The Schoharie Bridge
Collapse
Group 18
Introduction
 Design
 History
 The Collapse
 Failure Modes
 How disaster could have been avoided.
 What can be learned from such cases.
Bridge Design
 165m long
112.5'
27.75'
57'
27.75'
Symmetrical about
CL
Deck
Stringer at
8'-6" o.c.
Floor Beam at
approx. 20' o.c.
Knee Brace
Main Girder
Cantilever Floor
Beam Ends
Bearing
7'-0" sq Column
5'-0" wide X10'-0" deep
Tie Beam
Column
Plinth Reinforcement
Plinth
Footing
Figure 1 - Pier Section ( after "Collapse," 1987 )
 5 simply supported
spans
 Spans supported by
Concrete frames
 2 piers on shallow
footings in creek
 2 piers on bank
History
 Completed in 1954
 In 1957 vertical cracks developed in piers
 Reinforcement added to strengthen piers
 1987 bridge collapses
 10 die in tragedy
The Actual Collapse
 Pier 3 collapsed first
Sloped
Embankment
NORTH
Riprap
 Spans 3 and 4 fell
instantly
 90 mins later pier 2 and
span 2 fell
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 )
 Finally 2 hrs later, Pier
1 and Span 1 shifted.
Reason for Failure - Scour
 Scour is the removal of sediment from a
streambed due to water erosive action
Factors Influencing Scour
 Shallow footings
 Foundation on erodible soil.
 Could not resist scour.
 Riprap
 Sheet-piles removed
How Scour Effected Pier 3
Ways it could have been prevented
 Continuous slab used instead
 Piles used instead
 Sheet piling left in place
 Better communication
 Better inspection and maintenance
Conclusion
 Need regular inspection
 Importance of adequate erosion protection
Questions?