Research on flutter-mode transition of a triple-tower suspension bridge based on structural nonlinearity

Abstract

As the typical span of suspension bridge increases and multi-tower suspension bridges are developed, the linear flutter theory cannot meet the design requirements of modern flexible bridges, and the study of nonlinear flutter of bridges becomes necessary. The author discovered the flutter-mode transition phenomenon in a full-bridge aeroelastic model wind tunnel test of the Maanshan Bridge; that is, the bridge vibration was transformed from first-order anti-symmetric torsion mode (A-T-1) to first-order symmetric torsion mode (S-T-1) and diverged when the flutter critical wind speed was approached. A vertical bending mode acted as a medium for energy transfer between A-T-1 and S-T-1. This phenomenon greatly increased the critical wind speed of flutter, and therefore it is interesting to study its mechanism. Starting from the nonlinear nature of the bridge structure itself, this paper discusses the mechanism of the flutter-mode transition phenomenon, and analyzes the typical characteristics of flutter-mode transition of Maanshan Bridge in depth. A nonlinear discrete mathematical model of the Maanshan Bridge is built, and the transition between the vertical bending mode and torsional mode of the bridge is realized. Adopting the Mathieu function theory and based on the single-degree-of-freedom vibration equation of the Maanshan Bridge corresponding to each mode, the evolution between A-T-1 and S-T-1 is realized, the mechanism of which is also explained.