Effect of recurrent impulse load actions on a crane

The purpose of this numerical research is to study a derrick crane under repeated loads. The numerical analyses were carried out considering two different geometrical crane configurations, and two different rope lengths. After a preliminary analysis in order to evaluate both static and dynamic (modal) crane performance, many different analyses were carried out applying different load sequences. These actions were characterized by several impulse loads, which can be applied during the crane active use. Two parameters characterize the impulse load, i.e. the impulse duration and the delay between two successive actions. This load condition, which is not present in the crane design standards, was experimentally checked during the machine use in the marble quarry where it was installed. The results show that in specific crane configurations, characterized by the main arm position and the rope length and with a specific load sequences, both the vibration and the displacement magnitude increase in time, inducing high stress value in the crane components that can collapse the crane itself.