
1.8
1.6
1.4
1.2
1
0.8
0.6
0.4
0.2
0
Only Mainshock
I.O.(0.7% from MS, Unchanged) + AS
L.S.(2.5% from MS, Unchanged) + AS
C.P.(5.0% from MS, Unchanged) + AS
0
0.05
0.1
0.15
Drift
0.2
0.25
13
Spectral accleration (g)
Structural Collapse Capacity
Mainshock Damaged Building + Different Aftershocks
2
1.8
1.6
1.4
1.2
1
0.8
0.6
0.4
0.2
0
Damaged from MS +different AS
Only Mainshock
MS + Scaled AS 0.25g (Unchanged)
MS + Scaled AS 0.85g (Unchanged)
MS + Scaled AS 1.40g (Unchanged)
0
0.05
0.1
Drift
0.15
0.2
0.25
14
Spectral accleration (g)
Structural Collapse Capacity
Mainshock Damaged Building + Different Aftershocks
2
1.8
1.6
1.4
1.2
1
0.8
0.6
0.4
0.2
0
Damaged from MS +different AS
Only Mainshock
MS + Scaled AS 0.25g (Unchanged)
MS + Scaled AS 0.85g (Unchanged)
MS + Scaled AS 1.40g (Unchanged)
0
0.05
0.1
Drift
0.15
0.2
0.25
15
Probability of Exceedence
Collapse Fragility Curves
1.0
0.9
0.8
0.7
0.6
0.5
0.4
0.3
0.2
0.1
0.0
Only mainshock
I.O.(0.7% from MS) + AS
L.S.(2.5% from MS) + AS
C.P.(5.0% from MS) + AS
0.0
1.0
2.0
Sa (g)
3.0
4.0
16
Combination of Mainshock-aftershock Sequences
1. Mainshock + repeated aftershock (Far-Field)
2. Mainshock + random aftershock (Far-Field)
3. Mainshock (Far-Field) + aftershock (Near-Field)
4. As-recorded mainshock + aftershock sequences
17
Collapse Capacity for MS-AS Sequences
18
Summary and On-going Research
•
Damaged building from mainshock may have significantly
reduced collapse capacity
•
Structural collapse capacity depends on combination of
mainshock - aftershock sequences, particularly the
frequency contents in earthquake ground motions
•
•
•
Investigation of portfolio of representative steel buildings
Effects of as-record MS-AS sequences to be investigated
Wood frame buildings – collaborative work at University
of Alabama (Prof. John van de Lindt, Co-PI)
19
Thank you!
Contact Information:
Dr.Yue Li
Associate Professor
Michigan Technological University
yueli@mtu.edu