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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.
concentration points. The presence of sulfides, by their restriction of the $ \mathrm{H}_{2} $ recombination reactions, would inhibit the escape of hydrogen produced during corrosion from the steel surface. Atomic hydrogen would diffuse to stressed areas in the steel and cause embrittlement and eventual failure. The role of the chloride ion probably was not to initiate a crack by itself but to reinforce the corrosion reaction thereby facilitating cracking in the presence of $ \mathrm{H}_{2} \mathrm{S}. $ "
f. The final section of the Battelle report covers investigations of the fracture toughness properties of the A7 steel, based on samples extracted from the chain bent post at panel point zero, north truss, Ohio shore, which was believed to be typical of the steel used in the stiffening trusses.
It was doubted from the outset that linear fracture mechanics techniques would be appropriate for use with this steel because of its ductility at normal temperatures and static loadings. The first attempt to determine the critical stress intensity parameter by use of a surface flaw specimen confirmed these doubts. The fractures were accompanied by much ductile deformation, and the nominal stress level at fracture was 55,000 psi., well above the yield point for this material. A second test at $ 0^{\circ} \mathrm{F} $ gave similar results.
Since it was evident that brittle fractures could be produced only at high strain rates or at low temperatures, the program was modified to make use of the Charpy impact test to obtain the required data. Although a conventional Charpy specimen and apparatus were used, the tests were supplemented with special instrumentation which permitted the measurement of the instantaneous loading imposed on the specimens throughout the period of loading and rupture. This technique permitted the detection of any plateau in the load-deformation curve associated with ductile yielding prior to fracture. The results of these experiments, together with the results of slow bend tests on Charpy type specimens are displayed in Figure 23. The instrumented Charpy tests were conducted at a temperature range from -120 degrees Fahrenheit to +220 degrees Fahrenheit. The test points are those associated with the solid lines on the figure. General yielding prior to fracture was detected only for tests above zero degrees Fahrenheit and are associated with the straight line in the diagram. It will be noted that the loading at which general yield occurred, decreased from about 2900 lbs. at zero degrees Fahrenheit to approximately 2300 lbs. at 220 degrees Fahrenheit. The fracture of these specimens occurred at higher loadings for the region above zero degrees Fahrenheit as indicated by the upper solid line. Loadings were in general in excess of 3000 lbs. at fracture. Below zero degrees Fahrenheit, fracture occurred prior to any ductile yielding and at decreasing loads with further reduction in temperature. The data indicate a transition Document, cited by the archive. The PDF is mirrored here; the original link is under it. The text was read from the page images by an OCR model; expect the odd misread word. 202 pages are in the text index: search them above, or from the library's search.