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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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When an attempt was made to simulate the second type of joint separation it was found that eyebar No. 33 could not be forced to "walk" along the pin with the loading regime corresponding to that in the prototype. This was in spite of the 0.5 degree pin cant which had been introduced. The dead load was reduced to one-half its proper value, but the eyebar still did not walk. Only when the dead load was reduced to a very small value was any walking of eyebar No. 33 along the pin produced, and even then it was arrested before any portion of the eyebar hole extended out beyond the end of the pin. Further attempts to simulate the type B failure were, therefore, abandoned.
Some supplemental tests were conducted with a spare set of eyebars to measure stress concentration effects and residual stresses produced by application and release of loads. Strain gages were applied to the outside face of the bar representing eyebar No. 330 along a line through the center of the pinhole at right angles to the longitudinal axis of the bar. These gages were 0.08", 0.23", 0.38", 0.54", 0.88", and 1.56" from the edge of the hole on the lower limb, and 0.08", 0.81" and 1.55" from the edge of the hole on the upper limb, the last gage in each set being near the outer edge. The measured strains for a load which placed a nominal stress of 16,000 psi on the shank of the bar indicate (by extrapolation) a strain at the edge of the hole of 1600 microinches/inch for the upper limb and 1100 microinches/inch for the lower limb. These strains correspond to stresses of 46,500 psi and 31,900 psi, respectively, assuming a modulus of elasticity of $ 29 \times 10^{6} $ psi. The stress concentration factors are 2.90 and 2.00, with an average of 2.45. The difference between these factors in the upper and lower limb is believed to be due to a difference in the transverse bending effects, but this could not be confirmed because there were no strain gages on the inside face of the bar.
A loading producing a unit stress of 36,600 psi in the shank of the bar, corresponding to the dead load stress in eyebar No. 330, produced strains of 4000 microinches/inch and 2600 microinches/inch at the edge of the hole in the upper and lower limbs respectively. Both these strains are above the strains of 2410 microinches/inch at the yield strength of 70,000 psi appropriate to the material from which the model eyebar was made, since this was cut from the core or inner layers of a prototype eyebar. The initiation of plastic strain was also indicated by the change in the strain concentration factors, which became 3.17 and 2.06 for the upper and lower limb respectively. A further increase in load to that which produced a unit stress of 46,200 psi in the shank of the bar raised the unit strains at the edge of the hole to 6200 microinches/inch and 4300 microinches/inch for the upper and lower limbs respectively. After release of this load, the strain gage 0.08" from the edge of the hole in the lower limb indicated a residual compression of 22,000 psi. Values at the edge of the hole, estimated by extrapolation, were 37,000 psi for the lower limb and 59,000 psi for the upper limb. 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.