Buffeting Response Research Articles

Study on Wind-Induced Vibration Control of a Long-Span Cable-Stayed Bridge Using TMD-Type Counterweight

AbstractIt has been widely acknowledged that a tuned mass damper (TMD) can effectively control the wind-induced vibration of the main deck of long-span bridges. However, the unfavorable effect on static characteristics of the increased dead load cannot be avoided if the TMD is installed straight on the main deck. A TMD-type counterweight is designed in this paper, where the counterweight originally designed for reducing the live load–induced displacements at the central span are taken as the mass block in the TMD. The Sutong Cable-Stayed Bridge (SCB), with a main span of 1,088 m, is taken as an example. The buffeting responses of the bridge with the stationary counterweight and the proposed TMD-type counterweight are compared, and the control performance of the bridge with and without auxiliary piers is also investigated. Results indicate that the TMD has notable effects on reducing the vibration of the main deck without auxiliary piers, whereas the impact is not significant for the presence of the auxili...

Flutter and Buffeting Control of Long-span Suspension Bridge by Passive Flaps: Experiment and Numerical Simulation

Flutter stability and buffeting response have been the topics of most concern in the design state of long-span suspension bridges. Among approaches towards the aerodynamic stability, the aerodynamic-based control method which uses control surfaces to generate forces counteracting the unstable excitations has shown to be promising. This study focused on the mechanically controlled system using flaps; two flaps were attached on both sides of a bridge deck and were driven by the motions of the bridge deck. When the flaps moved, the overall cross section of the bridge deck containing these flaps was continuously changing. As a consequence, the aerodynamic forces also changed. The efficiency of the control was studied through the numerical simulation and experimental investigations. The values of quasi-steady forces, together with the experimental aerodynamic force coefficients, were proposed in the simulation. The results showed that the passive flap control can, with appropriate motion of the flaps, solve the aerodynamic instability. The efficiency of the flap control on the full span of a simple suspension bridge was also carried out. The mode-by-mode technique was applied for the investigation. The results revealed that the efficiency of the flap control relates to the mode number, the installed location of the flap, and the flap length.

Linear regression analysis of buffeting response under skew wind

This paper presents a new analysis framework for predicting the internal buffeting forces in bridge components under skew wind. A linear regressive model between the internal buffeting force and deformation under normal wind is derived based on mathematical statistical theory. Applying this regression model under normal wind and the time history of buffeting displacement under skew wind with different yaw angles in wind tunnel tests, internal buffeting forces in bridge components can be obtained directly, without using the complex theory of buffeting analysis under skew wind. A self-anchored suspension bridge with a main span of 260 m and a steel arch bridge with a main span of 450 m are selected as case studies to illustrate the application of this linear regressive framework. The results show that the regressive model between internal buffeting force and displacement may be of high significance and can also be applied in the skew wind case with proper regressands, and the most unfavorable internal buffeting forces often occur under yaw wind.

Impact of Stochastic Traffic on Modified Cross-Section Profiles of a Slender Long-Span Bridge: Wind Tunnel Experimental Investigation

For a slender long-span bridge, the global aeroelastic and aerodynamic phenomena, such as flutter stability and buffeting response, induced by wind turbulence significantly affect the safety and lifetime performance of the bridge. To investigate these phenomena, a wind tunnel experimental technique with bridge section models is typically required to identify some critical aerodynamic coefficients, such as flutter derivatives, which are dependent on the specific profile (shape) of a bridge cross section and the functions of reduced frequencies. Obviously, this practice is based on the assumption that the shape of the cross section of a long-span bridge does not vary over time. Such an assumption may not remain valid when the stochastic traffic on the bridge is considered, because of the simple fact that the presence of vehicles changes the profile of the bridge cross section. The current study aims to provide some insights through experimental assessment of traffic impacts on flutter derivatives of the modified bridge cross section because of the presence of traffic. A bridge section model with scaled vehicle models distributed on the bridge deck is tested in the wind tunnel following the simulated stochastic traffic flow. Several scenarios are tested to provide insights on the variations of the flutter derivatives over different sections along the bridge and at different time instants for the same location. In addition, some extreme situations, such as under evacuation or serious congestion, are also studied.

공용 사장교의 동적특성을 반영하는 버페팅 응답보정법

설계를 위한 교량의 해석모델은 구조물의 안전성을 확보하기 위해 자중 및 외부하중은 되도록 크게, 구조물의 강성은 되도록 작게 평가하는 것이 일반적이다. 때문에 설계모델을 이용한 버페팅 응답은 실제 공용교량의 버페팅 응답과 차이를 나타낸다. 공용교량의 버페팅 응답을 정확하게 예측하기 위해서는 공용교량의 동적특성을 계측하여 해석모델이 계측값을 반영하도록 수정하여야 한다. 일반적으로, 실제교량과 동일한 고유진동수를 갖는 MBM(Measurement -based Model)을 구축하기 위해 설계모델의 다양한 물성치를 파라미터로 조정하며 계측된 고유진동수와 일치시키는 MTM(Manual Tuning Method)이 사용되고 있다. MTM은 파라미터의 초기치 설정에 따른 임의성이 높고 여러 수렴점을 가질 수 있어 분석에 상당한 노력이 소요된다. 본 연구는 버페팅해석에 널리 적용되고 있는 단일모드 주파수영역 해석법이 구조물의 모드형상, 고유진동수 및 감쇠비의 동적특성만을 이용하는 점에 착안하여 MTM과정 없이 설계모델의 버페팅 응답을 공용교량의 버페팅 응답으로 보정하는 BRCM(Buffeting Response Correction Method)을 제안하였다. BRCM은 설계모델의 모드형상 별 버페팅 응답을 공용교량의 고유진동수만으로 보정하는 방법이다. 공용교량의 고유진동수는 상시진동에 의한 계측 가속도로부터 산정하였다. BRCM의 적용성을 단순보 모델의 시간이력 버페팅해석을 수행하여 수치적으로 평가하였으며 공용교량모델을 이용한 버페팅해석결과, BRCM과 MTM의 응답 차이는 3% 이하로 나타났다. 공용교량의 실시간 계측시스템에 BRCM을 도입할 경우 사장교의 유지관리 효율성을 높일 수 있을 것으로 기대된다. According to design specifications for structural safety, a bridge in initial design step has been modelled to have larger self-weight, external loads and less stiffness than those of real one in service. Thereby measured buffeting responses of existing bridge show different distributions from those of the design model in design step. In order to obtain accurate buffeting responses of the in-site bridge, the analysis model needs to be modified by considering the measured natural frequencies. Until now, a Manual Tuning Method (MTM) has been widely used to obtain the Measurement-based Model(MBM) that has equal natural frequencies to the real bridge. However, since state variables can be selected randomly and its result is not apt to converge exact rapidly, MTM takes a lot of effort and elapsed time. This study presents Buffeting Response Correction Method (BRCM) to obtain more exact buffeting response above MTM. The BRCM is based on the idea the commonly used frequency domain buffeting analysis does not need all structural properties except mode shapes, natural frequencies and damping ratio. BRCM is used to improve each modal buffeting responses of the design model by substituting measured natural frequencies. The measured natural frequencies are determined from acceleration time-history in ordinary vibration of the real bridge. As illustrated examples, simple beam is applied to compare the results of BRCM with those of a assumed MBM by numerical simulation. Buffeting responses of BRCM are shown to be appropriate for those of in-site bridge and the difference is less than 3% between the responses of BRCM and MTM. Therefore, BRCM can calculate easily and conveniently the buffeting responses and improve effectively maintenance and management of in-site bridge than MTM.

Buffeting Reliability Analysis of Long Span Concrete-Filled Steel Tube Arch Bridge during Construction Stage

In construction stage, a large buffeting response would endanger construction safety and quality for a long span concrete-filled steel tube (CFST) arch bridge. Developing the study on buffeting security is indispensable to CFST arch bridge in construction stage. Combining random vibration analysis of structure with modern probability theory, taking an actual large span CFST arch bridge as example, dynamic reliability of buffeting responses research and analysis is developed, which is based on the buffeting analysis on time domain at the longest cantilever construction stage. The paper gives quantitative valuation on wind-vibration safety performance of the bridge in construction phase and offers a new thought and reference for homologous project.

The Wind-Induced Response of High-Pier Long-Span Continuous Rigid Frame Bridge

The fluctuating wind field is simulated for digital by using the AR method. A three-dimension finite element model of high-pier long-span rigid frame bridge is presented in this paper. Based on this model, the gust-induced static response of the bridge under the longest cantilevered construction stage is computed. By comparing with those of two similar span rigid frame bridges with low piers, the gust-induced response characteristics of the internal force under the bottom of the piers of the high-pier long-span bridges are investigated, which is helpful for the safe design of bridges. The buffeting responses of the bridge under the longest cantilevered construction stage are also calculated in the time domain, taking account of the longitudinal and vertical turbulence action. Through the spectral analysis of the response, the comfort index of Diekemann is obtained. The effects of buffeting response on the workers’ safety under the most unfavorable construction stage are discussed.

Wind study for City Island cable-stayed bridge over Eastchester Bay in the Bronx, New York City

The existing seven-span bridge connecting the Bronx and City Island was opened to traffic in 1901. The existing bridge is planned for replacement by a new single-span asymmetrical cable-stayed bridge with a span length of 185 meters and a width of 20.85 meters. The steel tower (pylon) will be 50 meters high above the composite concrete deck and will be placed in Pelham Bay Park in the Bronx. The minimum vertical clearance above the water will be 4.50 meters. A wind study was initiated to determine: 1) the response of the bridge to vortex induced motions; 2) critical flutter wind speeds; and 3) buffeting responses of the bridge to design wind speeds, in its final configuration. The study also aimed to determine mitigating measures, if needed, to make the performance of the bridge acceptable. This paper presents the details and results of the study.

Buffeting Prediction of a Square Cylinder with Inflow Turbulence

It is known that the fluctuating structural load is caused by turbulent eddies flowing past or impinging upon the structure in case of turbulence buffeting. The prediction of the response of a structure to turbulence buffeting may be very important. In this paper the buffeting response of square cylinder with constant damping ratio (5%) based on FSI theory proposed by Zhe Liu [6] is simulated. And the movement of bluff body is controlled in the across-flow direction, and two types of inlet boundary conditions are considered to compare the different influence of them on the flow around the square cylinder, one is the steady inlet boundary and the other is the unsteady one.

Wind Tunnel Investigations for the Free Standing Tower of the Penang Second Bridge

The Penang Second Bridge is a new bridge under construction in Penang, Malaysia. The aerodynamic behavior of the bridge was one of the main concerns. This paper summarizes of the wind tunnel testing of the 1:40 scaled aeroelastic model testing for the free standing tower. The wind tunnel Investigations were carried out with the objective of verifying the detailed design of bridge towers through measurement of the buffeting response to turbulent wind, susceptibility to galloping instabilities and susceptibility to vortex shedding excitation in smooth oncoming flow.The test results show that explicit vortex-induced vibration was observed for the completed free standing tower, however it will not affect the safety of the tower, and the buffeting response of tower is within acceptable range under the designed wind speed.

Research on Wind-Induced Vibration Reduction Solution of the Longest Cantilever State of Jiashao Bridge

A research based on Jiashao Bridge is carried out to reduce buffeting response under strong wind of the control section of main girder of the longest cantilever state and to ensure the security of the bridge during the construction period. A method that the ends of cantilevers are connected with several temporary damping cables is considered as wind-resistant measure. 4 modes with different damping cable arrangement are supposed, and the wind-resistant effect corresponding to the 4 modes are compared by FEM analysis. A mode with the best wind-resistant effect and economical meanwhile is selected out and local optimization is added to the selected mode. Some valuable conclusion obtained from the research could be adopted in Jiashao Bridge and the similar projects.

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.

Wind Tunnel Test and the Analysis of Buffeting Performance of Free-Standing Tower of Cable-Stayed Bridge under Yaw Wind

The buffeting performance of free-standing tower of JiangHai Navigation Channel Bridge, a cable-stayed bridge, under yaw wind is investigated by means of wind tunnel test of aeroelastic model. It is found that the variation of buffeting response of free-standing tower with wind yaw angle is not monotonous. The lateral buffeting response on the top of the free-standing tower reach their minimal values and maximal values at around 150°and 180°of wind yaw angle respectively and the longitudinal buffeting response attain their maximal values at around 90°of wind yaw angle. Also, at the 2/3 height of the tower the lateral buffeting response and torsional buffeting response get their minimal values at around 150°of wind yaw angle, and at around 180°achieve the maximal values. It is also seen that, the buffeting response changes with the wind speed at a conic curve approximately.

Wind-induced performance of long-span bridge with modified cross-section profiles by stochastic traffic

The presence of traffic on a slender long-span bridge (SLB) deck has two types of primary impacts: (1) modification of the bridge cross-section profiles, which may influence the flutter derivatives and in turn, wind-induced aeroelastic loads acting on the bridge and (2) additional dynamic loads acting on the bridge including dynamic interactions from the vehicles. As compared to the investigations on the impact of traffic as external dynamic loads, those on the impact from the modification of bridge cross-section profiles are rather rare. A scaled bridge section model with vehicle models distributed on the bridge deck has been tested in the wind tunnel laboratory following the simulated stochastic traffic flow. With the flutter derivatives obtained from the wind tunnel experiments of various modified bridge cross-section profiles by traffic, the present study is to numerically evaluate the impact on the wind-induced performance of the long-span bridge, such as the aeroelastic performance, buffeting response and potential fatigue accumulation.

Buffeting Time-Domain Analysis of Long-Span and Slender Suspension Bridge with a Steel Truss Stiffened Girder

Consideration of natural wind related features, improved use of the harmonic synthesis, along with a high degree of change Simiu spectrum and Lumley-Panofsky spectrum as the goal of full-bridge stochastic wind field were simulated, generating a bridge structure of discrete points of vertical and horizontal wind pulse of time. Carried on the simulation using large universal finite element ANSYS, and the overall evaluation structure’s geometry misalignment, the host cable bridge tower wind load, the effective wind angle of attack’s influence, has calculated of the beam self-excited forces and obtained the long-span and slender suspension bridge with steel truss stiffened girder buffeting response result.

Statistical buffeting response of flexible bridges influenced by errors in aeroelastic loading estimation

This study discusses the development of an algorithm for predicting the “statistical” buffeting response of a long-span bridge using Monte Carlo (MC) and Quasi-Monte Carlo (QMC) methods. The proposed methodology, based on the standard multi-mode approach for bridge buffeting, was used to compute the power spectral density of the buffeting modal forces and to derive the dynamic bridge response in the case that measurement errors in the aeroelastic loading were anticipated. Closed-form solution, derived through standard numerical integration, was used to validate the MC and QMC algorithms. Preliminary simulations were used for validation of the algorithms and the optimal selection of the number of integration points.In the second part of the study, fragility curves and surfaces of the dynamic response were numerically derived by accounting for experimental errors in the estimation of the aeroelastic loading. A collection of these curves describes the conditional exceedance probability of representative indicators, associated with a specific feature of the dynamic response, at a given mean wind velocity and direction. A set of thresholds, derived from such indicators, was proposed to characterize the structural performance.

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.

Aerodynamic Analysis in Time Domain of a Cable-Stayed Bridge

To determine its actual dynamic responses under the wind loads, modal identification from the field tests was carried out for the Kao Ping Hsi cable-stayed bridge in southern Taiwan. The rational finite element model has been established for the bridge. With the refined finite element model, a nonlinear analysis in time domain is employed to determine the buffeting response of the bridge. Through validation of the results against those obtained by the frequency domain approach, it is confirmed that the time domain approach adopted herein is applicable for the buffeting analysis of cable-stayed bridges.

Conditional simulation of non-Gaussian wind velocity profiles: Application to buffeting response of Vincent Thomas suspension bridge

For a proper prediction of wind-induced vibrations of a long suspension bridge, it is necessary to use a representative wind velocity profile at the bridge site. However, as the simultaneous collection of wind velocity data at closely spaced locations of the entire bridge is not a viable option, simulation has become a powerful tool for this purpose. In this study, a new iterative approach of non-Gaussian conditional simulation is proposed to conditionally simulate the wind velocity profiles by utilizing the measured wind velocities at a few locations. The approach utilizes the well-known spectral representation technique in conjunction with nonlinear Gaussian to non-Gaussian mapping technique. Focusing on Vincent Thomas suspension bridge on which three anemometers have been installed recently at three strategic locations, this study compares buffeting responses evaluated using different simulation schemes. It has been found that the bridge response evaluated using the non-Gaussian simulation scheme may be higher when compared with other simulation schemes.