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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.
“R.G.”1 page
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People from vehicles in the vicinity of panel points 3 and 4 reported an experience of a short drop, then a hesitation before complete fall. This is compatible with the collapse sequence. Those who were on the west end of the main span reported a momentary hesitation after a fall of the upstream side of about three feet, but only momentary. This could possibly be due to the gradual fall of these elements followed by free fall after the fracture of hangers at panel points 17, 19 and 21. Out in the middle of the main span, at about panel point 28 or 30, a witness was able to get out of the back seat of a two door car between the time it dropped the first three feet and the final fall. This is possibly due to the fact that this portion held for several seconds due to cantilever action of the north truss. ## E. Status of Bridge Design Practice in 1926 Adequate interpretation of the evidence developed in this investigation requires a consideration of the status of professional knowledge of the principles of bridge design which existed at the time of the design and erection of the Point Pleasant Bridge in 1926 and 1927. This portion of the report discusses some of the basic assumptions and concepts which were in general use and widely accepted at the time of the design of, the Point Pleasant Bridge: 1. In the design of large structures, as in the design of most systems, there is no such thing as absolute safety. Even when the completed structure is subjected to a so-called "proof loading," one cannot be certain that he has eliminated all possibility that some rare combination of loading and/or environmental conditions may cause a failure. What the designer attempts to do is to reduce the probability of failure to an extremely remote one by setting the loads to be carried by the elements of the structure to some fraction of their actual strength. The ratio of this computed load on the member to its actual strength is sometimes referred to as the safety factor, and the design specification for any particular structure attempts to maintain this factor more or less uniform for all elements in the structure. What constitutes a proper factor of safety for each class of structure has evolved largely through experience and judgment although in recent years attempts have been made to derive such factors of safety on a rational basis. In order to select an adequate factor of safety, one must consider the fact that his estimates of the loads to be imposed upon the structure and the estimates of the strength of the individual components are both subject to a range of error. The errors in estimating the strength of the members are caused by variations in the manufacture of the materials and fabrication and erection tolerances. The latter affect both the cross section areas provided and the geometric lines along which the loads are applied to the members. The
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