Structural Issues And 2009 Repairs

STRUCTURAL ISSUES

Tom Hoffman, P.E. R-1 Structures Engineer

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BRIDGE STATISTICS • BRIDGE IDENTIFICATION NUMBER:

5521180

• AGE:

Built in 1929

• LENGTH:

14 spans, 2,184 feet

• ROADWAY WIDTH:

26.1 feet

• STRUCTURE TYPE:

Combination of thru truss, deck truss, and deck plate girders

• BIKE / PED ACCOMMODATIONS:

None

• VERTICAL CLEARANCE ON BRIDGE:

14 feet

• MAX VERTICAL CLEARANCE OVER WATER:

95 feet

• AVERAGE ANNUAL DAILY TAFFIC (2008): • WEIGHT CAPACITY:

3,150 vehicles per day -Restricted since 1994 to less than 102,000 pounds. -Currently reduced to a single lane/ 40 ton posting.

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“RECENT” WORK HISTORY •1990-91 Bridge Rehabilitation Project

•Appx $7.0 million in 1989 (Appx. $17.3 in 2007 dollars) • Bearings - Some Cleaned, Some Replaced • Spot Painting (Span 4-9, bearings) • Deck Replacement With Lightweight System • Floor Beam Replacement and Strengthening (some spans) • Joint Replacement • Bridge Rail • Approach Slab Replacement • Concrete Repairs on Piers and Abutments • Pier 4 Compression Straps Added (Now occur on Piers 4-8) -The first strapped in 1974 to arrest crack development

• Emergency Repair Contract – Compression Band Replacement - $125,000 in 2005 Pier Repairs - $100,000 in 2008 Steel Repairs - $1 million estimated in 2009 • Maintenance Repair of Bridge Joints – 2005, 2006, 2008 3

INITIAL PROBLEM IDENTIFICATION Bridge Condition Rating • Score 3.375 out of a possible 7 points (2009) • Scores between 3 and 4 indicate ”serious deterioration or not functioning as originally designed” • Problems are with main carrying members, bearings, joints, concrete, paint, and wearing surface

Federal Sufficiency Rating • Score 29.2 (2008) out of a possible 100 points • Scores less than 65 qualify for Federal funding

Load Restricted • 40 Ton limit restricts all overloads, including log trucks and milk trucks

Limited roadway vertical clearance of 14’-0”

• Trucks in excess of 14’ have struck the bridge on several occasions, requiring the bridge to be closed for repair 4

Truss Terminology

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Channel Piers

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Concrete Compression Strap Replacement

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Concrete Deterioration

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Concrete Deterioration Pier 3- Before

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Concrete Deterioration Pier 3- After

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Pier 8 Condition (Before)

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Pier 8 Condition (After)

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Steel and Paint Condition

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Steel and Paint Condition

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Joints

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Bearings

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Recent Repairs-

Floorbeams Pier 5 and 8

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Recent Repairs-

Floorbeams Pier 5 and 8

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Recent RepairsBottom Chord

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Recent RepairsBottom Chord

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Recent RepairsSteel Pier

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Recent RepairsSteel Pier

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Recent RepairsGusset Plates

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Other Yellow Flags

Many yellow flags for gussets and strap ties are not being addressed at this time. All red flags, and yellow flags of significance are being repaired. 25

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What Now?

1) Paint of Select Areas – Some areas are being blasted and painted to slow deterioration of critical areas. 2) Finish Chord Repairs 3) Finish Floorbeam Repairs and Add Troughs 4) Re-Inspect in the Spring

Repair as Needed

5) Possibly Paint Selected Truss Members and under Joint Areas -Chords of Spans 4, 5 and 9 - Entire Truss of Spans 6 and span 8, span 7 (splash zone down) - Under Joint Areas at Piers 3, 5 and 8 - Estimated at $6 Million 27

General Questions….

1) Why was the load posting reduced? 2) What does it mean? 3) Does a single lane really make things better? 4) $64,000 question….Is the bridge safe?

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Questions????

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