Transcript G11 The Mianus River Bridge Collapse - Powerpoint.ppt

The Mianus River Bridge
Collapse
Introduction
• Multiple span
structure
• Effectively two
bridges carrying
over 100,000 cars
per day
• Two suspended
spans supported
from main spans
Design Flaws
• Pin and hanger
assembly used to hang
suspended spans
• Structural design flawed
as no redundancy
measures
→If a member failed,
structure would fail
Reasons for Failure
• Pins are corroded and
weaken
• Hanger slips off pin in
south-eastern corner
due to rusting and
lateral overloading
• North-eastern hanger
fails due to added
load
Failure
• Only 3 corners in the
suspended span now
supported due to lack
of redundancy
• Weight of 2 lorries
and a car break the
remaining
connections and
bridge collapses
Lack of Maintenance
• No regular bridge
inspections
• No regular drainage
checks
• Gullies were paved
over
• Improper investigation
of effects of chloride
ingress on
connections
New Guidelines
•
•
•
•
Bridges inspected more regularly
Bigger budget for maintenance of bridges
Reopening of gullies
Investigation into all pin and hanger bridges, in particular
those with no redundancy measures