Department of Civil, Structural and Environmental Engineering
Trinity College Dublin
The Schoharie Creek
Thruway bridge collapse
SS structures project, group 18
Cormac Carroll
Laura Dowdall
Patrick Heck
David Steinboim
Summary
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Introduction
Structural history
Mode of failure
Reasons for failure
Conclusions
Introduction
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I 90 New York-Buffalo Thruway
4 pier (2 in water), 5 span beam bridge.
Total length 165 m, span width 34.3 m
Piers founded on pad footings on
alluvial soil.
112.5'
27.75'
57'
27.75'
Symmetrical about
C
L
Main Girder
Deck
Stringer at
8'-6" o.c.
Floor Beam at
approx. 20' o.c.
Knee Brace
Cantilever Floor
Beam Ends
Bearing
7'-0" sq Column
5'-0" wide X10'-0" deep
Tie Beam
Plinth reinforcement
Column
Plinth Reinforcement
Plinth
Footing
Figure 1 - Pier Section ( after "Collapse," 1987 )
Sloped
Embankment
NORTH
Riprap
Sloped
Embankment
East
Abutment
West Abutment
Flow
PIER 1
100'
SPAN1
PIER 2
110'
SPAN2
PIER 4
PIER 3
120'
SPAN3
110'
SPAN4
100'
SPAN5
Figure 2 - Schematic plan of bridge ( after "Collapse," 1987 )
Structural history
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Constructed 1954
1955: 100 year flood
1957: extensive repairs
5 April 1987: 50 year flood, pier 3
collapsed suddenly
Result: 10 people died
Aerial view of collapsed bridge
Mode of failure
• Pier 3 suffered from « scour »
phenomenon
• Pier was undermined by 9 m
• Hole 3 m deep
• Pier 3 suddenly fell into the hole
• Spans 3 and 4 failed immediately
• 90 minutes later: failure of pier 2
Scour failure illustrated
Reasons for failure
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« As built » not same as on paper
Riprap used too light and not replaced
No underwater foundation inspections
Lack of redundancy in structure
Later modification of course of river
Added stiffness due to plinth
reinforcement
Conclusions
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Need for clear design objectives
Scrupulous attention to construction
Appropriate maintenance of structures
Implementation of legislation
Knock-on effect of later structures
Redundancy to avoid sudden failure