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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.
“The Advance”2 pages
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yield point or yield strength of the material). (b) The establishment of standard loadings for those loads which will act on the structure in addition to its own weight. An attempt is made in the establishment of these loads to project likely trends for traffic loadings into the future, and to estimate the extreme environmental loadings such as those due to wind which have a 50 percent probability of occurrence within the proposed lifetime of the structure. (c) The refinement with which the stress analysis is to be conducted is either implied or stipulated and the basis upon which the strength of members other than tension members is to be computed is prescribed. (d) The materials quality control which is believed consistent with the other considerations is stipulated, as well as the fabrication and erection tolerances which control the degree to which the behavior of the members correspond to the design assumptions. As an example of the above, the 1931 edition of the American Association of State Highway Officials Specification for the design of highway bridges stipulated a basic allowable tensile stress of 16,000 pounds/sq. in. for A7 carbon steel members for which the prescribed minimum yield point was 30,000 psi., giving a nominal factor of safety of 1.87 against yielding. A somewhat higher unit stress of 24,000 psi. was permitted for members subject to dead load only.* Three classes of loadings were specified for traffic. The heaviest class was designated as H20 and consisted of a two axle 20 ton truck followed by and proceeded by 15 ton trucks at 30 feet spacing. For elements in the structure requiring the loading of more than 60 feet of length, simplified loadings consisting of 640 pounds/linear foot/lane were permitted together with single concentrated loads of 18,000 pounds where bending moments in the member were being computed, or 26,000 pounds where the shearing stresses were being computed. The introduction to this specification stipulates it is intended for structures not in excess of 400 feet in length. This specification reflected the practice of making reductions in the load as the improbability of the load pattern increased. Section 5.2.10 of the specification permitted load reductions of up to 25 percent on roadways carrying four lanes of traffic when the occupancy of all four lanes was required to produce maximum stress in the member. *Members carrying combined dead load and live load were proportioned for the sum of the areas required for each of the prescribed unit stresses, subject to the overload provision that a 100% increase in live load not produce unit stresses in excess of those permitted for dead load.
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.