1. The Schoharie Creek Thruway bridge collapse
Department of Civil, Structural and Environmental Engineering
Trinity College Dublin
The Schoharie Creek Thruway bridge collapse
SS structures project, group 18
Cormac Carroll Patrick Heck
Laura Dowdall David Steinboim

2. Summary Introduction Structural history Mode of failure
Reasons for failure
Conclusions

3. Introduction 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.

4. Plinth reinforcement

6. Structural history Constructed 1954 1955: 100 year flood
1957: extensive repairs
5 April 1987: 50 year flood, pier 3 collapsed suddenly
Result: 10 people died

7. Aerial view of collapsed bridge

8. 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

9. Scour failure illustrated

10. Reasons for failure « 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

11. Conclusions 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