Autor: David Howard Sanders Fecha: 2017/11/09

1. David H. Sanders MAE Presentation
11/9/2017 1
Impact of Earthquake Duration on Bridge
Performance
1
David H. Sanders
University Foundation Professor
Department of Civil and Environmental
Engineering
University of Nevada, Reno
2
• Chile (2015, 2014 and 2010), Japan (2011), China (2008),
and Indonesia (2004) earthquakes are reminders of the
importance of the effect of ground motion duration on
structural response.
• Long fault ruptures including subduction zones
• Chile Earthquake Ruptured over ~ 500 km
Duration ~ 20-90 seconds
• Tohoku Earthquake Fault size ~ 500 km x 210 km
Duration ~ 90-270 seconds
Earthquakes typically last less than 30
seconds
Why Long Duration?
• California

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11/9/2017 2
Ground Motion Duration Definitions
3
Arias Intensity=∫a2.dt
• Significant Duration (5‐95% of the Arias Intensity)
Recommended by Jack Baker
and Greg Deierlein (2012)
Vu and Saiidi (2005)
Rinaldi -1/3 scale
• Design Code: AASHTO
• L/D= 4.5 (flexural control)
Target Displacement
demands for our tests
(50%)
4
9.8 in.
Specimen Design/Pre-test Analysis

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Specimen Design/Pre-test Analysis
5
- OpenSees model was used to simulate Vu and Saiidi’s Column
- Selection of the motions was based on this model (the displacement
demands to be around half the capacity)
-80 long-duration ground motions from Japan 2011 and Chile 2010
were used in the pre-test analysis
6
Damage Prediction Before Testing
Modified Park-Ang damage index was used to quantify the damage
•δ max = Maximum displacement demand during the ground motion
•δ u =Ultimate displacement capacity (taken 9.8 in. from Vu and
Saiidi’s test)
•β = Constant (taken 0.15 for concrete structures)
•Eh = Hysteretic energy
•Fy = Yield force

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Modified Park-Ang damage index was used to quantify the damage
Data from past shake-table and cyclic load tests on seismically designed
bridge columns (about 25 models) were used to correlate the damage
index with different damage states.
Experimental Fragility Curves
0
10
20
30
40
50
60
70
80
90
100
0 0.5 1 1.5 2 2.5 3 3.5
Probabilityofexceedinga
damagestate(%)
DI (Park and Ang.)
Minor Spalling
Extensive Spalling
Exposed Reinforcement
Bar Buckling
Bar Fracture
‐Example:
Run #, DI=1.5
1.5 7
40% Bar Buckling
0% Bar Fracture
90% Exposed RFT.
Damage Prediction Before Testing
8
Japan
Long-dur.
Loma Prieta
Short-dur.
Japan
Long-dur.
0
0.5
1
1.5
2
2.5
3
0 1 2 3 4
SpectralAcceleration(g)
Period (sec.)
Crescent City, CA (2475 years)
FKSH20 N-S (Original)
FKSH20 N-S (Modified)
Column LD-J1
(Long-Duration)
Japan
0
0.5
1
1.5
2
2.5
3
3.5
0 1 2 3 4
SpectralAcceleration(g)
Period (sec.)
Seattle, WA
Port Angeles, WA
Newport, OR
Crescent City, CA
Eureka, CA
2475 yr return period
Selected
Spectral Matching
0
0.5
1
1.5
2
2.5
0 1 2 3 4
SpectralAcceleration(g)
Period (sec.)
Crescent City, CA (2475 years)
MYG006 E-W (Original)
Initial Period
Shake Table Tests

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9
Japan
Long-dur.
Loma Prieta
Short-dur.
-0.8
-0.6
-0.4
-0.2
0
0.2
0.4
0.6
0.8
0 50 100 150 200 250
Acceleration(g)
Time (sec.)
Ds (5-95%) = 88 sec.
-0.8
-0.6
-0.4
-0.2
0
0.2
0.4
0.6
0.8
0 50 100 150 200 250
Acceleration(g)
Time (sec.)
Ds (5-95%) = 9 sec. 0
0.5
1
1.5
2
2.5
0 1 2 3 4
Acceleration(g)
Period (sec.)
Japan
Short
Design codes
These motions are the same
Japan
Long-dur.
Shake Table Tests
10
Axial Load
Mass Rig
System Lateral
Load cell
Axial
Load
Rigid
frame
String pots
Shake
table
Specimen
Shake Table Tests

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11
Mass Rig
Shake Table
Rigid Frame
Axial Load
Shake Table Tests
12
100% of GM
+
AfterShock
+
125% of GM
+
150% of GM
+
etc… (Until Failure)
Loading Protocol

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13
Max. Disp.= 4.5” Max. Disp.= 3.88”
South
• 4.4” spalling
• Spirals Exposed
North
• 3.0” spalling
• Spirals Exposed
South
• Cracks (max
width= 0.4mm)
North
• 4.5” spalling
• No RFT. Exposed
Column 1
(Japan- Long Dur.)
Column 2
(Short-duration)
100 % of the Ground Motion
Max. Disp.= 4.7”
South
North
• Minor spalling
• No RFT. Exposed
Column 3
(Japan – Long Dur.)
• 7.5” spalling
• Spirals Exposed
14
Max. Disp.= 4.98” Max. Disp.= 4.8”
South
North
South
North
Column 1
(Japan- Long Dur.)
Column 2
(Short-duration)
Max. Disp.= 7.38”
South
North
Column 3
(Japan – Long Dur.)
• 8.5” spalling
• 4 Bars fractured
• 6.4” spalling
• Core Damage
• 4.5” spalling
• Spirals exposed
• 4.5” spalling
• Spirals exposed
• 8.0” spalling
• 3 Bars buckled
• 5” spalling
• 1 Bar fractured
125 % of the Ground Motion

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15
Max. Disp.= 4.98” Max. Disp.= 4.8”
South
North
South
North
Column 1
(Japan- Long Dur.)
Column 2
(Short-duration)
Max. Disp.= 7.38”
South
North
Column 3
(Japan – Long Dur.)
• 8.5” spalling
• 4 Bars fractured
• 6.4” spalling
• Core Damage
• 4.5” spalling
• Spirals exposed
• 4.5” spalling
• Spirals exposed
• 8.0” spalling
• 3 Bars buckled
• 5” spalling
• 1 Bar fractured
-4
-2
0
2
4
6
8
350 400 450 500 550
Displacement(in.)
+ 7.38 in.
- 2.3 in.
Bar FractureA Column 3
125 % of the Ground Motion
16

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17
Column 1
(Japan- Long Dur.)
Column 2
(Short-duration)
Column 4
(Japan – Long Dur.)
Max. Disp.= 7.3”
South
North
• 6” spalling
• Spirals exposed
• 9” spalling
• Spirals exposed
NotApplicable
BarsFracturedat
125%
Max. Disp.= 4.98”
NotApplicable
BarsFracturedat
125%
Max. Disp.= 7.38”
150 % of the Ground Motion
18
Column 1
(Japan- Long Dur.)
Column 2
(Short-duration)
Column 4
(Japan – Long Dur.)
Max. Disp.= 9.22”
NotApplicable
BarsFracturedat
125%
Max. Disp.= 4.98”
NotApplicable
BarsFracturedat
125%
Max. Disp.= 7.38”
South
North
• 1 bar fractured
• 2 bars buckled
• 4 bars buckled
175 % of the Ground Motion

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19
Force Displacement
20
Short-Duration
Long-Duration
(Japan-1)
Long-Duration
(Japan 2)
Strain History

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21
Column LD-J1 (Japan-125%)
Column SD-L (Short-175%)
Spectral Acceleration at Final Damage State
22
‐Concrete01 with STC
‐Steel02
‐Wehbe’s method for bond slip
0
20
40
60
80
100
0 0.5 1 1.5 2 2.5 3 3.5 4 4.5
Probabilityofexceedinga
damagestate(%)
DI (Park and Ang.)
Minor Spalling (M.S.)
Extensive Spalling (E.S.)
Exposed Reinforcement (E.R.)
Bar Buckling (B.B.)
Bar Fracture (B.F.)
50 % probability
Post-Test Analysis

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23
Incremental Dynamic Analysis (IDA)
0
10
20
30
40
50
60
70
80
90
100
0 5 10 15
ProbabilityofCollapse(%)
Could be any INDEX
OpenSees Model #
Long-Duration Short-Duration
Set A
- Example on how
the comparative
collapse fragility
curves look like
- Each point
represents a ground
motion that was
scaled until failure
Post-Test Analysis
672 total motions that were scaled until collapse
24
Maximum Displacement
Comparative Collapse Analysis
(Collapse Fragility Curves)
Post-Test Analysis

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25
Spectral Acceleration
Comparative Collapse Analysis
(Collapse Fragility Curves)
Post-Test Analysis
Conclusions
26
1) Ground motion duration has a significant effect on the collapse
capacity of bridge columns.
3) A significant reduction in the spectral accelerations at collapse
in case of long duration motions with respect to the short
duration motions.
2) A significant reduction in the displacement capacity was observed
in case of long duration motions compared to the short duration
motions for both the experimental and analytical studies.
Approximate reduction of about 25%
Approximate reduction of about 20%
4) Ground motion duration is an important parameter when
selecting ground motions for nonlinear analysis of structures.

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Rapid Construction
By using precast components to accelerate the onsite construction
I5, Grand Mound Bridge Replacement Project, 2012 (Khaleghi et al. 2012)
27
By using pretensioned rocking columns to reduce the residual
displacements and to mitigate earthquake damage
Resilient Bridge Using Conventional Materials
ReinforcingSteel
SteelTubes
Strands
Grout
Concrete
28Faster Construction and Better Seismic Performance-You Can Have Both
Shape Memory
Alloys (SMA)
Engineered
Cementious
Composites
(ECC)
Resiliency

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System Development
29
Damage Mitigation
1- By confining the end of the columns to reduce the damage to
concrete
2- By debonding the longitudinal reinforcement at critical zones
to control the fracture of the longitudinal bars
ConfiningTube
DebondedBars
30

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+ =
Moment-Rotation
Strand Rebar Total
31
System Development
Moment-Rotation
Strand Rebar Total
+ =
32
System Development

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Moment-Rotation
Strand Rebar Total
+ =
33
System Development
Moment-Rotation
Strand Rebar Total
+ =
34
System Development

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Moment-Rotation
Strand Rebar Total
+ =
35
System Development
Moment-Rotation
Strand Rebar Total
+ =
36
System Development

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Moment-Rotation
Strand Rebar Total
+ =
37
System Development
38
Bridge Description

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39
Column Description
40
Bridge Construction

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1- N-S component Century City
Country Club North (CCN) station
1994 Northridge California
Earthquake
2-N-S components Sylmar- Olive
View Med. Center (SYL)
1994 Northridge California
Earthquake
3-N-S component Takatori (TAK)
record
1995 Kobe, Japan Earthquake
Motion Record PGA (g) Design Level (%)
14A CCN 0.25 33%
14B1 SYL 0.20 -
14B2 SYL 0.40 -
14C TAK 0.25 -
15 CCN 0.50 67%
16 CCN 0.75 100%
17 CCN 1.00 133%
18 CCN 1.33 177%
19 CCN 1.66 221%
20A CCN 0.75 100%
20B SYL 0.843 -
21A TAK 0.40 -
21B TAK 0.611 -
21C TAK 0.80 -
41
Ground Motions
42
Ground Motions

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Conventional Bridge
Motion 19 (221%DE)
Resilient vs Conventional
43
Resilient Bridge
Motion 19 (221%DE) 44
Resilient vs Conventional

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Behavior Comparison (Mantawy et al. 2016)
45
Resilient vs Conventional
Damage Comparison (Mantawy et al. 2016)
46
Resilient vs Conventional

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Damage Evaluation
47
Bar fracture occurred but
after the design level
earthquake. (133%)
Fracture of Reinforcing Bars
Motion 17 18 19 20A 20B 21A 21B 21C Total
# of
Fractures
1 24 29 5 5 0 1 5 70
Method 1:Fracture Estimation
by Acoustic Emissions
48

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Fracture of Reinforcing Bars
1- Bar buckling in the columns was inhibited by
a confining tube detail;
2- Strains in the reinforcement were distributed
over deliberately debonded length;
3- All 72 of the column’s longitudinal
reinforcement fractured during testing; and
4- Because the system deformed by rocking, the
strain response histories could be calculated
from the measured rotations at columns’ ends
after the deformation capacities of the strain
gauges were exceeded.
Method 2:Fracture Estimation by
Connection Rotation
49
Method 2: Fracture Estimation
by Connection Rotation
50
Fracture of Reinforcing Bars

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Numerical Model Development
51
Method 3:Fracture Estimation by
Low Cycle Fatigue Model
52
Numerical Model Development

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Numerical Model Assessment
53
Fracture Excluded Motion 20B (SLY 0.834 g)
54
Fracture Included Motion 20B (SLY 0.834 g)
Numerical Model Assessment

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Total Base Shear Envelope
55
COM Displacement during Motion 19 (221%DE)
Numerical Model Assessment
v v
56
Number of Fractured Bars
Numerical Model Assessment

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Parametric Studies
Using CCN Motion 125%, 150%, and 175% DE
Bent Height and Column Diameter
Steel Ratio, Strand Ratio and Initial Pretensioning
Bar Size - #6, #7, #8
Unbonded Length of conventional reinforcement
What is the impact of configuration on
facture and can the unbonded length of
conventional reinforcement delay fracture?
Impact of Debonding
58
Debonding the longitudinal
steel at the rocking interfaces in
the column, using 24 times bar
diameter was effective to delay
the fracture of longitudinal
bars during the Design Level
Earthquake while keeping
residual displacement low.

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Conclusions
1- The precast system enables the bridge bents to be built
faster in the field than conventional construction.
2- The system used conventional technologies while
mitigating damage such as:
• Confining steel tubes at the ends of the columns
mitigate the damage of concrete and eliminate the
buckling of longitudinal reinforcement.
• Debonding delayed yielding and bar facture.
• Rocking system was effective at keeping residual
displacement low.
59
The impact of earthquake duration
can be significant through
increased strain history,
decreased displacement capacity,
and increased chance of bar
fracture.
60
Conclusions

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Thank you!
This is great honor and very much
appreciated.
61