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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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effects of live load, (2) secondary stresses, and (3) fatigue from wind induced oscillations leading to fatigue. The extensive experiments on the St. Marys Bridge have shown the first two to be incapable of producing significant stresses in critical members. Computations of the critical flutter velocity and the lack of reports of wind-induced long period oscillations eliminated the latter. 1. On the superstructure defect path, all fractures in possible critical locations in the stiffening truss were found to have been caused by high strain rates, indicating that they occurred subsequent to the initiation of collapse. The fracture in L12N-L13N, although it contained evidence of a small pre-existent crack, also falls in this category and therefore could not have been the initial fracture. There were three failures in the hanger system which might have been initiating fractures. The tearing out of the hanger connection at U13N has been established to have occurred during the collapse after some rotation of the hanger with respect to its proper vertical position. It is believed to have been pulled out when the hanger, still connected to the upper pin C13N and the pair of eyebars extending from C13N to the Ohio tower, acted with these eyebars as a linkage such that the fall of the north leg of the tower pulled them into a straight line and ripped the connection from the truss. The two hangers at panel points 17 and 19 of the north truss contained cleavage fractures. Paint was found on the fracture surface at the upper end of hanger 17N suggesting the possibility of a rather large pre-existent crack. The nature of the fracture and the deformations of the member, however, established that this fracture occurred under high strain rates and in conjunction with a twisting moment on the member. Therefore, this fracture must also be eliminated as possible "trigger" of the collapse. The fracture in hanger 19N was also found to be associated with bending and twisting. This leads to the final path of the logic diagram on Figure 3. There are several types of evidence which eliminate the possibility that eyebar No. 33 slipped off or "walked off" the end of pin C13N. The metallurgical examination of the burr at the outboard edge of the hole in this eyebar failed to show any evidence of progressive terraces which are characteristic of "walking" action. The fracture of eyebar No. 330 shows little evidence of any bending moment perpendicular to the plane of the bar, indicating that the pin could not have been rotating with respect to this plane at the instant of failure. Finally, the results of the FHWA model test in which the brittle fracture in eyebar No. 330 was simulated produced fractures and permanent deformations remarkably similar to those found in prototype parts, whereas the attempt to simulate the "walk off" action, even with the pin canted at about one half degree, failed. 2. The laboratory work at NBS located and measured the preexistent crack in eyebar No. 330. Fracture mechanics work at Battelle
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