Overturning Mechanisms of Jacks, Cranes and Pile Driving Machines: Fid-Bau Portal

Overturning Mechanisms of Jacks, Cranes and Pile Driving Machines

Toma, Shouji / Chen, Wai Fah

Overturning accidents involving jacks, movable cranes and pile driving machines during construction have often occurred in Japan. In this article, a theoretical study is made by assuming that structural stability, like buckling, is related to a fundamental cause. Overturning mechanisms can be categorized as: (1) the overturning moment exceeds the resisting moment; (2) the load exceeds the critical load; and (3) the deformation exceeds the stability limit. In order to study these three mechanisms, two structural analysis approaches, i.e. the moment approach and the stability approach, are applied. By the moment approach, mechanism (1) is explained by comparing the overturning moment with the resisting moment, which has been utilized mostly in past investigations. On the other hand, the stability approach is applied to cases of types (2) and (3), by which the overturning mechanism of movable heavy machines on soft ground can be rationally explained. On soft ground, theoretically even with no overturning moment there is a possibility that machines could overturn. This article investigates the fundamental cause of overturning accidents based not only on the overturning moment approach but mainly on the structural stability approach. By understanding the overturning mechanisms, further accidents may be prevented.