Abstract: The three-dimensional models and the finite element models of the two schemes (Scheme 1: The structure circular section of the traction beam；Scheme 2: The octagon section structure of the traction beam）for traction beam on the central frame is established. Under the same boundary conditions，the strength and stiffness of both schemes in extreme conditions are calculated，analyzed and compared. The results are shown as follows: at scheme 1，the maximum stress is 141.5 MPa，and the maximum deformation is 0.53 mm;at scheme 2，the maximum stress is 137.5 MPa，and the maximum deformation is 0.503 mm. According to the calculated result，the stress and deformation at scheme 2 are lower than that at scheme 1. So the scheme 1 is the better. Through comparing these two schemes from their manufacturing process，it is shown that the traction beam is made of large-diameter circular cross section structure in scheme 1，and molded with special equipment and complex manufacturing process. The traction beam in scheme 2 is made of octagon shaped structure，and formed by two welding and bending steel plate with simple manufacturability. So，the scheme 2 is the better in the manufacturing process. The conclusion is that scheme 2 with octagon section frame of traction beam is optimal because its strength and stiffness can meet the requirements with a better manufacturing process.

Key words: Traction beam, Strength, Stiffness, Manufacturing process