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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.
“Cooper”1 page
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To check this possibility, additional computations were made to examine the susceptibility of this structure to aeroelastic excitation and to assess the magnitude of stresses in the eyebar chain which might have been produced during such oscillations, assuming that a suitable wind was available as an excitation agent. The conclusions reached in this analysis are to the effect that the relationships between the natural frequencies of the structure, the frequency of possible exciting aerodynamic forces, and the energy absorption characteristics of the structure make such excitations improbable, and that even if they were excited, the high energy absorptions would limit them to small amplitudes such that stress level in the eyebar chain would be insignificant. This conclusion is consistent with history of the structure since there are no reports or records of any instances in which the structure had developed large amplitude oscillations of the type required, which would have probably resulted in at least the temporary closing of the structure. Persons using the bridge have commented to the effect that it "vibrated quite a lot." Witnesses who were on the structure at the time of its collapse were in some disagreement as to whether the vibrations then were any different from those they had felt previously. Among those who were commuters using the bridge on a daily basis, most indicated that the bridge always vibrated as much as they experienced it doing the day of the collapse. An analysis of the witnesses' testimony indicates that these were probably short period vibrations (0.1 to 0.3 seconds per cycle) and not of the longer periods associated with general excitation of the deck structure. 3. Some of the laboratory work was directed at obtaining a reliable estimate of the actual level of stress at the edge of the hole in a typical eyebar in a location where the fracture of eyebar No. 330 initiated on a plane through the center of the hole perpendicular to the axis of the bar. It was well known at the time of the design of the Point Pleasant Bridge that stress concentrations existed at such a location. Theoretical solutions from the theory of elasticity and experimental solutions by photoelastic techniques had been obtained (References 32, 33, and 34), in which it was found that the stress at this point would be about 2.77 times the nominal stress in the shank of the bar. The actual stress level at the critical location would be different from that found by this solution for the following reasons: (a) The geometry of the head assumed in the references cited was somewhat different from that of the Point Pleasant Bridge eyebars. (b) The special geometry of the hole, which in the Point Pleasant Bridge eyebars was bored 0.005 inches larger than the nominal pin diameter on the bearing
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