Performance-Based Seismic Assessment of Skewed Bridges

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Performance-Based Seismic Assessment of Skewed Bridges

PEER

byErtugrul Taciroglu, UCLA

Farzin Zareian, UCI

PEER Transportation Systems Research Program

2

CollaboratorsMajid Sarraf, PARSONSAnoosh Shamsabadi, Caltrans

StudentsPeyman Khalili Tehrani, UCLAPeyman Kaviani, UCIAli Nojoumi, UCLAPere Pla-Junca, UCI

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Outline1. Skew bridges & project goals

2. Modeling skew abutment response

3. Developing NLTH simulation models for skew bridges

4. Exploring and quantifying skew-bridge response

5. Discussion

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General ProblemPerformance assessment of skewed abutment

bridges

• Appropriate modeling of bridge superstructure.• Appropriate modeling of bridge abutment.• Selection of appropriate input ground motions.

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Previous Studies

Straight Abutment:Aviram, Mackie, and Stojadinovic 2008 Johnson et al. (2009), Kotsoglou and Pantazopoulou (2010), Mackie and Stojadinovic (2007), Paraskeva et al. (2006)

Skewed Abutment:Abdel-Mohti and Pekcan (2008)Meng and Lui (2000), Maragakis (1984), Wakefield et al. (1991), Ghobarah and Tso (1974)

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Ground Motions

Pulse-Like

Faul

t-Nor

mal

Faul

t-Par

alle

l

0 0.5 1 1.5 2 2.5 3 3.5 40

0.5

1

1.5

2

2.5

3

Period [sec]

Sa[g

]

0 0.5 1 1.5 2 2.5 3 3.5 40

0.5

1

1.5

2

2.5

3

Period [sec]

Sa[g

]

0 0.5 1 1.5 2 2.5 3 3.5 40

0.5

1

1.5

2

2.5

3

Period [sec]

Sa[g

]

0 0.5 1 1.5 2 2.5 3 3.5 40

0.5

1

1.5

2

2.5

3

Period [sec]

Sa[g

]

0 0.5 1 1.5 2 2.5 3 3.5 40

0.5

1

1.5

2

2.5

3

Period [sec]

Sa[g

]0 0.5 1 1.5 2 2.5 3 3.5 4

0

0.5

1

1.5

2

2.5

3

Period [sec]Sa

[g]

Soil-Site Rock-Site

Three sets of GMs were selected by the PEER Transportation Research Program

40 GMs per setThree types of GMs: Pulse-like, soil-site, and rock-siteFault Normal: longitudinal direction; Fault parallel: transverse directionThe GMs are from mid- to large-magnitude Near-source GMsSelected GMs have a variety of spectral shapes, durations, and

directivity periods

4.02.00.0

1.0

2.0

3.0

4.02.00.0

1.0

2.0

3.0

4.02.00.0

1.0

2.0

3.0

4.02.00.0

1.0

2.0

3.0

4.02.00.0

1.0

2.0

3.0

4.02.00.0

1.0

2.0

3.0

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Anatomy of an Abutment

Seat-type

There are also “monolithic abutments”

plan view

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Skew Bridge Challenges

Deck rotation (esp. for single span bridges)

Backfill response (near field)Shear key failure

Unseating

High seismic demands on columns

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Skew Bridge Challenges

Deck rotation (esp. for single span bridges)

Backfill response (near field)Shear key failure

Unseating

High seismic demands on columns

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Skew Bridge Challenges

Deck rotation (esp. for single span bridges)

Backfill response (near field)Shear key failure

Unseating

High seismic demands on columns

11

Skew Bridge Challenges

Deck rotation (esp. for single span bridges)

Backfill response (near field)Shear key failure

Unseating

High seismic demands on columns

12

Skew Bridge Challenges

Deck rotation (esp. for single span bridges)

Backfill response (near field)Shear key failure

Unseating

High seismic demands on columns

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Skew Bridge Challenges

Deck rotation (esp. for single span bridges)

Backfill response (near field)Shear key failure

Unseating

High seismic demands on columns

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Skew-angled AbutmentsSkew happens

??

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Input parameters for “Hardening Soil” PLAXIS model

Lnom

Abutment Modeling

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Abutment Modeling

Lskew ≠ Lnom

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straight abutment with wall-width wr

skew abutment with wall-width wr

skew abutment with deck-width wr

Abutment Modeling

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Bridge ModelingThe Jack Tone Road On-Ramp Overcrossing

The La Veta Avenue Overcrossing

The Jack Tone Road Overhead

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Bridge MatrixBridges Col.

Elev. Symmetry Asymmetry

00° 15° 30° 45° 60° 00° 15° 30° 45° 60° 2 Span-Single Col. (A)

Higher AUS0 AUS1 AUS2 AUS3 AUS4 AUA0 AUA1 AUA2 AUA3 AUA4 Lower ALS0 ALS1 ALS2 ALS3 ALS4 ALA0 ALA1 ALA2 ALA3 ALA4

2 span-Multi Col. (B)

Higher BUS0 BUS1 BUS2 BUS3 BUS4 BUA0 BUA1 BUA2 BUA3 BUA4 Lower BLS0 BLS1 BLS2 BLS3 BLS4 BLA0 BLA1 BLA2 BLA3 BLA4

3 Span-Multi Col. (C)

Higher CUS0 CUS1 CUS2 CUS3 CUS4 CUA0 CUA1 CUA2 CUA3 CUA4 Lower CLS0 CLS1 CLS2 CLS3 CLS4 CLA0 CLA1 CLA2 CLA3 CLA4

Developed after: Mackie & Stojadinovich

Abutment Spring

Elastic Deck Abutment Spring

Plastic Hinge

Simple Support for Multi-Column

Fixed Support for single column

Plastic Hinge

ddeck = 0.04L

Dcol = 0.8 ddeck

r = roriginal

Hmax = 8Dcol

Horiginal

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Abutment Modeling

aa aa

Simplified Model

Dual-Rigid Model

Friction Model

Skewed Model

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0

50

100

150

200

0 2 4 6 8 10

Forc

e (k

ips)

Displ. (in)

ZL-1 ZL-2 ZL-3 ZL-4 ZL-5

€

β =tanα

tan60o × 30%

Abutment Modeling

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-2800

-2400

-2000

-1600

-1200

-800

-400

0-10 -8 -6 -4 -2 0

Forc

e (k

ips)

Displ. (in)

Bridge-A Bridge-B Bridge-C

VN,C= 2360 kips VN,B= 1810 kips VN,A= 755 kips

Brid

ge “C

”

Brid

ge “B

”

Brid

ge “A

”

Shear Key Modeling

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Deck Rotation – Bridge A

0 15 30 45 60

0.002

0.004

0.006

0.008

0.01

0.012

Skew Angle

Dec

k R

otat

ion

(rad

)

PULSESOILROCK

Bridge “A”, Lower, Symt.:

Old Models

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0 15 30 45 60

2

4

6

8

Skew Angle

Col

umn

Drif

t Rat

io (

%)

PULSESOILROCK

Column Drift Ratio – Bridge A

Bridge “A”, Lower, Sym.

Old Models

25

0 15 30 45 60

2

4

6

8

Skew Angle

Col

umn-

1 D

rift R

atio

(%

)

PULSESOILROCK

Column Drift Ratio – Bridge B

Bridge “B”, Lower, Sym.

Old Models

26

0 15 30 45 600

0.25

0.5

0.75

Skew Angle

Dec

k R

otat

ion

(rad

x10e

-3)

0306090120150

Deck Rotation – Bridge A

Median Response, Bridge “A”, Lower, Symt.

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0 15 30 45 600

2

4

6

8

10

12

14

16

Skew Angle

Dec

k R

otat

ion

(rad

x10e

-3)

0306090120150

Deck Rotation – Bridge A

Median Response, Bridge “A”, Lower, Symt.NO SHEAR KEY MODELED

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0 15 30 45 600

1

2

3

4

Skew Angle

Col

umn

Drif

t Rat

io (%

)

0306090120150

Column Drift Ratio – Bridge A

Median Response, Bridge “A”, Lower, Symt.

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0 15 30 45 600

2

4

6

8

Skew Angle

Col

umn

Drif

t Rat

io (%

)

0306090120150

Column Drift Ratio – Bridge A

Median Response, Bridge “A”, Lower, Symt.NO SHEAR KEY MODELED

30

Deck Rotation – Bridge A

0 15 30 45 600

0.25

0.5

0.75

Skew Angle

Dec

k R

otat

ion

(rad

x10e

-3)

0306090120150

Pulse 1, Bridge “A”, Lower, Symt.

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0 15 30 45 600

1

2

3

4

Skew Angle

Col

umn

Drif

t Rat

io (%

)

0306090120150

Column Drift Ratio – Bridge A

Pulse 1, Bridge “A”, Lower, Symt.

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Probability of Collapse – Bridge A

Skew Angle = 0o Skew Angle = 30o Skew Angle = 60o

2

4

6

30

210

60

240

90

270

120

300

150

330

180 0

Number of GMs Caused CollapseBridge "A"Abut. skew= 015%

10%

2

4

6

30

210

60

240

90

270

120

300

150

330

180 0

Number of GMs Caused CollapseBridge "A"Abut. skew= 6015%

10%

2

4

6

30

210

60

240

90

270

120

300

150

330

180 0

Number of GMs Caused CollapseBridge "A"Abut. skew= 3015%

10%

Bridge “A”, Lower, Symt.

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0 15 30 45 600

0.25

0.5

0.75

Skew Angle

Dec

k R

otat

ion

(rad

x10e

-3)

0306090120150

Deck Rotation – Bridge B

Median Response, Bridge “B”, Lower, Symt.

34

0 15 30 45 600

1

2

3

4

Skew Angle

Col

umn

Drif

t Rat

io (%

)

0306090120150

Column Drift Ratio – Bridge B

0 15 30 45 600

1

2

3

4

Skew Angle

Col

umn

Drif

t Rat

io (%

)

0306090120150

Median Response, Bridge “B”, Lower, Symt.

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5

10

15

30

210

60

240

90

270

120

300

150

330

180 0

Number of GMs Caused CollapseBridge "B"Abut. skew= 60

5

10

15

30

210

60

240

90

270

120

300

150

330

180 0

Number of GMs Caused CollapseBridge "B"Abut. skew= 30

5

10

15

30

210

60

240

90

270

120

300

150

330

180 0

Number of GMs Caused CollapseBridge "B"Abut. skew= 0

Bridge “B”, Lower, Symt.,

Probability of Collapse – Bridge B

Skew Angle = 0o Skew Angle = 30o Skew Angle = 60o

38%25%

38%25%

38%25%

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Shear Key Performance – Bridge A

1

2

3

4

5

6

0

10

20

0

15

30

45

60

Abutment S

kew

Angle

150

12090

6030

0

Intercept Angle

Num

ber

of F

aile

d Sh

ear

Keys

out

of

40

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Shear Key Performance – Bridge B

150

12090

6030

0

Intercept Angle Abutment S

kew

Angle

1

2

3

4

5

6

0

10

20

0

15

30

45

60

Num

ber

of F

aile

d Sh

ear

Keys

out

of

40

1. Develop a three-DOF macro-element through numerical simulations with 3D continuum FE models and analytical considerations for torsionally flexible bridges. 2. Finalize the bridge models including the new abutment model.

3. Rotate Ground motions?4. Quantify the Sensitivity of Skew Bridge

Response and Damage Metrics to Key Input Parameters

5. Update Caltrans Seismic Design Criteria for Skew-Angled Bridges

Next Steps – August Meeting

Next Steps – This Meeting1. Develop a three-DOF macro-element

through numerical simulations with 3D continuum FE models and analytical considerations for torsionally flexible bridges. 2. Finalize the bridge models including the new abutment model.

3. Rotate Ground motions?4. Quantify the Sensitivity of Skew Bridge

Response and Damage Metrics to Key Input Parameters

5. Update Caltrans Seismic Design Criteria for Skew-Angled Bridges