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This paper proposes a new generalized semi-empirical model to simulate fluid–structure interaction forces experienced by a transversely oscillating square-section cylinder by a more comprehensive approach. The total fluctuating transverse aerodynamic forces determined by this new modeling approach are composed of three main unsteady excitation modules. The first component relates to the conventional fluid inertia effect; the second component represents the varying incidence angle effect, including the wavelength-changing effect of downstream wake undulation by introducing a circulation lag function; and the last one denotes the excitation effect due to the strong resonant interaction between wake undulation and Karman vortex shedding. In addition, the new model establishment process follows the “simple-to-use” principle, so it can be applicable even when few experimental data are available. Good agreements are observed between the predictions by this model and unsteady force coefficient results taken from harmonically forced vibration experiments. Moreover, the new model developed in this study can not only simulate the interaction effects between the vortex-induced vibration (VIV) and galloping, but also retain the predictive capability for the cases of pure vortex resonance and pure galloping phenomena. Finally, some significant findings are also presented in the context of the aeroelastic instability phenomena.

The work presented in this study concerns the existing link between fluctuating transverse force characteristics and aeroelastic instability phenomena, which is a step toward further understanding the complex nature of the interactions between square cylinders and air flow. First, by using experimental data from forced vibration, a predictive calculation of the free vibration of an elastically mounted cylinder is carried out. It is found that the prediction results appeared to be qualitatively in agreement with the experimental measurements. This agreement indicates that the measurements using the forced vibration technique is a valuable tool for analysis of free vibration behavior of an elastically mounted cylinder, particularly in cases where the quasi-steady theory is not entirely valid. Furthermore, a new and simple insight into the link between the unsteady force characteristics and the free vibration amplitudes is proposed in this study. Although this approach does not offer details about the nature of the separated flow field around the cross-sections of cylinders, certain complex free-vibration behaviors of square cylinders can be easily interpreted from this perspective.

This study investigates the vortex-induced vibration (VIV) behavior of a twin-box girder bridge by means of aerodynamic sectional wind tunnel test and particle image velocimetry (PIV) measu...

In order to investigate the wind characteristics of coastal areas of China, a long-term field measurement of natural wind was carried out. Based on the field measurement results, this paper presents the natural wind characteristics of typhoons and strong monsoons at the site of Xi-hou-men Bridge, including mean wind speed, mean wind direction, mean wind elevation angle, turbulent intensity, gust factor, turbulence integral length scales, power spectrum of wind speed and spatial correlation of gusty wind, the profiles of mean wind speed and turbulent intensity, etc. The correlation among wind characteristics is analyzed in detail, and the similarities and differences of wind characteristics between typhoons and monsoons are analyzed. These results can provide detailed wind characteristics of coastal areas of China.

Streamline box girders are widely applied in the design and construction of long-span bridges all over the world. In order to study the influence of modifications of aerodynamic configuration and accessory components on flutter and vortex-induced vibration (VIV), more than 60 cases were tested through a 1:50 scale section model. The test results indicates that the aerodynamic configuration and accessory components of streamline box girders can significantly affect the wind-induced vibration of bridge, which is in good agreement with the experience of past researchers. From the tests carried out, it is observed that if the horizontal angle of the inclined web of the streamline box girder is below 16°, the critical flutter wind speed of bridge will increase remarkably, and the VIV will diminish. The test results also show that the 15° inclined web can restrain the formation of vortex near the tail, and consequently improve the performance of aerodynamic stability of long-span bridges. Finally, a new streamline box girder with 15° inclined web was presented and strongly recommended in the aerodynamic configuration design of long-span bridges.

In order to provide reliable parameters for wind-resistant evaluation of Xihoumen Bridge, four 3-D ultrasonic anemometers were installed in the middle of the main span of Xihoumen Bridge. A long-term field measurement was carried out. The field data such as wind speed, wind direction, attack and yaw angles, etc, were measured. Detailed analysis of the field data and further study were conducted to investigate the wind characteristics. The measured wind data are analyzed to obtain parameters such as mean wind speed and wind direction, turbulence intensities, gust factors, turbulence integral length scales and spectrum of gust components. It is found that the turbulence intensities were larger than normal, and the ratio among the three components wasn't in good agreement with the recommended quantities in Wind-resistent Design Specification for Highway Bridges of China. And there was a tendency for the longitudinal and lateral turbulence intensities and gust factors to decrease with the increase of mean wind speed. The Kaimal spectrum and Panofsky spectrum models were identified to describe the energy distribution fairly well for the wind speed component in the longitudinal and vertical direction. Key word: field measurement, turbulence intensity, gust factor

In design of a long-span bridge, gust response of the bridge is very important and must be taken into account. The long-span structure has low natural frequency, small mass and extremely low inherent damping. The spatial correlation and spectrum of the wind in the low-frequency range affect the gust response However, there are very limited field data about spatial correlation of natural wind and wind spectrum. In the wind-resistance design, the decay factor is set to be 7, which affects the wind-resistance design of a long span bridge. Therefore, natural wind were measured at Xihoumen Bridge and the wind speed spectrum and spatial correlation are calculated. The results show that the spatial correlation of the natural wind is lower than that specified in the wind-resistance design specification of China in the low-frequency ranges. The most appropriate wind spectrum and decay factors fitting to the field measurements are recommended. This means that there is a possibility of being able to modify the design specification of long span bridge concerning gust response. The calculated results provide credible technical guide to construction of Xihoumen Bridge and ensure wind resistance safety.