Consideration of dynamic loads in the design of metal structures of gantry cranes

The design calculation of crane metal structures is usually performed according to load combinations, for which the dynamic coefficients are strictly defined in the regulatory documentation. In fact, these coefficients depend on the departure and the length of the suspension of the load, they are different when lifting loads of different weights. A review of the literature has revealed a clear gap in the studies of the dynamics of gantry cranes, which are characterized by a change in the characteristics of their design even during one cycle of their operation. In this paper, to study the influence of the parameters of the gantry crane system on the magnitude of the dynamism coefficients, a dynamic model consisting of the mass of the crane's metal structure brought to the point of suspension of the load and the weight of the load is applied. The weight of the rope, the elasticity of the lifting mechanism, and the damping of vibrations are not taken into account, and the characteristic of the drive is considered absolutely rigid. A method for determining the parameters of a dynamic model such as structural rigidity, its reduced masses is presented, and the results of calculating the dynamism coefficients for the metal structure of a crane and a rope suspension under various parameters and operating modes are presented. Calculations for a gantry crane with a lifting capacity of 10 tons have shown that with small departures, the dynamic load coefficient in the rope is always less than for a metal structure, while its value is maximum. For large departures, the values of the dynamics coefficients are close to those accepted for calculations according to regulatory documents. These circumstances should be taken into account both in the static calculation of portal cranes and in the calculation of their elements for durability, which will increase their reliability in determining the loading of metal structures.