Results of analysis on load capability of I-beam using as a railway of hoist in single girder crane show that the standard I-beam is applicable only for the crane with short span and light capacity. This paper presents a combined beam, make of I-beam and steel plate to change the cross section to triangular type with goal increasing the load capability of the beam, loaded in both vertical and horizontal directions, and improves the torsion resistance as well. The dimensions of the combined beam are determined by establishing and solving the structure optimizing problem with the goal to minimize the beam's weight in the terms of strength, stiffness and technology of the structure. The globalized reduced gradient method, integrated in Excels as Solver tool is used to solve this nonlinear optimization problem.