Department of Transportation

Seismic Design of South Park Bascule Seismic Design of South Park Bascule BridgeBridge

Yang Yang JiangJiang

TT--8 AASHTO Technical Committee8 AASHTO Technical Committeefor Moveable Bridgesfor Moveable Bridgesfor Moveable Bridgesfor Moveable Bridges

Sacramento, CASacramento, CAMay 24, 2010May 24, 2010y ,y ,

•• Located in Located in south south Seattle across Seattle across Duwamish Duwamish waterwaywaterway

•• Subsurface consists of silty sand Subsurface consists of silty sand to significant depth and medium to significant depth and medium stiff stiff clay underneathclay underneath

•• Numerous Numerous earthquakes of earthquakes of magnitudes magnitudes up to 6.8 up to 6.8 on the on the Richter Richter scalescaleSouth Park Bridge Richter Richter scalescaleSouth Park Bridge

•• OpenOpen--grate deckgrate deck

•• 9.59.5--foot foot lane widthlane width99

•• Constructed in Constructed in 19291929--19311931

•• DeterioratingDeteriorating

•• Solid deckSolid deck

•• 1111--foot lane widthfoot lane width

•• Architectural features of Architectural features of existing bridgeexisting bridge

•• StateState--ofof--thethe--artart

South Bascule Pier North Bascule Pier

Sil S dTimber Piles

Silty Sand

Tip Elev -145 0

Medium Clay

Primary Bascule Pier Movements• North Pier moves towards west• South Pier rotates• Both Piers moved 2” toward waterway Tip Elev. 145.0

Dense Clay

• Both Piers moved 2 toward waterway• Pattern changed after 2001 Nisqually EQ

Teeth as designed

Teeth after Nisqually Nisqually

Earthquake

•• AASHTO “LRFD Movable Highway Bridge Design AASHTO “LRFD Movable Highway Bridge Design Specifications ” 2nd Edition 2007 with 2008 InterimsSpecifications ” 2nd Edition 2007 with 2008 InterimsSpecifications, 2nd Edition, 2007 with 2008 Interims.Specifications, 2nd Edition, 2007 with 2008 Interims.

•• AASHTO “AASHTO LRFD Bridge Design Specifications,” AASHTO “AASHTO LRFD Bridge Design Specifications,” customary U.S. units, 4th Edition, 2007 with 2008 customary U.S. units, 4th Edition, 2007 with 2008 y , ,y , ,Interims.Interims.

•• WSDOT “Bridge Design Manual LRFD,” May 2008WSDOT “Bridge Design Manual LRFD,” May 2008..

•• AASHTO “Guide Specifications for LRFD Seismic AASHTO “Guide Specifications for LRFD Seismic Bridge Design,” 1Bridge Design,” 1stst Edition, 2009 for approach Edition, 2009 for approach structures.structures.

•• TwoTwo--Level Earthquake DesignLevel Earthquake Design

Operational Earthquake Operational Earthquake –– 100 Year Event100 Year Event

Design Earthquake Design Earthquake –– 1000 Year Event 1000 Year Event

•• Bridge Importance “Essential”Bridge Importance “Essential”

•• Seismic Performance Zone 4Seismic Performance Zone 4

•• Site Class “E”Site Class “E”

•• SiteSite--specific response specific response spectra for two levels of spectra for two levels of earthquakes were earthquakes were earthquakes were earthquakes were developed by Shannon & developed by Shannon & Wilson, Inc. Wilson, Inc.

R t R t •• Response spectrum Response spectrum analysisanalysis

•• SpectrumSpectrum--compatible time compatible time histories were developed histories were developed by Earth Mechanics, Incby Earth Mechanics, Inc..by Earth Mechanics, Incby Earth Mechanics, Inc..

•• Nonlinear time history Nonlinear time history analysisanalysis

•• Operational EarthquakeOperational Earthquake

the bridge should be able to open to traffic the bridge should be able to open to traffic -- the bridge should be able to open to traffic the bridge should be able to open to traffic immediately after immediately after a minor earthquakea minor earthquake

•• Design EarthquakeDesign EarthquakeDesign EarthquakeDesign Earthquake

-- the bridge can only be closed to traffic for a the bridge can only be closed to traffic for a limited period time for repairs after a major limited period time for repairs after a major p p jp p jearthquakeearthquake

•• Operational EarthquakeOperational Earthquake

Some damage to expansion jointsSome damage to expansion joints Some damage to expansion jointsSome damage to expansion joints

No apparent permanent displacementsNo apparent permanent displacements

No damages to the machineryNo damages to the machinery

Limit displacement between trunnion and Limit displacement between trunnion and pinion to 0 5”pinion to 0 5”pinion to 0.5”pinion to 0.5”

•• Design EarthquakeDesign Earthquake

Damage to expansion jointsDamage to expansion joints

Limited permanent displacementsLimited permanent displacements

Some damages to the machinerySome damages to the machinery

1.1. Sunken Caisson Sunken Caisson foundationsfoundations

22 C ll ibl t j i tC ll ibl t j i t2.2. Collapsible center jointCollapsible center joint

3.3. Isolated trunnion Isolated trunnion framesframes

N th PiS th Pi North PierSouth Pier

Silty SandSilty Sand

Tip Elev ‐145 0

Tip Elev. ‐110.0 Medium Clay

Tip Elev.  145.0

Tip Elev. ‐145.0Dense Clay

S th Pi N th PiSouth Pier North Pier

MHW Elev. 8.0

Silty Sand

Tip Elev. ‐70.0

Silty Sand

Tip Elev ‐145 0 Tip Elev 105 0

Medium Clay

Tip Elev.  145.0 Tip Elev. ‐105.0

Dense Clay

Push-over Curves for Shaft and Caisson Foundations

40,000

30,000

35,000

s)

20,000

25,000

al L

oad

(kip

s

5 000

10,000

15,000

Late

ra

0

5,000

0 1 2 3 4 5

Displacement (ft)

Caisson Shaft-Long Shaft-Trans

Collapsible Joint

Elevation – Longitudinal Frame

Gap

Elevation – Longitudinal Frame

•• Minimize displacement between trunnion and pinionMinimize displacement between trunnion and pinion

•• Provides Provides simple means to jack the girderssimple means to jack the girders•• Provides Provides simple means to jack the girderssimple means to jack the girders

•• Does not involve wall when adjusting trunnion Does not involve wall when adjusting trunnion framesframes

•• PrePre--assemble the frame in shopassemble the frame in shop

•• TrunnionTrunnion frames are elastic frames are elastic –– no damagesno damages

•• Damages are concentrated at the collapsible jointsDamages are concentrated at the collapsible joints

Stand-Alone Model

Global Model

2 5E 04

3.0E+04

3.5E+04

1 0E+03

2.0E+03

Base Contact Side Friction

0 0E+00

5.0E+03

1.0E+04

1.5E+04

2.0E+04

2.5E+04

Sprin

g (p

sf)

-1.0E+03

0.0E+00

1.0E+03

-1.0 -0.5 0.0 0.5 1.0

Sprin

g (p

sf)

0.0E+00-0.5 0.0 0.5 1.0 1.5

Downward Disp. (ft)

-2.0E+03Disp. (ft)

Base Friction Passive Pressure

5.0E+03

1.0E+04

psf)

2 0E+04

3.0E+04

4.0E+04

(psf

)

Base Friction Passive Pressure

-1.0E+04

-5.0E+03

0.0E+00-1.0 -0.5 0.0 0.5 1.0

Sprin

g (p

Disp. (ft)

0.0E+00

1.0E+04

2.0E+04

-0.5 0.0 0.5 1.0

Sprin

g

Disp. (ft)p ( ) p ( )

RS Global RS Stand‐alone NL Time History

•• Seismic Seismic articulation of bridge components is critical articulation of bridge components is critical in satisfying seismic performance in satisfying seismic performance requirementsrequirements

•• NonNon--linear analysis is invaluable for seismic design of linear analysis is invaluable for seismic design of bascule bridgesbascule bridges

•• Sunken caisson foundations provide superior seismic Sunken caisson foundations provide superior seismic performance performance

•• SoilSoil--foundationfoundation--structure structure interaction such as rocking interaction such as rocking reduces seismic demandsreduces seismic demands

•• Tim Tim Lane of King CountyLane of King County

•• Po Lam and Hubert Law of Earth Mechanics, Inc.Po Lam and Hubert Law of Earth Mechanics, Inc.

•• Hisham Sarieddine of Shannon & Wilson, Inc.Hisham Sarieddine of Shannon & Wilson, Inc.

•• Rich Johnson, Rich Johnson, HNTB Project ManagerHNTB Project Manager