Performance of Bridge Columns Under Long Duration Ground ... · Problem Statement and Objectives 7 • The 2010 M8.8 Chile and 2011 M9.0 Tohoku, Japan earthquakes are a reminder of

Performance of Bridge Columns Under Long Duration Ground Motions (Shake Table Tests)

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Presented by :Mohammed Saeed Mohammed

David Sanders and Ian Buckle

Research Assistant, PhD StudentDept. of Civil and Environmental Engineering

ProfessorsDept. of Civil and Environmental Engineering

University of Nevada, Reno

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Presented by :

Mohammed Saeed Mohammed






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Problem Statement and Objectives

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• The 2010 M8.8 Chile and 2011 M9.0 Tohoku, Japanearthquakes are a reminder of the importance of theeffect of ground motion duration on structural response.

• Comparing these ground motion durations with otherearthquakes in California which has typically lasted lessthan 30 seconds, shows that the durations of the Chile andthe Tohoku earthquakes are very long.

• Chile Earthquake Ruptured over ~ 500 kmDuration ~ 20-90 seconds

• Tohoku Earthquake Fault size ~ 500 km x 210 kmDuration ~ 40-110 seconds

Why Long Duration ?


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• Current seismic design codes do not consider durationeffects and they are mainly based on the peak response.

The big differences in conclusions of previous researchwith regard to the effect of strong ground motionduration on structural performance.

AND THIS IS DUE TO :

The lack of the available long duration ground motionrecords which made the researchers to conduct theirstudies using simulated records.

Why Long Duration ?


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• But now, and after recording a number of long durationground motions from 2008 China, 2010 Chile and 2011 Japanearthquakes, extensive data are now available for studyingthis topic.

Instrumentation in Japan

The Japanese event is the bestrecorded mega earthquake for a longtime come.

Why Long Duration ?

Japan is the best instrumentedplace in the world.


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• What makes this study even more important is thepossibility of occurrence of another large magnitude longduration subduction earthquake along the PacificNorthwest coast of the United States which lies near theCASCADIA SUBDUCTION ZONE.

More than twice the lengthof the Tohoku fault.

From the literature, there aresome similarities between theJapan and the CascadiaSubduction Zone.

Why Long Duration ?

Research Questions

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• Should the current seismic codes be modified totake the effect of ground motion durations intoaccount?

• How do we characterize the difference in damagebetween a short and long duration earthquake?

Ground Motion Duration Definitions

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• Bracketed Duration

0.05g or 0.1gThresholds

Bracketed Duration

• More than 30 definitions of ground motion duration in theliterature.

0.05g

0.05g

The measure of the time interval between the first and lastexceedance of an absolute acceleration threshold

Ground Motion Duration Definitions

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• Significant Duration (5-95% of the Arias Intensity)

Recommended by Jack Baker and Greg Deierlein (2012)

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Path to the test (Pre-test work)1- Choose a previously tested column that was tested under

regular motions to be our specimen, in this case we canknow the maximum displacement capacity of the columnsbefore testing.

Vu and Saiidi (2005) - Rinaldi - 1/3 scale

• Design Code: AASHTO• L/D= 4.5 (flexural behavior)• Axial Load ratio= 8.0%• Long. steel ratio= 2.2%• Trans. steel ratio= 1.1%

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1- Choose a previously tested column that was tested underregular motions to be our specimen, in this case we canknow the maximum displacement capacity of the columnsbefore testing. Displacement Capacity= 9.8 in.

Path to the test (Pre-test work)

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2- A simple OpenSees model is used to simulate Vu and Saiidi’sColumn.

The selection of the motions is based on this model (thedisplacement demands are almost half the capacity).


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3- Two identical specimens are tested :

Long duration motion from the Japan 2011 Earthquake Short duration motion from Loma Prieta 1989 Earthquake

0

0.5

1

1.5

2

2.5

3

3.5

0 0.5 1 1.5 2 2.5 3 3.5 4

Acc.

(g)

Period

2475 Years Response Spectra (USGS)(Site Class D)

Crescent City (California)

NewPort (Oregon)

Port Angeles (Washington)

Eureka (California)


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3- Two identical specimens are tested :

Long duration motion from the Japan 2011 Earthquake Short duration motion from Loma Prieta 1989 Earthquake

0

0.5

1

1.5

2

2.5

3

3.5

0 0.5 1 1.5 2 2.5 3 3.5 4

Acc.

(g)

Period

2475 Years Response Spectra (USGS)(Site Class D)

Crescent City (California)

NewPort (Oregon)

Port Angeles (Washington)

Eureka (California)

The two motions are modified to match the response spectrum of Crescent City (2475 years)


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This approach was suggested by Deierlein (2012) .


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1) Japan, Tohoku 2011 /Station: FKSH20 (N-S)

0

0.5

1

1.5

2

2.5

3

0 1 2 3 4

Acc.

(g)

Period (sec)

Japan Modified

Japan Original

Crescent City 2475

Significant Duration = 88.3 seconds


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2) Loma Prieta 1989/Station: Bran 00

Significant Duration = 9.0 seconds

0

0.5

1

1.5

2

2.5

3

0 1 2 3 4

Acc.

(g)

Period

Short Modified

Short Original

Crescent City 2475


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Final Motions

0

0.5

1

1.5

2

2.5

3

0 1 2 3 4

Acc.

(g)

Period

Japan Modified

Short Modified

0

0.5

1

1.5

2

2.5

3

0 1 2 3 4

Acc.

(g)

Period

Japan Modified

Short ModifiedPeriod

Column 1

Japan, TohokuSig. Dur. (Prototype)

= 88.3 secSig. Dur. (Specimen)

= 50.9 sec

Column 2

Short, Loma PrietaSig. Dur. (Prototype)

= 9.0 secSig. Dur. (Specimen)

= 5.2 sec

Prototype Model

Period


OpenSees Pre-AnalysisColumn 1 Column 2

Japan, Tohoku Short duration

Maximum displacement demands of about 4 inches23

4 4

Design codes These motions are the same


Earthquake Engineering Laboratory

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Test Setup

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Axial Load

Test Setup

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Axial Load

Specimen

Test Setup

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Axial Load

Shake table

Specimen

Test Setup

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Axial Load

Mass Rig System

Shake table

Specimen

Test Setup

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Axial Load

Mass Rig System Lateral

Load cell

Shake table

Specimen

Test Setup

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Axial Load


Load cell

Axial Load cell

Shake table

Specimen

Test Setup

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Axial Load


Load cell

Axial Load cell

Rigid frame

String pots

Shake table

Specimen

Test Setup

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Mass Rig

Shake Table

Rigid Frame

Axial Load

Test Setup

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Instrumentation• 48 Strain Gages• LVDT’s

• String Potentiometers• HD and Go-Pro cameras

LVDT’s

Go-Pro camera in each corner

String pots connected to the rigid frame

• Accelerometers

Loading Protocol

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100% of GM +

AfterShock+

125% of GM+

150% of GM+

etc………

Test Results

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100 % of the Ground MotionColumn 1(Japan)

Column 2(Short duration)

Max. Disp.= 4.5 in. Max. Disp.= 3.88 in.

Test Results

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100 % of the Ground Motion

Max. Disp.= 4.5” Max. Disp.= 3.88”

South

• 4.4” spalling• Spirals ExposedNorth

• 3.0” spalling• Spirals Exposed

South

• Cracks (max width= 0.4mm)

North

• 4.5” spalling• No RFT. Exposed

Column 1(Japan)


0

0.5

1

1.5

2

2.5

3

0 1 2 3 4

Acc.

(g)

Period

JapanModifiedShortModified

Test Results

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Max. Disp.= 4.98” Max. Disp.= 4.8”

South

• 8.5” spalling• 4 Bars fracturedNorth

• 6.4” spalling• Core Damage

South

North

• 4.5” spalling• Spirals exposed

• 4.5” spalling• Spirals exposed

Column 1(Japan)


Test Results

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150 % of the Ground MotionN

ot A

pplic

able

Max. Disp.= 7.3”

South

North

• 6” spalling• Spirals exposed

• 9” spalling• Spirals exposed

Bar

s Fra

ctur

edat

12

5%Column 1(Japan)


Test Results

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Max. Disp.= 9.22”

South

North

• 1 bar fractured• 2 bars buckled

• 4 bars buckled

Column 1(Japan)


Not

App

licab

le

Bar

s Fra

ctur

edat

12

5%

Test Results

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Force-Displacement Comparison

4 Bars Fractured

1 Bar Fractured

Test Results

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Strain Comparison (100%of GM)

4 in. above the footing

Response Spectra Comparison

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Response Spectra at final damage state

Testing Extension

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• Three more columns were tested under long duration motions from the Chile 2010 and Japan 2011 events.

0

0.2

0.4

0.6

0.8

1

1.2

1.4

1.6

1.8

2

0 0.5 1 1.5 2 2.5 3

Acc.

(g)

Period (sec)

Japan, MYG006 E-W

0

0.5

1

1.5

2

2.5

3

0 0.5 1 1.5 2 2.5 3

Acc.

(g)

Period (sec)

Chile, ConcepcionLong. (200%)

• Two of the motions were used without modifications and real aftershocks were also used.

Work in Progress

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Extensive Analytical WorkLong Duration Ground Motion Set

• 1985 Valparaiso, Chile M7.8• 1985 Michoacan, Mexico M8.1• 2003 Hokaido (Tokachi-Oki), M8.0• 2005 Off Miyagi Prefecture, M7.2• 2010 Maule, Chile M8.8• 2011 Tohoku, Japan M9.0• 2012 Kamaishi, Japan M7.3•2014 Chile, M8.1

• 1999 Chi-Chi, Taiwan M7.6• 2004 Niigata, Japan M6.6• 2004 Southeast of Kii Peninsula, M7.4• 2007 Chuetsu, Japan M6.5• 2008 Iwate Eastern Honshu, M6.9• 2008 Wenchuan, China M8.0• 2010 El Mayor Cucapah M7.2• 2011 Fukashima Hamadori, M6.7

SUBDUCTION EARTHQUAKES CRUSTAL EARTHQUAKES

Two sources of long duration ground motion

Long RuptureSite Effects

Modified Park-Ang Damage Index

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•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 = Force causing yield


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0

10

20

30

40

50

60

70

80

90

100

0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1 1.1 1.2 1.3 1.4 1.5 1.6 1.7 1.8 1.9

Prob

abili

ty %

Park and Ang Damage Index

Cracks Throughout

Localized Spalling

Extensive Spalling

Exposed Reinforcement

Bar Buckling

• Data used from past shake-table and cyclic load tests on seismically designed bridge columns (around 25 models) to correlate the damage index with different damage states.


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0102030405060708090

100

0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1 1.1 1.2 1.3 1.4 1.5 1.6 1.7 1.8 1.9

Prob

abili

ty %


Cracks Throughout

Localized Spalling

Extensive Spalling

ExposedReinforcementBar Buckling

Column 2

Column 3

After 100% of the ground motion• Column 1 (Japan) DI = 0.46 +0.87 = 1.33

• Column 2 (Chile) DI = 0.54 +0.46 = 1.00

• Column 3 (Short) DI = 0.40 +0.15 = 0.55

Exposed reinforcement


Extensive Spalling

Actual Damage State

Column 1

Preliminary Conclusions

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• Ground motion duration has a significant effect on the collapse capacity of bridge columns.


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• Reduction in the displacement capacity of about 50% is observed in case of long duration motions compared to the short duration ones.


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• A significant reduction in the response spectrum at collapse (about 40%) of long duration motions with respect to short duration ones.


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• Seismic design provisions are recommended take the effect of ground motion duration into account, not only design response spectra.




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• Seismic design provisions are recommended take the effect of ground motion duration into account, not only design response spectra.

• Ground motion duration is an important parameter when selecting ground motions for nonlinear analysis of structures.



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Thank you

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Questions ?


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•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 = Force causing yield


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0

10

20

30

40

50

60

70

80

90

100

0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1 1.1 1.2 1.3 1.4 1.5 1.6 1.7 1.8 1.9

Prob

abili

ty %


Cracks Throughout

Localized Spalling

Extensive Spalling


Bar Buckling

• Data used from past shake-table and cyclic load tests on seismically designed bridge columns (around 25 models) to correlate the damage index with different damage states.


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0102030405060708090

100

0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1 1.1 1.2 1.3 1.4 1.5 1.6 1.7 1.8 1.9

Prob

abili

ty %


Cracks Throughout

Localized Spalling

Extensive Spalling


Bar Buckling

Column 2

Column 3


• Column 2 (Chile) DI = 0.54 +0.46 = 1.00

• Column 3 (Short) DI = 0.40 +0.15 = 0.55



Extensive Spalling

Actual Damage State

Column 1


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0102030405060708090

100

0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1 1.1 1.2 1.3 1.4 1.5 1.6 1.7 1.8 1.9

Prob

abili

ty %


Cracks Throughout

Localized Spalling

Extensive Spalling


Bar Buckling

Column 2

Column 3


• Column 2 (Short) DI = 0.40 +0.15 = 0.55


Extensive Spalling

Actual Damage State

Column 1


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0102030405060708090

100

0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1 1.1 1.2 1.3 1.4 1.5 1.6 1.7 1.8 1.9

Prob

abili

ty %


Cracks Throughout

Localized Spalling

Extensive Spalling


Bar Buckling

At the final damage state (bar fracture)• Column 1 (Japan) DI = 0.51 +1.94 = 2.45

• Column 3 (Short) DI = 0.98 +1.32 = 2.30

Bar Fracture

Bar Fracture

Actual Damage State

Documents

Performance of Bridge Columns Under Long Duration Ground ... · Problem Statement and Objectives 7 • The 2010 M8.8 Chile and 2011 M9.0 Tohoku, Japan earthquakes are a reminder of