Buffeting Response Research Articles

Effect of non-Gaussian turbulence on extreme buffeting response of a high-speed railway sea-crossing bridge

The non-Gaussian property of turbulence has been emphasized in some measured wind data. However, the classic Scanlan buffeting theory with the Gaussian distribution assumption of turbulence may cause errors in predicting the structural extreme response. In this study, a hybrid approach for predicting bridge's extreme buffeting response is proposed and validated, which considers multi-dimensional non-Gaussian random variables. Then the extreme buffeting response of a cable-stayed bridge under the attack of non-Gaussian wind is investigated, where the in-situ measured wind data of Typhoon ‘Bailu’ is adopted. The sensitivity of extreme buffeting response to turbulence skewness and kurtosis is also analyzed. The study results show that the lateral and vertical buffeting displacements are in skewed distributions under the attack of Typhoon ‘Bailu’. Compared to the Gaussian wind assumption, the non-Gaussian typhoon decreases the lateral extreme response, while increases the vertical extreme response. The results from the sensitivity analysis reveal a strong correlation between the non-Gaussian intensity of component u and that of the lateral buffeting response. In addition, the lateral extreme buffeting response increases significantly with the skewness and kurtosis of component u at a high probability level.

Buffeting Response Prediction of Long-Span Bridges Based on Different Wind Tunnel Test Techniques

The traditional method for calculating the buffeting response of long-span bridges follows the strip assumption, and is carried out by identifying aerodynamic parameters through sectional model force or pressure measurement wind tunnel tests. However, there has been no report on predicting the buffeting response based on the sectional model vibration test. In recent years, the author has proposed a method, based on the integrated transfer function, for predicting the buffeting response of long-span bridges through theoretical and full-bridge tests. This provided an idea for predicting the buffeting response based on the sectional model vibration test. Unfortunately, the effectiveness and accuracy of this method have not been proven or demonstrated through effective tests. To solve this problem, a long-span suspension bridge was taken as a background. Parameters such as aerodynamic admittance were identified through a sectional model force measurement test and the integrated transfer functions were identified through a sectional model vibration test. A taut strip model test was also conducted. Furthermore, the buffeting response prediction results based on three kinds of wind tunnel test techniques were compared. The results showed that if the strip assumption was established, the results of the three methods aligned well, and that selecting a reasonable model aspect ratio for the test could effectively reduce the influence of the 3D effect; moreover, identifying the integrated transfer function by the sectional model vibration test could effectively predict the long-span bridge buffeting response. Furthermore, when the strip assumption failed, the results of the traditional calculation method using 3D aerodynamic admittance became smaller. A larger result would be obtained by neglecting the influence of aerodynamic admittance.

Design, fabrication, and dynamic testing of a large-scale outdoor aeroelastic model of a long-span cable-stayed bridge

To overcome the limitations of existing experimental methods (including wind tunnel tests and field measurement experiments) for the study of bridge wind engineering, the research group at the Dalian University of Technology recently proposed to study the wind-resistance behaviours of long-span bridges through large-scale outdoor full-bridge aeroelastic models in natural wind. Several full-bridge aeroelastic models have been constructed, including a 1:50 model of a long-span cable-stayed bridge, which had a total length of 41.76 m and a height of 6.0 m. This paper systematically introduces the design, fabrication, and dynamic testing of the aeroelastic model. Taking the safety, adjustability, durability, and cost of the aeroelastic model into account, new approaches for the design of the main girder envelope, core beam of the bridge tower, and connections of the aeroelastic model are proposed. Free vibration tests and ambient vibration tests were utilised to measure the modal parameters of the aeroelastic model. The identified modal parameters were consistent with those calculated by finite element analysis, suggesting that the design and fabrication of the model were valid. The representative wind field data and measured buffeting responses of the aeroelastic model were presented.

Non-Gaussian turbulence induced buffeting responses of long-span bridges based on state augmentation method

Traditionally, the structural turbulence-induced buffeting vibrations is analyzed along the famous Davenport chain through turbulence, wind loads and structural response based on one fundamental assumption: the random processes about the above three subsequent stages should be all Gaussian process. This assumption simplifies the mathematical derivation of turbulence-induced vibration, and were widely used in field of wind engineering for structures. However, several recent studies reveal that turbulence with non-Gaussian distribution is observed in the boundary-layer atmosphere during wind storm events, especially typhoons or hurricanes. For the turbulence-induced vibration, traditional Gaussian assumption may lead to non-conservative results, especially for non-Gaussian turbulence with positive skewness. Based on the state augmentation method, this paper derives formulations to calculate the moments of buffeting response. The non-Gaussian turbulence-induced buffeting forces are approximated by Hermite polynomials of the underlying Gaussian process, modeled as Ornstein–Uhlenbeck process in the state augmentation method. The state augmentation method is verified for bridge buffeting vibration caused by Gaussian turbulence, and the approximation of buffeting force by the Ornstein–Uhlenbeck process is also validated. Applying the state augmentation method on the bridge buffeting response excited by non-Gaussian turbulence, the corresponding bridge buffeting response RMS, skewness and kurtosis can be computed sequentially. The results show that the RMS of buffeting responses induced by non-Gaussian turbulence is slightly higher than Gaussian turbulence results. However, the extreme responses are greatly affected by the skewness of non-Gaussian turbulence.

High-mode vortex-induced vibration of stay cables: monitoring, cause investigation, and mitigation

Herein is described a case study using long-term field monitoring data from a cable-stayed bridge to investigate the cause of high-mode vortex-induced vibration (VIV) observed in stay cables. Wind characteristics and dynamic responses of girders and stay cables were analyzed to investigate two possible vibration sources–interactions with girders and vortex shedding. To this end, a modal decomposition procedure that included automated peak picking and successive band-pass filtration was proposed. These novel steps revealed a relationship between the shedding frequencies of stay cables and corresponding critical wind velocities. The main cause of large-amplitude VIVs was diagnosed using a novel damping identification procedure that consisted of automated modal decomposition, temporal correlation, and optimization-based curve fitting techniques. The damping identification results demonstrated how the modal VIV amplitudes of stay cables have a strong dependency on damping capacity. The effectiveness of Stockbridge dampers in mitigating high-mode cable VIVs was subsequently examined through field application and comparison analysis during a typhoon. The unique interaction between stay cable vibrations and the buffeting response of bridge girders observed during this period was additionally discussed.

Aerodynamic design, analysis, and validation techniques for the Tianwen-1 entry module

The clear differences between the atmosphere of Mars and the Earth coupled with the lack of a domestic research basis were significant challenges for the aerodynamic prediction and verification of Tianwen-1. In addition, the Mars entry, descent, and landing (EDL) mission led to specific requirements for the accuracy of the aerodynamic deceleration performance, stability, aerothermal heating, and various complex aerodynamic coupling problems of the entry module. This study analyzes the key and difficult aerodynamic and aerothermodynamic problems related to the Mars EDL process. Then, the study process and results of the design and optimization of the entry module configuration are presented along with the calculations and experiments used to obtain the aerodynamic and aerothermodynamic characteristics in the Martian atmosphere. In addition, the simulation and verification of the low-frequency free oscillation characteristics under a large separation flow are described, and some special aerodynamic coupling problems such as the aeroelastic buffeting response of the trim tab are discussed. Finally, the atmospheric parameters and aerodynamic characteristics obtained from the flight data of the Tianwen-1 entry module are compared with the design data. The data obtained from the aerodynamic design, analysis, and verification of the Tianwen-1 entry module all meet the engineering requirements. In particular, the flight data results for the atmospheric parameters, trim angles of attack, and trim axial forces are within the envelopes of the prediction deviation zones.

A Refined Measuring Method for the Transfer Function Used to Predict Bridge Buffeting Response Through Segmental Model Vibration Test

A Refined Measuring Method for the Transfer Function Used to Predict Bridge Buffeting Response Through Segmental Model Vibration Test

Bridge buffeting by skew winds: A revised theory

An improved bridge buffeting theory is established with an emphasis on skew wind directions, for both turbulence- and motion-dependent forces. It provides simplifications and generalizations of previously established methods. The formulation starts with a preferred 3D approach, which is suitable when aerodynamic coefficients for different yaw and inclination angles are readily available. The 3D approach includes a new convenient choice of coordinate systems and an intuitive derivation of transformation matrices, supporting clear and compact wind load expressions as well as a more accurate formulation of the quasi-steady motion-dependent forces. When the aerodynamic coefficients have only been obtained for wind normal to the bridge girder, an alternative 2D approach is provided. The 2D approach, where only the normal projection of the wind is considered, is further expanded to include mean wind directions that are both yawed and inclined, axial forces in the longitudinal direction (1D) in an optional 2D ​+ ​1D format, and forces due to all in-plane and out-of-plane motions. All expressions are first presented in a compact non-linear format and then linearized through numerous multivariate Taylor series approximations. A general, more straightforward and more accurate framework is thus established for both time- and frequency-domain analyses of the buffeting response.

Prediction of Vertical Tail Buffet Using CFD/CSD Coupling Method

The vertical tail buffet induced by the vortex breakdown flow is numerically investigated. The unsteady flow is calculated by solving the RANS equations. The structural dynamic equations are decoupled in the modal coordinates. The radial basis functions (RBFs) are employed to generate the deformation mesh. The buffet response of the flexible tail is predicted by coupling the three sets of equations. The results show that the presence of asymmetry flow on the inner and outer surface of the tail forced the structural deflection offsetting the outboard. The frequency of the 2nd bending mode of the tail structure meets the peak frequency of the pressure fluctuation upon the tail surface, and the resonance phenomenon was observed. Therefore, the 2nd bending responses govern the flow field surrounding the vertical tail. Finally, the displacement of the vertical tail is small, while the acceleration with a large quantitation forces the vertical tail undergoing severe addition inertial loads.

Buffeting analysis of a suspension bridge under construction based on adjacent wind field data

Buffeting analysis of long-span suspension bridge has received considerable attention in the past decades. In current practice, it is challenging to determine the wind turbulence spectrum at bridge site accurately if the field measured wind data is insufficient. To address this issue, this paper proposes a novel framework for bridge buffeting responses evaluation. The framework first proposes an approach based on long short-term memory (LSTM) network to compose long term data on wind characteristics for estimating the wind turbulence spectrum at bridge site via leveraging the wind field data acquired from the long-term monitoring data at adjacent locations (e.g., nearby meteorological station and bridges). Afterwards, the obtained wind spectrum at bridge site will be utilized for the buffeting analysis. To demonstrate the usage and performance of the proposed framework, a long-span cross-sea suspension bridge under construction is used throughout the paper as an example to investigate the buffeting-induced responses. The analysis results show that buffeting responses are significantly affected by wind speed and the identified bridge frequencies are consistent with the design frequencies.

Wind-induced fatigue analysis of Yueyang Dongting Lake Suspension Bridge

Recent demand for a longer span has complicated the dynamic behaviours in the strong wind. The limited amplitude but frequent occurred buffeting response of bridge affect fatigue resistance of the bridge, which should be considered. The time-domain buffeting response and fatigue performance of Yue yang Dongting Lake Suspension Bridge are realized by mixed programming with MATLAB and ANSYS. The gusty wind was simulated by the WAWS method, while the self-excited force was modelled as the elemental aeroelastic stiffness and damp matrices by the element Matrix 27. The mode superposition method was then adapted to calculate the buffeting response of the bridge in ANSYS, and its accuracy is verified by the results of the RMS and PSD using the traditional frequency-domain method. It was found that the fatigue life reliability of the suspender neat tower of the leeward side is 97.54% during the structure's service in the design wind speed.

Influences of structural system characteristics on the dynamic characteristics and wind-induced buffeting response of multi-tower cable-stayed bridge

This study explores the dynamic characteristics and the nonlinear wind-induced buffeting response of the bridge based on a six-tower cable-stayed bridge, the Jiashao Bridge. The effect of structural system characteristics (number of anchor piers and different conditions of longitudinal constraints) on the dynamic characteristics and the wind-induced buffeting performance of multi-tower cable-stayed bridges has been studied in detail. The analysis indicates that the different amounts of anchor piers have a limited effect on changing the overall stiffness of the bridge, but have an obvious effect on the buffeting displacement response of the side spans to which they belong. As for the condition of longitudinal constraints between the girder and towers, it mainly changes the vertical and transverse bending stiffness of the girder which means with the enhancement of the longitudinal constraints, the bending stiffness of the girder increases, and meanwhile significantly influence the transverse buffeting response of the girder.

Twisted-wind effect on the flow field of tall building

Tall buildings in hilly terrain are very likely being attacked by topography-induced twisted wind. In this study, the effects of three wind profiles on second-generation benchmark building, i.e. conventional wind profile (CWP), two twisted wind profiles (TWP15 and TWP30) with maximum twisted angle (MTA) of 15°and 30°, are investigated by large eddy simulation. Wind tunnel tests under the same wind profiles are replicated to verify reliability of numerical results. Wind loads, flow motion, spatial correlation and mode patterns are comprehensively analyzed to elucidate underlying mechanism of TWP. The results show that with MTA increasing from 0° to 30°, mean lateral and torsional wind loads are significantly magnified while along-wind force is reduced, this variation is attributed to TWP-induced modification in flow field. Under TWP, fluctuating base moment are all weakened due to suppressed vortex shedding, moreover, fluctuating energy of DMD modes tend to accumulate toward low-frequency region, which could amplify background component of buffeting response. Notably, “twisted extensibility” is discovered in TWP, which magnifies vertical correlation and momentum exchange, thus generating larger torsional responses. These findings provide references for designing and constructing tall buildings in mountainous areas where twisted flows occur frequently.

Aerodynamic admittance of a 6:1 rectangular cylinder: A computational study on the role of turbulence intensity and integral length scale

The evaluation of the aerodynamic admittance is a fundamental step in the calculation of the buffeting response of flexible structures immersed in turbulent flows such as long-span bridges and slender towers. As it is well-known, bluff sections immersed in turbulent flows often exhibit a complex aerodynamic behavior, which can be greatly affected by the turbulence intensity and the integral length scales of the impinging turbulence. In this paper, computational fluid dynamics is used for the evaluation of the admittance functions of a 6:1 rectangular cylinder. Firstly, the incoming turbulence is synthetically generated. Then the aerodynamic admittance functions are evaluated considering five different inflow conditions using Large Eddy Simulations. The use of synthetic inflows allows to easily separate the role played by each characteristic of the inflow turbulence, so allowing to separately study the effect of the turbulence intensity and the length scales.

Nonuniform wind characteristics and buffeting response of a composite cable-stayed bridge in a trumpet-shaped mountain pass

Due to the spatial differences in wind fields in mountainous areas, it is an urgent problem to accurately estimate the buffeting response of long-span bridges in mountainous areas. In this paper, the spanwise variations in the mean and fluctuating wind characteristics of a bridge site are obtained based on a terrain wind tunnel test of a trumpet-shaped mountain pass. Additionally, the aerodynamic admittance function of a Π-shaped composite girder under different wind attack angles is measured in the wind tunnel. The buffeting response calculation theory considering the spanwise variations in the mean wind and fluctuating wind characteristics along the main girder is established. The influence of the nonuniform wind characteristics on the buffeting response of the main girder is analyzed. The results show that the spanwise variation in wind characteristics at the bridge site is affected by the direction of inflow and can be described by a quadratic polynomial. Nonuniform wind parameters have obvious effects on the buffeting response, and a nonuniform wind attack angle is a key factor affecting the buffeting response. It may not be appropriate to predict the buffeting response by using the single-point wind field observation results in mountainous areas.

Generalized framework for identification of indicial response functions from flutter derivatives of long-span bridges

The hypothesis that the Wagner and Kussner functions, conventionally used in the thin-airfoil aerodynamics, can also be used in the bridge aerodynamics, is often suggested in the literature. However, this assumption may lead to an inaccurate prediction of the buffeting response of bridges with increasing spans, which calls into question the validity of this assumption. This paper presents a generalized framework for the identification of bridge-related aerodynamic and aeroelastic indicial response functions (IndRFs) to simulate the buffeting response of long-span bridges under turbulent winds. For that, the direct relationships between IndRFs and experimental data of flutter derivatives are developed with the help of the Fourier transform, followed by the extraction of IndRFs through an optimization technique. Compared with the conventional Wagner and Kussner functions, the identified IndRFs exhibit the overshooting behavior, which can change the bridge aerodynamics significantly. To check the efficacy of the proposed framework, the numerical example of a suspension bridge is presented, and buffeting analysis is performed for two cases considering ① the identified aeroelastic and aerodynamic IndRFs, and ② the Wagner and Kussner functions. The simulation results are also compared with the field measurements, showing that the identified IndRFs are adequately reliable and unique functions for a bridge deck to simulate its buffeting response accurately.

Development of nonlinear framework for simulation of Typhoon-induced buffeting response of Long-span bridges using Volterra series

This paper presents a nonlinear time-domain analysis framework to simulate the buffeting response of long-span bridges subjected to the typhoon winds. The analysis framework separates the aerodynamic forces generated on the bridge deck into low- and high-frequency components modelled by the quasi-steady and Volterra series-based wind load models, respectively. The aerodynamic nonlinearity and non-stationary wind effects existing in the wind-bridge interaction are incorporated in the analysis framework in terms of the ① static force coefficients measured at low-frequency effective angle of attack, ② flutter derivatives identified at varying angles of attack, ③ higher order fluid memory terms of the Volterra series and ④ time-varying mean wind speed. The efficacy of the proposed framework is verified by presenting the numerical example of a suspension bridge fully immersed in the typhoon winds with aerodynamic characteristics sensitive to the effective angle of attack. The dynamic analysis results show good agreement in the simulation of the typhoon-induced buffeting response of the bridge deck. Moreover, the simulation results are also compared with the measurements, and the existing linear and nonlinear wind load models to elucidate the efficiency of the proposed framework.

Identification of linear and nonlinear flutter derivatives of bridge decks by unscented Kalman filter approach from free vibration or stochastic buffeting response

This study presents an unscented Kalman filter (UKF) approach for identification of linear or nonlinear flutter derivatives (FDs) of bridge decks from free vibration or buffeting response time history. The nonlinear FDs, which are dependent on torsional vibration amplitude, are represented in polynomial functions of torsional displacement. The augmented state variables of the two degrees of freedom (2DOF) bridge deck system, which include bridge deck motions and unknown FDs, are estimated simultaneously with the UKF approach based on response measurement data. Firstly, the steady-state vortex-induced vibration and flutter of a streamlined bridge deck section are used to illustrate the performance of UKF approach in extracting nonlinear FDs. The equivalent linear FDs are also identified from the same response data which reveals the deficiency of the linear model. Secondly, the stochastic buffeting responses of the bridge deck contributed from two modal responses with linear FDs are generated, and the performance of UKF approach with unknown excitations is examined. It is pointed out that the buffeting response must be separated into two modal response components, such that the unknown buffeting force excitations can be modeled as white noise processes, and the UKF approach offers satisfactory identification of FDs.

Numerical study of aeroelastic suppression using active control surfaces on a full-span suspension bridge

In this study, the aeroelastic active control of a suspension bridge was studied using both experimental and numerical methods. Two flat plates attached on either side of the suspension bridge were used as the control surfaces. With a suitable rotation of the control surfaces, the turbulent flow around the bridge was modified, thus addressing the problem of aeroelasticity. An appropriate feedback control law was determined using a two-dimensional numerical model. Next, a wind tunnel experiment was conducted to validate the numerical results. The numerical analysis was conducted for a suspension bridge with a span of 3000 m. The effectiveness of the control was considered based on the arrangement of the control wings along the span of the suspension bridge. The ratio between the total length of the control surfaces and the span length was investigated. The coupling of the modes of the suspension bridge also affected the control results. It was suggested that aerodynamic stability could be enhanced by using a partially installed control surface. Moreover, the buffeting responses of bending and torsion of the suspension bridge could be reduced.

Influence of wind yaw angle and pylon interference on the buffeting responses of cable-stayed bridges during construction

The present study focuses on the effects of wind yaw angle and pylon interference on the buffeting responses of bridge decks during construction. Two typical cable-stayed bridges with rhombus pylons (RPs) and single-column pylons (SPs) in the maximum double cantilever state were selected as research objectives. The influence of the wind yaw angle and pylon interference on the lateral, vertical and torsional buffeting displacements were systematically analyzed through full bridge model aeroelastic wind tunnel tests. The research results show that the maximum buffeting responses appear when the wind yaw angle is in the range of to The effects of the wind yaw angle on the buffeting responses become more obvious in cases of high mean wind speeds. The pylon interference effects on the lateral buffeting displacements are more significant than those on the vertical and torsional buffeting displacements. The strong pylon interference effects may lead to non-conservative buffeting response estimation results using traditional buffeting analysis methods. This study demonstrates that it is of paramount importance to take into consideration the combined effects of the wind yaw angle and pylon interference in the design of long-span cable-stayed bridges during their construction stages.