Airong Chen

Identification of 18 flutter derivatives of bridge decks

Abstract An identification method has been developed to extract all the flutter derivatives defined by R.H. Scanlan. In the present work, the signals of the coupled vertical–torsional free vibration of the spring-suspended section model are used. The flutter derivatives of a thin plate obtained using the present method are compared with the corresponding Theodorsen theoretical values. The present method is then used in the identification of flutter derivatives of the Jiangyin suspension Bridge over Yangtze River. The flutter critical wind speed of this bridge obtained from the full bridge aeroelastic model test in a wind tunnel shows good agreement with the estimated result from Scanlans flutter analysis method with the flutter derivatives using the present method.

Coupled flutter analysis of long-span bridges by multimode and full-order approaches

Abstract The coupled flutter problem of long-span bridges is addressed in this paper. Firstly, a multimode flutter analysis is proposed based on Scanlans linear self-excited forces. The proposed multimode method is single-parameter, non-iterative and offers simplicity, automaticity and robustness. Secondly, a new full-order analysis for the flutter problem is developed. The presented full-order method overcomes partly the defects of the previous direct flutter analysis and is also single-parameter and efficient. Since any assumption is not included on computation, the full-order method is a strict and accurate flutter analysis from the viewpoint of methodology. Moreover, the coupled flutter analysis of the Jiangyin Yangtse River Suspension Bridge with 1385m-long main span is performed.

A practical method of passive TMD for suppressing wind-induced vertical buffeting of long-span cable-stayed bridges and its application

Abstract Formulas for the reduction ratio of tuned mass dampers (TMD) for suppressing the wind-induced vertical buffeting response of long span bridges and the optimal solutions of the parameters of TMD for engineering purposes are derived. The accuracy of the formulas relevant to the design of TMD is confirmed. An aeroelastic test of a full model of the Yangpu Bridge with and without TMD was done, and it was found that the results for the reduction ratio obtained from the test were in good agreement with those from the formulae. Some meaningful results are obtained from the detailed analysis. In addition, “TMD design wind speed” and the constraint conditions are further stressed and discussed. Finally, the Yangpu Bridge is taken as an example to show the application of these formulae.

Determination of 18 Flutter Derivatives of Bridge Decks by an Improved Stochastic Search Algorithm

This paper addresses the determination of the 18 flutter derivatives of bridge decks from three degrees-of-freedom (3DOF) free vibration data using an improved stochastic search algorithm (ISSA) combined with the unified least-squares (ULS) method. The ISSA is capable of circumventing the local optimum dilemma in pursuing the optimal solution experienced in the traditional ULS method. The validity and accuracy of the ISSA are demonstrated by one numerical example and two long-span, cable-stayed, bridge deck sections. The attractive merit of using different lengths of vertical, torsional, and lateral vibration data in flutter derivatives identification is investigated. The identification error and modal participations in flutter are easily examined through a decomposition of modal components from the original vibration data. The underlying complexities in aeroelastic parameter identification are studied, and the causes of low accuracy of some flutter derivatives are unveiled. Based on the comparative investigation on the aerodynamic characteristics of typical streamlined and bluff bridge decks, an improved understanding of the coupled bridge flutter is achieved.

An introduction to the Chinese wind-resistant design guideline for highway bridges

Abstract Some main comments upon the Chinese Wind Resistant Design Guideline for Highway Bridges are explained. The determination of bridge design wind speeds, the calculation of wind loads including the static part and dynamic part, some empirical formulas for basic frequency estimation of cable-stayed bridges and suspension bridges, critical flutter wind speed estimation at the preliminary design stage of bridges and the response spectrum method for estimating the buffeting response of bridges after completion are introduced.

Analysis of Reynolds number effects on bridge deck sections by the PSE method

ABSTRACT Reynolds numbers play an important role in fluid dynamics, because flow separations and reattachments are often Reynolds-number dependent, even if the bodies have sharp edges. To satisfy Reynolds scaling in experiments, the model scale can be very large. Computational fluid dynamics (CFD) provides an interesting alternative to wind tunnel tests, especially when Reynolds effects have to be assessed for a design stage. In this paper, the particle strength exchange (PSE) of vortex methods is introduced for assessing Reynolds number effects on bridge deck cross-sections. For this purpose, this study analyses how the aerodynamic forces of two different bridges sections are influenced by these effects. The computation results with PSE are compared with wind tunnel tests. The relation between Strouhal numbers and Reynolds numbers are also analyzed and compared with experimental results. All the results show that the particle strength exchange method can be efficiently used to calculate Reynolds effects on 2-dimensional bridge deck sections.

Effect of Cable Vibration on Aerostatic Response and Dynamics of a Long Span Cable-Stayed Bridge

In this study, the static response and dynamic modal properties of a cable-stayed bridge with a main span of 1088m under strong winds are addressed focusing on the effect of cable vibration on overall bridge behavior. Two modeling systems for stay cables are considered in the finite element modeling of the overall bridge, i.e., one element cable system (OECS) and multiple element cable system (MECS). The aerostatic analysis under varying wind speeds and angles of attack is conducted with an iterative procedure taking into account the nonlinearities of wind forces and cables. The modal analysis is then performed under the statically deformed conditions to quantify the changes in bridge modal properties with increasing wind speed. The analysis results are further compared with the measurements using a full aeroelastic bridge model in a wind tunnel. The results of this study revealed the importance of using the MECS for accurate modeling and response prediction of long span cable-stayed bridges to strong winds.