Collapse of Ashtabula Bridge on December 29, 1876

The design, fabrication, erection, and performance of an iron railroad bridge built in 1863–65 at Ashtabula, Ohio, is examined. The bridge collapsed after 11 years of service, very likely due to fatigue and brittle fracture at a flaw in an iron casting. The bridge was built by a master builder/entrepreneur, using prestressing procedures developed for wooden Howe trusses. At the time, structural analysis was an evolving art, the capacity of slender compressive elements was still an issue, standard design specifications did not exist and fatigue was largely an unknown phenomenon. The failure was investigated extensively by engineers. Most focused exclusively on static strength issues; only one observed the flawed casting. The failure bolstered the call for consulting bridge engineers and standard design specifications. It brought in focus the issue of reliability of iron castings and by 1888 Cooper's specifications explicitly forbade use of cast iron in any part of a bridge structure.