Time-domain simulations of turbulence effects on the aerodynamic flutter of long-span bridges

Shuqian Liu,C S Cai,Yan Han

doi:10.1186/s43251-020-00007-6

Abstract

Aerodynamic flutter instability has been a major concern for long-span flexible bridges, such as suspension and cable-stayed bridges, subjected to wind actions that result in the so-called self-excited forces. Though turbulence effects on bridge flutter have been studied in the last few decades, its true effects remain a debate due to the limitation of previous wind tunnel facilities, such as using turbulence scales that are too small in these experiments. In this paper, the characterizations of self-excited forces are presented in both the frequency-domain and in the time-domain. Then, the flutter analysis is conducted under both smooth flow and turbulent flow in order to investigate the effect of wind turbulence on the flutter instability. The effect of wind turbulence is directly modeled in the time-domain in order to avoid the complicated random parametric excitation analysis of the equation of motion used in previous studies. By comparing the results of different turbulence intensities with that of the smooth flow, it is found that the turbulence has a stabilizing effect on bridge flutter. The turbulence can change the vibration patterns and weaken the spatial vibration correlation to some extent. As a result, the critical flutter velocity can be increased by 5% to 10% over that under smooth flow.

Highlights

The aerodynamic instability of long-span bridges under strong wind excitations has been a major concern in recent years, especially with the continuously increasing span length built around the world, especially in China
In the time-domain method, the self-excited forces are represented in the form of the indicial functions (Scanlan et al 1974; Zhang et al 2010; Caracoglia and Jones 2013; Zhang et al 2019) or rational functions (Chen et al 2000; Chowdhury and Sarkar 2005), which can be identified through experimental tests or numerical approaches from available flutter derivatives
The results showed that wind turbulence with high intensity might have adverse effects that reduce bridge flutter instability (Bucher and Lin 1988a, 1988b; Cai et al 1999)

Summary

Introduction

The aerodynamic instability of long-span bridges under strong wind excitations has been a major concern in recent years, especially with the continuously increasing span length built around the world, especially in China. Based on the experiments carried out in wind tunnels on full aeroelastic models of long-span suspended bridges, it is shown that the level of wind turbulence generated in wind tunnels influences the aerodynamic instability of the structure (Diana et al 1993) Based on their observations on the measured flutter derivatives, Scanlan and Jones (Scanlan and Jones 1991; Scanlan 1997) found that the flutter instability performance can be enhanced in a turbulent wind field because the turbulence may weaken the inherent correlation of the self-excited forces along the bridge deck. Three approaches: (i) the frequency-domain approach based on flutter derivatives, (ii) the time-domain approach based on rational functions under smooth flow, and (iii) the time-domain approach under turbulent flow, haven been applied to predict the critical flutter velocity These results are compared and discussed based on the analysis of a prototype long-span bridge.

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Findings

Conclusions