Study on the fluctuating wind responses of constructing bridge towers with magnetorheological elastomer variable stiffness tuned mass damper

2021 ◽  
pp. 1045389X2110145
Author(s):  
Qingshan Yang ◽  
Yu Yang ◽  
Qi Wang ◽  
Liuliu Peng
Keyword(s):  
Flexible Structures ◽  
Variable Stiffness ◽  
Dynamic Responses ◽  
Superposition Method ◽  
Control Performance ◽  
Magnetorheological Elastomer ◽  
Main Structure ◽  
High Rise ◽  
Tunable Device ◽  
Fluctuating Wind

Constructing bridge towers are high-rise and flexible structures subjected to significant wind induced vibrations. Tuned Mass Dampers (TMDs) have been widely used to reduce dynamic responses of high-rise structures under fluctuating wind loadings. By resonance with main structure, TMD can effectively suppress structural vibrations. However, the natural frequencies of bridge tower usually decrease continuously during its construction progress. The frequency shift characteristic will cause the detune of TMD, leading to a great control efficiency loss. As a novel stiffness tunable device made of magnetorheological elastomer (MRE), MRE-TMD can adjust its natural frequency in real-time to track the main structure, avoid detuning and achieve better control performance. To study the wind induced vibration control performance of MRE-TMD, this paper explores the fluctuating wind responses of constructing bridge towers in along wind and cross wind directions. The fluctuating wind loads are generated by harmonic superposition method with the along wind fluctuating wind speed spectrum and the empirical power spectrum of fluctuating lift force. By comparing among the uncontrolled, TMD controlled and MRE-TMD controlled constructing bridge towers, the simulation results show that the MRE-TMD system can effectively maintain the tuning state, and significantly reduce the wind induced vibrations during whole construction process.

Influences of Wind Barriers on the Train Running Safety on a Highway-Railway One-Story Bridge

2021 ◽  
pp. 2140009
Author(s):  
Ye Liu ◽  
Yan Han ◽  
Peng Hu ◽  
C. S. Cai ◽  
Xuhui He
Keyword(s):  
Dynamic Responses ◽  
Response Analysis ◽  
Train Track ◽  
Wheel Load ◽  
Wind Barrier ◽  
The Mean ◽  
Wind Pressures ◽  
Track Bridge ◽  
Fluctuating Wind ◽  
Bridge System

In this study, the influences of wind barriers on the aerodynamic characteristics of trains (e.g. a CRH2 train) on a highway-railway one-story bridge were investigated by using wind pressure measurement tests, and a reduction factor of overturning moment coefficients was analyzed for trains under wind barriers. Subsequently, based on a joint simulation employing SIMPACK and ANSYS, a wind–train–track–bridge system coupled vibration model was established, and the safety and comfort indexes of trains on the bridge were studied under different wind barrier parameters. The results show that the mean wind pressures and fluctuating wind pressures on the trains’ surface decrease generally if wind barriers are used. As a result, the dynamic responses of the trains also decrease in the whole process of crossing the bridge. Of particular note, the rate of the wheel load reductions and lateral wheel-axle forces can change from unsafe states to relative safe states due to the wind barriers. The influence of the porosity of the wind barriers on the mean wind pressures and fluctuating wind pressures on the windward sides and near the top corner surfaces of the trains are significantly greater than the influence from the height of the wind barriers. Within a certain range, decreasing the wind barrier porosities and increasing the wind barrier heights will significantly reduce the safety and comfort index values of trains on the bridge. It is found that when the porosity of the wind barrier is 40%, the optimal height of the wind barrier is determined as approximately 3.5[Formula: see text]m. At this height, the trains on the bridges are safer and run more smoothly and comfortably. Besides, through the dynamic response analysis of the wind–train–track–bridge system, it is found that the installation of wind barriers in cases with high wind speeds (30[Formula: see text]m/s) may have an adverse effect on the vertical vibration of the train–track–bridge system.

scholarly journals Wind-Induced Vibration Control of High-Rise Structures Using Compound Damping Cables

2021 ◽  
Vol 2021 ◽  
pp. 1-9
Author(s):  
Jianda Yu ◽  
Zhibo Duan ◽  
Xiangqi Zhang ◽  
Jian Peng
Keyword(s):  
Vibration Control ◽  
Damping Ratio ◽  
Viscosity Coefficient ◽  
Structural Vibration ◽  
Vibration Displacement ◽  
High Rise ◽  
Main Cable ◽  
Small Vortex ◽  
Wind Induced Vibration ◽  
Fluctuating Wind

Based on the vibration reduction mechanism of compound damping cables, this study focuses on the wind-induced vibration control of high-rise structures with additional mass at the top. The differential equation of motion of the system under the action of the composite damping cable is established, and the analytical solution of the additional damping ratio of the structure is deduced, which is verified by model tests. The vibration response of the structure under the action of simple harmonic vortex excitation and randomly fluctuating wind loads is studied, and the effect of different viscous coefficients of the dampers in the composite damping cable and different installation heights of the damping cable on the vibration control is analyzed. The results show that a small vortex excitation force will cause large vibrations of low-dampened towering structures, and the structure will undergo buffeting under the action of wind load pulse force. The damping cable can greatly reduce the amplitude of structural vibration. The root means square of structural vibration displacement varies with damping. The viscosity coefficient of the device and the installation height of the main cable of the damping cable are greatly reduced.

Fundamental solution and its validation by numerical inverse Laplace transformation and FEM for a damped Timoshenko beam subjected to impact and moving loads

2018 ◽  
Vol 25 (3) ◽  
pp. 593-611
Author(s):  
Xiayang Zhang ◽  
Haoquan Liang ◽  
Meijuan Zhao
Keyword(s):  
Timoshenko Beam ◽  
Laplace Transformation ◽  
Impact Load ◽  
Moving Load ◽  
Numerical Results ◽  
Dynamic Responses ◽  
Superposition Method ◽  
Load Case ◽  
Inverse Laplace Transformation ◽  
Damping Effect

This paper, taking the clamped boundary condition as an example, develops Su and Ma's fundamental solutions of the dynamic responses of a Timoshenko beam subjected to impact load. Based on that, a further extension regarding the general moving load case is also established. Kelvin–Voigt damping, whether proportionally or nonproportionally damped, is incorporated into the model, making it more comprehensive than the model of Su and Ma. Numerical inverse Laplace transformation is introduced to obtain the time-domain solution, where Durbin's formula and the corresponding convergence criteria are utilized in numerical experiments. Further, the real modal superposition method is applied at an analytical level to validate the numerical results by applying a proportionally damped condition. Total comparisons are made between the methods by sufficient case studies. The dynamic responses with and without damping effect are computed with wider slenderness to verify the correctness and effectiveness of the numerical results. Furthermore, parametric studies regarding the damping coefficients are performed to explore the nonproportional damping effect. The results show that the structural damping has significant influences on the dynamic behaviors and is especially stronger at small slender ratios. As the damping decreases the inherent frequencies and excites the low-frequency modal components more actively, a resonant phenomenon appears in high slenderness case when the beam experiences a low-speed moving load. Additionally, the computations in the moving load case indicate that the algorithm convergence is preferable when the number of grids exceeds 1000.

Study on Variable Stiffness Mechanism Using Magnetorheological Elastomer

Polymer Korea ◽  
2021 ◽  
Vol 45 (6) ◽  
pp. 948-954
Author(s):  
Dahoon Ahn ◽  
Yujeong Shin ◽  
Kyungwho Choi
Keyword(s):  
Variable Stiffness ◽  
Magnetorheological Elastomer

scholarly journals Feasibility Study of Fluctuating Wind Pressure around High-Rise Buildings as a Potential Energy-Harvesting Source

Energies ◽  
2019 ◽  
Vol 12 (21) ◽  
pp. 4032 ◽  
Author(s):  
Park ◽  
Kim ◽  
Jung
Keyword(s):  
Energy Source ◽  
Energy Harvesting ◽  
Wind Turbine ◽  
Wind Pressure ◽  
Experimental Conditions ◽  
Energy Harvesters ◽  
High Rise ◽  
New Locations ◽  
Noise Vibration ◽  
Fluctuating Wind

As the importance of sustainable energy increases, wind power generation systems utilizing wind energy around high-rise buildings are being developed. However, in existing wind turbine systems, it is necessary to solve noise, vibration problems, and structural issues for the installation of large-sized systems. In addition, small wind turbine systems can be installed only in limited areas such as roofs and corners, because their efficiency is limited to high and stable wind speed. For this reason, the distribution of fluctuating wind pressure around high-rise buildings was analyzed, and its feasibility as an energy source was evaluated, reflecting that fluctuating wind pressure can be used in vibration-based energy-harvesters. To achieve this, firstly, experimental conditions and theories were established to check the characteristic of wind pressure around high-rise buildings. The experiment was divided into the environment without surrounding buildings and the urban environment. Next, the pressure distribution around high-rise buildings and the quantitative results obtained from the experiment were determined. Finally, based on the results obtained from the experiments, the feasibility of fluctuating wind pressure as an energy-harvesting source was analyzed. From this study, it was found that fluctuating wind pressure can be used as a new energy source at new locations of high-rise buildings that were not utilized previously.

Resonance Analysis of Cantilever Plates Subjected to Moving Forces by a Semi-Analytical Method

2020 ◽  
Vol 20 (04) ◽  
pp. 2050049
Author(s):  
Qi Li ◽  
Xing Li ◽  
Qi Wu
Keyword(s):  
Analytical Method ◽  
Ritz Method ◽  
High Order Mode ◽  
Dominant Frequency ◽  
High Order ◽  
Dynamic Responses ◽  
Mode Shapes ◽  
Superposition Method ◽  
Cantilever Plate ◽  
Exciting Frequency

Cantilever plate structures are widely used in civil and aerospace engineering. Here, a semi-analytical method is proposed to calculate the dynamic responses of cantilever plates subjected to moving forces. The Rayleigh–Ritz method is used to obtain the semi-analytical modal frequencies and shapes of a thin, isotropic, and rectangular cantilever plate using the assumed mode shapes that fulfill the boundary conditions of the plate. The modal superposition method is used to decouple the motion equations of the cantilever plate to obtain a series of modal equations. Then, the generalized forces are transformed into a Fourier series in terms of discrete harmonic forces. The dynamic responses of the cantilever plate are obtained by superimposing the analytical responses of a number of single-degree-of-freedom modal systems under discrete harmonic forces. The proposed semi-analytical method is verified through comparison with the numerical method. Then, the vibration of the cantilever plate under the action of moving forces is investigated based on the semi-analytical results. It is found that the contribution of the high-order modes to the dynamic responses of the plate cannot be ignored. In addition, the wavelengths of the mode shapes not only affect the magnitude of the modal forces but also the dominant frequency of the modal forces. Resonant responses of the plate are produced by the moving forces when the load interval equals the wavelength of the mode shape of a high-order mode and the exciting frequency of the moving forces equals the natural frequency of this mode.

scholarly journals Magnetorheological Elastomer Precision Platform Control Using OFFO-PID Algorithm

2020 ◽  
Vol 2020 ◽  
pp. 1-9
Author(s):  
Ying-Qing Guo ◽  
Jie Zhang ◽  
Dong-Qing He ◽  
Jin-Bao Li
Keyword(s):  
Real Time ◽  
Fractional Order ◽  
Pid Controller ◽  
Vibration Isolation ◽  
Dynamic Responses ◽  
Magnetorheological Elastomer ◽  
Controlled System ◽  
Pid Algorithm ◽  
Fractional Order Pid ◽  
Fractional Order Pid Controller

The magnetorheological elastomer (MRE) is a kind of smart material, which is often processed as vibration isolation and mitigation devices to realize the vibration control of the controlled system. The key to the effective isolation of vibration and shock absorption is how to accurately and in real time determine the magnitude of the applied magnetic field according to the motion state of the controlled system. In this paper, an optimal fuzzy fractional-order PID (OFFO-PID) algorithm is proposed to realize the vibration isolation and mitigation control of the precision platform with MRE devices. In the algorithm, the particle swarm optimization algorithm is used to optimize initial values of the fractional-order PID controller, and the fuzzy algorithm is used to update parameters of the fractional-order PID controller in real time, and the fractional-order PID controller is used to produce the control currents of the MRE devices. Numerical analysis for a platform with the MRE device is carried out to validate the effectiveness of the algorithm. Results show that the OFFO-PID algorithm can effectively reduce the dynamic responses of the precision platform system. Also, compared with the fuzzy fractional-order PID algorithm and the traditional PID algorithm, the OFFO-PID algorithm is better.

Seismic Protection of Structures Using Tuned Mass Dampers with Resettable Variable Stiffness

2012 ◽  
Vol 83 ◽  
pp. 75-84
Author(s):  
Chi Chang Lin ◽  
Tsu Teh Soong
Keyword(s):  
Active Control ◽  
Control Strategy ◽  
Good Control ◽  
Variable Stiffness ◽  
Seismic Protection ◽  
Control Law ◽  
Control Performance ◽  
Deformation Diagram ◽  
Tuned Mass Dampers ◽  
Engineering Structures

Vibration control of civil engineering structures using tuned mass dampers (TMD) is a widely accepted control strategy after numerous analytical and experimental verifications. Although the design and application of traditional linear TMD systems are well developed, nonlinear TMD systems that may lead to better control performance are still in the developmental stage. There are two main problems associated with TMD systems, i.e. (1) detuning effect and (2) excessive stroke of TMD. In order to improve the performance of TMD systems, a novel semi-active TMD named resettable variable stiffness TMD (RVS-TMD) is proposed in this study. The RVS-TMD consists of a TMD and a resettable variable stiffness device (RVSD). The RVSD is composed of a resettable element and a controllable stiffness element. By varying the stiffness element of the RVSD, the force produced by the RVSD can be controlled smoothly through a semi-active control law. By resetting the resettable element, the hysteresis loop of the RVSD can cover all four quadrants in the force-deformation diagram and thus results in more energy dissipation. The harmonic and seismic responses of a building equipped with the RVS-TMD are investigated numerically and compared with those by its active control counterpart and an optimal passive TMD system. The results show that the proposed RVS-TMD system has good control performances as its active control counterpart and is able to alleviate detuning effect and reduce TMD’s stroke.

Switched Stiffness Vibration Controllers for Fluidic Flexible Matrix Composites

2009 ◽  
Author(s):  
Amir Lotfi-Gaskarimahalle ◽  
Christopher D. Rahn
Keyword(s):  
Equations Of Motion ◽  
Active Vibration Control ◽  
Flexible Structures ◽  
Variable Stiffness ◽  
Flow Coefficient ◽  
Step Response ◽  
Semiactive Control ◽  
Matrix Composites ◽  
Mass System ◽  
3D Elasticity

This paper investigates semi-active vibration control using Fluidic Flexible Matrix Composites (F2MC) as variable stiffness components of flexible structures. The stiffness of F2MC tubes can be dynamically switched from soft to stiff by opening and closing an on/off valve. Fiber reinforcement of the F2MC tube changes the internal volume when externally loaded. With an open valve, the fluid in the tube is free to move in or out of the tube, so the stiffness is low. When the valve is closed, the high bulk modulus fluid resists volume change and produces high stiffness. The equations of motion of an F2MC-mass system is derived using a 3D elasticity model and the energy method. The stability of the unforced dynamic system is proven using a Lyapunov approach. To capture the important system parameters, nondimensional full order and reduced order models are developed. A Zero Vibration (ZV) state switch technique is introduced that suppresses vibration in finite time, and is compared to conventional Skyhook semiactive control. The ITAE performance of the controllers is optimized by adjusting the open valve flow coefficient. Simulation results show that the optimal ZV controller outperforms the optimal Skyhook controller by 13% and 60% for impulse and step response, respectively.

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