DOUBLE MAIN GIRDER DESIGN OF AN OVERHEAD TRAVELLING CRANE FOR MINIMUM COST

Abstract

A crane structure of two doubly symmetric welded box beams is designed for an overhead travelling crane for minimum cost. The following design constraints are considered: local buckling of web and flange plates, fatigue of the butt K weld under rail and fatigue of fil-let welds joining the transverse diaphragms to the box beams. The rails are placed over the inner webs of box beams. To increase the fatigue strength of the last mentioned welds, an efficient post welding treatment (PWT) is considered. For the formulation of constraints the relatively new standard for cranes EN 13001-3-1 [1] is used. The cost function consists of cost of material, assembly, welding and PWT. PWT is economic, since it is used only for diaphragms near the span centre of box beams, where the bending stresses are high. The optimization is performed by systematic search using a MathCAD program.