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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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only 0.19" to the west. This leaves a clearance of 0.81" at this point. The main span was deflected vertically downward approximately 2.93" at midspan. The West Virginia side span was deflected vertically upwards. The amount of this deflection was not given by the output of the computer analysis but is estimated to have been on the order of three inches. Similar consideration of the combined effects of loading and temperature shows that there was a clearance of 5.49" in the expansion joint at the Ohio tower and 12.24" in the expansion joint at the West Virginia tower. 2. The discussion of the sequence of collapse will be arbitrarily divided into seven steps. Time will be reckoned from the instant at which the brittle fracture in the lower limb of the C13N head of eyebar No. 330 occurred. The estimates of time are based on the computed rate of free fall for those portions of the structure which lost essentially all support after the final separation of eyebar No. 330. Evidence found on tower wreckage is summarized in Fig. 35, and damage to trusses is documented in Appendix A. ## Step 1 Time = 1.0 seconds Results of the scale model tests of the eyebar joint at C13 indicated that this joint did not become instable at the instant when the lower limb of eyebar No. 330 fractured. Some short period of time, on the order of a second, was required to complete the rupture of eyebar No. 330 through the upper limb of its C13 head. This process required 1.2 seconds in the model test. Similitude relationships indicate a somewhat longer time at prototype scale, but this analysis assumes that the prototype time was also about one second, in view of the fact that the prototype chain probably maintained its full load to a greater degree than did the model. During this one second of time, there was an extension of about three inches in the effective length of the chain. It is assumed that the north leg of the Ohio tower moved slightly to the east, permitting one third of this extension to be accommodated in the main span and two thirds of it to be accommodated in the Ohio side span. The resulting vertical deflections, computed from chain length/sag relationships, indicate a vertical deflection of about two inches in the center of the main span and six inches in the center of the side span. This deflection in the north truss of the Ohio side span had two immediate consequences. First of all, it instituted a rapid increase in the tension stress of the lower chord members of the north truss, which momentarily carried a portion of the load by simple truss action between panel points 0 and 15. It was able to do so at this stage, since there was still enough tension in the upper chord members from U1N to U7N to compensate for tendencier to compression in these members. Secondly, this deflection was large enough to result in a
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