Failure Analysis of a Stair Tread Wood Failure:

Failure analysis expert examined a failed wood stair tread that was the cause of a fall and an injury. The failed tread is shown still mounted in the photo on the left. The re-assembled tread is shown in the photo on the uper right. This tread was screwed in place when the wood was green; in addition, there were no pilot holes drilled for the screws. Failure analysis shows that as the wood dried, the pressure from the screws wedged into the wood caused a wood failure (i.e. the wood split). In additon, the bracket was 0.8 inches from the nose of the tread. Thus, the force from a foot placed on the nose of the tread created enough moment to split the wood apart and cause the person steppimg onto it to slip and fall.