Use of Forensic Engineering to Determine the Cause of a Crane Tip-Over

A large Manitowoc crane mysteriously overturns while sitting idle for approximately 10 minutes after completing a lift. The boom falls on a nearby building, damaging property; but fortunately, no one is injured. Although the crane operator was accused of not operating the crane properly, a geotechnical engineer was called to analyze unusual occurrences that were noted prior to and immediately after the failure. Some factors in the tip-over were: (1) the crane was operating near an open excavation and (2) an underground waterline had ruptured a day or two before the crane was positioned for the lift. This paper explains how by considering various subsurface effects; it was possible to show that transient loss of soil strength resulted in a bearing capacity failure under the crane.