Many of our cases have dealt with bolt failures. In this case, an overhead crane collapsed when four bolts holding its overhead rail supports failed.

The rails had been replaced a few years earlier; the contractor had used smaller diameter bolts than the originals. One of the bolts showed signs of metal fatigue, two showed evidence of metal shear; the fourth had fallen into an acid tank, and its surface was heavily corroded.

Geometric reconstruction documented a small step between adjacent rails that loosened and pounded the bolts when the crane rolled down the rails; calculations showed that the forces generated at the step were sufficient to create metal fatigue. Eventually, two of the bolts failed in fatigue, one end of the rail fell, and the bolts holding the other end sheared.

We had proved that the contractor was at fault, but the subrogation went unrewarded because the contractor was in default.