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nonlinear flutter of a narrow truss girder

JOURNAL OF WIND ENGINEERING AND INDUSTRIAL AERODYNAMICS 2023年 242卷

作者： Zhang, Yuanbo Ma, Cunming Li, Jiankun Pei, Cheng Southwest Jiaotong Univ Sch Civil Engn Chengdu 610031 Peoples R China Key Lab Wind Engn Sichuan Prov Chengdu 610031 Peoples R China State Key Lab Bridge Intelligent & Green Construct Chengdu 610031 Peoples R China Civil Aviat Flight Univ China Airport Coll Guanghan 618307 Peoples R China

The nonlinear flutter of a narrow railway truss girder are studied through free vibration and forced vibration wind tunnel tests. Four functions are used to fit the structural amplitude-varying damping ratio under no wind condition, and the fourth-order polynomial has higher goodness-of-fit. The narrow truss girder shows nonlinear flutter of a velocity-restricted type without amplitude hysteresis. At large angles of attack (AoA), the vertical participation and the AoA have little effect on the onset wind speed and amplitude. While at medium AoAs, even a low vertical participation level will increase the onset wind speed and decrease the amplitude. At small AoAs, there is no vibration observed. The flutter derivative A2* is positive only in the limited reduced wind speed and amplitude range. The nonlinearity of self-excited lifting moment is higher only in the limited reduced wind speed and amplitude range, while that of self-excited lift is weaker and becomes stronger with the increasing amplitude and reduced wind speed. The negative aerodynamic damping is mainly provided by the flutter derivative A2* at small or large AoAs. Generally, the nonlinear flutter response is mainly controlled by the first-order component of the self-excited force, and the influence of high-order components can be ignored.

关键词： Narrow truss girders nonlinear flutter nonlinear self-excited force nonlinear flutter derivatives

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Investigation on nonlinear flutter modes competition of a long-span suspension bridge based on full-bridge aeroelastic model tests

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ENGINEERING STRUCTURES 2025年 322卷

作者： Song, Jun Li, Kai Han, Yan Wang, Xiangjun Li, Chunguang Changsha Univ Sci & Technol Sch Civil Engn Changsha 410114 Peoples R China Changsha Univ Sci & Technol Elite Engn Sch Changsha 410114 Peoples R China Changsha Univ Sci & Technol State Key Lab Disaster Prevent & Reduct Power Grid Changsha 410114 Peoples R China

nonlinear flutter has attracted wide attention due to the bottleneck caused by linear flutter theory on flutter- resistant design of super-long-span bridges. The longer the span, the more closely spaced the natural modes, which may cause competition among flutter-modes in a nonlinear flutter, but it is rarely reported so far. To this end, this study experimentally investigates the 3D nonlinear flutter characteristics of a long-span suspension bridge with closely spaced natural modes based on full-bridge aeroelastic model wind tunnel tests. Since there are two unstable flutter-modes within the interested post-critical regime and thus various complex but interesting flutter-modes competition processes were observed, such as continuous modes competition where the vibration amplitude evolution exhibits various different types of "sawtooth" shapes during stable vibration stages. Meanwhile, the complex nonlinear bifurcation behaviors caused by modes competition were also observed. The evolutionary characteristics of flutter-modes competition are analyzed in detail and relevant mechanisms are discussed. As the wind speed increases, the flutter of the studied bridge mainly undergoes a transition from being dominated by the symmetric mode to being dominated by the antisymmetric mode, accompanied by a continuous modes competition zone in between as a transitional zone. The results show that the continuous modes competition will result in a decrease in the maximum amplitude RMS of the full-span, which is beneficial for the structure. But it may also lead to a transient increase in the maximum amplitude of the full-span due to the coupling vibration shape formed by the two significant flutter-modes, which may be bad for the structure.

关键词： Suspension bridge Full-bridge aeroelastic model Wind tunnel test nonlinear flutter flutter modes competition

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Control of the nonlinear flutter of a rectangular cylinder using auxiliary flexible films

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nonlinear DYNAMICS 2024年第18期112卷 15741-15756页

作者： Zhang, Ziqiang Yin, Yapeng Wang, Hanfeng Cent South Univ Sch Civil Engn Changsha 410075 Peoples R China Cent South Univ Natl Engn Res Ctr High Speed Railway Construct Tec Changsha 410075 Peoples R China

Wind tunnel experiments were conducted to test the effects of auxiliary flexible films (FFs) attached at the leading edges of a rectangular cylinder on its nonlinear flutter. The aspect ratio (B/D) of the tested cylinder was 5, with the cylinder height D of 70 mm. The FFs with length of 0.3 D were arranged along span of the tested cylinder. Both free- and forced-vibration tests were carried out with the reduced velocity (Ur) ranging from 1.0 to 9.2, to reveal the control effects and mechanism of the FFs. It was found that the flapping FFs significantly increase the flutter critical wind speed (Ucr) of the tested cylinder by 93%. Moreover, the FFs have reasonable control robustness under external excitations. The forced-vibration results show that the flapping FFs successfully reduce the energy absorption of the tested cylinder from surrounding flow, because of the reducing of both aerodynamic torque and the phase lag between the aerodynamic force and torsional vibration angle. According to the variation of aerodynamic force, flutter derivative and energy map, it seems that the auxiliary FFs make the rectangular cylinder behaves more like a streamlined body, rather than a bluff one.

关键词： Rectangular cylinder nonlinear flutter Flexible film Flow control

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nonlinear flutter mechanism of a single-layer truss bridge deck based on hysteresis loop and energy budget analysis

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STRUCTURES 2025年 76卷

作者： Qiu, Zhixiong Li, Kai Han, Yan Hu, Peng Cai, C. S. Yang, Fei Changsha Univ Sci & Technol Sch Civil Engn Changsha 410114 Peoples R China Changsha Univ Sci & Technol Elite Engn Sch Changsha 410114 Peoples R China Southeast Univ Sch Transportat Dept Bridge Engn Nanjing 211189 Peoples R China

The dynamic mechanism of limit cycle oscillation (LCO) and subcritical Hopf bifurcation for a single-layer truss bridge deck, which are of great significance for the flutter design of bridges and have received little research attention before, was studied in this study. Firstly, a two-degree-of-freedom bending-torsion coupled nonlinear self-excited force model was proposed, and the equations to solve the work and energy of aerodynamic forces were derived. Further, the time-varying characteristics of nonlinear self-excited forces were investigated, as well as their contribution to accurately predicting nonlinear flutter response. It was found that self-excited forces contain higher-order octave components, as identified through the hysteresis loop analysis method. Subsequently, the characteristics of the self-excited forces under varying wind speeds were summarized via the analysis of the work done by the self-excited forces. The energy feedback mechanism of LCO was revealed, which highlighted the important role of non-wind-induced and linear terms of self-excited torsional moment in the generation of LCO. Finally, the driving mechanism of the subcritical Hopf bifurcation was explained by combining hysteresis loop analysis, energy budget analysis, and damping ratio as a function of vibration amplitude analysis. It is found to result from the competition between self-excited torsional moment and torsional nonlinear mechanical damping.

关键词： Single-layer truss bridge nonlinear flutter nonlinear self-excited force Limit cycle oscillation Subcritical Hopf bifurcation Energy budget analysis

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nonlinear flutter of composite laminates with curvilinear fibres using a full linearized aerodynamic theory

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JOURNAL OF FLUIDS AND STRUCTURES 2022年 115卷

作者： Akhavan, Hamed Ribeiro, Pedro Univ Porto Fac Engn INEGI DEMec Rua Dr Roberto Frias P-4200465 Porto Portugal Univ Porto Fac Engn DEMec INEGI Rua Dr Roberto Frias P-4200465 Porto Portugal

This paper studies nonlinear flutter of rectangular variable stiffness composite laminates (VSCLs) subjected to a low supersonic airflow. The VSCLs are formed by different individual laminae where a polymeric matrix is reinforced by curvilinear carbon fibres. The plate's displacement field follows a Third-order Shear Deformation Theory (TSDT);a p-version finite element is employed to discretize the displacement components. A full linearized (inviscid, potential flow) aerodynamic theory is used to approximate the aerodynamic pressure. The self-exciting vibrational model is formed using the principle of virtual work. The equations of motion representing the model are solved using Newmark method. Limit cycle oscillations (LCOs) of these plates are studied using time histories, phase-plane plots and FFT spectra. A damage onset criterion is utilized to control the structural health of the laminates during nonlinear flutter. Effects of curvilinear fibre path angles on linear and nonlinear flutter behaviour, as well as the damage onset in VSCLs are investigated.(c) 2022 Elsevier Ltd. All rights reserved.

关键词： nonlinear flutter Composite laminates Curvilinear fibres Finite element Low supersonic airflow

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Experimental Investigations on nonlinear flutter Performance of the Old Tacoma Narrows Bridge Deck under Skew Winds

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JOURNAL OF STRUCTURAL ENGINEERING 2025年第7期151卷

作者： Wang, Pinqing Xu, Fuyou Cai, Xinyu Dalian Univ Technol Sch Infrastruct Engn Dalian 116024 Peoples R China

This paper investigates the nonlinear flutter performance of a 1:25 sectional model of the Old Tacoma Narrows Bridge deck (OTNBD) using a large-amplitude free vibration testing device enabling skew wind cases. The study focuses on the effects of wind velocities, yaw angles (0 degrees, 10 degrees, 20 degrees, and 30 degrees), initial attack angles (0 degrees and +/- 5 degrees), and structural damping ratios on the nonlinear flutter. First, large-amplitude free decay vibration tests in still air are carried out to extract modal parameters, showing the device exhibits constant low structural damping ratios. Second, amplitudes versus wind velocities for different cases and amplitude-dependent aerodynamic damping ratios for typical limit cycle oscillations are studied. It is found that yaw angles can reduce the amplitudes and the difference of nonlinear flutter performance under different initial attack angles. Then, the torsional aerodynamic damping ratios at different wind velocities, amplitudes, and yaw angles are extracted, and their maps are established. The maps indicate that the nonlinear flutter performance are closely related to the wind directions, reduced wind velocities, and structural damping ratios. The supercritical hopf bifurcation is the main bifurcation pattern for most cases. The subcritical hopf bifurcation and velocity-restricted flutter are found for some specific cases under skew winds. Based on the maps, the possible torsional structural damping ratios of the OTNB are analyzed for different yaw angles. This study contributes to further elucidating the failure mechanism of the OTNB.

关键词： Old Tacoma narrows bridge (OTNB) Wind tunnel test nonlinear flutter Limit cycle oscillation Skew wind Structural damping ratio

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Effects of Vertical Motion on nonlinear flutter of a Bridge Girder

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JOURNAL OF BRIDGE ENGINEERING 2020年第11期25卷

作者： Wu, Bo Wang, Qi Liao, Haili Mei, Hanyu Southwest Jiaotong Univ Dept Bridge Engn Res Ctr Wind Engn Chengdu 610031 Peoples R China Southwest Jiaotong Univ Dept Bridge Engn Wind Engn Key Lab Sichuan Prov Res Ctr Wind Engn Chengdu 610031 Peoples R China

This study addresses the effects of vertical motion on the nonlinear flutter response of a double-deck truss girder based on section model wind tunnel tests. Six dynamic systems with the same bridge deck section were tested under various wind angles of attack. The nonlinear flutter characteristics under different cases were fully captured. The potential effect of vertical motion on coupled nonlinear flutter was investigated by conducting an additional single-degree-of-freedom wind tunnel test. The aeroelastic mechanism concerning the vertical motion that affects the nonlinear flutter performance is revealed by qualitatively estimating the contribution of coupled aerodynamic damping to the total damping. Results showed that vertical motion introduces noticeable negative damping to the system thus increases vibration amplitude and reduced onset wind speed at lower wind angles of attack, while the vertical motion will be less important at large wind angles of attack since its contribution to the total damping is relatively small. Finally, a preliminary method is proposed to identify nonlinear aerodynamic damping, which helps to understand the participation of vertical motion on coupled nonlinear flutter and to interpret the amplitude dependence of nonlinear flutter. (C) 2020 American Society of Civil Engineers.

关键词： Double-deck truss girder nonlinear flutter Vertical motion Aerodynamic damping Amplitude dependence

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Hysteresis response of nonlinear flutter of a truss girder: Experimental investigations and theoretical predictions

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COMPUTERS & STRUCTURES 2020年 238卷 106267-106267页

作者： Wu, Bo Wang, Qi Liao, Haili Mei, Hanyu Southwest Jiaotong Univ Dept Bridge Engn Chengdu 610031 Peoples R China Key Lab Wind Engn Sichuan Prov Chengdu 610031 Peoples R China

nonlinear flutter response with hysteresis loop characteristics is a special aerodynamic instability phenomenon, and is of great importance and of practical interest to long span bridge designs. This paper presents a comprehensive study on nonlinear flutter of a bridge deck that has hysteresis loop characteristics over a range of wind speeds close to the flutter onset speed, using a section model wind tunnel test and theoretical analyses. The evolutions of the hysteresis loop in both the single degree of freedom (SDOF) system in torsion and the 2 degrees of freedom (2DOF) system in the vertical direction and in torsion are studied. The formation mechanism of the hysteresis loop is discussed using the equivalent total damping as a function of vibration amplitude. Two nonlinear mathematical models for the SDOF and the 2DOF systems are proposed to predict the nonlinear flutter responses, in which both the structural and aerodynamic damping are expressed as functions of time-varying displacements. An approach is proposed to identify the aerodynamic parameters based on the displacement time histories using a harmonic balancing technique. Using the identified aerodynamic parameters, a distinct dynamic system with the same section was used to validate the accuracy of the proposed models. (C) 2020 Elsevier Ltd. All rights reserved.

关键词： Bridge deck nonlinear flutter Hysteresis loop nonlinear mathematical model Aerodynamic damping

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nonlinear flutter and limit-cycle oscillations of damaged highly flexible composite wings

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nonlinear DYNAMICS 2019年第1期97卷 247-268页

作者： Hoseini, Hanif S. Hodges, Dewey H. Georgia Inst Technol Atlanta GA 30332 USA

A study on nonlinear flutter of damaged high- wings is presented. Because an undamaged, high- wing is long and slender, it may be properly modeled as a 1D beam, using a geometrically exact beam formulation. However, structural damages in the form of cracks and delaminations are in fact 3D phenomena. Therefore, the area near a crack cannot be accurately modeled as a reduced-dimensional beam. However, finite element analysis of a wing structure modeled entirely as a 3D continuum is computationally expensive. To address this issue, a joined 3D/1D finite element approach has been proposed in which a small area surrounding the crack is regarded as a 3D continuum, and the rest of the wing structure is modeled as a reduced-dimensional 1D beam undergoing large displacements and rotations. The continuity conditions at the intersection between the 3D and 1D models are derived using the variational asymptotic method, by which the two parts are rigorously connected. Hence, the joined 3D/1D method provides a computationally inexpensive, yet accurate, analysis for slender wings. The structural model is then coupled with a reduced-order unsteady aerodynamic model to compute the aerodynamic forces and moments acting on the wing. The resulting nonlinear aeroelastic element is integrated into Abaqus, a commercial finite element computer code as a nonlinear user-defined element. Through nonlinear time-marching, using a generalized method, limit-cycle oscillations associated with the free response of both undamaged and damaged wings undergoing large deformations are studied, and the differences are highlighted.

关键词： nonlinear flutter LCO Damaged HALE wings

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Characterization of vibration amplitude of nonlinear bridge flutter from section model test to full bridge estimation

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JOURNAL OF WIND ENGINEERING AND INDUSTRIAL AERODYNAMICS 2020年 197卷 104048-000页

作者： Wu, Bo Chen, Xinzhong Wang, Qi Liao, Haili Dong, Jiahui Southwest Jiaotong Univ Dept Bridge Engn Chengdu 610031 Peoples R China Texas Tech Univ Natl Wind Inst Dept Civil Environm & Construct Engn Lubbock TX 79409 USA

This paper presents a comprehensive study of nonlinear flutter characteristics of a bridge deck section through free vibration wind tunnel testing and theoretical analysis. The section model is spring-supported in a single degree of freedom (SDOF) in torsion and 2DOFs in both vertical direction and torsion, respectively. The amplitude-dependent aerodynamic damping and other response characteristics are determined through use of Hilbert Transform of response time histories at different wind speed of smooth flow. An approach is proposed to extract flutter derivatives as nonlinear functions of amplitude of torsional motion at various reduced wind speeds. The flutter derivatives are then used to estimate the nonlinear flutter response of bridge section and a prototype suspension bridge with a main span length of 1700 m. The results showed that the magnitude of negative aerodynamic damping increases with increasing wind speed but decreases with vibration amplitude. The flutter of this bridge example is initialed from torsion but the coupled vertical motion further generates negative damping, thus reduces the flutter onset wind speed and increase the vibration amplitude. The estimation using three-dimensional bridge model with coupled vertical and torsional modal responses leads to increase in flutter onset wind speed and decrease in flutter amplitude as compared to section model estimation.

关键词： nonlinear flutter Wind tunnel test nonlinear aerodynamic damping nonlinear flutter derivatives

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