OPTIMAL DESIGN OF THE HYBRID I-GIRDER OF THE SINGLE BEAM BRIDGE CRANE

Abstract

This paper presents the optimal design of the main girder of the single-beam bridge crane, where the main goal of the research is to reduce the weight, i.e. the cross-sectional area of the main girder. The objective function is the cross-sectional area of the mono-symmetric I-profile. To rationally use materials, plates of different types of structural steel were considered, so S355 grade steel was used for the bottom flange of the main girder and S235 grade steel for the other segments of the main girder. The reason for this is primarily the reduction of the thickness of the bottom flange, as the wheels of the trolley that move on it cause an increase in stress, which is especially pronounced with high load capacities, and taking into account the standard thickness of the plates. This research uses the strength criteria in the characteristic points of the I-profile, the stiffness and dynamic stiffness criteria of the main girder, and the stability criterion of the main girder as constraint functions in this multi-criteria optimization problem. Achieved savings in the main girder weight are between 54.45% and 64.67%, depending on the considered examples, which confirms the justification of the application of the proposed design methodology.