A nonlinear self-excited force model for soft flutter phenomenon of a twin-side-girder bridge section

作者：ZHU Ledong; GAO Guangzhong

来源：振动与冲击, 2016, 35(21).

DOI：10.13465/j.cnki.jvs.2016.21.005

• twin-side-girder section
• soft flutter
• post-critical LCO
• nonlinear self-excited force model
• nonlinear aerodynamic damping
• soft flutter mechanism

To investigate the soft flutter phenomenon,i.e.,nonlinear post critical limit cycle oscil1 ation (LCO)of a twin-side-girder section,a series of spring-suspended sectional model tests were conducted.Experimental results showed that the sectional model exhibits violent soft flutter phenomena in post flutter range;the observed soft flutter is a quasi-harmonic nonlinear torsional vibration with a slight bending-torsion coupling effect;the classical linear self-excited force model by Scanlan is not applicable to soft flutter.To model the aerodynamic nonlinearity during large-amplitude oscillation of soft flutter,a nonlinear self-excited force model was proposed by expressing flutter derivatives of the classical Scanlan's linear model as functions of transient torsional vibration amplitude.The identified results of the amplitude-dependant flutter derivatives showed that the nonlinearity is strong for the aerodynamic damping and very weak for the aerodynamic stiffness.The feasibility of the proposed model and the reliability of the identified aerodynamic parameters were verified by comparing the computed vibration responses of soft flutter with the corresponding experimental data.The mechanism of soft flutter was then explored with the identified nonlinear relationships of aerodynamic damping and structural damping with respect to the transient torsional vibration amplitude.

• 单位
  同济大学