THE EFFECT OF VARIABLE CROSS-SECTION OF PRESTRESSED BEAMS ON THE LOAD-BEARING CAPACITY OF THE STRUCTURE

This paper examines issues related to increasing the load-bearing capacity of span beams of bridge-type cranes by the method of prestressing. A new mathematical model of a bridge crane with prestressed beams has been developed, which is based on the general theory of the stability of elastic systems and allows taking into account the real conditions of the construction of span structures. In this work, the equations of the deflection curve of this beam were obtained, which allow us to consider and analyze the influence of eccentric longitudinal forces on the stressed-deformed state of the span beam, taking into account the variable moment of inertia of its cross-section along the length of the span with a dangerous load combination. The work provides a more detailed calculation coefficient for the critical longitudinal force, which depends on the ratios of the moments of inertia of the cross sections of the span main beam, as well as the length of the support sections of the beam to the length of the beam itself. Based on the results of the obtained equations, a study of the static stiffness of the main beam was conducted depending on the ratio of longitudinal and transverse forces acting on the beam. The analysis of the obtained results revealed the recommended ratio of the lengths of the supporting and middle parts of the bridge, taking into account their geometric cross-section characteristics. The results obtained in this work can be used in the future for the modernization of cranes in order to increase their load capacity, extend their service life without dismantling, as well as for the improvement of existing structures and engineering calculation methods both at the stages of their design and in the conditions of real operation.