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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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Administration. The first of these developed basic data on the fatigue properties of the eyebar steel (Reference 26) and the second consisted of scale model tests of a portion of the eyebar chain in which the possible modes of separation of joint C13N were investigated (Reference 27). a. The results of the fatigue tests are summarized by the data presented in Figure 26. This figure shows the relation between the stress range (the change of stress between minimum and maximum loads) and the number of cycles to produce a fatigue fracture. As is customary in such data interpretation, the number of cycles to failure is presented on a logarithmic scale. It is significant to note three specific points on the line of best fit to these data. Namely, (1) the indicated numbers of cycles to failure if the stress range were equal to the full 50,000 lbs/sq. in. allowable stress is 550,000 cycles; (2) a stress range of approximately 45,000 lbs./sq. in. would carry about a million cycles prior to failure; and (3) a stress range of 15,000 lbs./sq. in., which is probably typical of that which occurred near the edge of the eyebar hole indicates a life in excess of one billion cycles. The specimens for these fatigue experiments were prepared from eyebars salvaged from the wreckage of the Point Pleasant Bridge which appeared to have suffered least damage from the collapse and subsequent salvage operations. The form of the specimen used is shown in Figure 27. It will be noted that the original surfaces of the eyebar form the narrow edges of the specimen, and that these edges were left in their natural state. Inspection of a number of the fatigue fractures obtained in the experiment showed that these fractures invariably originated on this original bar face, and usually at the location of a small corrosion pit. Where large corrosion pits were responsible for the fracture, the number of cycles to failure was typically lower than the curve of best fit for all data. Control tests on tensile specimens cut from material from the same eyebars showed an average of 79,000 lbs./sq. in. yield strength and 116,000 lbs./sq. in. tensile strength, indicating that the material used in the fatigue experiments was typical of material examined by other laboratories and of eyebars Nos. 33 and 330. b. The scale model tests were performed to resolve the question of the sequence of events in the separation of Joint C13N. In test A, a brittle fracture was induced in the eyebar corresponding to prototype eyebar No. 330, the north bar connecting C11N and C13N. In test B, an attempt was made to cause the eyebar corresponding to prototype bar No. 33 to "walk off" the pin by canting the pin at an angle of approximately 0.5 degrees and imposing a loading regime patterned after the prototype deadload and liveload variations. Complete details on the two tests are covered in Reference 27. A general view of the test
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