Wind-induced vibrations, such as vortex-induced vibrations, occur on long-span bridges because of their flexibility, especially for bridges with centrally slotted box girders, which may severely affect structural safety and driving comfort. In this research, the influence of wind barrier parameters on the wind field of the driving space on a centrally slotted bridge deck under crosswind was experimentally investigated. Particle image velocimetry (PIV) was employed in wind tunnel tests conducted in the low-speed test section to obtain the wind field on the bridge deck. The effects of wind barriers on the average wind speed, turbulent kinetic energy (TKE), and mean vorticity were analyzed under both with-vehicle and without-vehicle conditions. The effects of the height, porosity, and layout of the wind barriers on the driving space were also quantitatively presented by the equivalent wind speed reduction coefficients. The results show that vehicles on the bridge deck can induce the formation of vortices and high turbulence in the driving space. The parameters of the wind barriers affect both the distribution and magnitude of the average wind speed on the windward side. The corresponding results are important for the wind barrier design of long-span bridges to ensure driving safety on bridge decks.

To address the safety hazards of coastal outdoor billboards under extreme wind disasters and the limitations of existing design codes, this study conducts systematic wind tunnel tests on three kinds of typical billboards (floor-standing single-panel, single-column double-panel, and single-column triple-panel configurations) using 1:20 scale rigid models. The surface pressure distribution is measured through pressure tap measurements. Key findings reveal: (1) the high pressure zone on windward panel shifts toward the wind direction with the increasing wind angle; (2) the extreme values of positive/negative local wind pressure occur in the 45°/90° wind direction cases, and the local wind pressure coefficients can be up to 1.39/−1.28, respectively, exceeding the values specified in the codes; (3) the extreme positive value of overall average wind pressure, up to 0.95, occurs in the 0° wind direction case. The findings provide quantitative benchmarks for wind-resistant design optimization of billboard.

Aerodynamic forces and coefficients are essential for explaining the mechanism and suppression of the vortex-induced vibrations (VIVs) of bridge decks in large-span bridges. However, in a wind-tunnel test, the aerodynamic force usually cannot be directly measured. In this research, a modified particle filter with unknown inputs that combines a particle filter algorithm and a Kalman filter (PKF-UI) is proposed to identify the aerodynamic coefficients and forces of VIVs. The effectiveness of the proposed PKF-UI method is firstly verified using three-degree-of-freedom nonlinear structures. The effects of the number of particles and noise level are discussed. The results show that the proposed method can effectively identify both structural parameters and unknown inputs. With the addition of 10 % white noise for the measurement, the identified structural parameter errors are 10 %, indicating that such a method can be applied effectively to the experimental data. Wind-tunnel tests are conducted on the bridge deck of a large-span bridge, and VIVs are obtained. With the utilization of the proposed method, the accelerations and displacements, which can be measured in the experiment, are fused to identify the aerodynamic forces and coefficients in the VIV lock-in regions.

Accurate wind speed prediction is essential for wind power generation and wind-resistant structural design. In this research, a short-term wind speed prediction model that combines the wavelet decomposition (WD) method and a fractal-based long short-term memory (LSTM) network is proposed. The fractal dimensions of the dataset at each level, which are decomposed using the WD method, are calculated using the box-counting method. With the dynamic learning rate in the loss function updated by fractal dimensions, the gradient-enhanced LSTM network is applied for wind speed prediction. Experimental wind speed data collected during wind field measurement experiments in Pingtan, Fujian Province, China, were used to validate the proposed wind speed prediction model. The predicted wind speed results at different considered time intervals are compared with those of the traditional LSTM method. The results suggest that the proposed method significantly improves the accuracy of wind speed forecasting.

In this study, numerical simulations of wind fields at bridge locations in complex terrain are conducted with utilization of Fluent. Terrain modeling was performed based on the GIS data, wind characteristics and the ground roughness coefficient are obtained by numerical simulation different wind directions. the acceleration effect of the terrain on the wind field under different working conditions are explored. Results show that the wind speed ratio of the bridge site area is 1.38 and the minimum value is 0.84, which may provide references for the wind resistance design of the large span bridges.

Large-span bridges often exhibit complex and variable flow fields around their bridge decks because of the coupling of natural and structural winds, which induce vortex-induced bridge vibrations, threatening the driving safety and comfort of vehicles. To capture the response characteristics of vehicles crossing bridges in this type of environment, a novel framework is proposed in this paper from aerodynamic and system dynamics perspectives for analyzing the dynamic responses and ride comfort of vehicles under the coupled effects of crosswinds and vortex-induced vibrations. The real driving behavior of a vehicle is simulated by establishing a 14-degree-of-freedom dynamic model, incorporating a driver preview controller, for the entire vehicle. Subsequently, a wind tunnel test and a numerical simulation are combined to measure the vortex-induced bridge vibrations and the aerodynamic loads imposed on the vehicle body, producing dynamic response parameters that are used to evaluate the driving stability and ride comfort of the vehicle under these disturbances. The results show that the proposed analytical framework effectively reproduces the driving characteristics of the vehicle under different levels of crosswinds and vortex-induced vibration excitations, accurately simulating the dynamic responses of the vehicle.

Extreme events such as tropical cyclones frequently occur in coastal areas in China. With high wind speeds and rainfall during such extreme events, the vehicles on sea-crossing bridges may face severe instability problems. In this study, the dynamics of vehicles on a cross-sea bridge under the wind–rain coupling effect were analyzed based on field measurement data using computational fluid dynamics (CFD). Wind field parameters of the coastal area in China were obtained using wind speed data from measurement towers. Based on CFD, the sliding grid method was applied to establish an aerodynamic analysis model of a container truck moving on a bridge under wind and rain conditions. The discrete phase model based on the Euler–Lagrange method was used to investigate the influence of rain and obtain the aerodynamic characteristics of the truck under the coupled wind and rain effects. Based on the computational analysis results, considering the turbulence intensity, the yaw angle peaks of the tractor and trailer increased by 5.2% and 3.8%, respectively, and the lateral displacement of the truck’s center of mass increased by 9.8%. Rainfall may cause the vehicle to have a higher response, resulting in a high risk of skidding. The results show that skidding occurs for the considered container truck when rainfall is at 9.8%. These results can provide parameters for traffic control strategies under such extreme climate events in coastal areas.

In this study, a comparative analysis of the impact of the attack angle and windscreen height on the vortex-induced vibration (VIV) in a streamlined closed-box girder was conducted using a 1:50 scaled model of a coastal cable-stayed bridge through wind tunnel tests and numerical simulations covering a range of attack angles and windscreen heights. The simulations were validated through experimental data, grid sensitivity analysis, and time-step independence. The results revealed that the VIV amplitude increased with increasing attack angle because of the interaction between vortices from the traffic lane and those in the wake region. Specifically, under a + 5 degrees attack angle, pronounced VIV was observed in the section, with the maximum torsional VIV amplitude reaching up to 4.1times the code-specified limit. Spectral analysis revealed that within different wind speed lock-in ranges, the vibrations consistently corresponded to the torsional fundamental frequency mode. Further insight from proper orthogonal decomposition (POD) based on singular value decomposition (SVD) revealed that the large-amplitude torsional VIV of the section was caused by separated vortices over the traffic lane persistently transferring energy to the wake K & aacute;rm & aacute;n vortices, forming large-scale vortices that could lock in with the torsional mode of the main girder. Windscreens on both sides of the section effectively reduce the VIV amplitude through distinct mechanisms: the windward screen delays flow separation. Moreover, the leeward screen altered the path of the vortices toward the wake region. When the windscreen height reached 4.5m, the vortex movement path to the leeward side was completely blocked, fully suppressing the VIV. The effect of windscreen height on VIV was closely linked to lift, surface pressure, and their correlation. These findings provide valuable insights into wind-induced vehicular safety measures and VIV suppression strategies for sea-crossing bridges.

In fractal theory, the fractal dimension has been accepted as a quantitative parameter to measure the complexity of fluctuations and the persistence of wind speeds. Typhoons are extreme wind events that damage structures. In this study, on the basis of wind field measurements, the fractal dimension characteristics of four typhoons in southeastern China are examined. Typhoon wind speeds at different heights and locations are presented. Monofractal dimension analysis was first conducted, and the results revealed that the typhoon wind speeds were persistent, with fractal dimensions smaller than 1.5. For all four typhoons considered, with the onset of landfall, the fractal dimensions approach 1.5, indicating unpredictable trends in the time series. Multifractality is accepted to exist in the typhoon wind speed dataset, and multifractal analysis was also conducted on the basis of the measured typhoon wind speeds. The results show that the fractal parameters calculated by multifractal analysis are generally greater than those calculated via monofractal analysis. This research aims to improve the understanding of the inner dynamic characteristics of typhoon wind speeds. These fractal parameters can provide quantitative references for future typhoon simulations and predictions.

Terrain conditions may significantly affect the near-ground-layer wind speed in coastal areas. In this research, wind tunnel tests and computational fluid dynamics (CFD) were performed to investigate the impact of topographic changes on the local wind field at coastal bridge sites. Considering the geographic information system (GIS) information of an offshore bridge site, a 1:1000 topographic model was constructed to conduct tests in the wind tunnel lab under different wind directions. The influences of terrain conditions on localized wind characteristics such as the wind speed and wind attack angle under different test conditions were obtained. The results show that the wind angle varied between −6° and 6° under different conditions. To more comprehensively show the radius of influence on the local terrain, a CFD simulation was conducted. To verify the results of the wind tunnel tests, the SST k-ω model was compared and selected for simulation in this research. The influence radius of localized wind characteristics was determined by CFD simulation. The results indicate that the original topography showed “reverse amplification” on the leeward side, resulting in complex wake flows. These results may provide a reference for the design of wind-resistant structures such as bridges and offshore wind turbines in coastal areas.

Water-filled barriers have been reported to significantly affect the vortex-induced vibrations (VIVs) of large-span bridges. However, few studies have systematically investigated the influence mechanisms of water-filled barriers on bridge decks. In this research, both wind tunnel tests and numerical simulations were conducted to analyze the VIV behavior of the considered bridge model with various arrangements of water-filled barriers on the bridge deck. Six configurations with different water-filled barrier positions on the bridge deck were tested in a wind tunnel, and numerical simulations were conducted to explore the influence mechanisms of water-filled barriers. The results show that with the installation of water-filled barriers, the maximum RMS of the vertical VIV amplitudes are increased by 100% compared with that in Case 1 without water-filled barriers, whereas the torsional VIV amplitudes may slightly decrease. Compared with the most unfavorable case, where the water-filled barriers were positioned near the crash barriers, moving the water-filled barriers further away from the upstream or adopting a sparse arrangement along the bridge deck may reduce the VIV amplitudes. Therefore, it is important to consider both the incoming flow direction and the positioning of water-filled barriers on the deck should be considered in bridge maintenance to avoid the most unfavorable scenarios.

The influence of twin-box girder attachments on the driving wind environment of a long-span coastal bridge under crosswind was experimentally studied in a boundary layer wind tunnel. First, the particle image velocimetry (PIV) technique and anemometers were used to determine the optimal PIV window size. Then, the effects of attachments and vehicles on average wind speed, turbulent kinetic energy, Reynolds stress, and equivalent wind speed reduction coefficient on the driving wind environment were analyzed. Results indicate that bridge attachments alter both the magnitude and distribution of average wind speed on the windward side of the vehicle. Turbulent kinetic energy peaks were observed near the windward side of attachments, particularly in the wake region above the vehicle. Reynolds stress peaks were primarily located on the windward side of the attachments; increasing the height of the attachments expanded the peak area above the vehicle while reducing the wake region’s area. The coefficient of equivalent wind speed reduction provides a reasonable quantification of changes in the driving wind environment. However, the difference between conditions with and without the vehicle was significant, suggesting that practical wind barrier solutions should prioritize aerodynamic measurements of vehicles behind wind barriers.

This study examines the impact of the flow disruption coupling effect between bridge towers and railings on the bridge deck’s flow field and the aerodynamic stability of vehicles. The wind field distribution pattern of the bridge was determined through particle image velocimetry (PIV) experiments and computational fluid dynamics (CFD) simulations. The transverse controller is designed based on the radial basis neural network with the sliding mode control method (RBF-SMC). Finally, the aerodynamic stability of traffic on the bridge is evaluated by incorporating the two-way coupling method. Results indicate: Bridge deck railing disturbance reduces the high-speed wind zones significantly. Higher equivalent wind speeds occur in Lane 3 (windward) and Lane 6 (leeward), with Lane 6 posing the highest vehicle risk. The RBF-SMC controller achieves excellent anti-interference: peak lateral displacements in Lanes 3 and 6 decrease by over 96

Structures such as large-span flexible bridges and high-rise buildings exhibit significant nonlinearity due to their flexibility. Therefore, a nonlinear identification method is essential for structural parameter identification in these cases. Based on the strong nonlinear Bouc-Wen model, the particle filtering (PF) method is employed to identify the dynamic response and structural parameters of nonlinear structures under seismic loading. To show the performance of parameters identification, the PF method is compared with Unscented Kalman Filter method as well. The results show that the particle filtering method effectively identifies the strong nonlinear model with multiple degrees of freedom with partial measurements. As the number of particles increases, the identification error decreases; however, this also leads to increase of simulation time. Considering both the accuracy of identification results and the efficiency of the process, the best performance is achieved when N = 150 in this simulation. Based on response data from verified numerical simulation by computational fluid dynamics (CFD) method, results show that the PF method can be applied on fluid-structure vibration systems. This study provides a reference for the application of particle filtering in the health monitoring of large nonlinear structures.

Sensitivity evaluation of nonlinear systems to system parameters is critically important in nonlinear dynamics, though current focuses in the field are mainly on the sensitive dependence of nonlinear systems upon initial conditions. The present research intends to develop an approach for quantitatively measuring the sensitivity of nonlinear dynamic systems to system parameters. A single-value sensitivity index is created via a theoretical approach. Numerical simulations are conducted to demonstrate the reliability and applicability of the index in quantifying and analyzing the system parameter-dependent sensitivity for nonlinear systems. With the implementation of the sensitivity index, a diagram illustrating the sensitive and insensitive regions and degree of sensitivity over a large range of system parameters is constructed for a typical nonlinear dynamic system. The sensitivity index developed shows effectiveness and convenience in quantitatively evaluating and analyzing the parameter-dependent sensitivity for nonlinear systems. The results of the research show that chaos and quasi-periodicity of a nonlinear system are sensitive to the system’s parameters, independent of its sensitivities to initial conditions. Based on the proposed method, region diagrams regarding to different parameters are presented, which may help to avoid high sensitivity parameter values such as stiffness, mass and damping values in the design of mechanical systems.

In this paper, detailed wind field data of the full path of typhoon "Bailu" were obtained based on site measurements. Typhoon "Bailu" made first landfall southeast of the Taiwan Strait with a wind speed of approximately 30 m/s near the center of the typhoon eye and a second landfall in Dongshang County in Fujian Province. The moving process is classified into 3 regions for analysis and comparison. Detailed analyses of wind characteristics including wind profile, turbulence intensity, gust factor, turbulence integral scale and wind power spectral density function at the full process of the typhoon are conducted, and the findings are presented in this paper. Wind speed shows significant dependence on both the direction of the moving path and the distance between the typhoon center and measurement site. Wind characteristics significantly vary with the moving path of the typhoon center. The relationship between turbulence intensity and gust factor at different regions is investigated. The integral turbulence scales and wind speed are fitted by a Gaussian model. Such analysis and conclusions may provide guidance for future bridge wind-resistant design in engineering applications.

Background Vortex-induced vibration may cause adverse effects on the safety and usability of bridges. The study of the vortex-induced vibration of bridges is mainly based on empirical mathematical models. Nevertheless, with these models, it is difficult to solve for all complex fluid-structure interaction problems for all types of section models. Purpose The major aim of this study is to identify the aerodynamic load on bridge deck in wind tunnel test, which can be generally applied on various bridge decks. Methods In this research, a wind tunnel experiments with a centrally slotted box deck are performed, two lock-in regions of vortex-induced vibration are found during the experiments. An unscented Kalman filter with unknown input method is applied to identify wind-induced forces. Pure aerodynamic force and nonlinear self-excited force are separated directly at both vortex induced vibration lock-in regions. Conclusions Aerodynamic stiffness and damping at different wind speeds in the vortex-induced vibration phase are identified and proven to show dependence on wind speeds. Based on the calculated standard deviation of forces, the percent of nonlinear self-excited force over all wind-induced forces can be up to 83%, and a minimal percentage of 30% indicates that the nonlinear self-excited cannot be ignored in lock-in phases. The identified values at two lock-in regions are discussed and compared as well. Results indicate the stiffness and damping show similar change pattern in the two lock-in regions. The approach of this research can be applied to obtain system information of vortex-induced vibration events for section models of different bridge deck types.

—With the application of boundary layer theory, the N-S equation in the boundary layer of the wall is simplified in this research. Combined with the boundary conditions, the relationship between the wall pressure gradient and the velocity gradient near the wall is obtained, therefore the roof pressure characteristics and the location of the separation point are analyzed. The rigid model of low-rise building with flat roof was fabricated. The combination of wind tunnel test and theory is utilized to analyze the distribution characteristics of roof pressure. The suction device is designed to complete the wind tunnel pressure test of the low-rise building model under active suction. The influence of the suction position on the roof wind pressure is studied, and the mechanism of the suction-to-wall turbulence control is proposed. Research results show that the arrangement of the suction device in the separation bubble area has a significant influence on the average wind pressure coefficient of the roof, which can greatly reduce the suction of the roof.

Stationary models are usually applied for wind characteristics analysis. However, nonstationarity has been found in the field measurements of typhoons in recent studies; therefore, using traditional models with stationary assumptions to conduct wind characteristics is inadequate. In this research, data acquisition of typhoon wind speeds and monsoon are conducted based on the wind field measurements. Wind speeds of typhoon “Maria” passing through Pintan, Fujian Province, China and the monsoon from 2017.10–2018.10 were obtained to investigate wind characteristics. The run test method is utilized to show that non-stationarity exists in both typhoon and monsoon wind speed, and the percent of non-stationary increases with the increase in time interval. Additionally, results show that stronger non-stationarity exists in typhoon wind speed compared with monsoons. Based on a self-adaptive procedure to extract time varying mean wind speed, a non-stationary model is established to compare with the non-stationary model, which has been applied in the traditional wind characteristic analysis. The fluctuating wind characteristics such as turbulence intensity, gust factor, turbulence integral scale, and wind speed spectrum are analyzed to compare the two models. Results show that the difference of such characteristics between the two models increases with the time interval, indicating the necessity of consideration of non-stationary models, especially for design specifications with larger time intervals. Influences of time intervals are investigated, and relevant recommendations are provided for wind resistance specifications. Our conclusions may provide reference for wind resistance design in engineering applications.

To explore the influence of bridge wind barriers, with their specific opening shapes and arrangements, on bridge deck wind fields and vehicle driving stability under different crosswinds, five bridge wind barrier schemes were designed. For two incoming wind speeds, the wind speed at different heights over three traffic lanes and the aerodynamic six-component force of the vehicle model were measured, and the influence of the wind barrier parameters on the vehicle driving stability was analyzed. The equivalent wind speed reduction coefficient of the wind barrier was compared with the dimensionless coefficients of the aerodynamic side force, roll moment, and aerodynamic lift to verify the accuracy of the shielding effect evaluation indices. The final conclusions provide a useful reference for designing bridge wind barriers.