Dynamical overloading of lifting appliances submitted to vertical movements: use of one degree of freedom oscillating systems, equivalent to two degrees of freedom systems

Certification authorities recommend the use of more complete elastic-kinetic models of the crane, which usually presents two or even more degrees of freedom. The Crane European Standard simplify the lifting system under consideration as a system with a single degree of freedom. The above Standards suggest some linear expressions of Φ2, the parameters of which are classified in a limited number of Hoisting Classes, usually four, on the base of crane service and of the more or less elevated 'roughness' of lifting operations. A direct methodology is indicated, which allows to consider a simple one degree of freedom system, the mass and elasticity parameters of which can be easily deduced by convenient combination of mass and elasticity parameters of corresponding systems with two degrees of freedom. For simplicity reasons, in this paper we only refer to the case of 'sudden lifting' of a free suspended load.