Optimization of the box section of the main girder of the bridge crane with the rail placed above the web plate

The paper considers the problem of optimization of the box section of the main girder of the bridge crane. Reduction of the girder mass is set as the objective function. The method of Lagrange multipliers was used as the methodology for approximate determination of optimum dependences of geometrical parameters of the box section. The criteria of permissible stresses and strains, lateral stability and dynamic stiffness were applied as the constraint functions. The obtained results of optimization of geometrical parameters were verified on numerical examples and the comparison with some solutions of cranes was made. The comparative analysis of the optimization results and the solutions was the basis for recommendations which are significant for designers during construction of cranes.