Wind-induced Vibration Of Structures Research Articles

Buffeting reliability of high-rise bridge tower in mountain area based on CNN-BiLSTM

In recent years, the wind-induced vibration of structures has received a great deal of scholarly attention due to the increasing scale of large structures. In this study, an algorithm that combines a stochastic pseudo excitation method (SPEM), a convolutional neural network (CNN) and a bidirectional long short-term memory network (BiLSTM), named as SPEM-CNN-BiLSTM (SCBL), is proposed. The SCBL is a surrogate model consisting of three different computational modules, in which the SPEM can provide training samples for CNN-BiLSTM (CBL) network architecture, a convolutional layer extracts features of stochastic parameters and a BiLSTM handles time histories of bridge response. The accuracy of the SCBL prediction results is ensured by the set error threshold. The model also accounts for structural uncertainty in the inputs and is adapted during the training step to be more suitable for reliability analysis. According to the output qualified prediction data, the dynamic reliability based on the 99 % threshold is calculated by obtaining its probability density function, and the wind-induced vibration responses of uncertain bridge towers are studied. Firstly, the wind environment of the bridge tower was analyzed, and the average wind speed of 20 m/s among the bridge area was obtained by field measurements, and Computational Fluid Dynamics (CFD). Secondly, the proposed artificial neural network algorithm is applied to bridge jitter reliability analysis and compared with the traditionally recognized methods: the Monte Carlo method (MCM) and the stochastic pseudo excitation method (SPEM). The results of SCBL calculations are closer to the results of MCM than those of other methods. Additionally, the computational efficiency of the method is improved by 40 times over MCM and 2 times over SPEM. Finally, the data generated by the SCBL method will be used for reliability analysis. Uncertainties in structure, wind speed, and yaw angle all contribute to the uncertainty and dispersion of the stochastic response prediction. Among them, the uncertainty in wind speed has the greatest impact on the reliability.

Study on Wind-Induced Dynamic Response and Statistical Parameters of Skeleton Supported Saddle Membrane Structure in Arching and Vertical Direction

Wind tunnel tests and numerical simulations are the mainstream methods to study the wind-induced vibration of structures. However, few articles use statistical parameters to point out the differences and errors of these two research methods in exploring the wind-induced response of membrane structures. The displacement vibration of a saddle membrane structure under the action of wind load is studied by wind tunnel tests and numerical simulation, and statistical parameters (mean, range, skewness, and kurtosis) are introduced to analyze and compare the displacement data. The most unfavorable wind direction angle is 0° (arching direction). The error between experiment and simulation is less than 10%. The probability density curve has a good coincidence degree. Both the test and simulation show a certain skewed distribution, indicating that the wind-induced vibration of the membrane does not obey the Gaussian distribution. The displacement response obtained by the test has good stability, while the simulated displacement response has strong discreteness. The difference between the two research methods is quantitatively given by introducing statistical parameters, which is helpful to improve the shortcomings of wind tunnel tests and numerical simulations.

Aeroelastic metastructure for simultaneously suppressing wind-induced vibration and energy harvesting under wind flows and base excitations

This paper proposes an innovative dual-functional aeroelastic metastructure that effectively suppresses wind-induced structural vibrations under either pure aerodynamic galloping or concurrent galloping and base excitations, while simultaneously harnessing the vibratory energy to potentially allow for self-powered onboard low-power sensing applications. Two configurations are theoretically and experimentally analysed and compared, one consisting of simply regular locally resonating masses subjected to no external forces, while the other comprising locally resonating bluff bodies which experience additional aerodynamic galloping forces. Numerical investigation is conducted based on an established aero-electro-mechanically coupled model. Wind tunnel wind tunnel and base vibration experiments are carried out using a fabricated aeroelastic metastructure prototype to characterize the energy transfer mechanisms and validate the numerical results. The mutual effects of key system parameters, including the frequency ratio, mass ratio, load resistance and electromechanical coupling strength, on the dual-functional capabilities are examined, providing a comprehensive design guideline for efficiently enhancing the energy transfer and conversion. Experimentally, the galloping displacement of the primary structure is attenuated by 78% with a measured power output of 2.63 mW from a single auxiliary oscillator at a wind speed of 8 m s−1. This research opens new possibilities for designing novel metastructures in practical scenarios where both wind-induced vibration suppression and energy harvesting are crucial.

Fluid–structure interaction on vibrating square prisms considering interference effects

Existing research on interference effects predominantly focuses on rigid structures. However, studies based on rigid models tend to overlook the feedback of structural motions on the flow field, thus failing to capture the intrinsic dynamics of the interference effect induced by wind-induced structural vibrations. This paper provides a comprehensive analysis of the fluid–structure interaction mechanisms considering interference effects involving two parallel square prisms, employing large-eddy simulation (LES). Various factors, including wind speed, arrangement, and vibration amplitude, are meticulously considered in the analysis. The study utilized three-dimensional LES simulations, incorporating the narrowband synthesis random flow generator method for inlet turbulence generation and adjusted through the “feedback” approach to ensure accuracy and efficiency. The research highlighted different structural arrangements exhibited distinct interference effects, and the end effect of the structure could substantially modify the flow pattern at various heights. In the tandem arrangements, the study observed several flow phenomena, including early reattachment, attenuation of the end effect, premature formation of roll structures, increased turbulence in the flow field due to vibration, resulting in wider second leading-edge separation, and a fragmented wake flow on the downstream structure. For side-by-side arrangements, the “acceleration effect” was identified and found to be further intensified by structural vibrations. The vibration of the interfering structure was noted to cause changes in vortex shedding frequencies and alterations in the wake flow pattern. In addition, vibration would enhance the interference effect but increasing amplitude and wind speed might diminish the interference effect. Overall, this study offers valuable insight into the intricate interplay of factors influencing the aerodynamics of parallel structures across diverse arrangements and under varying conditions.

Numerical Analysis and Validation of Irregularity in Moment Frame Structure Due to Varying Location of Tuned Mass Damper

Abstract: Within the construction industry, the number of higher and lighter structures that are adaptable and have a low damping value has been steadily increasing in recent years. Those constructions will simply fail as a result of earthquake and wind-induced structural vibrations. There are a variety of approaches available today to reduce structural vibration, and one of the oldest is the use of dampers. The tuned mass damper is tuned to the structural frequency of the structure if the stiffness and damping values are kept constant. The main goal is to investigate the mass and torsional irregularity in the structure. This study is divided into two phases - first phase involves the investigation and validation of structure having tuned damper with varying location along the height of building. The second phase involves the location of tuned mass damper with the plan projection of the building. Non-Linear Time history analysis is used to identify the behavior of frame elements in the structure based on considered cases using ETABS. The parameters such as displacement was evaluated. The result shows that the dampers should be carefully placed in order to tune the frequency of the structure.

Investigating the Vibration Mitigation Efficiency of Tuned Sloshing Dampers Using a Two-Fluid CFD Approach

The efficiency of a Tuned Sloshing Damper (TSD) when mitigating wind-induced structural vibrations is investigated. We assessed the performance in terms of peak structural displacements and accelerations, compared to that of the Tuned Mass Damper (TMD). One load scenario considers oncoming gusts due to natural turbulence, whereas the other assumes predominant vortex shedding at a low turbulence intensity. The known optimum tuning rules for TSDs and TMDs were adopted. We combined numerical models for fluids and structures to simulate the dynamic effects caused by wind loading. A two-fluid Computational Fluid Dynamics (CFD) approach was used for the realistic simulation of the TSD. The interaction between the flow, the structural behavior and the added devices was captured. All of these computational methods and respective models represent the necessary components of a modular and flexible simulation environment. The study demonstrates that this workflow is suited to model the inclusion of TSDs and TMDs, as well as to capture the effect of transient wind at full scale. We specifically used it to quantify the efficiency of added dampers. The process highlights challenges in properly tuning a TSD and its reduced efficiency compared to that of a TMD. Such an outcome is attributed to the water mass and potential added damping only being partially activated. The computational framework promises the ability to improve such designs by enabling numerical optimization for better efficiency.

Investigation of vortex-induced vibration of a cable-stayed bridge without backstays based on wind tunnel tests

Cable-stayed bridges without backstays located in the abrupt valley are sensitive to wind-induced structural vibrations. The understanding of vortex-induced vibration for specific aerodynamic configuration with glass deck is of great importance for structure design. This paper thus aims to investigate the vortex-induced vibration of a cable-stayed bridges without backstays through the segmental model test and scaled full-aeroelastic model wind tunnel test. The results indicate that the bridge presents the vertical vortex-induced vibrations at the low wind speed whereas the maximum wind velocity causing the torsional vortex-induced vibrations increases to 41 m/s, which is much larger than that of the traditional bridge. The vertical and torsional vortex-induced vibrations in the smooth flow are observed at the positive wind angle of attack, owing to the responses for the bridge deck present a sharp single-frequency amplitude when the frequency of vortex-shedding is close to the flexural vibration frequency. The turbulence can effectively suppress the vortex-induced vibrations and only some small peaks are visible in the turbulent flow. The vortex-induced response of the bridge deck is significantly alleviated with increasing of damping ratio. Finally, the vortex-induced vibrations in the uniform flow disappear and the wind-induced responses are impaired with the ventilated railing in place of the airtight railing because the flow can go through the railing. It can provide a designing basis for engineering reference of cable-stayed bridges without backstays.

Wind-induced vibrations of structures using design spectra

This paper discusses the estimation of wind dynamic response of two types of structures by following classical and novel approaches. A new method for structural analysis based on wind design spectra is introduced and tested against simulated and experimental data. Design spectra are derived from the dynamic response of a group of oscillators subject to wind, using similar techniques than those used to derive design spectra for seismic engineering applications. The method is used on three chimneys of different height as well as on a regular building which has been experimentally tested in the past. The chimneys and building are also submitted to simulated wind fields to provide additional sets of results. It is observed that the spectral approach is consistent with experimental and simulated results and therefore is concluded that design spectra can cover broad range of practical applications.

構造物の空力振動

構造物の空力振動

A Novel Concept for Describing the Wind Sensitivity of Structures

A number of methods for assessing wind-induced vibration of structures are available ranging from simplified procedure using quasi-static methods to the detailed procedure using statistical methods. The appropriate procedure should be selected in accordance with wind sensitivity of structures. However, it still remains unresolved concerning how to provide a universal criterion with physically meaningful and convenient for the concept of the wind sensitivity until now. In order to solve the previous problem of how to distinguish between those structures for which the wind effects can be treated by simplified procedure, and those for which the wind effects must be treated by detailed procedure, a concept of sensitivity for wind-resistance is presented in this paper. The essential idea of this theory is to provide a general expression of wind sensitivity of structures by synthesizing three factors between wind load and the structure, including the size-effect factor, frequency-effect factor and mode-effect factor, which are based on the analytical derivation and take duly into account the influence of all the significant parameters for the response. Based on that, two case studies of cantilevered roof and single-layer reticulated shell structures under wind actions are demonstrated as illustrative examples.

Robust active control against wind-induced structural vibrations

Slender flexible structures are vulnerable to vibrations under wind loads. The dynamic model of a frame-like structure is obtained by finite element approximation in this paper and used further for the design of an active control mechanism. The behavior of the structure is described by simplified linear equations. A linear quadratic regulator and an H 2 optimal control method are used for the suppression of the extended vibration effects. Structured uncertainties are considered to reflect the errors between the model and the reality. To accommodate directly the plant uncertainties and to obtain a best possible performance in the face of uncertainties a robust H ∞ optimal control for active control structure is used. The two latter robust controllers take into account as well incompleteness of the measured information, a fact that cannot be neglected in civil engineering, and lead to applicable designs of smart structures. The numerical simulation shows that vibrations can be suppressed by means of the proposed methods.

Study on soil-pile-structure-TMD interaction system by shaking table model test

The success of the tuned mass damper (TMD) in reducing wind-induced structural vibrations has been well established. However, from most of the recent numerical studies, it appears that for a structure situated on very soft soil, soil-structure interaction (SSI) could render a damper on the structure totally ineffective. In order to experimentally verify the SSI effect on the seismic performance of TMD, a series of shaking table model tests have been conducted and the results are presented in this paper. It has been shown that the TMD is not as effective in controlling the seismic responses of structures built on soft soil sites due to the SSI effect. Some test results also show that a TMD device might have a negative impact if the SSI effect is neglected and the structure is built on a soft soil site. For structures constructed on a soil foundation, this research verifies that the SSI effect must be carefully understood before a TMD control system is designed to determine if the control is necessary and if the SSI effect must be considered when choosing the optimal parameters of the TMD device.

Development of Active Control System for Wind-induced Vibration of Structures

To reduce wind-induced vibration of tall buildings and bridge towers, tuned mass dampers are often used. These dampers are called “passive type” while the methods which reduce the vibration by controlling the motion of a large mass with an actuator are called “active type”. For these types we have to change or control the structural vibration characteristics themselves, therefore they need very large exciting forces, and the system will become very large for large structures. In this view point, new concepts have just begun to be studied, where the driving forces themselves will be controlled. In this paper, we proposed a new system for reducing the flow-induced vibration of the structures by utilizing fluid excitation force itself. In this system, as we control the direction of the driving forces, this system does not need so large control forces and the system becomes smaller and simpler. We investigated the feasibility of this system when applied to a bridge, a building and evaluated the effectiveness of driving forces by the wind test using a reduced scale model.

A study on Elasto-Plastic Behavior of Tall Buildings Under Wind Loads in Hybrid Vibration Technique

The Hybrid vibration technique, which was proposed by Dr. Kanda, is combined a movable mechanical system with a personal computer for simulating the wind-induced vibration of structures in wind tunnel tests. Authors attempted to investigate the wind-induced response of scale models with various-type of elasto-plasticity by means of Hybrid vibration system. The results of wind tunnel tests shows as follows: (1) Hybrid vibration system can simulate wind-induced vibration of models with a elasto-plasticity or a non-linear elasticity, (2) the across-wind response of models with a hysteretic damper was always reduced, (3) the across-wind response of models with a non-linear elasticity was increased around the wind condition of just below the vortex-excitation and decreased in the vortex-excitation, (4) the along-wind response of models was not controlled, and was remarkably increased, when the mean response was in the second stiffness and (5) the event of which the response was increased and/or decreased is explained in a viewpoint of frequency domain.

TUNED LIQUID DAMPER (TLD) USING HEAVY MUD

重泥水はベントナイト液に加重材 (バライト) を加えて製成された高粘性, 高比重の特性を有する材質が安定な液体である. これをTLDに用いると, 高比重と最適スロッシング減衰によりTLDの小型化と制振効果の向上が可能となる. 本研究では, 非ニュートン流体である重泥水の減衰特性を把握した後, 重泥水TLDの挙動を模型実験, 等価減衰を導入した非線形波動理論解析ならびに高橋脚施工時の鋼管柱の加振実験により検討した. その結果, 重泥水TLDは水を用いる同じ寸法のTLDの2～3倍の減衰付加性能を有することを確認した. また, 重泥水TLDの簡易設計手法を提案した.

Tuned Liquid Damper (TLD) Using Heavy Mud

This paper presents an investigation and an implementation of a Heavy Mud Tuned Liquid Damper (TLD) for suppressing wind-induced vibration of structures. Heavy Mud TLD is one kind of the passive dampers utilizing heavy mud sloshing in rigid containers. A shaking table experiment was carried out to verify the effectiveness of Heavy Mud TLD. The simulations based on the wave theory shows the good agreement between the measurement and the prediction. Heavy Mud TLD was applied to a high RC bridge pier for reducing wind induced vibration. The free vibration tests show that the structural damping ratio was increased from about 0.8% to 2.4% by installing the Heavy Mud TLD.

Mitigation of Earthquake and Wind Induced Structural Vibrations

Seismic activity and wind loads cause significant losses to life, property and infrastructuralfacilities. Research in civil structural contral is aimed at Improving the safety and reliability of thesefacilitIes by reducing the hazardous responses caused by such natural phenomena. In this context, a capsule of recent collaborative efforts by the authol5, aimed at developing passive/active contral devices and control algorithms, is presented. Among the techniques considered here are designs of active mass dampel5for wind and seismic excitation, multiobjective control, specialized passive damper design, and sampled data stepped control. For the active mass dampers, simplified structural models are used to obtain analytic design parameters. In the multiobjective contral method reviewed, a technique to synthesize a structural controller (such as an active tendon) capable Of satisfyIng several simultaneously Imposed design criteria is presented. The specialized passive dampel5 reviewed here have been shown, In ...

A Semi-Analytical Model for Tuned Liquid Damper (TLD) with Wave Breaking

Recently, the applicant of vibration-control devices against wind-induced vibration of structures has become an accepted technology. A Tuned Liquid Damper (TLD) is a kind of passive control device relying upon liquid sloshing to suppress structural vibration. An analytical model for a TLD using a rectangular tank filled with shallow liquid has been proposed by the authors. The model has been experimentally verified to be able to predict liquid sloshing in the TLD with satisfactory accuracy. Since it was assumed that the free surface is continuous, the model was valid as long as no breaking of waves occurs in the TLD. To account for breaking waves, in this paper, the model is modified by introducing two coefficients into the equation of motion. The first, C da , is termed the damping coefficient and represents the increase in liquid damping due to breaking waves; the other coefficient, C fr , is termed the frequency shift coefficient and is introduced to represent phase velocity shift of liquid motion due to breaking waves. They are empirically determine by shaking-table experiments using various tank sizes and liquid depths. It is found that C da is dependent upon the base amplitude of excitation, while C fr , remains almost constant for all the experiments carried out. The empirical formulate for C da and C fr to account for breaking waves are obtained based on the nondimensionalized equation of motion, and they are expected to be valid for a wide range of TLD dimensions. The modified model is employed to predict response of a structure fitted with a TLD, in which breaking waves are expected to occur. TLD-structure interaction is also experimentally investigated. It is found that the modified model can predict structural response very well, even in the presence of breaking waves in the TLD.

WIND-INDUCED VIBRATIONS OF STRUCTURES

WIND-INDUCED VIBRATIONS OF STRUCTURES

Review of Various Mechanical Means Suppressing Wind-Induced Vibration of Structures

A variety of means for suppressing wind-induced vibration of structures could be divided into aerodynamic means and mechanical ones.Out of these two means, the latter is dis-cussed in this paper.First, various mechanical means for suppressing wind-induced vibration are classified as follows;A. augumentation of stiffnessB. addition of massC. augmentation of damping, No.1 untuned typeD.augmentation of damping, No.2 tuned typeE. application of control forceEach vibration-suppressing means classified above is discussed one by one making up a list of proposed ideas and actually applied cases.Finally, the design procedure and things to be considered are described in the case of the planning of these mechanical means for suppressing wind-induced vibration.