Equivalent Inertia Moment in Linear Stability Calculation of Stepped Beam

In the process of simplifying the stability calculation for light main boom of crawler crane, the structure can be considered as non-symmetrical one with variable cross-section beam. The equivalence of the simply supported beam with asymmetrical cross-section has not been solved. This paper attains the equivalent inertia moment of the stepped beam with the small deformation by using the differential and energy methods. In addition, comparing with the software ANSYS, the results of differential method is better than energy method. Then the results of differential errors are amended and reduced. Then, the paper presents the equivalent inertia moment coefficients curves, which greatly simplifies the calculation process of critical load and provides the reference for boom design.