Buffeting Response Of Bridge Research Articles

Floating bridge response under combined ship collision, wind and wave loads

ABSTRACT Floating bridges over navigable fjords with exposed substructures are at risk of accidental ship collisions. Other hazards such as extreme wind and wave loads are also critical for floating bridges. This study investigates the global dynamic responses of a floating bridge subjected to different combinations of ship collision, wind and wave loads. A numerical model of a floating bridge is developed using OrcaFlex. The ship-bridge interaction is modelled by defining a constraint element attached to the striking ship. The stiffness of the constraint is described by a nonlinear force-displacement curve. The full turbulent wind field is generated using TurbSim, and the bridge buffeting response is calculated in time domain based on the linear quasi-steady theory. The wind-bridge interaction is accounted for by considering the relative angle of attack and the relative wind velocity at each time step. The bridge responses under individual hazards are compared with those considering multi-hazards.

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.

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.

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

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.

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.

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.

Integrated transfer function for buffeting response evaluation of long-span bridges

An experimental approach to the prediction of the buffeting response of long-span bridges is presented, and the concept of the integrated transfer function, which directly relates the fluctuation characteristics of turbulent flow to the buffeting response of bridge structures, is introduced in this paper. The integrated transfer function is independent of the characteristics of turbulent flow, so once the integrated transfer function is identified in wind tunnel experiments, it can be directly used to calculate the buffeting response of the actual bridge in the atmospheric boundary layer. To verify the presented approach, a long-span suspension bridge is taken as an example and a series of experiments are carried out in a wind tunnel. Experiments in two different flow fields at the design wind velocity are performed to investigate the effects of turbulent flow characteristics on the integrated transfer functions, and the results measured at another wind velocity are given for comparison. The results show that the integrated transfer functions of the bridge measured in the two flow fields are almost identical, which confirms that it is independent of the flow field. An application example is also performed to evaluate the buffeting response with the use of the measured integrated transfer functions. Compared to the traditional approach, the presented experimental approach based on the integrated transfer function avoids errors caused by the inaccurate simulation of the turbulent flow (such as the integral scales, wind spectra and wind spatial correlations) and provides a more accurate prediction of the buffeting response of long-span bridges.

Flow distortion recorded by sonic anemometers on a long-span bridge: Towards a better modelling of the dynamic wind load in full-scale

The turbulent wind field around a suspension bridge deck is studied using eleven months of full-scale records from sonic anemometers mounted above the girder. Using the mean and turbulent velocity characteristics, we demonstrate that the bridge structure can significantly distort the flow. More precisely, the friction velocity, the variance of the fluctuating vertical velocity and the mean wind incidence angle are underestimated on the downstream side of the deck. The local topography is also found to influence the flow in a non-negligible way, such that turbulence characteristics differ significantly from those observed in flat and homogeneous terrains. For a hexagonal girder with a width to height ratio B∕H ≈ 4.5, deck-induced flow distortion is still observed on the downwind side of the girder at a height above the road equal to 3.6H. This further supports the idea that wind measurements from a suspension bridge should rely on anemometers on both sides of the deck to mitigate flow distortion. The improved flow description combined with high-resolution acceleration records of the deck provides a simulation of the wind-induced response of the bridge with a level of accuracy that is rarely achieved in full-scale. In particular, the limits of a wind model based on flat terrain assumption as well as the limits of the strip theory are highlighted by the recorded data and the improved modelling of the bridge buffeting response.

Changing Bridge Aerodynamics under Nonstationary Winds

The nonstationary winds during tropical cyclones and non-synoptic events have been extensively observed and analysed; however, the significance of nonstationarity in the consideration of wind load effects has not been widely investigated yet. In this study, the effects of nonstationarity on changing bridge aerodynamics have been discussed from both linear and nonlinear viewpoints. For linear aerodynamics change, the conventional 1-D indicial response function has been extended to a 2-D case since an additional time scale, resulting from the time-varying transient nonstationarity, is introduced in the wind–structure interactions. For nonlinear aerodynamics change, the conventional hybrid model has been generalized to consider the additional effective angle of attack due to the time-varying mean wind speed. The bridge buffeting response under the tropical-cyclone and downburst winds were comprehensively examined based on 1-D semi-empirical linear model, 2-D semi-empirical linear model, 1-D hybrid nonlinear model, 1-D generalized hybrid nonlinear model and 2-D generalized hybrid nonlinear model, where the ability of these models to capture the changing linear and/or nonlinear bridge aerodynamics under nonstationary winds is highlighted. The results demonstrated the important effects of the transient nature of nonstationary winds on the changing bridge aerodynamics and hence on the structural response.

Aerodynamic Admittance Research on Wide-body Flat Steel Box Girder

Aerodynamic admittance is a key parameter affecting the analysis accuracy of the bridge buffeting response. However, few articles have covered the issue of the wide-body flat box girder with much smaller depth-width ratio (such as 1/12 studied in this paper). Therefore, to explore the real buffeting force of the wide-body flat box girder, experiments of the static force coefficients and aerodynamic admittance are carried out in wind tunnel. Wooden segmental model has a scale ratio of 1/60 to an actual 42 m wide suspension bridge girder. Using the high-frequency-force-balance (HFFB) equipment fixed with the segmental model under the conditions of different wind speeds and different wind attack angles, wind power spectrums of the buffeting force are measured and the variation of aerodynamic admittance parameters is analyzed. The results show that the aerodynamic admittance of the box girder measured in the experiment with this so much smaller depth-width ratio differs from the corresponding classical Sears expression. Some inspiration can be presented for the future study of the buffeting response for this kind of much wider bridge with the similar ratio in this paper.

Buffeting response of a suspension bridge in complex terrain

The buffeting response of a suspension bridge in complex terrain is studied based on full-scale data from sonic anemometers and accelerometers installed on the Lysefjord Bridge in Norway. The influence of the topography on the wind field and the associated effects on the displacement response are investigated. The two main wind conditions observed display different characteristics, which requires a case by case approach, and a refined description of the wind co-coherence. The identification of the mode shapes and modal damping ratios is carried out using ambient vibration data as a verification procedure. The buffeting response of the bridge is computed in the frequency domain, and compared to the recorded response in terms of standard deviation and power spectral density of the displacement response. The overall comparison is found satisfactory, although some discrepancies are observed. These are attributed to large yaw angles and non-stationary wind fluctuations caused by the influence of a complex topography on the flow properties.

Investigation of Influence Factors of Wind-Induced Buffeting Response of a Six-Tower Cable-Stayed Bridge

This paper presents an investigation of the wind-induced buffeting responses of the Jiashao Bridge, the longest multispan cable-stayed bridge in the world. A three-dimensional finite element model for the Jiashao Bridge is established using the commercial software package ANSYS and a 3D fluctuating wind field is simulated for both bridge deck and towers. A time-domain procedure for analyzing buffeting responses of the bridge is implemented in ANSYS with the aeroelastic effect included. The characteristics of buffeting responses of the six-tower cable-stayed bridge are studied in some detail, focusing on the effects including the difference in the longitudinal stiffness between the side towers and central towers, partially longitudinal constraints between the bridge deck and part of bridge towers, self-excited aerodynamic forces, and the rigid hinge installed in the middle of the bridge deck. The analytical results can provide valuable references for wind-resistant design of multispan cable-stayed bridges in the future.

Extreme value of typhoon-induced non-stationary buffeting response of long-span bridges

This paper concerns the extreme value of typhoon-induced non-stationary buffeting response of long-span bridges. The framework of non-stationary buffeting analysis is briefly introduced first, in which the non-stationary buffeting response is regarded as the summation of a time-varying mean response and a dynamic response that can be represented by a zero-mean evolutionary Gaussian process characterized by an evolutionary power spectral density (EPSD) function. The formulas for determining approximate probabilistic characteristics of extreme non-stationary responses are then derived by extending the currently-used Poisson and Vanmarcke approximations. By comparing with the Monte Carlo solution, the extended approximations for extreme value of non-stationary responses are found reliable and accurate enough. Particularly, the extended Vanmarcke approximation can give closer results to the Monte Carlo solution than the extended Poisson approximation. The extended Vanmarcke approximation is finally applied to the Stonecutters Bridge to find the extreme value of non-stationary buffeting response of the bridge to a strong typhoon. The results show that the extreme displacement responses of the bridge from the non-stationary buffeting analysis are larger than those predicted by the conventional stationary buffeting analysis, and therefore the non-stationary buffeting analysis is necessary.

Research on Simplifying the Buffeting Response Spectrum of Suspension Bridge

In order to solve the problem of traditional buffeting analysis method is complex, the paper summarizes a calculation method of simplifying the suspension bridge buffeting response spectrum which considers the background response by simplifying the vibration mode function. Examples calculation shows that this function is efficient and accurate. With this method the paper analyzes the impact of parameters including structural damping ratio, aerodynamic admittance function, pneumatic self-excited forces, the main beam span and so on on the suspension bridge buffeting response. Results show that: First, the impact of the background response on concrete bridges with larger damping ratio cannot be ignored. Second, when aerodynamic admittance takes Sears function, the buffeting response analysis results may be partial dangerous. Third, the role of the background response on large long-span bridges of more than 2000 m can be ignored.

Analytical and experimental study on aerodynamic control of flutter and buffeting of bridge deck by using mechanically driven flaps

A passive control using flaps will be an alternative solution for flutter stability and buffeting response of a long suspension bridge. This method not only enables a lightweight economic stiffening girder without an additional stiffness for aerodynamic stability but also avoid the problems from the malfunctions of control systems and energy supply system of an active control by winglets and flaps. A time domain approach for predicting the coupled flutter and buffeting response of bridge deck with flaps is investigated. First, the flutter derivatives of bridge deck and flaps are found by experiment. Next, the derivation of time domain model of self-excited forces and control forces of sectional model is reported by using the rational function approximation. Finally, the effectiveness of passive flap control is investigated by the numerical simulation. The results show that the passive control by using flaps can increase the flutter speed and decrease the buffeting response. The experiment results are matched with numerical ones.

Dynamic Buffeting Response Analysis of High Pier and Long Span Continuous Rigid Frame Bridge with Stochastic Wind Field

The fluctuating wind field is simulated for digital by using the stationary Gauss processes, which Kaimal spectrum and Panofsky spectrum is used to the simulation of wind target spectrum with different direction and speed. According to Davenport quasi-steady buffeting force model formula, the time-history of wind velocity is converted to Buffeting force time history, which are applied to the Structure model node, combined with ANSYS for long-span continuous rigid frame bridge buffeting response analysis dynamic simulation.Taking a high pier and long span continuous rigid frame bridge as an example, analyzes dynamic buffeting response of the bridge under the action of the stochastic wind field, which as the guidance of high pier and long span continuous rigid frame bridge design work, practice has proved that the method is simple, reliable, also can be a way that dynamic analysis of buffeting response of large span bridge or tower structure under the action of stochastic wind field.

Comparative Study on Buffeting Performance of Sutong Bridge Based on Design and Measured Spectrum

The recent development in structural health monitoring (SHM) technology enables the buffeting responses of bridges to be evaluated in a more realistic manner. In this paper, the buffeting responses of the cable-stayed Sutong Bridge with a main span of 1,088 m is analyzed with the wind spectra used in the design phase and those obtained experimentally from a long-term SHM system to compare the actual buffeting response with design predictions. The autospectra of longitudinal and vertical fluctuating wind components are derived from the in situ strong wind data recorded by the monitoring system. The buffeting analysis is accomplished in the time domain with the aeroelastic effect included. Compared with the buffeting responses obtained from the measured spectrum, the girder responses from the design spectrum are larger in the horizontal direction and smaller in other directions, whereas the tower responses are larger and thus relatively conservative.

Study on the Indiscrete Tuned Mass Damper for Buffeting Control of Long Span Cable-Stayed Bridges

A study of buffeting control of the E-dong Bridge Using an indiscrete tuned mass damper (ITMD) system is performed in this paper. Different from the traditional multiple tuned mass damper (MTMD) system which is fixed along the main span of bridge discretely, this indiscrete tuned mass damper is attached to the centre region of the bridge’s main span continuously. A three-dimensional finite element model of E-dong Bridge, is completed by the software of ANSYS. By comparing the vertical and lateral buffeting response of bridge without dampers, the control efficiency of ITMD and MTMD is confirmed.