EVALUATING THE SEISMIC EFFECTS ON LIFTING EQUIPMENT

The purpose of this paper is to assess the dynamic behaviour of various lifting equipment (different types of cranes, elevating work platform, etc.) subjected to seismic actions, evaluating how these actions can both generate failures and affect the structural behaviour of the machine. The work is developed starting from the design of the different machines of interest (according to some classical standards and specific performance like working load, lifting speed, working area, etc.), determining their geometry. Subsequently are applied the characteristic load spectra to the structures, related to the magnitude of earthquake; the final step consist in the structural analysis of the machines, computing their maximum stresses, displacements and natural frequencies, using different finite element codes. The results show that the first natural frequencies of the structures are very low and consequently the effects of the seismic action, in general, are not dangerous. Otherwise it is important to underline that the maximum stress induced by the earthquake is detectable in different position in the lifting equipment respect to maximum stress position in the normal loading operations, therefore seismic analyses are indispensable for study these parts of machines.