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The flutter responses of the Nanjing No.4 bridge flat box girder under different wind attack angles were tested in detail through sectional model tests. The evolution of unsteady and steady critical amplitudes at different wind speeds was discussed. Based on the amplitude envelope of the flutter response and the Hilbert transform, the amplitude-dependent modal damping of the system was identified, and the mechanism of the flutter mode change with the wind angle of attack was initially explained. Secondly, the modal parameters of the system under different wind attack angles were extracted. With the bimodal coupled flutter analysis method, the nonlinear flutter derivatives of the section under different wind attack angles were identified, and the change law for the amplitude dependence of the key flutter derivatives on the wind attack angle and the potential influence on the section flutter morphology and characteristics, were studied. Finally, the effects of the wind attack angle on the uncoupled and coupled aerodynamic damping were analyzed through analyses of the modal damping subterms one by one, and the dynamic mechanism of the differential flutter performance caused by fractional damping was illustrated. [ABSTRACT FROM AUTHOR]

In order to analyze the change characteristics and influencing factors of the total suspended particulate ( TSP)concentration in the atmosphere of coal port area, using the monitoring data of the typical coal port area in 2020, based on the K-means clustering method, the change characteristics of the TSP concentration in the port area were analyzed; combining with the characteristic parameters of meteorological environment in the port area, the correlation between TSP pollutant concentration changes and humidity and wind speed were analyzed. The results show that the overall TSP mass concentration in the port area has a positive and negative correlation with humidity and wind speed, respectively. The concentration daily change trend is "single peak and single valley" type, the peak and valley values arrive at 5： 00 -7： 00 and 17： 00 -18： 00respectively. Abnormal fluctuations are prone to occur in summer and winter. And it shows 6 different clustering characteristics of hourly variation patterns. The research results can provide theoretical support for the prevention and control of particulate pollution in coal port areas [ABSTRACT FROM AUTHOR]

Field measurement of wind characteristics at site of long-span bridges is one of the basic research areas on bridge wind engineering. The wind characteristics parameters based on field measurement can provide a basis for the verification and modification for wind tunnel testing and simulation technology. A long term and continuous field measurement was carried out with the ultrasonic anemometers and propeller anemometers installed at site of Xi-hou-men Bridge. Based on the data of field measurement, this paper presents the field measurement results of natural wind characteristics of strong monsoon at site of Xi-hou-men Bridge, including turbulent intensities, gust factors, turbulence integral length scales, power spectral density, the profiles of mean wind speed and spatial correlation of gusty wind, and so on. These field measurement results can provide detailed wind characteristics of coastal areas which can be taken as a reference for the design and construction of other similar long span bridges. [ABSTRACT FROM AUTHOR]