The Schoharie Bridge
Collapse
Group 18
Introduction
Constructed in early 1950’s
 165m span comprising of 5 simple spans
 Two Piers on shallow footings in Schoharie
Creek
 Two Piers on creek banks
 Collapsed in 1987

Pier Section
112.5'
27.75'
57'
27.75'
Symmetrical about
C
L
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 )
Plan of Bridge
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 )
Summary of Events
1954: Construction completed
 1955: Bridge survived 100 year flood
Vertical cracks began to appear in
Pier Plinths
 1957: Plinth reinforcement added and
other minor problems corrected
 1987: Bridge Collapsed

The Collapse
The Bridge collapsed
on April 5 1987 during
an estimated 50 year
flood
 Pier 3 was the first to
fail
 This caused the
collapse of span 3
and span 4

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 )
The Collapse
Pier 2 and Span 2 fell
ninety minutes after
Span 3 had dropped
 10 people were killed

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 )
The Collapse
Collapse of Span 2
Cause of Collapse
Shallow footings were not deep enough to resist scour
Pier 3 was bearing on erodable soil
 Riprap (Broken stones for protection of Piers) had not
been adequately maintained
 Area around footing had been backfilled with erodable
soil, not Riprap
 Original Riprap layer is thought to have been moved
during the 100 year storm of 1955
 Cofferdams used for pier construction had been
removed, contrary to designers’ specifications
 Plinths were initially under reinforced and the additional
reinforcement added wasn’t adequately anchored and
contributed to sudden, brittle failure


Human Factors Contributing to
Disaster
Design Documents did not clearly state
that cofferdams were to be left in place
 Under reinforcement of plinths
 An inexpert state employee deleted all
reference to new Riprap in a maintenance
contract in 1980

Lessons Learnt
Piles could have been used for footings in order
to resist scour
 Cofferdams should have been left in place
 The use of a continuous span rather than 5
simple spans would have provided redundancy
once pier 3 failed
 Critical features that could have led to collapse
such as pier footings should have been
identified, inspected regularly and maintained
