Modal Characteristic and Nonlinear Dynamic Response of Suspension Bridge with Lateral Asymmetric Stiffness

Asymmetric stiffness in transverse direction of suspension bridge can be easily induced by many causes during its long-term service. Such phenomenon may cause the coupling effect between vertical and torsional vibrations. A cross-section model of suspension bridge with seven-degree of freedom is proposed, to investigate the asymmetry effect on the dynamic behavior of the system. Corresponding modal analysis is firstly carried out. Results show that the asymmetric stiffness will induce veering phenomenon when natural frequency loci of vertical and torsional modes approach each other. In the veering region, mode hybridization phenomenon can be observed between these two modes. In addition, asymmetry-induced nonlinear vibration of hybrid vertical and torsional modes is studied using the extended incremental harmonic balance method. The effect of asymmetry extent is also investigated in this study. Results show that both hybrid modes can be excited by either the vertical or torsional excitation. Moreover, the energy can be transferred between these two modes, because of the nonlinear stiffness introduced by the significant swaying motion of hanger and cable.