No full-text available
To read the full-text of this research,
you can request a copy directly from the authors.
Abstract
Tuned liquid column damper (TLCD) was developed mainly for the purpose of suppressing horizontal motion of structures. No relevant research has been found on the suppression of structural pitching vibration by using TLCD. This paper thus aims to investigate the possibility and effectiveness of applying TLCD to suppress pitching motion of structures. Both theoretical and experimental investigations are carried out. A mathematical model of tuned liquid column damper for suppressing structural pitching vibration is developed. The TLCD-structure interactive equations are derived and solved in both time domain and frequency domain. A series of free and forced vibration experiments with different TLCD configuration and parameters are performed. The influences of variable TLCD parameters on control effectiveness are determined. Numerical simulations corresponding to the experimental cases are carried out and compared with the experiments. A close agreement is obtained between the experimental results and theoretical simulation. This also verifies the developed theoretical model. Both theoretical and experimental studies show that TLCD can efficiently reduce structural pitching motion.
... Many mechanical and civil structures tend to be built slender [1], a problem when subjected to external forces such as strong winds and seismic vibrations [2][3][4]. These forces can cause damage and the structures can be lost. ...
... To help mitigate this problem, vibration control devices have been conceived and developed. For example, we can cite as devices already implemented the tuned mass damper (TMD) [5][6][7], tuned liquid damper (TLD) [8], tuned liquid column damper (TLCD) [1,[9][10][11], and pendulum type liquid column damper (PTLD) [12]. It is believed that the first TLCD was created in 1989 by Sakai et al [9] and it was applied in structures to reduce their motions. ...
... Inserting equation (28) into equation (21), we developed and obtained a system of algebraic equations in sin ( ) and cos ( ) . By separating them, we obtain after algebraic manipulations the following equation: with (31) = 0 cos ( + ) and u = u 0 cos ( + ) Table 1 and 2 give physical properties of the mechanical structure and the TLCD [1], respectively. Figure 4 presents the amplitude of vibration of the system as function of external frequency obtained through analytical and numerical investigations. ...
Purpose and Background
This paper aims to show how we can reduce rotational motions of a rigid mechanical structure subjected to a harmonic excitation using a tuned liquid column damper (TLCD). The studied mechanical structure here is a nonlinear horizontal deck regularly found in on/offshore. In civil and mechanical engineering, structures could be subjected to various types of external excitations leading to undesirable high amplitude of vibration.Methods
This paper presents the modeling of a nonlinear horizontal deck with a TLCD and how it can be arranged to mitigate the vibrations. The Routh–Hurwitz criterion is used to derive the stability condition of the controlled system.ResultsThe stability domain is displayed in the function of coupling parameters between the structure and the TLCD.Conclusion
Some physical parameters of the TLCD such as the head loss coefficient δ, the horizontal length Lh and the crosssection ratio ν are optimized in order to the reduce considerably vibration amplitude of the mechanical structure.
... All these dampers have been found effective in suppressing horizontal motion of buildings and other types of structures. Recently Xue et al. [10] explored, both theoretically and experimentally, the possibility of applying TLCD to reduce the rotational vibration of structures under harmonic excitation. The investigation showed that the rotational vibration could be effectively reduced if the properties of the TLCD are properly selected. ...
... The investigation showed that the rotational vibration could be effectively reduced if the properties of the TLCD are properly selected. In practice, large rotational vibrations may be encountered in many civil engineering structures, such as along the deck of long span bridges due to gusts [10] and tension leg platforms due to ocean waves. Xu and Shum have carried out an experimental investigation under harmonic excitation [11] and a theoretical one under white noise [12] using Multiple Tuned Liquid Column Dampers (MTLCD) to reduce rotational vibration. ...
... The effectiveness of MTLCD under extensive parametric studies proved greater than that of the single Tuned Liquid Column Damper. In the case of the TLCD, the position of the damper relative to the rotational axis of the structure has been proven [10,12] to be an important factor for achieving significant rotational vibration reduction, thus introducing an architectural and practical limitation. ...
Under severe sea and wind conditions. Tension Leg Platforms may experience large response amplitudes that affect their serviceability and structural integrity. The idea of using mass dampers has been introduced for reduction of the effects of these types of dynamic loadings. For achieving larger vibration suppression, appropriate tuning of the parameters of the dampers is necessary. A robust stochastic design approach is presented in this study for this purpose. Stochastic simulation is considered for evaluation of the system's performance in the design stage. This way, nonlinear characteristics of the structural response and excitation are explicitly incorporated into their respective models. Model parameters that have some level of uncertainty are probabilistically described. In this probabilistic setting, the system reliability is adopted as the system design objective. In this framework, the complex relationship between the coupled dynamics of the platform, the stochastic excitation and the vibration of the dampers is fully addressed in the design stage. Copyright © 2008 by The International Society of Offshore and Polar Engineers (ISOPE).
... The force field f acting on the particle and the absolute acceleration a of the liquid particle are also shown in Figure 2. Based on Eq. 2 Sakai et al. [29] derived the equation of motion of passive TLCDs attached to horizontally vibrating high-rise structures. Xue et al. [30] enhanced this equation for pitching structures. Hochrainer et al. [17] derived the equation of motion for TLCGDs attached to horizontally vibrating high-rise structures according to the approach developed by Sakai. ...
... The integral of the pressure gradient along the streamline of the S-TLCD equals to the pressure loss ∆p, which is caused by turbulance and local friction effects in the tank. Analytical methods for the calculation of pressure loss can be found in the literature, such as in Eq. 4 according to [30] ...
This paper presents a new type of semi-active tuned liquid column damper (S-TLCD) for the lateral vibration control of high-rise civil engineering structures. Analogous to the passive tuned liquid column damper (TLCD), the S-TLCD comprises a U-shaped tank consisting of two vertical columns, which are arranged at a distance from each other and communicating through a horizontal passage. The tank is partially filled with a Newtonian fluid until the liquid reaches a certain level in the columns. In contrast to the passive TLCD, the S-TLCD provides also mechanisms for a continuous adaptation of both its natural frequency and damping behaviour in real-time. In the first part of the paper, the governing equations of the S-TLCD are derived based on the Bernoulli equation of a non-stationary incompressible liquid flow. The natural frequency of the S-TLCD is revealed to depend on the scaled length of the liquid. The scaling amount of the liquid length is formulated in dependence of the cross-sectional area ratios of the tank segments. The mathematical description of the S-TLCD is concluded by providing the state-space representation of a multi-degree-of-freedom structure with several S-TLCDs. In the second part of the paper, the derived natural frequency equation is verified and the proof of concept of the S-TLCD is shown by experimental investigations, which are performed on an S-TLCD model utilizing a test structure and shaking table tests.
... The tuned liquid column damper (TLCD) has also been investigated for the purpose of vibration suppression, and its use on the wind turbine structural control has been proven to be effective. [16][17][18][19][20][21][22] Attempting to deploy the damping system close to the platform, Coudurier et al 18 installed the TLCD inside the offshore wind turbine platform to reduce its rotational motions. The pitch motion of the platform can be reduced by up to 25% with the TLCD installed inside the platform. ...
... The pitch motion of the platform can be reduced by up to 25% with the TLCD installed inside the platform. Xue et al 22 demonstrated the importance of parameters tuning of the TLCD on damping pitch motions. However, the aforementioned control schemes have a common disadvantage: a large mass is needed. ...
We propose to mitigate the barge pitch and roll motions of floating hydrostatic wind turbine (HWT) by combining the advantages of the bidirectional tuned liquid column damper (BTLCD) and the tuned mass damper (TMD). This is achieved by enabling the container of the BTLCD to move freely, connecting it to the main structure through springs and dampers, creating what we call a bidirectional tuned liquid column mass damper (BTLCMD). The BTLCMD is made by the hydraulic reservoir of the HWT, saving costs by avoiding the addition of extra mass and fluids. The HWT simulation model is obtained by replacing the geared drivetrain of the NREL 5‐MW barge wind turbine model with a hydrostatic transmission drivetrain. The dynamics of the BTLCMD are then incorporated into the HWT. Two simplified mathematical models, describing the barge pitch and roll motions of the HWT‐BTLCMD coupled system, are used to obtain the optimal parameters of the BTLCMD. Simulation results demonstrate that the BTLCMD is very effective in mitigating the barge pitch motion, barge roll motion, and the tower base load. The BTLCMD also largely outperforms the BTLCD in suppressing barge motions.
... This was proposed by [21] and it consists in suppressing the wind-induced motion by dissipating the energy through the motion of the liquid mass through an orifice in a U-shaped tube [22]. The use of TLCDs in mitigating vibrations within civil engineering structures has also been extensively studied [23]- [25]. Yalla and Kareem [26] presented an approach to compute the optimum head loss coefficient for a given level of wind or seismic excitation in a single step without resorting to iterations. ...
... The lumped mass of each structural level is from 131T (top) to 338.6T (bottom) and the damping ratio is assumed to be 3% in each mode. The natural frequencies are computed to be 0. 23 compared to the uncontrolled case. Figure 3 indicates the profile of the variation in head loss coefficient (ξ(t)) as a function of time. ...
Wind and wave dynamic loads might cause undesirable vibrations that affect the structure in tegrity and system performance of floating offshore wind turbin es. This paper addresses the problem of dynamic load mitigat ion by using semiactive control techniques with the tuned liquid column dampers placed on the turbine's tower. The control law is formulated based on the mixed H2/H ∞ methods for ensuring the system stability and reliability. Furthermore, the proposed controller only uses output feedback so as to avoid the dependence on the knowledge of the states of the sy stem.
... The fluid mass m f = L 0 ρh(x, t) dx is independent of time. This pivoting TLD setup is of interest to engineers, because it is a good mechanism for suppressing torsional vibrations on bridges caused by aerodynamic effects (Xue et al., 2000;Chen et al., 2008), which are a danger to high sided vehicles (Chen and Cai, 2004). ...
... The instability transition is associated with the emergence of homoclinic behaviour in the weakly nonlinear problem. The existence of this instability would have a detrimental effect on mechanical systems which use a rotational tuned liquid damper to stabilise the structure, such as on bridges destabilized by aerodynamic effects (Xue et al., 2000;Chen et al., 2008). For the stable sloshing modes, we were able to show that a 1 : 1 fluid resonance exists in the system, where the symmetric sloshing modes oscillate with the same frequency as the coupled vessel and anti-symmetric sloshing modes, as was the case in the Cooker bi-linear pendulum experiment (Alemi Ardakani et al., 2012a). ...
Suspending a rectangular vessel partially filled with an inviscid fluid from a single rigid pivoting rod produces an interesting physical model for investigating the dynamic coupling between the fluid and vessel motion. The fluid motion is governed by the Euler equations relative to the moving frame of the vessel, and the vessel motion is given by a modified forced pendulum equation. The fully nonlinear, two-dimensional, equations of motion are derived and linearised for small-amplitude vessel and free-surface motions, and the natural frequencies of the system analysed. It is found that the linear problem exhibits an unstable solution if the rod length is shorter than a critical length which depends on the length of the vessel, the fluid height and the ratio of the fluid and vessel masses. In addition, we identify the existence of 1:1 resonances in the system where the symmetric sloshing modes oscillate with the same frequency as the coupled fluid/vessel motion. The implications of instability and resonance on the nonlinear problem are also briefly discussed.
... This was proposed by [21] and it consists in suppressing the wind-induced motion by dissipating the energy through the motion of the liquid mass through an orifice in a U-shaped tube [22]. The use of TLCDs in mitigating vibrations within civil engineering structures has also been extensively studied [23]- [25]. Yalla and Kareem [26] presented an approach to compute the optimum head loss coefficient for a given level of wind or seismic excitation in a single step without resorting to iterations. ...
... The lumped mass of each structural level is from 131T (top) to 338.6T (bottom) and the damping ratio is assumed to be 3% in each mode. The natural frequencies are computed to be 0. 23 Figure 3 indicates the profile of the variation in head loss coefficient (ξ(t)) as a function of time. Finally, the static H ∞ control signal is plotted in Figure 4. ...
Offshore wind energy is one of the fastest growing powers in the field of renewable energy. An offshore wind farm situated sufficiently far away from the coast can generate more wind power and will have a longer operation life since the winds are stronger and more consistent than those on or near the coast. It can also avoid some major problems of the traditional wind farms like the visual and noise impacts and potential damage to wildlife. From the technical point of view, it is difficult to anchor the wind turbines directly on the seabed in deep water. Thus, new constructive solutions based on floating support substructures are proposed. One of the main challenges is to reduce the fatigues of a floating offshore wind turbine so as to guarantee its proper functioning under the constraints imposed by the floating support substructures subject to a greater range of motion than that of the conventional fixed ones. This paper addresses the problem of designing semiactive controllers to mitigate the dynamic wind and wave loads on floating offshore wind turbines, which might cause undesirable vibrations that affect the structure integrity and system performance. The output feedback control strategy is proposed to avoid the dependence on the knowledge of the states of the system. The H ∞ output feedback control technique is used for formulating the semiactive control law, which will be implemented using a TLCD. Numerical simulation is done to verify the obtained results.
... There are basically four fundamental mechanisms of vibration control [2,4,6,8,18,22,24], which are: control of the natural frequencies in order to avoid resonance under external imposed loads, introduction of damping or any energy spendthrift mechanism, use of insulating elements in supports and/or bases that reduce force transmission, and the incorporation of dynamic vibration absorbers or vibration neutralizers. ...
... Through the years, different types of absorbers have been created. Some of them use viscous damping generated by fluids motion [10,24], meanwhile others act mechanically using a mass-spring damper system [22]. There are also some absorbers designed to operate based on the movement of a pendulum attached to the structure [2]. ...
In this paper we present an experimental study of a three dimensional physical model of a three-floor structure subjected to forced vibrations by imposing displacements in its support. The aim of this work is to analyze the behavior of the building when a dynamic vibration absorber (DVA) is acting. An analytic simplified analysis and a numerical study are developed to obtain the natural frequencies of the structure. Experiments are carried out in a vibrating table. The frequency range to be experimentally analyzed is determined by the first natural frequency of the structure for which the DVA damping effects are verified. The equipment capabilities, i.e. the frequencies, amplitudes and admissible load, limit the analyses. Nevertheless, satisfactory results are obtained for the study of the first mode of vibration. The effect of different amplitudes of the imposed support motion is also analyzed. In addition, the damping effect of the DVA device is evaluated upon varying its mass and its location in the structure. The characteristic curves in the frequency domain are obtained computing the Fast Fourier Transformation (FFT) of the acceleration history registered with piezoelectric accelerometers at different checkpoints for the cases analyzed.
... Tuned liquid dampers (Xue, Ko & Xu 2000;Frandsen 2005;Love & Tait 2014;Novo et al. 2014), storage containers (Shrimali & Jangid 2003;Lyu et al. 2020), elevated tower tanks (Gavrilyuk et al. 2013), ship tanks (Chen & Chiang 2000;Turner, Bridges & Ardakani 2015;Huang et al. 2018) and the offshore Draugen monotower can be classified as the Sretenski-Moiseev-type coupled mechanical system whose eigenfrequencies differ from the natural sloshing frequencies in its containers. Bearing in mind the importance of the resonant sloshing response in closed fish tanks (Tan, Shao & Read 2019) as well as remembering this difference, we consequently constructed nonlinear analytical sloshing theories for a two-dimensional rectangular tank whose lateral motions are affected by the sloshing-related hydrodynamic force. ...
... To further explore the suppressing mechanism of TLD for coupled TLD-SSP system with external excitations, several experimental and numerical investigations have been carried out [21][22][23]. In addition, a realtime hybrid testing method has been developed to evaluate the acceleration of the model under dynamically excited motions [24]. ...
A liquid storage container installed on the top of a fixed offshore platform is used as a tuned liquid damper (TLD) to suppress structural vibration through sloshing motion and viscous energy dissipation. To further optimize TLD capability on suppressing vibration and accurately predict nonlinear coupled processes between TLD and offshore platform, a two-way coupling numerical model was developed to investigate the nonlinear vibration of TLD and elastic supporting structural platform (SSP). Meanwhile, laboratory experiments of TLD interaction with the SSP were also conducted on a six-degree-of-freedom motion simulator to validate the developed model. The bottom plate of the SSP was fixed to the motion simulator and subjected to sinusoidal excitation in the horizontal direction. The natural frequency of bare SSP was obtained firstly by shaking table tests at a wide range of external excitation frequencies and finite element modal analysis. The developed numerical model was validated by using the present experimental data in terms of both the roof plate displacements of the SSP and the free surface elevation and waveforms in TLD. Effects of TLD in suppressing the nonlinear vibration of the elastic SSP were further investigated numerically by varying the mass and frequency ratio of TLD to the SSP. Wavelet transform was used to analyze the nonlinear interaction and energy distribution characteristics of the sloshing wave in TLD. It was shown that the peak displacement response of the roof plate had been significantly reduced, and at the same time a frequency shift occurred after TLD installed on the SSP. In addition, the sudden excitation breaks the balance of energy absorption and production in fluids, resulting in larger wave height. Finally, a mass ratio of 2% and a frequency ratio of 1 were found to be optimal by considering the frequency shift and energy dissipation.
... As described in Reiterer and Ziegler, 31 from Equation 29 by substituting the time harmonic function u = U 0 cos D t, the equivalent viscous damping ratio D D is determined proportional to the vibration amplitude U 0 as shown in Equation 30. ...
This paper presents a new type of semi‐active tuned liquid column damper (S‐TLCD) for the lateral vibration control of high‐rise civil engineering structures. Analogous to the passive tuned liquid column damper (TLCD), the S‐TLCD comprises a U‐shaped tank consisting of two vertical columns, which are arranged at a distance from each other and communicating through a horizontal passage. The tank is partially filled with a Newtonian fluid until the liquid reaches a certain level in the columns. In contrast to the passive TLCD, the S‐TLCD provides also mechanisms for a continuous adaptation of both its natural frequency and damping behaviour in real time. In the first part of the paper, the governing equations of the S‐TLCD are derived on the basis of the Bernoulli equation of a nonstationary incompressible liquid flow. The natural frequency of the S‐TLCD is revealed to depend on the scaled length of the liquid. The scaling amount of the liquid length is formulated in dependence of the cross‐sectional area ratios of the tank segments. The mathematical description of the S‐TLCD is concluded by providing the state‐space representation of a multi‐degree‐of‐freedom structure with several S‐TLCDs. In the second part of the paper, the derived natural frequency equation is verified, and the proof of concept of the S‐TLCD is shown by experimental investigations, which are performed on an S‐TLCD model utilizing a test structure and shaking table tests.
... There are basically four fundamental mechanisms of vibration control [1][2][3][4][5][6][7], which are: control of the natural frequencies in order to avoid resonance under external imposed loads, introduction of damping or any energy spendthrift mechanism, use of insulating elements in supports and/or bases that reduce force transmission, and the incorporation of dynamic vibration absorbers or vibration neutralizers. Several dynamic absorbers have been designed; some of them are based on the impact of a mass on the structure (IVA) [8], while others are used in aeronautical applications to minimize vibration and noise levels in the piloting cabin [9]. ...
Three floors building model made from carbon steel was tested in the current work to show its vibrational behavior under transient excitation. The main contribution of the current work is to show the effect on adding vibrational damper in first floor with numerous orientations on the vibrational modes, then studying the effect of adding second set of dampers on the second floor. Numerical and experimental analyses were carried out on the tested model for both modal and transientanalysis. Results show that the adding of vibrational damper will boost the ability of the tested structure to withstand against all modes of vibrations for all selected damper's orientation. Best enhancement in the vibrational modes of the tested structure was satisfied with adding double vibrational damper the orientation of 45åt first and second floor respectively. Index Term-Vibrational behavior; finite element analysis, three floors structures.
... Also, the performance of MCLD in reducing buffeting responses of the bridge is greatly affected by the aeroelastic effects due to the interaction between turbulent wind and bridge motion. Xue et al. (2000a) studied the applicability of TLCD in reducing pitching motion of the structures, which they further extended to determine the optimum TLCD parameters for the purpose of controlling pitching motion (Xue et al., 2000b). Wu et al. (2008) extended the above study for investigating wind-induced interaction between TLCD and a bridge deck in pitching motion. ...
Increasing Space problems in urban areas are resulting construction of tall structures, which are often made relatively light and comparatively flexible, possessing quite low damping, thus making the structure more vibration prone. Several techniques are available today to minimize the vibration of structure. Use of liquid dampers is one among them. This paper presents a state-of-the-art review of recent developments occurring in the application of tuned liquid damper technology. In addition, discussions on application of this technique in few full scale structures are also presented.
... Under other circumstances, optimal TLCDs were designed to suppress structural translational motions through numerical optimisation approaches [23,22]. For structures in rotational motions, Xue et al. [24] validated that the TLCD could effectively damp structural pitch motions. Wu et al. [25] modelled the interaction between the TLCD and the primary structure in pitch motions more accurately, by employing the Lagrange's equation approach. ...
We propose to make use of the hydraulic reservoir of a floating barge hydrostatic wind turbine (HWT) to suppress the pitch and roll motions of the barge by making the reservoir into a shape of an annular rectangular to serve as a bidirectional tuned liquid column damper (BTLCD). This means that we have made a barge‐motion damper with negligible extra costs as an HWT needs a reservoir for fluid storage anyway. The barge HWT simulation model is transformed from the NREL (National Renewable Energy Laboratory) 5‐MW geared equipped ITI Energy barge wind turbine model within the FAST (fatigue, aerodynamics, structures, and turbulence) code by replacing its drivetrain with a hydrostatic transmission drivetrain and incorporating the coupled dynamics of the barge‐reservoir system. We use 2 simplified turbine‐reservoir models to optimize the parameters of the BTLCD reservoir, which describe the pitch and roll motions of the turbine‐reservoir system, respectively. Simulation results based on the transformed NREL 5‐MW barge HWT model show that the optimal BTLCD reservoir is very effective in mitigating pitch and roll motions of the barge under realistic wind and wave excitations, which reduces the tower load and improves the power quality.
... Tuned liquid column damper (TLCD) was connected for the most part to tall structures or lean structures to lessen horizontal movement. Tuned fluid segment damper is such a sort of vibration control gadget which depends on the movement of a fluid mass in a tube-like holder to check the outside energy while a hole in it incites damping compels that disseminates energy [4]. For more application Magnetorheological damper was important to make a scientific model of the damper. ...
The liquid flow through orifices produces larger damping, whereas the cushioning effect comes from the fluid’s compressibility. The hydraulic damper design is subjected to constant high pressure necessary to achieve the required forces, which drastically increases during the dynamic operation. Damper has different orifices or piston valves that lead to different flow losses. The main objective behind this work is to investigate the effect of number of orifices on the damping force at different velocities for rear side two-wheeler automobile mono tube damper. Three different orifice opening cases are considered for simulations and experiments such as two-orifice opening, six-orifice opening and ten-orifice opening.
... This study concluded that increasing the ratio between the vertical and horizontal cross-sectional areas can shorten the horizontal length of TLCD, which made the TLCD be more suitable for practical application. Xue et al. [2000] proved through theoretical and numerical studies that TLCD could efficiently suppress the pitching motion of structures. Colwell et al. [2008] investigated the effectiveness of TLCD given different types of liquid (water, glycol, and a magnetorheological (MR) fluid). ...
This article presents real-time hybrid simulation (RTHS) in a single-degree-of-freedom (SDOF) steel frame incorporated with tuned liquid column damper (TLCD). The SDOF steel frame is numerically simulated, and the TLCD alone is physically experimented on a shaking table. The delay-dependent stability of RTHS system for TLCD investigation is first assessed; and the delay-dependent accuracy is verified by comparing the responses obtained through the RTHS, the conventional shaking table test and an analytical solution. Then, RTHSs are carried out to evaluate the effects of mass ratio, structural damping ratio, structural stiffness and peak ground acceleration on the reduction effectiveness of STLCD. The nonlinear behavior of the STLCD is experimentally captured. Finally, the structural responses under STLCD and multiple TLCDs (MTLCD) control are compared. It is found that the performance of STLCD strongly depends on structural parameters and properties of earthquakes; both MTLCD and STLCD induce approximately the same response reductions, and the former can enhance the control performance in certain cases. These results presented here may contribute to improve the design and application of TLCDs in practical engineering.
... In the passive mode, a sealed piping system with gas pressure in the equilibrium state properly adjusted extends the frequency range of application of TLCD up to about five Hertz. Xue et al. [10], Shum and Xu [11] and [12], considered torsional motions and validated their simulations experimentally. Reiterer [13] developed the detailed model of TLCD interacting with the bridge in coupled oblique bending-torsional vibration paralleled by laboratory testing, see also [14]. ...
Sealed tuned liquid column dampers, with a gas-spring effect taken into account are ideally suited to increase the effective structural damping of bridges vibrating in the low frequency band up to about five Hertz. Modal tuning in analogy to the classical mechanical damper followed by fine-tuning in state space, render the parameter optimal and the control more robust. They are ideally suited to counteract the horizontal component of vibrations. A novel design counteracts even predominant vertical vibrations. Long span bridges under wind-, traffic- and/or pedestrian excitations are effectively damped. Application in the critical phase of the cantilever method of construction during bridge-erection is emphasized. In seismic areas, TLCD are ideally suited to counteract the tip motions of high columns supporting bridges. Computer simulations of several built bridges convincingly approve the increase of the effective structural damping above the required "cut-off value. The experimentally proven presence of an averaged turbulent damping of the fluid flow stabilizes the system in extreme situations. The gas-spring effect in sealed TLCD provides another mildly overlinear restoring force in case of overload. Applications in retrofit or integrated in new designs are proposed, with easy in-situ fine tuning of frequency.
... The pendulum-slosh problem is more difficult, due to the rotary motion of the vessel, than coupling with horizontal motion, such as tuned liquid damping (TLD) systems (e.g. Frandsen (2005); Xue et al. (2000); Idir et al. (2009); Gardarsson et al. (2001); Alemi Ardakani and Bridges (2010)). The motion of a fluid in a stationary or forced vessel, whether studied experimentally, theoretically or numerically, is already very complicated. ...
Suspending a rectangular vessel which is partially filled with fluid from a single rigid pivoting pole produces an interesting theoretical model with which to investigate the dynamic coupling between fluid motion and vessel rotation. The exact equations for this coupled system are derived with the fluid motion governed by the Euler equations relative to the moving frame of the vessel, and the vessel motion governed by a modified forced pendulum equation. The nonlinear equations of motion for the fluid are solved numerically via a time-dependent conformal mapping, which maps the physical domain to a rectangle in the computational domain with a time dependent conformal modulus. The numerical scheme expresses the implicit free-surface boundary conditions as two explicit partial differential equations which are then solved via a pseudo-spectral method in space. The coupled system is integrated in time with a fourth-order Runge-Kutta method. The starting point for the simulations is the linear neutral stability contour discovered by Turner et al. (2015, Journal of Fluid & Structures 52, 166-180). Near the contour the nonlinear results confirm the instability boundary, and far from the neutral curve (parameterized by longer pole lengths) nonlinearity is found to significantly alter the vessel response. Results are also presented for an initial condition given by a superposition of two sloshing modes with approximately the same frequency from the linear characteristic equation. In this case the fluid initial conditions generate large nonlinear vessel motions, which may have implications for systems designed to oscillate in a confined space or on the slosh-induced-rolling of a ship.
... The equation of motion for a typical TLCD system can be presented (Sakai et al. 1989, Lee andJuang 2012) as 1 2 2 ALy A y y Agy ABx . Now by installing the TLCD system on a primary structure of SDOF subjected to ground vibration u , the equation of motion can be modeled into a two degree of freedom system (Xue et al. 2000) ...
MR-TLCD (Magneto-Rheological Tuned Liquid Column Damper) is a new developed vibration control device, which combines the traditional passive control property with active controllability advantage. Based on traditional TLCD governing equation, this study further considers MR-fluid viscosity in the equation and by transforming the non-linear damping term into an equivalent linear damping, a solution can be obtained. In order to find a countable set of parameters for the design of the MR-TLCD system and also to realize its applicability to structures, a series of experimental test were designed and carried out. The testing programs include the basic material properties of the MR-fluid, the damping ratio of a MR-TLCD and the dynamic responses for a frame structure equipped with the MR-TLCD system subjected to strong ground excitations. In both the analytical and experimental results of this study, it is found that the accurately tuned MR-TLCD system could effectively reduce the dynamic response of a structural system.
... Yallah and Kareem [9] studied determination of the optimum parameters of T LCD under wind and earthquake loads and suggested a method for head loss coefficient calculations. Xue et al. [10] examined the capability of T LCD in suppressing pitching motion of structures where through theoretical and experimental simulations they found that T LCD can efficiently reduce structural pitching motion. Also different researches such as using T LCD for seismic vibration control of short period structures [11], dynamics of vibrating systems with tuned liquid column dampers and limited power supply [12], optimum design of T LCDs under stochastic earthquake load considering uncertain bounded system parameters [13] and modified tuned liquid column damper [14] have previously been carried out on T LCDs. ...
This paper proposes a systematic optimization method to design optimal multiple tuned liquid column dampers (MT LCDs) for improving the seismic behavior of structures. A constrained optimization problem is formulated and solved using Genetic algorithm (GA) to generate the optimum parameters of T LCDs that minimizes an objective function defined in terms of minimization of either (a) the maximum displacement or (b) the maximum acceleration of the structure. To illustrate the design procedure, a ten-storey shear frame subjected to a filtered white noise excitation has been considered and for different values of MT LCD mass ratios and T LCD numbers, optimal MT LCDs have been designed for both objective functions and tested under real earthquakes. The results of numerical simulations show the simplicity and effectiveness of the method. Also it has been found that the performance of MT LCDs has been affected by its mass ratio and earthquake characteristics while in this case study, increasing the number of T LCDs has had no significant effect on its performance. Finally, comparison has been made between the performance of MT LCDs and multiple tuned mass dampers (MTMDs), which show no significant difference in performance of these control systems in most of the simulated cases especially under the design record
... In considering the 2 dimensional, 3 degree of freedom motion (surge as X, heave as Y and pitch as θ and the corresponding velocity and acceleration), the equations of motion modified from previous studies (Xue et al. 2000, Lee et al. 2006) by incorporating with Eq. (5) for the UWTLCD device in a TLP system equipped with two sets of UWTLCD devices are presented as (7) (8) ...
In this research, a typical tension-leg type of floating platform incorporated with an innovative concept of underwater tuned liquid column damper system (UWTLCD) is studied. The purpose of this study is to improve the structural safety by means of mitigating the wave induced vibrations and stresses on the offshore floating Tension Leg Platform (TLP) system. Based on some encouraging results from a previous study, where a Tuned Liquid Column Damper (TLCD) system was employed in a floating platform system to reduce the vibration of the main structure, in this study, the traditional TLCD system was modified and tested. Firstly, the orifice-tube was replaced with a smaller horizontal tube and secondly, the TLCD system was combined into the pontoon system under the platform. The modification creates a multipurpose pontoon system associated with vibration mitigation function. On the other hand, the UWTLCD that is installed underwater instead would not occupy any additional space on the platform and yet provide buoyancy to the system. Experimental tests were performed for the mitigation effect and parameters besides the wave conditions, such as pontoon draught and liquid-length in the TLCD were taken into account in the test. It is found that the accurately tuned UWTLCD system could effectively reduce the dynamic response of the offshore platform system in terms of both the vibration amplitude and tensile forces measured in the mooring tethers.
... In the past two Corresponding author, Assistant Professor, E-mail: gisella.tomasini@polimi.it decades, other interesting research has also been conducted on the performance or application of single and multiple TLCDs (Sadek et al. 1998, Gao et al. 1999, Hitchcock et al. 1997, Balendra et al. 1995, Sun 1994, Xue et al. 2000. Some research focused mainly on the definition of optimal design parameters (Yalla et al. 2000) under external forcing, the most common of which is the stochastic one (Won et al. 1996). ...
One of the most common solutions adopted to reduce vibrations of skyscrapers due to wind or earthquake action is to add external damping devices to these structures, such as a TMD (Tuned Mass Damper) or TLCD (Tuned Liquid Column Damper). It is well known that a TLCD device introduces on the structure a nonlinear damping force whose effect decreases when the amplitude of its motion increases. The main objective of this paper is to describe a Hardware-in-the-Loop test able to validate the effectiveness of the TLCD by simulating the real behavior of a tower subjected to the combined action of wind and a TLCD, considering also the nonlinear effects associated with the damping device behavior. Within this test procedure a scaled TLCD physical model represents the hardware component while the building dynamics are reproduced using a numerical model based on a modal approach. Thanks to the Politecnico di Milano wind tunnel, wind forces acting on the building were calculated from the pressure distributions measured on a scale model. In addition, in the first part of the paper, a new method for evaluating the dissipating characteristics of a TLCD based on an energy approach is presented. This new methodology allows direct linking of the TLCD to be directly linked to the increased damping acting on the structure, facilitating the preliminary design of these devices.
... Xue et al. [15] have presented an experimental study on the application of TLCDs for the reduction of the pitching motion of the structures and have carried out some tests in order to outline the influence of the different parameters of the damper on the performance of the TLCD. ...
Very recently the tuned liquid column damper (TLCD) is receiving an increasing interest from researchers concerned with vibration control, to be considered an alternative device with respect to the tuned mass damper (TMD), since the former has low cost, easy adjustment, flexible installation. However, in recent studies the authors [1] have pointed out that for TMD the analytical formulation provides results that
are in good agreement with the experimental ones, while for TLCD it has been deducted that the analytical formulation needs further investigation. In fact using the classical formulation of the problem, numerical results are very different from the experimental results obtained by the authors using the facilities at the
experimental dynamic laboratory of University of Palermo. In particular it has been shown that the total liquid length should be corrected in an effective one, but in a different way from what has been done in literature, where only the variation of section of the vessel has been taken into account. On the other hand, from experimental investigations it is seen that the liquid moves more in the central area of the tube and less in the area in contact with the side walls. This aspect plays a fundamental role for capturing the real performance of TLCD. In fact, being the TLCD a special type of auxiliary damping device which relies on the inertia of liquid column in a U-tube to counteract the forces acting on the structure, then it is necessary to identify the effective moving liquid mass. To aim at this, in this paper the authors differentiate the total liquid
mass into a liquid dead mass and a liquid dynamic mass, then introducing these values into a properly modified mathematical formulation numerical results match the experimental ones for all tests.
... The TLCD has also been studied for suppressing a structure in pitching motion, and optimal parameters for such a design are presented by Xue et al. [15] and Taflanidis et al. [16]. ...
Tuned liquid column dampers (TLCDs) or tuned mass dampers (TMDs) are attached to structures to suppress their vibrations, which are normally excited by dynamic environmental loadings. In this paper, a study is reported on a passive hybrid type damper derived from the configurations of a pendulum type TMD and a TLCD, which can be attached to a primary structure as a compound pendulum (herein called a PLCD). One main advantage of such a system is that the source of damping is the liquid damping at an orifice as in a typical TLCD. As this concept increases complexity in the analysis by introducing an extra degree of freedom, the focus in this paper is kept limited to formulate a mathematical model for a two-dimensional case and to prove its validity through an experimental study; furthermore, the basic characteristics of the system are identified for the benefit of its design. All mathematical models presented here are derived from the energy expression by using the Lagrange’s equation. A cantilever beam orientated vertically and attached with a mass at the free end, which can vibrate in a two-dimensional plane, is fabricated as a primary structure. Initially, the primary structure fitted with a general compound pendulum type mass damper is numerically studied to approximately optimize the mass of the PLCD. Following that, a model of the PLCD is fabricated to carry out the experimental study. Finally, the theoretical and the experimental results for the combined structure-damper system are compared; this validates the mathematical model used here and demonstrates that implementation of such a concept is possible.
... The resulting TLD-structure model had to be numerically analyzed using the Runge-Kutta-Gill method due to its nonlinearity. Xue et al. (2000) also studied the effectiveness of TLCD on controlling the pitching motion of the bridge based on linear shallow water theory. Both TLD and TLCD were numerically and experimentally proven effective in suppressing pitching motion of the structure. ...
Smooth and safe traffic on the highway system is crucial for a modern society. As the backbone of a highway system, key long-span suspension bridges as well as moving high-sided vehicles on the bridges are vulnerable to strong wind. Excessive vibration of bridges and vehicles may cause the bridge aerodynamic instability and vehicle accidents. When wind is strong, the excessive torsional response of the bridge also contributes to the discomfort of drivers or the occurrence of overturning accidents of vehicles moving on it. Potentials of adopting the tuned-liquid-damper (TLD) system as an enhancement measure for the stability of suspension bridges with high-sided vehicles are evaluated. Firstly, a general shallow water sloshing model in rectangular containers under off-axle rotation, lateral and vertical excitations is developed. The analytical platform of the general 3-D bridge—vehicle—TLD system under wind and road roughness excitations is introduced. Secondly, a parametric study of the off-axle TLDs in controlling torsional motion of a simple single torsional mode bridge model under broadband white noise excitation is conducted to investigate the effectiveness and mechanism of the TLD on torsional motion. Finally, a numerical analysis of TLDs installed on a real suspension bridge—vehicle—wind system in time history is carried out considering interactions between the multimode bridge structure, multiple vehicles and the wind excitation. The results suggest that the off-axle TLD system can effectively suppress the torsional response of the suspension bridge through acting as a pendulum damper in addition to a typical sloshing damper, but has little direct suppression effect on the vibrations of vehicles.
Tuned mass dampers (TMDs) to improve long-span bridges' critical flutter wind speed have been widely investigated. However, the optimization of the parameters of TMDs to increase the aerodynamic stability of the long-span bridge girders in the most efficient way has not been properly considered. The present study shows a novel approach in optimizing the parameters of TMDs installed in the sectional model of the long-span bridge to maximize the critical flutter wind speed of the system based on a multi-objective optimization method. The objective functions, maximizing critical flutter wind speed and minimizing TMDs’ mass, are included simultaneously. The configuration parameters of TMDs are considered as design variables. Balancing composite motion optimization (BCMO), a recently published meta-heuristic optimization algorithm, is utilized as the optimization tool in this research. The present study can be considered as the primary research in multi-objective optimization of the bridge-TMDs systems. The simulation results indicate that when installing optimized TMDs, the critical flutter wind speed of the system is significantly increased. The proposed approach can be extended to design long-span bridges optimally with other devices.
Passive control systems are practical systems that use the system's energy to absorb its energy to control the dynamic effects on the structure. In the control of these systems, which store energy with the help of a spring and mass, the effect of mass and spring is great. Based on this logic, different types of passive control systems are derived according to the type of material used. Tuned mass dampers (TMD) and tuned liquid dampers (TLD) in the passive control group are often used to solve various engineering problems. In these two systems, which have the same properties, a solid mass is usually chosen for TMD, while this mass is liquid for TLDs. In this study, passive control systems, which have important effects on building control, are explained in general terms, the historical development of TMDs and TLDs from the early times when the concept of structural control emerged until today, and the studies that have been done are included.
Toroidal tuned liquid column dampers (TLCDs) are recently designed devices that extend the application of TLCDs to multidirectional vibration control. Toroidal TLCDs are promising in suppressing the horizontal vibration response of structures. This study further explores the potential and optimization scheme of toroidal TLCDs for multidirectional pitching vibration mitigation. Firstly, equations of motion for a toroidal TLCD-structure system in pitching motion are presented. A non-iterative analytical closed-form solution for calculating the dynamic response of the system under harmonic loading is developed. Subsequently, optimized frequency tuning ratio and flow resistance coefficient can be obtained. The optimization results theoretically confirm the direction-independent control performance of toroidal TLCDs. A design example of toroidal TLCDs is presented in detail as a reference. Finally, a pendulum rotational structure for TLCDs testing in pitching motion is constructed. The multidirectionality, effectiveness and robustness of toroidal TLCDs in mitigating pitching vibration are verified by free vibration tests.
Vibrations jeopardize both the integrity and the serviceability of structures and can be induced by natural events, such as wind and earthquake, and anthropogenic activities, such as traffic. Particularly modern structures built by lightweight materials and with slender architecture exhibit low damping and respond highly sensitive to vibrations. Traditional structural design has relied so far on the strength and ductility of structures. However, this approach seems to reach its limits and can not provide sufficient protection to prevent vibrations and their aftereffects. Developments of the modern era both in economics and architectural design as well as rapidly changing environmental conditions require a more efficient approach. Based on recent progresses in computer science and cybernetics, modern structural control is initiating an increasing number of alternative methods, such as active and semi-active damping systems, which enable a new level of safety for vibration prone engineering structures. This book provides the necessary theoretical background and a comprehensive overview of conventional vibration control methods followed by detailed insights into some of the newest developments.
The first part of the book covers the theoretical background, which is required for the implementation of general structural control methods in the context of structural engineering. In Chapter 1, the most important aspects of structural dynamics are summarized. Governing mathematical context is presented with examples. The analytical solutions are provided as MATLAB codes. In Chapter 2, a historical development of structural control is introduced together with a general definition and classification of the so far applied devices, materials and strategies. In Chapter 3, the most important principles of structural control are highlighted including state-space representation of systems with a general overview of structural control algorithms. For the application of state-space representation, examples are provided.
The second part of the book presents numerous examples for conventional vibration damping systems, which are grouped as dissipators and tuned mass dampers. In Chapter 4, examples of dissipators, metallic, friction, viscoelastic and viscous fluid dampers are introduced. In Chapter 5, examples of tuned mass dampers, classical tuned mass dampers, pendulum tuned mass dampers, tuned liquid dampers and tuned liquid column dampers are introduced. In both chapters, the mathematical background is described and design examples are provided.
The third part of the book is concerned with some advanced newly developed damping systems. In this regard, in Chapter 6, active and semi-active damping systems are described and application examples are given. Chapter 7 presents two semi-active tuned liquid column dampers. Mathematical modeling approaches are proposed and validated by experiments. Numerical studies are conducted to explore the control capability. Chapter 8 treats shape memory alloy based damping systems and focuses on challenges regarding the constitutive modeling of their dynamic behavior. Experimental and numerical studies are conducted including real-time hybrid simulation. The final Chapter 9 connects the control approaches with monitoring by providing a Kalman filter based system identification algorithm, which detects structural parameters via sensors for the applied damping systems.
Tuned liquid control dampers (TLCDs) was proposed the first by Sakai in 1989 and was used mainly for tall bulding or flexible structures to reduce horizontal movement. Tuned liquid control dampers is a device to control vibration base on movement of a liquid block in a water container against external actions to make dissipate energy. TLCDs has advantage in comparison with the other damper devices, for example as adjusting frequency easily, handling easily, low cost, customising shape and producting easily in accord with different structures, … For this reason, it is an apropriate device to control vibration of large structures. Almost literatures about TLCDs emphasize effective research of TLCDs device on different applications. Several literatures have been discussed about determining optimal parameters as optimal frequency adjust ratio and optimal coefficient of headloss of the orifice. In this article, i only research mainly about effectiveness of TLCDs for vibration reduction for cable-stayed bridge tower through determining effective displacement ratio of bridge tower when install TLCDs and do not install TLCDs.
The effectiveness of the Tuned Liquid Column Damper (TLCD) has been established in controlling the vibration of structures from wind or earthquakes. The present study demonstrates the effectiveness of the Circular Liquid Column Ball Damper (CLCBD), in conjunction with the Tuned Liquid Column Ball Damper (TLCBD) in controlling torsionally coupled vibration of building subjected to wind excitations. Unlike TLCDs, these devices are equipped with moving orifice, implemented via steel balls, placed at the middle of the liquid tube. The set of equations of motion of the combined structure–damper system are derived using the Lagrange’s approach. The optimal performance is ensured through selection of optimal parameters by minimization the stochastic responses, obtained from random vibration analysis. This is in order to adequately take care of the stochastic excitations. The optimal performances are further verified in respect to the time history responses under simulated wind excitations. Parametric studies are conducted to assess the performance robustness. The proposed TLCBD–CLCBD system offers enhanced control efficiency and significant reduction of the displacement of liquid column than the TLCD. Experimental investigation using Shake table test facility also corroborate with the findings from the analysis.
Die vorliegende Dissertation behandelt die Schwingungsdämpfung von Baukonstruktionen, insbesondere von Brücken, durch den Einsatz von optimal abgestimmten Flüssigkeitstilgern. Diese bestehen aus einem teilweise mit Flüssigkeit gefüllten U-förmigen Rohrsystem. Die zufolge einer äußeren Anregung induzierten Strukturschwingungen rufen eine phasenverschobene Bewegung der Flüssigkeitssäule hervor. Die Schwingungsenergie wird dann über eine viskose und turbulente Rohrströmung dissipiert. Zur Erzielung des gewünschten Dämpfungsverhaltens wird eine mechanische Blende in den Flüssigkeitsstrom eingebaut. Der Anwendungs-bereich der Tilger beschränkt sich dabei auf Frequenzen bis ca. 3,5 - 4,0 Hz, wobei ab ca. 0,5 Hz unbedingt eine Luftfeder durch Verschließen der Rohrenden auszuführen ist.
Im ersten Teil wird in Verallgemeinerung der bisherigen wissenschaftlichen Betrachtungen, die kombinierte horizontale und vertikale Erregung von Baukonstruktionen mit Flüssigkeitstilgern, untersucht. Aufgrund des Einsatzes von Flüssigkeitstilgern bei Gebäuden unter allgemeiner Erdbebeneinwirkung und insbesondere im Hinblick auf die Anwendung des Tilgers zur Reduzierung von Brückenschwingungen, wird die Empfindlichkeit des Flüssigkeitstilgers auf vertikale Anregungen untersucht. Es wird gezeigt, dass die vertikale Erregung schädliche Auswirkungen auf das optimale Dämpfungsverhalten von ungenügend gedämpften Flüssigkeitstilgern haben kann. Zur sicheren Vermeidung dieser schädlichen Auswirkungen wird eine hinreichende Stabilitätsbedingung in der Form einer erforderlichen Flüssigkeitsdämpfung angegeben. Insbesondere kann gezeigt werden, dass in allen praktischen Fällen, wo ein geschlossener Flüssigkeitstilger mit Luftfeder ausgeführt wird, die optimale Dämpfung des Tilgers weit über dem erforderlichen Wert liegt. Eine detaillierte Untersuchung der vertikalen Anregung und deren Auswirkung kann dann unterbleiben.
Im zweiten umfangreichen Teil der Dissertation wird der Einsatz von Flüssigkeitstilgern zur Reduzierung von Brückenschwingungen numerisch und experimentell untersucht. Die gekoppelte schiefe Biegedrillschwingung des kontinuierlichen Brückenträgers mit Flüssigkeitstilger wird in allgemeiner Form beschrieben. Insbesondere werden personeninduzierte Schwingungen von Fußgängerbrücken betrachtet, und die dynamischen Kontaktkräfte des komplexen Systems „Mensch“ während des Bewegungsvorganges werden analysiert. In weiterer Folge wird auf das für Fußgängerbrücken äußerst gefährliche Rückkoppelungs- bzw. Synchronisationsphänomen näher eingegangen, bei dem eine anfangs regellos fortbewegende Fußgängergruppe die Schrittfrequenz an eine benachbarte Eigenfrequenz der Brücke in natürlicher Reaktion auf die Bewegung der Unterlage anpasst. Zu dessen sicherer Vermeidung wird eine Grenzbedingung in der Form einer erforderlichen Systemdämpfung präsentiert. Außerdem wird gezeigt, dass Brücken zufolge Fußgängeranregung parametererregte Schwingungen ausführen, die unter bestimmten Bedingungen zu Parameterresonanz und damit zu einer unerwünschten Aufschaukelung der schiefen Biegeschwingung der Brücke führen. Aufgrund dieser Tatsache wird eine weitere hinreichende Grenzbedingung vorgelegt, die eine Parameterresonanzgefahr von Fußgängerbrücken verhindert. In Anlehnung an diese theoretischen Untersuchungen wird die Tilgung von personeninduzierten Schwingungen anhand ausgewählter schwingungsanfälliger Fußgängerbrücken, nämlich der Millennium Bridge in London, der Toda Park Bridge in Japan und einer selbst entworfenen fiktiven Fußgängerbrücke, dargelegt. Simulationen zeigen, dass die unzulässigen Schwingungsantworten aller Fußgängerbrücken durch die Installation von optimal abgestimmten geschlossenen Flüssigkeitstilgern mit Luftfeder erfolgreich und wirtschaftlich reduziert werden können. Im Falle der Millennium Bridge wären insgesamt fünf optimierte Flüssigkeitstilger mit Luftfeder zu installieren gewesen. Diese hätten zur Gebrauchstauglichkeit geführt, mit einem Bruchteil der tatsächlich aufgewendeten Sanierungskosten. Gleichermaßen könnte auch die Auckland Harbour Bridge in Neuseeland für den Marathonlauf gebrauchstauglich gemacht werden.
Aufgrund der zunehmenden Bedeutung von dynamischen Windbelastungen für weitgespannte Brücken wird abschließend eine Methode zur optimalen Abstimmung von Flüssigkeitstilgern speziell für winderregte Schwingungen vorgestellt. Es wird eine Brücke betrachtet, die sich zufolge Windanregung (z.B. zufolge einer Windböe) in einem beliebig ausgelenkten Momentanzustand befindet. Die optimale Abstimmung der geschlossenen Flüssigkeitstilger mit Luftfeder soll zu einem möglichst raschen Abklingen der freien Schwingungsantwort der Brücke führen. Anhand numerischer Simulationen wird gezeigt, dass durch die Installation von drei optimal abgestimmten Flüssigkeitstilgern im Brückenfeld das Ausschwingverhalten zufolge Windanregung erfolgreich und wirtschaftlich verbessert werden kann. Damit lässt sich insbesondere die Scruton-Zahl über ihren kritischen Wert anheben. Auf die Komplexität der Windanregung braucht dann nicht näher eingegangen zu werden. Auf die Anwendung von Flüssigkeitstilgern im kritischen Zustand des Vorbau-verfahrens bei der Brückenherstellung wird besonders hingewiesen.
This paper aims to investigate the possibility and effectiveness of applying a tuned liquid column damper (TLCD) to suppress pitching motion of a floating box structure. A mathematical model of the TLCD-floating structure interaction system is developed, and the associated equations of motion are derived using a Lagrangian approach. Then, the procedures for numerically obtaining the optimum parameters of the TLCD for the undamped system under harmonic excitation are proposed using Den Hartog's method. The presented examples demonstrate that the TLCD can efficiently suppress the pitching motion of the floating box structure and has potential for applying to the development of floating housing.
Structures constructed in developing world are typically RC frames with masonry infill. These structures have little resistance for lateral loads caused by earthquake and wind. Even for adequately designed structures also, due to permissible deformation beyond elastic limits, failure of masonry causes severe loss of life and property. In the case of structures designed to sustain excessive deformation such as of defence establishments, functioning and serviceability of machines and equipment installed therein are adversely affected. This co-lateral damage may be reduced by adopting another design philosophy of structure response control. In this methodology, a supplementary damping device is incorporated in the primary structure, which absorbs most of the seismic energy imparted to it, restricting the structural response within serviceable limits. These devices may be passive, active, semi-active or hybrid types. Other than passive all options are technology-intensive and dependent on external energy source, not a favourable proposition for developing nations. Among all the passive devices, tuned liquid dampers (TLDs) promise to be most suitable. Here, existing overhead water tanks (OHWT) may be used as TLD with slight adjustment and modification. This method will be able to control the structural response without putting any extra load on the existing or newly-designed buildings. This paper reviews various types of dampers and discusses evolution of tuned liquid dampers. A method has also been proposed for incorporating TLDs in existing and new structures. This methodology may be very useful for structures of defence establishment which are scattered and remotely placed by location, housing important equipments sensitive to vibrations, as it is free from external power dependence and regular maintenance.
In this paper, the state-of-the-art review and the research progress of the technology of the bridge vibration control are summarized. The major achievements and the recent progress in the bridge vibration control are discussed on the basis of three sides: active control, passive control and control algorithms. Some existing problems are mentioned. And the direction of the further research on bridge vibration control in the future is also pointed out.
Recently, due to the dramatic requirement of petroleum from new developed countries, the price of crude oil reached skyrocketing height. Therefore, in this study, a new type of wave-energy converting system is developed and installed in an offshore platform structure to take the advantage of stronger motion of the platform subjected to waves. By utilizing the sloshing power of the fluid stored in an U-shape tube, the turbine of the electric power generator is driven and electricity can be generated. Some advantages are found from this system. Firstly, because the vibration in surge, heave and other motions of the platform induce the sloshing motion of fluid, the motion of the platform can be eased and the platform becomes more stable for the operation. Secondly, the power generated is a by-product of the platform operation, which aims to a self-content system for the power-supply in the platform. Thirdly, due to the simple structure and common material applied to the wave-converting system, the maintenance of the system is much easier compared to the others. From the testing results, it shows that with respect to various periods and amplitudes of the stroke in the experimental tests, the wave-power converting system can effectively generate electricity.
Tuned liquid column damper (TLCD) is more advantageous in terms of space than TLD so that it is far more advantageous when it comes to installation on the actual building. To investigate the effectiveness of a tuned liquid column damper (TLCD) in mitigation wind-induced excitation motion of a tall building, aeroelastic experiments were conducted. A 1: 200 scaled model of an aeroelastic tall building was built, and TLCD models of mass ratio of 1.5% and 3%, respectively, were designed and tested with the aeroelastic model. As such, this study has installed TLCD with different lengths of horizontal pipes at the top most floor of realistic model. This is similar to the actual structure, centred on the interval where the vortex-induced vibration of low wind speed occurs, by conducting aeroelastic model tests in suburban areas and the vibration response in across-wind direction shall be found in order to figure out the wind vibration control effect according to various types (horizontal length, mass ratio) changes.
A new constructive solution for the offshore wind power generation is to use floating wind turbines. An offshore wind farm situated sufficiently far away from the coast can generate more wind power and will have a longer operation life since the wind is stronger and more consistent than that on or near the coast. One of the main challenges is to reduce the fatigue of a floating wind turbine so as to guarantee its proper functioning under the constraints imposed by the floating support platforms. This paper will discuss the structural control issues related to the mitigation of dynamic wind and wave loads on the floating wind turbines so as to enhance the offshore wind power generation.
In this paper, the control performance of the novel sealed, torsional tuned liquid column gas damper (TTLCGD) to reduce the coupled flexural torsional response of plan-asymmetric buildings under wind or seismic loads is investigated. Applications of the TTLCGD with a sealed piping system to tall building effectively increase the modal structural damping. If the modal center of velocity lies within the floor plan, TTLCGD with its in plane curved piping section encloses this center for best efficiency. Based on the linearized equation of motion for the TTLCGD-main structure system with respect to a selected natural frequency, the optimal parameters of TTLCGD are modally tuned by means of a geometrical transformation in analogy to the classical torsional tuned mechanical damper, TTMD, followed by fine-tuning in the state space domain considering the influence of neighboring modes to improve the performance of TTLCGD. Numerical simulations of plan-asymmetric space frames illustrate that TTLCGD is an effective control device in suppressing the time-harmonic excitation and the earthquake response. Copyright © 2010 John Wiley & Sons, Ltd.
In the first part of the paper, the optimal design parameters for tuned liquid column dampers (TLCD) in harmonic pitching motion were investigated. The configurations in design tables include uniform and non-uniform TLCDs with cross-sectional ratios of 0.3, 0.6, 1, 2 and 3 for the design in different situations. A closed-form solution of the structural response was used for performing numerical optimization. The results from optimization indicate that the optimal structural response always occurs when the two resonant peaks along the frequency axis are equal. The optimal frequency tuning ratio, optimal head loss coefficient, the corresponding response and other useful quantities are constructed in design tables as a guideline for practitioners. As the value of the head loss coefficient is only available through experiments, in the second part of the paper, the prediction of head loss coefficients in the form of a design chart are proposed based on a series of large scale tests in pitching base motions, aiming to ease the predicament of lacking the information of head loss for those who wishes to make designs without going through experimentation. A large extent of TLCDs with cross-sectional ratios of 0.3, 0.6, 1, 2 and 3 and orifice blocking ratios ranging from 0%, 20%, 40%, 60% to 80% were inspected by means of a closed-form solution under harmonic base motion for identification. For the convenience of practical use, the corresponding empirical formulas for predicting head loss coefficients of TLCDs in relation to the cross-sectional ratio and the orifice blocking ratio were also proposed. For supplemental information to horizontal base motion, the relation of head loss values versus blocking ratios and the corresponding empirical formulas were also presented in the end.
A Computational Fluid Dynamics model is presented in this study for the simulation of the complex fluid flows with free surfaces inside the Tuned Liquid Column Dampers in horizontal motion. The characteristics of the fluid model of the TLCD in horizontal motion include the free surface of the multiphase flow and the horizontal moving frame. In this study, the time depend unsteady Standard turbulent model based on Navier-Stokes equations is chosen. The volume of fluid (VOF) method and sliding mesh technique are adopted to track the free surface of water inside the vertical columns of TLCD and treat the moving boundary of the walls of TLCD in horizontal motion. Several model solution parameters comprising different time steps, mesh sizes, convergence criteria and discretization schemes are examined to establish model parametric independency results. The simulation results are compared with the experimental data in the dimensionless amplitude of the water column in four different configured groups of TLCDs with four different orifice areas. The predicted natural frequencies and the head loss coefficient of TLCDs from CFD model are also compared with the experimental data. The predicted numerical results agree well with the available experimental data.
The dynamic characteristics of the passive, semi-active, and active tuned-liquidcolumn dampers (or TLCDs) are studied in this paper. The design of the latter two are based on the first one. A water-head difference (or simply named as water head in this paper) of a passive TLCD is pre-set to form the so-called semi-active one in this paper. The pre-set of water head is released at a proper time instant during an earthquake excitation in order to enhance the vibration reduction of a structure. Two propellers are installed along a shaft inside and at the center of a passive TLCD to form an active one. These two propellers are driven by a servo-motor controlled by a computer to provide the control force. The seismic responses of a five-story shear building with a passive, semiactive, and active TLCDs are computed for demonstration and discussion. The responses of this building with a tuned mass damper (or TMD) are also included for comparison. The small-scale shaking-table experiments of a pendulum-like system with a passive or active TLCD to harmonic and seismic excitations are conducted for verification.
The natural frequencies of a long span bridge vary during its construction and it is thus difficult to apply traditional tuned liquid column dampers (TLCD) with a fixed configuration to reduce bridge vibration. The restriction of TLCD imposed by frequency tuning requirement also make it difficult to be applied to structure with either very low or high natural frequency. A semi-active tuned liquid column damper (SATLCD), whose natural frequency can be altered by active control of liquid column pressure, is studied in this paper. The principle of SATLCD with adaptive tuning capacity is first introduced. The analytical models are then developed for lateral vibration of a structure with SATLCD and torsional vibration of a structure with SATLCD, respectively, under either harmonic or white noise excitation. The non-linear damping property of SATLCD is linearized by an equivalent linearization technique. Extensive parametric studies are finally carried out in the frequency domain to find the beneficial parameters by which the maximum vibration reduction can be achieved. The key parameters investigated include the distance from the centre line of SATLCD to the rotational axis of a structure, the ratio of horizontal length to the total length of liquid column, head loss coefficient, and frequency offset ratio. The investigations demonstrate that SATLCD can provide a greater flexibility for its application in practice and achieve a high degree of vibration reduction. The sensitivity of SATLCD to the frequency offset between the damper and structure can be improved by adapting its frequency precisely to the measured structural frequency.
Passive control of the flutter condition of suspension bridges using a combined vertical and torsional tuned mass damper (TMD) system is presented. The proposed TMD system has two degrees of freedom, which are tuned close to the frequencies corresponding to vertical and torsional symmetric modes of the bridge which get coupled during flutter. The bridge-TMD system is analyzed for finding critical wind speed for flutter using a finite element approach. Thomas Suspension Bridge is analyzed as an illustrative example. The effectiveness of the TMD system in increasing the critical flutter speed of the bridge is investigated through a parametric study. The results of the parametric study led to the optimization of some important parameters such as mass ratio, TMD damping ratio, tuning frequency, and number of TMD systems which provide maximum critical flutter wind speed of the suspension bridge.
This paper analyzes the loads and dynamic response of floating support structures and addresses the problem of designing semiactive controllers to mitigate the dynamic wind and wave loads on floating wind turbines. The output feedback control strategy is proposed to avoid the dependence on the knowledge of the system states. The H∞ output feedback control technique is used for formulating the semiactive control law, which is implemented using a tuned liquid column damper (TLCD). Numerical simulation is done to verify the obtained results.
We consider a simple model of spring-mass block placed over a constant velocity v rolling plate. The map of the dynamic is presented in the (v,r) space where r accounts for the possible variation of the periodic shape profile of the rolling carpet. In order to characterize each type of motion, we found that evaluating the area of the phase space trajectories is more relevant than attempting on one hand, to solve analytically the asymptotic behavior, or on the other hand, to obtain an equivalent of the entropy and the free energy. First-order transition reveals to be the characteristic route from one type of motion to another. Later, we investigate the influence of the classical TMD1 and TLCD2 on the dynamic of this mass. Moreover, we numerically study the effects of a modified TMD. Reduced order parameter provides a quick overview of the whole system than phase space representations and bifurcation diagrams. Comparison of performances in the (v,r) space is made. It reveals the efficiency of the modified TMD. It comes out that the new TMD we designed stabilizes the system better than the two above control systems.
A modified version of the traditional tuned liquid column damper (TLCD) absorber is proposed as a passive vibration control device for structures vibrating at low frequencies. This new version, denoted as tuned liquid column ball damper (TLCBD), is equipped with a coated steel ball, in place of the orifice in TLCD, immersed inside the horizontal column of the damper. The current study examines the performance of TLCBD for a harmonic excitation which is a simplified model for the vortex shedding forces on structures in the cross wind direction. A parametric study to investigate the effect of the ball size and absorber mass on the suppression capacity is carried out. The absorber damping characteristics is identified experimentally using a single point laser vibrometer system and the measured damping factor is used in the mathematical model. Intensive numerical simulations were conduced and the results are compared with the traditional TLCD with optimum parameters. The results revealed an improvement of the vibration suppression capability of the proposed version that exceeds around 66% reduction.
A lot of buildings which employed vibration damping devices or base isolation devices in order to reduce occupant discomfort and non-structural damage were constructed in the past four years in Japan.And various novel idears or devices for suppressing lateral vibrations are produced and developed.Here, the vibration controlling system which were developed recently are reviewed and those incorporated into actual buildings are introduced.The efficiency of the vibration damping system in improving the serviceability of buildings is stressed.
In this review, tuned mass dampers attached to single degree- of-freedom systems representing tall buildings are studied. System equations are formulated and solved for various input forcing functions. Design parameters of the damper are varied to study the response reduction. Experimental wind tunnel results are presented and a practical application of a large-scale damper is illustrated. 14 references. (A)
The existence and uniqueness of approximate solutions generated by the generalized method of equivalent linearization is considered. For the stationary analysis of systems with harmonic or Gaussian random excitation, it is shown that even though the equivalent linear system may not be unique, a simple element-by-element substitute system exists. Furthermore, this system is at least as good as any other similarly defined substitute system.RésuméOn considère l'existence et l'unicité de solutions approchées obtenues par la méthode généralisée de la linéarisation équivalente. Pour l'analyse stationnaire de systèmes avec une excitation aléatoire harmonique ou Gaussienne, on montre que, bien que le système linéaire équivalent puisse ne pas être unique, il existe un système simple substitué élément par élément. En outre ce système est ou moins aussi bon que n'importe quel autre système défini de la même manière.ZusammenfassungDie Existenz und die Eindeutigkeit von Näherungslösungen, die durch die verallgemeinerte Methode der gleichwertigen Linearisation erzeugt wurden, wird untersucht. Für die statiönare Behandlung von Systemen mit harmonischer oder Gausscher statistischer Erregung wird gezeigt, dass ein einfaches aus Elementen aufgebautes Ersatzsystem selbst dann existiert, wenn das gleichwertige lineare System nicht eindeutig ist. Weiterhin ist dieses System mindestens so gut wie irgend ein anderes ähnlich definiertes Ersatzsystem.
The effectiveness of a tuned liquid column damper (TLCD) in controlling structural vibration is studied. A numerical method is adopted to account for nonlinearity of the governing equation. Optimum parameters of the TLCD for maximum reduction of peak structural response to harmonic excitations in a wide frequency range are presented for a wide range of flexible structures. A variation of U-shaped TLCD with different cross-sectional areas in its vertical and horizontal sections is investigated. It is found that an increase in cross-sectional area ratio (vertical/horizontal) can greatly reduce the length requirement of a TLCD making it more attractive to flexible structures. A new type V-shaped TLCD is also investigated. This type of TLCD can suppress stronger vibrations such as those caused by strong wind. It is found that, like the tuned mass damper (TIVID), there is an optimum tuning ratio (damper frequency/structure frequency) for maximum reduction in response of a structure system which is independent of the excitation. The optimum coefficient of head loss will depend on the intensity of the excitation with smaller coefficient of head loss associated with stronger excitation.
A new kind of passive mechanical damper, tuned liquid damper (TLD). is studied that relies upon the motion of shallow liquid in a rigid tank for changing the dynamic characteristics of a structure and dissipating its vibration energy. A nonlinear model of two-dimensional liquid motion inside a rectangular TLD subjected to horizontal motion is developed on the basis of shallow-water wave theory, where the damping of the liquid motion is included semianalytically. Using the model, the response of a structure with TLD is also computed. The liquid motion inside the TLD under harmonic base excitation and, furthermore, the response of a single-degree-of-freedom structure with TLD, subjected to harmonic external force, are experimentally investigated. The agreement is good between the experiment and the prediction.
The effectiveness of tuned liquid column dampers (TLCD) in controlling the wind-induced vibration of towers is studied. The nonlinear governing equation of the TLCD is linearized to obtain the stochastic response of the towers due to along-wind turbulence. Through parametric studies, the optimum parameters for maximum reduction in acceleration and displacement are presented for a wide range of towers. It is found that for any tower of practical interest, almost the same amount of reduction in acceleration can be obtained by choosing an appropriate opening ratio of the orifice in the TLCD. The same opening ratio would give almost the maximum reduction in displacement. Generally, the opening ratio needs to be varied between 0.5 and 1.0, with smaller opening ratios for shorter towers.
An abstract is not available.
An investigation is made of the possible application of tuned liquid column dampers and tuned liquid column/mass dampers in reducing the along-wind response of wind-sensitive structures. The structure is modeled as a lumped mass multi-degree-of-freedom system taking into account both bending and shear. The wind turbulence is modeled as a stochastic process that is stationary in time and nonhomogeneous in space. A random vibration analysis utilizing transfer matrix formulation is carried out to obtain response statistics. The nonlinear damping term in the fundamental equation of the tuned liquid damper is treated by an equivalent linearization technique. Numerical examples show that tuned liquid dampers, which have significant practical advantages, are as effective as the traditional tuned mass dampers if the parameters of the liquid dampers are properly selected. However, excess liquid motion in a tuned liquid column/mass damper may reduce the effectiveness of this damper. It is also shown that the wind-induced force- and acceleration-type responses of the structure with a damper, which is usually tuned to the fundamental frequency of the structure, should involve more than one vibration mode as higher-mode responses may become as large or even larger than the controlled-mode response.
The seismic performance of Tuned Liquid Column Dampers (TLCDs) for the passive control of flexible structures is investigated using random vibration analysis. A non-stationary stochastic process with frequency and amplitude modulation is used to represent the earthquake strong motion, and a simple equivalent linearization technique is used to account for the non-linear damping force in the TLCD. The governing equations of motion for the structure TLCD system are formulated and reduced to a first-order state vector equation, from which the differential equation for the system response covariance matrix is obtained. The TLCD performance is evaluated on the basis of selected structural response statistics, namely, the expected maximum and root-mean-square displacements, and root-mean-square absolute accelerations and interstorey shears. A parametric study and sensitivity analysis are conducted to assess the TLCD performance and identify critical design parameters. Illustrative examples are presented using SDOF and MDOF shear-beam structural models, a wide-banded stationary random base acceleration and two non-stationary random input ground motions representative of long- and short-duration ground accelerations with significant low-frequency content.
A tuned liquid damper (TLD), which consists of rigid tanks partially filled by liquid, is a type of passive control device relying upon liquid sloshing forces or moments to change the dynamical properties and to dissipate vibrational energy of a structure. An analytical non-linear model is proposed for a TLD using rectangular tanks filled with shallow liquid under pitching vibration, utilizing a shallow water wave theory. The model includes the linear damping of the sloshing liquid, which is an important parameter in the study of a TLD as it affects the efficiency of the TLD. Shaking table experiments were conducted for verification; good agreement between the analytical simulations and the experimental results was observed in a small excitation amplitude range. The simulations of TLD-structure interaction by using the proposed model show that the TLD can efficiently suppress resonant pitching vibration of a structure. It is also found that the effectiveness of a TLD for suppressing the pitching vibration depends not only on the mass of liquid in the TLD but also on the configuration of the liquid as well as upon the position where the TLD is located. If the configuration of the liquid, i.e. the liquid depth and the TLD tank size, is designed suitably, the TLD can have a large suppressing moment and can be very effective even with a small mass of liquid.
The method of equivalent linearization of Kryloff and Bogoliubov is generalized to the case of nonlinear dynamic systems with random excitation. The method is applied to a variety of problems, and the results are compared with exact solutions of the Fokker-Planck equation for those cases where the Fokker-Planck technique may be applied. Alternate approaches to the problem are discussed, including the characteristic function method of Rice.
Torsional vibration control of suspension bridge decks using tuned liquid column damper
- S D Xue
Xue, S. D. Torsional vibration control of suspension bridge decks using tuned liquid column damper. Ph.D. thesis. The Hong Kong Polytechnic University, Hong Kong, 1999.
Vibration control systems for civil engineering structures in Australia — actual installations and state-of-the-art research
- Samali
Samali B, Kwok KCS. Vibration control systems for civil engin-eering structures in Australia — actual installations and state-of-the-art research. In: Proc. 2nd Int. Conf. on Motion and Vibration Control, Yokohama, Japan, 1994:k22–35.
Tuned liquid column damper — new type device for suppression of building vibration
- F Sakai
- S Takaeda
- Tamaki
Sakai F, Takaeda S, Tamaki T. Tuned liquid column damper — new type device for suppression of building vibration. In: Proc. Int. Conf. on High-rise Buildings, Nanjing, China, 1989:926–31.
Tuned liquid column damper — new type device for suppression of building vibration
- Sakai