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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.
“Gray”1 page
1. A summary and comparison of the chemical compositions of the steel taken from portions of trusses, hangers and chain bent posts as obtained by the several laboratories is given in Table 2, along with the limits placed upon these elements in the ASTM specifications, where applicable. It is to be noted that the ASTM specifications for A7-24 steel placed only upper limits on the two elements sulfur and phosphorous, and that all samples tested by both NBS and U. S. Steel met this requirement.
2. The results of tension tests for the steel taken from trusses and chain bent posts are given in Table 3, together with the limiting values of those properties which were listed in the ASTM A7-24 specification, and some typical values obtained by others for steels rolled in the same era to these specifications. The following features of the ASTM A7-24 requirements should be noted:
(1) An acceptable range of tensile strengths was specified; namely, 55,000-65,000 psi.
(2) The yield point, as determined by "drop of beam" technique was required to be at least 50 percent of the tensile strength, but not less than 30,000 psi.
(3) Percent elongation was specified to be not less than 22 percent measured over a 2" gage length.
It is apparent that the data from both laboratories is in good agreement and indicates that the steel is within the specification requirements.
No requirement for fracture toughness was included in the A7-24 specification, but three of the participating laboratories ran series of Charpy impact tests to obtain such data on this steel. These results showed appreciable variability, probably due to the different locations and thicknesses from which the samples were taken. A comparison of some of the transition temperature curves is given in Figure 32. The corresponding "15 foot pound transition temperatures" are shown in Table 4.
Regardless of the differences in the data from the various laboratories, it is apparent that the A7-24 steel in this structure, when at the $ 32^{\circ} \mathrm{F} $ temperature which existed at the time of collapse, was operating below its transition temperature. At this temperature, all of the laboratories obtained Charpy values below 10 foot pounds, with an average of about 7 foot pounds. This would indicate that the steel at this temperature had low energy absorption capacity for loads applied at high strain rates compared to that exhibited at room temperature or above. The instrumented Charpy tests conducted by Battelle 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.