FATIGUE STRESS IN MAIN BEAMS OF SPAN-TYPE CRANES

This article presents calculated dependences for estimating stresses in the main beams of span-type cranes, which are necessary for fatigue resistance and residual life computations. The dependences are obtained by forming typical technological cycles of crane operation according to the predicted or actually recorded parameters of its motion. The dependences allow to calculate the largest, smallest, and average stresses during unsteady operation of mechanisms for lifting and moving the crane and trolley, taking into account the coefficients of dynamism and damping of oscillations. Assumptions and limitations, which are used for the calculated dependences of typical technological cycles, are formulated. We have established by calculation that the first 6–7 damped oscillations in the vertical plane and 5–6 oscillations in the horizontal plane, depending on the bridge design, have a damaging effect. An example of a typical technological cycle and the resulting stress pattern is shown.