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Northeast Bridge

Preservation ConferenceSeptember 28-30, 2010

Hartford, CT

Rocker Bearing IssuesBy

Franco Balassone, P.E.Executive Vice President

HAKS Engineers, P.C.

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Rocker Bearing

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Wh Discuss Rocker 

Bearings?

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Bridge Closed, July 28, 2005

Rocker Bearing Failure

Albany, NY (I-787, Exit 3 NB)

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Albany, NY (I-787, Exit 3 NB)

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Albany, NY (I-787, Exit 3 NB)

Contributing Factors:

• Misaligned / Over-expanded Bearing• Overly Flexible Pier 

Source: NYDOT

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Pittsburgh, PA (Birmingham Bridge)Bridge Closed February 8, 2008

Rocker Bearing Failure

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Pittsburgh, PA (Birmingham Bridge)

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Pittsburgh, PA (Birmingham Bridge)

Contributing Factors:

• Misalignment of Bearing• Cumulative Bearing Ratcheting

• Horizontal Force – Deflection of Pier 

Source: PennDOT

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Pittsburgh, PA (Birmingham Bridge)

Source: PennDOT

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Pittsburgh, PA (Birmingham Bridge)

Source: PennDOT

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Rocker Bearing Failure

Contributing Factors

• Corrosion (pack rust) below rocker 

or pivot point• Section Loss, Debris

 

 – Contracted position in warm

weather, Expanded in cold

• Misalignment, Ratcheting

• Substructure Movement

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Suffield Bridge, CT (Route 190)

Consists of 9 spans overConsists of 9 spans over

Connecticut River & AmtrakConnecticut River & AmtrakADT = 26,200ADT = 26,200

Length = 1,345ftLength = 1,345ftDeck Area = 80,344sf Deck Area = 80,344sf 

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Suffield Bridge, CT (Route 190)

Pack Rust – Displacements

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Suffield Bridge, CT (Route 190)

Flattened Rockers – Inhibited Movement

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Suffield Bridge, CT (Route 190)

Documentation – Section Loss & Pack Rust

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Suffield Bridge, CT (Route 190)

Impacts:

Pack Rust - Displacements• Deferential Displacement

• Racking Floorbeams

 • nt es expose• Potential for walking

Flattened Rockers – Inhibited Movement

• Increased stresses on girders

• Lateral loading on substructures

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Suffield Bridge, CT (Route 190)

• New Expansion Bearings

- designed by ConnDOT

- On-site

Replacement

Recommended

 

• Replacement

 – October 2010

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Suffield Bridge Gold Star  

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    I  n   f  r  a  s   t  r  u

  c   t  u  r  e   L   i  n   k

Gold Star Bridge, CT (Interstate - 95)

   V   i   t

  a   l

 

Largest Complex Bridge in CTLargest Complex Bridge in CT

ADT = 120,000 +ADT = 120,000 +

Length = 6000ftLength = 6000ftDeck Area = 1,000,000sf Deck Area = 1,000,000sf 

Main Span: L = 540ftMain Span: L = 540ft

140’ Vertical Clearance140’ Vertical Clearance

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Gold Star Bridge, CT (Interstate - 95)

Pack Rust- Bearing Pin / Gusset Plate

Interface

Frozen Rocker Bearings

Span 31 Span 30

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Gold Star Bridge, CT (Interstate - 95)

Impacts:Seized Rocker Pin

 – No Movement

• Increased stresses - Truss members

 • a era oa ng on su s ruc ures

Excessive Wear 

 – Pin / Gusset Interface

•  Non-uniform gaps and

contact area.

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Gold Star Bridge, CT (Interstate - 95)

Replacement RecommendedIntermediate Steps:

Determine the urgency of replacement:

- Instrumentation of Truss Members

- Quantify Induced Stresses

-

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E TI