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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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## C. LABORATORY INVESTIGATIONS SINCE SEPTEMBER 1968
This section is a summary of each of the laboratory investigations which have been conducted since September 1968 or which were not completed to the point of reduction of data and presentation of a report at that time. Investigations are reported and summarized on a basis of the laboratory conducting the work. Complete details are available in the formal reports by the individual laboratories listed in the references. The discussion of the significance of the results of each of these investigations will be deferred to the next section of this report.
A guide to the location and identification of the various laboratory specimens removed from the wreckage of the Point Pleasant Bridge is given in Figure 4 and Figure 5. Figure 4 indicates the locations in the structure from which the major specimens were removed and the laboratory to which they were shipped initially. Figures 5a through 5f indicate subsequent subdivision of these major specimens and the individual laboratory designations assigned to these subdivisions for various portions of the work. Specimen material being held for possible supplemental tests is indicated by the designation "reserve specimen."
## 1. Laboratory Investigations at the National Bureau of Standards
The results of the investigations conducted at the National Bureau of Standards are documented in a series of seven reports from that laboratory (References 17 through 23).
a. The first report describes the initial examinations made of the material in eyebar No. 330 (the north bar of the north chain, connecting points C11 and C13), to determine chemical composition, metallurgical and mechanical properties, and the results of the initial fractographic examination of the brittle fracture in the lower limb of the C13N head of this eyebar. Results of this investigation are summarized as follows:
(1) The chemical composition of the steel was in general conformance with the specifications for 1060 carbon steel (detailed results are given in Appendix B).
(2) The heat treatment which consisted of quenching in water from the austenitizing temperature (approximately $ 1 6 0 0^{\circ} \mathrm{F} $ ) and tempering from between 1150 and $ 1 2 0 0^{\circ} \mathrm{F} $ . produced a non-homogeneous micro-structure. It may therefore be characterized as a "slack-quenched" steel in which martensite was formed in a layer 1/4" to 3/8" thick adjacent to the surfaces and a ferrite-pearlite structure was formed in the interior. The outer 1/16 to 1/3-inch of the martensite layer was heavily decarburized. These facts were confirmed by hardness profiles taken through the thickness of the bar, with results as indicated in Figure 6. Document, cited by the archive. The PDF is mirrored here; the original link is above. The text was read from the page images by GLM-OCR; expect the odd misread word. 202 pages are in the text index: search them above, or from the library's search.