Transcript Mianus River Bridge Collapse.ppt

Mianus River Bridge Collapse
Contents…
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Introduction
Design
The Causes of Collapse
Mechanism of Failure
Lack of Maintenance
Consequences
Bibliography
Introduction…
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Constructed in 1957 in the Cos
Cob part of Greenwich,
Connecticut, USA
Effectively two bridges carrying
over 100,000 cars daily
June 28th 1983 a 100ft section of
suspended span on Eastbound
section collapsed
Design
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Multiple-span structure, with main anchor spans and suspended spans
hanging from these
Pin and hanger assembly used to hang suspended spans
Assembly recognized as unsafe since 1968
The causes of collapse…
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Gullies were paved over for 10
years previous to the collapse!!!
Inadequate drainage meant water
ran down through the pins
Pins rusted and weakened
Pin and hanger assembly failed
when 2 heavy lorries and a car
passed over
Mechanism of Failure…
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Rusting occurred between pins and hangers
Hanger slipped off Pin in SE corner of suspended span due to the rusting
and lateral loading due to vehicles
Another rusted hanger failed due to increased loading
Lack of redundancy in the structure meant only 3 corners in the suspended
span were now supported by weak hanger/pin connections
The weight of 2 lorries and a car broke the remaining connections and the
suspended section fell 70ft to the bank below
Lack of Maintenance…
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No money allocated for bridge maintenance
The state of Connecticut had 3,425 bridges at the time of the accident yet
only 12 engineers working in pairs to inspect them
Binoculars were used to view the inaccessible bridge from the banks! –
Rusted pins went undetected
Gullies should never have been paved over
Pins should have been investigated properly
The Consequences…
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3 dead and 3 seriously injured
Maintenance and inspection
program introduced
Paved-over drains reopened
Pin and hanger assembly
bridges designated for more
frequent inspection
Final repairs in excess $20
million USD
Bibliography…
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http://www.nycroads.com/roads/ct-turnpike/
http:// en.wikipedia.org/wiki/Mianus_River_Bridge
http://www.tcd.ie/Civil_engineering/Staff/Dermot.ODwyer/4A6/Disaster_2
004/Reports/Group%2011.doc
http://www.tcd.ie/Civil_engineering/Staff/Dermot.ODwyer/4A6/Disasters_
2005/The%20Mianus%20River%20Bridge%20Collapse.doc
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