Analysis and comparison of solution assumptions for the determination of critical flutter wind speed of long-span bridges via the step-by-step method

Abstract

The step-by-step method is a powerful tool for determining the critical flutter wind velocity of long-span bridge deck section models. This method was proposed by Prof. Matsumoto from Kyoto University. A notable advantage of this approach is its capability to analyse the aerodynamic instability of a bridge deck section in both heaving and torsional branches, while also describing the structural behavior over the entire wind velocity range, including the subcritical region, the critical state, and the postcritical region. In the publications of Matsumoto, the oscillation solution is assumed under three different cases. This study focuses on evaluating the differences in computational results corresponding to these three assumptions. Numerical simulations are conducted for the deck section models of the Akashi Kaikyo Bridge and the Gibraltar Bridge. Comparative analyses are performed in terms of flutter frequency and logarithmic decrement across the entire wind velocity range. The results provide insight into the influence of the assumed oscillation forms on flutter prediction using the step-by-step method and contribute to a more consistent interpretation of aeroelastic instability in long-span bridge decks.