The Analysis of Stiffness and Stability of Luffing Jib Cranes Based on Theory of Second Order

Abstract

Luffing jib cranes are large flexible complex truss structure, and their mechanical property is nonlinearity. So the Precise analysis method for the stiffness and stability problem has been paid attention to by the researchers. To solve this problem, the equivalent mechanical model of luffing jib crane was established by taking the lifting load, counter weight and dead weight into consideration. The stiffness and stability of luffing jib crane was analyzed by using the differential equation of deflection based on second-order effect. The calculating formulas of lateral deflection, amplification factor of deflection and stability was derived. Taking a luffing jib tower crane for example, the lateral stiffness was calculated respectively by the formula given by this paper, the traditional linear method and the finite element method, and show that the result calculated by the formula given by this paper is identical to that by finite element software ANSYS, the error is 1.8%. and the error of traditional method is 7.6%, It is clear that calculation expression of lateral deflection, deflection amplification factor and the stability in this paper are accuracy. This method can be applied to the analysis of calculation of luffing jib tower crane stiffness and stability.