Experimental and analytical study on elevating working platform

Abstract

This paper describes the research performed about the dynamical behavior on the mobile elevating work platform (MEWP). In particular, this research was inspired by that accident happened during a pruning operation. A big branch of three fell down and bumped the basket of MEWP. The consequent dynamical actions have made the operator jump out of the basket of MEWP. The main object of this work is to characterize the dynamic behavior of this machine (height=34 m, working load limit =200 kg) in order to estimate the actions induced by the branch on the MEWP. This load condition is not contemplated in the standards used for the design of this machine. For this purpose many experimental, analytical and numerical analyses were performed. In order to characterize the dynamical behavior of the machine (real damping, stiffness of the global arm and the sliding blocks positioned between each arms, etc.), on the similar MWEP, about 20 accelerometers and strain gauges were applied; subsequently the machine was subjected to different movements (extension and rotation the arms and the jib). The MEWP was subjected to geometrical relief with the aim to carry out the solid model necessary for finite element model (f.e.m.) analyses; which are performed using the parameters acquired in the previous step. The f.e.m. results were compared with the values obtained from the strain gauges. A lumped parameter model was created in order to apply the load condition induced by the branch to the jib. Numerical and analytical results show that in the geometrical configuration of MEWP (when the accident occurred), the acceleration of the basket is greater than gravity and it justifies the operator jumping out of the basket. The results achieved led to a revision of the standards (in a specific technical committee) both for designing this machine in order to consider this exceptional load condition and for designing the safety equipment for MWEPs operators.