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This is the final highway accident report (NTSB-HAR-71-1) from the National Transportation Safety Board, adopted in December 1970. It covers the collapse of the U.S. 35 bridge between Point Pleasant, West Virginia, and Kanauga, Ohio, on December 15, 1967, which killed 46 people. The Board found that the cause was a cleavage fracture in eyebar 330 at joint C13N. That fracture grew from a flaw produced over 40 years by stress corrosion and corrosion fatigue, in a spot that could not be seen or found by inspection.
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side and 0.0312 inches (1/32) larger than the pin on the non-bearing side, with the center for this side of the hole offset 1/8 inch. (c) The sensitivity of the results to pin fit. (d) Pin deformation, especially bending, tending to make stresses on one face larger than the other. (e) Residual stresses in the eye prior to loading. (f) Stresses under load which exceeded the yield strength, when considered together with the presence of the residual stresses. The work at the Battelle laboratory demonstrated that residual stresses due to the heat treatment process could be as much as 20,000 psi. In general, there were compressive stresses near the bar surfaces and tensile stresses in the interior. This pattern was altered at the pinhole due to the removal of material after the heat treatment by the final boring of the hole, probably resulting in some relief of the surface compression. Upon erection of the eyebar in the structure, the gradual application of dead load would raise the stresses across the section of the eye in a pattern very close to that indicated by the elastic theory, with the stress at the edge of the hole approximately 2.8 times the nominal. Since the nominal dead load stress in the shank of eyebar No. 330 is 36,000 psi, the unit stress at the edge of the hole exceeded the yield strength when between 70 and 90 percent of dead load had been applied, depending on the level of residual compression which existed at this location as a result of heat treatment. In any event, the first time the shank of the bar came up to full allowable stress of 50,000 psi due to the application of full live load with unfavorable temperature conditions, there must have been a considerable depth of material at the edge of the hole stressed to yielding. The stress level in this material would still probably be less than the yield strength of the material measured at 0.2% offset, since the strain pattern across the section could not have changed radically. Stresses on the order of 85,000 psi therefore appear likely, in spite of the fact that pin bending might have caused higher strains on one face than the other. These general observations are confirmed by the FHWA tests on model eyebars cut from the interior layers of the actual eyebars, which would have been essentially free of residual stresses, and by the full scale bar tested at Lehigh University which contained residual stresses due to the relief of loads which had been on the bar in service. The FHWA model tests gave somewhat lower average stress concentration factors, since the material around the hole had not been strain hardened by prior
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