Wind-induced Vibration Research Articles

Optimized passive/semi-active vibration control using distributed-multiple tuned facade damping system in tall buildings

To reduce wind-induced vibrations, Tuned Mass Dampers (TMD) are widely used in high-rise buildings. However, traditional TMD system requires large additional damping mass and huge installation space at the top floors of the building. In this paper, a novel distributed-Multiple Tuned Facade Damping (d-MTFD) system is investigated. This system employs the outer skin mass of the Double-Skin Facade (DSF) as the damping mass. In the upper stories, the DSF's outer skin, mounted on a guide rail system, is designed to be parallel moveable. The passive/semi-active d-MTFD system, which is assumed to be installed on a 76-story benchmark building under across-wind excitation, is optimized using multi-objective Genetic Algorithms (GA) for two defined objectives: minimizing the peak top floor acceleration and controlling the maximum peak relative displacement of all the moveable DSF's outer skins. On-off groundhook control and displacement-reducing bang-bang control are used as semi-active control strategies. The rolling friction caused by the guide rail system has a considerable impact on the optimization results. These results are presented in the form of Pareto fronts. Optimized parameters can be selected to yield a good trade-off between both objectives. The optimized passive/semi-active d-MTFD systems can highly improve the structural response. Compared with the optimized passive d-MTFD system, the use of semi-active control can reduce the vibration of the DSF's outer skin significantly. Comparing the selected optimized cases with similar peak top floor acceleration, the peak top floor facade relative displacement using displacement-reducing bang-bang control decreases 58.3%, and the Root Mean Square (RMS) value decreases 61.4%.

Aerodynamic Characteristics of a Square Cylinder with Vertical-Axis Wind Turbines at Corners

A preliminary study is carried out to investigate the aerodynamic characteristics of a square cylinder with Savonius wind turbines and to explain the reason why this kind of structure can suppress wind-induced vibrations. A series of computational fluid dynamics simulations are performed for the square cylinders with stationary and rotating wind turbines at the cylinder corners. The turbine orientation and the turbine rotation speed are two key factors that affect aerodynamic characteristics of the cylinder for the stationary and rotating turbine cases, respectively. The numerical simulation results show that the presence of either the stationary or rotating wind turbines has a significant effect on wind forces acting on the square cylinder. For the stationary wind turbine cases, the mean drag and fluctuating lift coefficients decrease by 37.7% and 90.7%, respectively, when the turbine orientation angle is 45°. For the rotating wind turbine cases, the mean drag and fluctuating lift coefficients decrease by 34.2% and 86.0%, respectively, when the rotation speed is 0.2 times of vortex shedding frequency. Wind turbines installed at the corners of the square cylinder not only enhance structural safety but also exploit wind energy simultaneously.

Dynamic response analysis of a whole steel frame solar greenhouse under wind loads

In recent years, whole steel frame steel greenhouses have become increasingly prevalent. With the characteristics of large flexibility and small mass, whole steel frame steel greenhouses are sensitive to wind loads. However, studies on the safety of whole steel frame steel greenhouses under wind loads are still limited. In this study, a 10 m span whole steel frame solar greenhouse was taken as the research objective. Taking the Davenport spectrum as the target spectrum, the time history of the wind speed was simulated by the harmonic superposition method. The finite element model of the greenhouse structure was established using ANSYS software. The simulated wind pressure was applied on the greenhouse structure for dynamic response analysis. The dynamic response results were compared with the static analysis results under average wind load. The results showed that the greenhouse structure mainly bears bending stress under wind load. The bending stress, axial stress and displacement of the greenhouse skeleton under average wind loads are lower than those under instantaneous wind loads. It is necessary to consider the dynamic characteristics of wind loads in the design of solar greenhouses. A wind-induced vibration coefficient is obtained, which can be used to convert the dynamic load into the equivalent static load and improve its design efficiency.

Aerodynamic characteristics of MIRA automobile model based on fluid–structure coupling

In this paper, the aerodynamic characteristics of a vehicle model are analyzed through numerical simulation considering the fluid–structure interaction (FSI) effect, and the accuracy of the simulation method is verified by comparison with the wind tunnel experiment. Then, the wind-induced vibration of vehicles under time-varying crosswind is studied and applied to engineering problems, such as vehicle sideslip and roll. The results show that the deviation between the FSI simulation and wind tunnel test is less than 10%, proving that the numerical method is feasible. The FSI effect on the aerodynamic lift is obvious, and its influence mechanism is mainly due to the change in body position, which changes the topological structure of the shedding or separated vortex in the flow field. As for the aerodynamic lift, a big gap exists between the results of the numerical simulations with and without coupling; high-intensity side wind will seriously affect the vehicle stability, and the uncoupled numerical simulation decreases the accuracy of the vehicle design.

Wind Field Characteristics of Butte and the Influence on the Wind-Induced Responses of Transmission Towers

The computational fluid dynamics (CFD) simulation on the butte was carried out to obtain the wind field characteristics for a specific mountain in the hilly area of eastern China. Then, the speed-up ratios of butte at each location distributed by height were calculated. The simulation results were compared with the specified value of mountain wind field acceleration ratio in various codes. The finite element model of the transmission tower line system is established by ANSYS, and the wind-induced vibration response of the structural system under the single mountain wind field is calculated, which is compared with the results of flat ground. The results show that the mountain will hinder the fluid passing through it. There is a deceleration zone in front of the mountain and a flow separation phenomenon behind the mountain. The speed-up ratios at the butte top where accelerating effect are the biggest among all positions of the butte. As the height increases, they approach 1. The speed-up ratios calculated by the Chinese code and the Australian code are linearly changing along the ridge of the butte and are symmetric at the windward side and leeward side. The biggest speed-up ratios are calculated by the Chinese code, and the smallest ratios are calculated by CFD. The wind-induced vibration response of the transmission tower line system is influenced by the wind speed-up ratios and reaches the maximum at the top of the butte. The simulation results at the windward side are close to the values calculated by the Australia code and the Euro code, but at the top and leeward side, they are far smaller than others.

Influence of Refined Wind Load Parameters and Wind-Loading Mode on Wind-Induced Responses of a Long Cross-Arm Angle-Steel Transmission Tower

This study aims to investigate refined wind load parameters on main rods and the influence of wind-loading mode on wind-induced responses of the angle-steel transmission tower. The wind load parameters discussed in this study include drag coefficients, wind load distribution factors and skewed wind load factors. To achieve the aim, wind tunnel tests were conducted to explore aerodynamic loads for integrated frame, single frame, and main rod models of cross-arm and tower body. The wind load parameters of the different models were investigated. In addition, a series of wind-induced vibration simulation was applied to examine the wind-induced responses of an ultra-high voltage (UHV) transmission tower with a long cross-arm under concentrated and distributed wind loads. The simulated results under the two types of wind loads were compared. The results show that the longitudinal drag coefficients of the main rods are smaller than the values of the integrated frame, and equivalent on average to the values of the single frame. The experimental shielding factor of the cross-arm is larger than those in different standards due to the joint drag effects of leeward, upper, and lower faces of the cross-arm in the wind tunnel test. The experimented shielding factor of the tower body is in line with those referring to the Chinese and AS/NZS standards, and slightly larger than those based on the British and JEC standards. The skewed wind load factors of the main rod models are quite different from other models for cross-arm and tower body. The wind-induced vibration simulation suggests that, the wind-loading mode has limited impact on the displacements, accelerations, and gust factors of the transmission tower, but significantly influences the maximum normal stresses (MNSs) of the rods’ cross-sections. The MNSs caused by the distributed wind loads are obviously greater than those caused by concentrated wind loads, especially for the rods at the two ends of the cross-arm.

Numerical Modeling of Ice Accumulation on Three-Dimensional Bridge Cables under Freezing Rain and Natural Wind Conditions

In order to accurately predict the ice accumulation on bridge cables under two typical freezing rain conditions, rime and glaze ice, this paper proposes a numerical simulation framework based on the three-dimensional Messinger theory. Two technical challenges of determining the flow direction of unfrozen water and solving three-dimensional Messinger equations are solved in this research. Based on the outflow, mass was calculated according to the three-dimensional Messinger theory, and the flow direction of unfrozen water in each cell was determined by the resultant force of air shear stress and water film gravity. To solve the three-dimensional equations, an iterative method without finding the stagnation line was introduced. The final iced geometries were determined when the inflow mass ratio was satisfied with the converge criteria. Moreover, this modified numerical model was programmed and embedded into computational fluid software. For both two typical freezing rain conditions, the effects of temperature and wind speed on iced geometries were studied. The aerodynamic characteristics and galloping instability of bridge cables with different iced geometries were also investigated. These preliminary aerodynamic simulations can provide the basis for the wind-induced vibration analysis of the whole structure.

Numerical analysis of passive toroidal tuned liquid column dampers for the vibration control of monopile wind turbines using FVM and FEM

The toroidal tuned liquid column damper (TTLCD) is a recently developed multidirectional vibration control device. This paper investigates the TTLCD for the vibration control of monopile fixed-bottom offshore wind turbines. The TTLCD with its circular versatile configuration can match the geometrical shape of wind towers and be tuned to control wind, wave and earthquake induced flexural tower vibrations. An effective numerical framework accounting for the liquid flow and sloshing as well as two-way fluid–structure interaction is developed for the TTLCD-structure system. Its accuracy is validated by comparing the numerical results with experimental ones. The design procedures of the TTLCD for monopile wind turbines are illustrated in detail. The control performance of the TTLCD under wind, wave and seismic loads is presented. The results show that the TTLCD can control the structural responses in both fore-aft and side-side directions simultaneously. Furthermore, it is revealed that for wind-induced vibrations, the control performance relies on the wind velocities and the related frequency components.

Aerostatic Performance Improvement Based on a Novel Aerodynamic Countermeasure: Simulation and Wind Tunnel Test

AbstractFlexible civil structures are prone to aerodynamic instabilities, such as long-span bridges and high-rise buildings, and wind-induced vibration is harmful to structural life-span and users’...

An in-plane omnidirectional piezoelectric wind energy harvester based on vortex-induced vibration

Variations in the wind direction over time mean that it is essential to improve the directional adaptability of wind energy harvesters (WEHs) based on wind-induced vibration (WIV) to expand their application potential. Several multi-directional WIV WEHs have been reported in the literature but most of them are not omnidirectional. In particular, no mathematical model has been proposed for omnidirectional WIV WEHs to date. In this Letter, an in-plane omnidirectional piezoelectric WEH with a cylindrical shell, acting as a bluff body and supported by internal piezoelectric composite beams, is proposed. It is deduced that the omnidirectionality of wind energy harvesting can be enhanced by improving the isotropies of the aerodynamic force, stiffness, and electromechanical conversion. For a WEH with three semicircular-shaped supporting beams, a mathematical model suitable for arbitrary wind directions in the horizontal plane was derived. Simulations show that the WEH's stiffness and electromechanical conversion are approximately isotropic. Simulations and experiments demonstrate that the wind direction's effect on the total power is small. The ratio of the experimental minimum to maximum total power is 0.88 at 9 m/s, verifying that the device is an in-plane omnidirectional harvester. An omnidirectionality index including contributions from all directions is proposed with the value of 0.86 at 9 m/s for the prototype. The proposed device configuration and design method may serve as a reference for the development of omnidirectional WIV WEHs.

Wind-induced vibration assessment of tower cranes attached to high-rise buildings under construction

When attached to slender super high-rise buildings, tower cranes are facing increasing risk of failure under extreme wind scenarios. To take an insight into such wind-induced vibration safety concern, some specifically customized computational fluid dynamics (CFD) modelling and simulation procedures are proposed to address the spatio-temporal feature of in-construction buildings and various working conditions of tower cranes. Based on a variety of CFD simulations, the shape coefficients of main building are determined for various construction scenarios. The dynamic response of a crane is analyzed by wind pressure history applied directly on its surface and the excitations at the supports transferred from main building. The construction stage, the uncertainties of predicted wind velocity, as well as overloading and connection stiffness, are included in the response simulation of the tower crane. All the possible failure scenarios can be well simulated by the proposed procedures combined with rational determination of related parameters.

Analysis of Wind-Induced Vibration Response of High-Rise Structure of Heat Sink Tower Based on Large Eddy Simulation

Analysis of Wind-Induced Vibration Response of High-Rise Structure of Heat Sink Tower Based on Large Eddy Simulation

Contribution of fluid viscous dampers on fatigue life of lattice-type offshore wind turbines

Given the recent developments in wind energy generation technology, offshore wind turbines have been widely used to exploit offshore wind energy. Supporting structures of offshore wind turbines play an important role in correct operation of wind turbines and their operational life. Supporting structures will experience millions of lateral load reversals due to wave- and wind-induced vibrations. Because of the stress concentration, more fatigue damages are expected at the structural joints. Supporting structures of offshore wind turbines have commonly small inherent damping and it is believed that because additional viscous damping can reduce structural vibrations and result in less stress concentration at the joints. In this study, vertically oriented fluid viscous dampers are used to increase fatigue life of a full-height Lattice-type Offshore Wind Turbine (LOWT). Obtained results indicated that the use of fluid viscous dampers significantly delayed fatigue failure and increased fatigue life of structural joints by up to 3 times.

Monitoring-based analysis of wind-induced vibrations of ultra-long stay cables during an exceptional wind event

Ultra-long stay cables characterized as high flexibility are prone to large-amplitude vibrations. Much attention has been paid to the vibrations of stay cables under normal wind conditions in the past decades, while the dynamic response under extreme winds is reported rarely. This study investigates the exceptional wind-induced vibration of the stay cables of a kilometer-level cable-stayed bridge based on the monitoring data. The mean wind velocity and extreme wind duration are firstly obtained using the wind records of the structural health monitoring system (SHMS). The effects of the turbulence intensity and mean wind velocity on the cable vibrations are then analyzed. To explore the motion trajectory features, the in-plane and out-of-plane dynamic displacements are estimated by an acceleration-based approach. Besides, the modal properties, including the frequencies and damping ratios, are identified. The result shows that the stay cables present multi-modal vibrations with frequencies higher than 3 Hz, which is different from rain-wind-induced vibration (RWIV). The out-of-plane vibration amplitude under the extreme wind is much larger than that of the in-plane due to the absence of dampers. Furthermore, the out-of-plane damper is suggested to mitigate the large-amplitude vibration of ultra-long stay cables under exceptional winds.

In-service failure of a support structure for traffic signaling

Traffic signals and their supporting structures are an essential complement in highways and local roadways all around the world. Their accurate operation is today a well-recognized issue by the respective transportation authorities, especially when located on major roadways because of exposure to fatigue cracking by wind-induced large-amplitude vibrations and severe environmental conditions or wind gusts resulting from the passing trucks. The present paper describes the research undertaken to analyze the fatigue failure of a bolted joint in an overhead porticoed structure for traffic signaling located close to a highway entrance to a tunnel. The structure had been in use for more than 25 years and the failure was preventively detected, during a maintenance inspection. The research is a forensic engineering analysis of failure involving optical and scanning electron microscopy observations of the in-service fractured bolts together with the experimental characterization of the fatigue behavior of the bolt steel by means of non-standardized fatigue tests. The failure analysis pointed to the existence of environmentally-induced fatigue initiators as the failure origin, the galvanized condition of the bolts and environment aggressivity gave rise to local dissolution and microcracking of the Zn-coating, damaging and weakening specific zones at the steel interface that acted as fatigue initiators.

How Do Water Filled Traffic Barriers Shake a Suspension Bridge?

The present study stems from the realization that the general problem relating to the analysis of wind-induced vibrations in suspension bridges still requires significant attention. Sidewalk railings, overhaul tracks, and deflectors are known to largely affect such dynamics. Here, the influence of a row of water-filled traffic barriers on the response of a sample suspension bridge is investigated numerically. It is shown that the existence of water barriers causes flow separation and non-negligible vortices with respect to the condition with no water barriers. The vortex shedding frequency at the far end is around 41.30 Hz, relatively close to the real vibration frequency. It is also shown how different incoming angles of attack can change the flow field around the bridge cross-section and the vortex detachment frequency.

Optimization of anti-wind disturbance ability of a long-span cable-driven parallel camera robot based on a Genetic Algorithm

The cable-driven parallel camera robot is a long-span cable-supported high-rise structure, which is easy to produce vibration response due to wind disturbance, which affects its normal work. In this paper, the method of structural optimization is used to improve the first-order natural frequency of the system to keep it away from the energy truncation frequency, so as to reduce the wind-induced vibration response of the system. In order to avoid the defect of premature convergence of standard genetic algorithm, an adaptive multi-island genetic algorithm based on population information entropy is proposed for structure optimization. the simulation results show that the algorithm can more effectively improve the first-order natural frequency of the system and improve the wind disturbance resistance of the system.

Experimental Study of Mitigation of Wind-Induced Vibration in Asymmetric Cable-Stayed Bridge Using Sharp Wind Fairings

This paper investigated the aerodynamic response features of an asymmetric cable-stayed bridge. The wind resistance design parameters for judging the response were first determined, afterwards the bridge dynamic characteristics were analyzed for subsequent aerodynamic analysis. The vortex-induced vibrations (VIV) and flutter response at various wind fairing angles were then examined by using a 1:50 sectional model in the wind tunnel test. Finally, a 1:150 full bridge aeroelastic model was employed to explore the aerodynamic stability and characteristics of the whole asymmetric bridge under different wind attack angles in various flow fields. The results show that the sharp wind fairings could reduce the VIV amplitude of the steel box girder cable-stayed bridge to some extent, and the example bridge has examined to have enough flutter stability through sectional and full bridge aeroelastic model wind tunnel tests. Unlike symmetric bridges, the bridge’s maximum displacement of first torsion mode shape is at the closure rather than the mid-span, which is the essential reason to lead this unique vibration feature. The results from the present study could highlight the important effect of structural asymmetry and fairing shape to the wind-induced bridge vibration and hence may facilitate more appropriate wind design of asymmetric cable-stayed bridges.

Experimental study on the coupling effects of wind-induced vibration of square-sectioned high-rise buildings with different stiffness ratios

In the wind-resistant design of high-rise buildings, the wind-induced response, excited by incident turbulence and vortex shedding of the wake flow, is an important design component. Larger self-excited across-wind responses occur when the wind speed closes to the vortex lock-in wind speed during which the vortex shedding frequency is basically equal to the natural frequency of the structure in the across-wind direction. Because of the similar natural frequency and damping in two sway directions in actual construction applications, the along-wind response will be significantly affected by the across-wind response. This phenomenon is called the coupling effect. In this paper, the coupling effect of wind-induced responses of high-rise buildings with square section is investigated using a stick aeroelastic model in wind tunnel tests. The effects of the sectional stiffnesses ratio on the along-wind and across-wind directions are clarified. Experimental results show that responses are significantly coupled when the wind speed approximates to the ‘lock-in’ region with a stiffness ratio close to 1:1. Compared with the wind-induced response measured in a single-degree-of-freedom system, the across-wind response of a two-degrees-of-freedom model decreases significantly and the along-wind response increases within the lock-in wind speed region. Furthermore, the characteristics of the along-wind response are observed to be shifted from buffeting to vortex-induced vibration with increasing responses and hardening Gaussian probability density function of the response within the lock-in region. The coupling effect can be identified from changes in the magnitude of dynamic response and probability density function of the along-wind response beyond the lock-in region. At a Scruton number of about 10.5, the coupling effect is strong with the stiffness ratios approximate 0.85:1, 1:1, and 1.15:1. However, at a Scruton number of about 20, the coupling effect only emerges when the stiffness ratio approaches 1:1.

Case study of vortex-induced vibration and mitigation mechanism for a long-span suspension bridge

The wind-induced vibration of long-span bridges mainly manifests as flutter, galloping, vortex-induced vibrations (VIVs), buffeting, etc. Among these, VIVs cause vertical or torsional single-mode vibrations of the main girder; these affect the comfort of drivers or pedestrians on the bridge when vortex-induced resonance occurs. In this study, field measurements, numerical simulations, and wind tunnel tests were used to systematically investigate triggering mechanism during the sudden first and secondary VIV phenomena of Humen Bridge, along with the structural mode and damping characteristics and VIV aerodynamic mitigation effects, etc. The results show that the sudden first VIV was caused by the temporary installation of water-filled barriers, as these changed the aerodynamic configuration of the box girder; the decisive removal of these water-filled barriers can effectively suppress the VIV amplitude to some extent. The succedent secondary VIV was caused by the reduction of the structural damping; therefore, aerodynamic control and damping control measures are proposed. The aerodynamic control measures include the implementation of suppressor plates on the top of handrails and removal of the maintenance rails under the girder, whereas the structural damping control measures involve the successive installation of tuned-mass damper (TMD) to compensate for the reduced damping owing to the former large-amplitude VIV performance. After verification based on reduced-scale model wind tunnel tests, the aerodynamic control measures and structural damping control measures are successfully adopted and applied to Humen Bridge. These measures are shown to effectively suppress VIVs, as confirmed via succedent long-term on-the-spot observations.