Collapse of U.S. 35 Highway Bridge, Point Pleasant, West Virginia, December 15, 1967 (HAR-71/01)

Read from the scan by GLM-OCR; expect the odd misread word.

5. The small size of the critical crack in eyebar No. 330, and its location on the inside surface of the hole, precluded its being found while the structure was intact, by the inspection techniques used, or by any other inspection technique available at this time for use in the field on heavy structures, without disassembly of the joint. (7,32,46)

6. The examination of other fractures which might have contributed to the brittle fracture of eyebar No. 330 by producing shock waves in the eyebar chain has shown that, although some of these fractures occurred at points of additional pre-existent cracks in the structure; there is sufficient evidence to demonstrate that these fractures occurred after the process of collapse had begun. (39, 40, 42, 45, 94)

7. The effect of surface corrosion (primarily ordinary rusting) on the load carrying capacity of the structure was carefully assessed by a corrosion survey of all main members at the reassembly site. Although there was deep rusting of some secondary elements such as stay plates, lacing bars, and diaphragms, there is no indication that the net critical sections of main members were reduced in cross section to the point where they were inadequate to carry the intended loads or those imposed by the loading just prior to collapse. (22)

## B. With Respect to the Elements Which Contributed to the Failure:

The failure of the Point Pleasant Bridge was a result of the convergence of several trends, each of which was common in engineering practice in the era in which it was designed, and the existence of a subtle form of time-dependent crack growth of which little was known at the time of its construction, namely:

1. The trend toward use of higher strength materials for steel structures. The steel in the eyebars was a heat treated, relatively high carbon steel (compared to ordinary structural carbon steel). (84, 118)

2. The use of higher allowable stresses when the confidence with which the applied loads was known was high, as is typical in a long span bridge where most of the load is due to its own weight. The allowable stress for the eyebars was set at 50,000 psi. or 67 percent of the elastic limit of 75 000 psi. specified for the material. Typically, 75 to 80 percent of the applied stress was due to the weight of the structure itself. (117)

3. The practice of not computing certain secondary stresses or local effects where these were produced by static loads, and where the range of stress due to traffic loads and other transient effects was small. This practice was particularly common for eyebars, where it was required that the fabricator demonstrate by actual tests that the areas of local high stress in the head of the eye did not control its load capacity (under static load). (89, 91, 92, 93, 119)