Point Pleasant, WV Silver Bridge Over Ohio River Collapses, Dec 1967
The Silver Bridge was an eyebar-chain suspension bridge built in 1928 and named for the color of its aluminum paint. The bridge connected Point Pleasant, West Virginia and Gallipolis, Ohio, over the Ohio River.
On December 15, 1967, the Silver Bridge collapsed while it was full of rush-hour traffic, resulting in the deaths of 46 people. Two of the victims were never found. Investigation of the wreckage pointed to the cause of the collapse being the failure of a single eyebar in a suspension chain, due to a small defect 0.1 inch (2.5 mm) deep. Analysis showed that the bridge was carrying much heavier loads than it had originally been designed for and was poorly maintained.
The collapsed bridge was replaced by the Silver Memorial Bridge, which was completed in 1969.
The bridge failure was due to a defect in a single link, eyebar 330, on the north of the Ohio subsidiary chain, the first link below the top of the Ohio tower. A small crack was formed through fretting wear at the bearing, and grew through internal corrosion, a problem known as stress corrosion cracking. The crack was only about 0.1 inch deep when it went critical, and it broke in a brittle fashion. Growth of the crack was probably exacerbated by residual stress in the eyebar created during manufacture.
When the lower side of the eyebar failed, all the load was transferred to the other side of the eyebar, which then failed by ductile overload. The joint was then held together only by three eyebars, and another slipped off the pin at the center of the bearing, so the chain was completely severed. Collapse of the entire structure was inevitable since all parts of a suspension bridge are in equilibrium with one another. Witnesses afterward estimated that it took only about a minute for the whole bridge to fall.
The damage to the link would have been difficult to see during inspection of the bridge:
Inspection prior to construction would not have been able to notice the miniature crack. ... the only way to detect the fracture would have been to disassemble the eye-bar. The technology used for inspection at the time was not capable of detecting such cracks.