MASS MINIMIZATION OF BRIDGE CRANES' MAIN GIRDER ACCORDING TO EUROCODE

Abstract

Double-beam bridge cranes are the most common in the industry compared to other types of bridge cranes. In addition to box girders, I-profiles are also present as the main girders of double-beam bridge cranes. Since I-profiles have defined dimensions, their geometry is often not optimally utilised for some of the criteria that must be satisfied; therefore, these beams are oversized in such cases. For this purpose, it is necessary to optimize the geometry of the I-profile, which is the topic of this research. This paper addresses the optimal design of a welded double-symmetrical I-girder for a double-beam bridge crane. The minimum mass, i.e. the cross-sectional area of the I-girder, is set as the objective function. The constraint functions include the stresses in the characteristic points of the I-profile at the critical location of the girder, the stress in the welded joint, the deflection at the middle of the girder, the oscillation period of the beam, as well as the global stability of the I girder. The strength and stability checking are performed according to Eurocode, and the cross-section of the girder is considered for Class 3. The optimization was carried out using a modern algorithm of optimization. Two bridge cranes were used as examples. Finally, the results obtained are compared to the geometrical values of the standard I-profiles in the considered examples of bridge cranes, where conclusions and recommendations for further research are presented.