Effects of an Antiseismic Device and the Posture on Dynamic Seismic Behavior of Continuous Unloaders in Hinged Leg Structure

Continuous unloaders play an important role in handling bulk materials at ports and so should be fitted with antiseismic devices to protect them in case of emergency by severe earthquakes. Continuous unloaders usually have a hinged-leg type structure and their posture changes over a wide range during operations. For the seismic design of continuous unloaders and to optimize antiseismic devices for them, these features must be taken into consideration and the dynamic behavior of unloaders under representative earthquakes must be clarified. This paper proposes an antiseismic device using linear ball bearing and laminated rubber bearings installed between the traveling gears and the fixed legs on the land side. To clarify the dynamic behavior of a continuous unloader in hinged-leg structure under representative earthquake excitations, experiments using a 1/15-scale model of an actual unloader, modal analysis and time history response analysis using the finite element method were conducted, and the performance of the proposed antiseismic device was investigated. The validity of the finite element analysis was evaluated by experiments using the 1/15-scale model, and the effects of posture on dynamic behavior were also studied in the analysis. The time history of the response acceleration, displacement and the response reaction force at leg points as well as the natural frequencies and modes were calculated and discussed.