Tuned Liquid Column Damper Research Articles

Shaking table test of TLD/TLCD vibration control for offshore wind turbine support structure

In this research, a scale-model with a similarity-ratio of 1:15 is specifically designed for shaking table test based on a 6.45MW OWT (Offshore wind turbine). The scale-model is equipped with a TLD (Tuned liquid damper) at the top and a TLCD (Tuned liquid column damper) at 2/3 of its height. Various external excitations with distinct spectral characteristics are applied to analyze the vibration characteristics of the OWT and the damping performance of the TLD/TLCD. The results indicate that the dynamic characteristics satisfy the similarity-ratio between the prototype-model and scale-model. The acceleration response of the OWT is significantly influenced by the external excitation spectrum, whereas the displacement response is primarily governed by the model 1st-order natural-frequency. With the mass eccentricity applied at the tower top and bidirectional excitation input, torsional deformation occurs in the tower, resulting in a ‘beat vibration’ phenomenon. Upon the incorporation of TLD/TLCD, the vibration response attenuation-ratio can reach up to 70 % under harmonic excitation, up to 25 % under seismic excitation and up to 50 % under equivalent base acceleration. After the implementation of vibration attenuation, there is a significant reduction in the time-domain response, and the rate of reduction is accelerated. In the frequency-domain response, the spectral peak at the natural-frequency disappears.

Optimal control of base-isolated systems with sliding TLCD under stochastic process

In this study, an innovative hybrid passive vibration control strategy, combining a base-isolated (BI) structure with a novel sliding version of a Tuned Liquid Column Damper (STLCD) to enhance the dynamic performance of BI structures, is explored from both theoretical and experimental perspectives. In contrast to conventional fixed TLCDs, the proposed STLCD consists of a U-shaped tank partially filled with water, mounted on a roller support, and linked to the BI subsystem through a spring-dashpot system. This configuration results in a more versatile tuning procedure utilizing the spring for tuning and obtaining supplementary damping through the dashpot. The optimal design of the STLCD device is discussed assuming a Gaussian white noise process as base excitation and the credibility of the presented mathematical formulation is assessed through a shaking table testing campaign, carried out at the Laboratory of Experimental Dynamics at the University of Palermo (Italy). For the experimentation, a reduced-scale model of a BI structure with the integrated STLCD is constructed, and its effectiveness is experimentally evaluated. Finally, comparisons to traditional TLCDs and TMDs are presented, emphasizing control efficiency and the reduction of base displacement in the BI system.

Experimental and numerical study on dynamic response of a photovoltaic support structural platform with a U-shaped tuned liquid column damper

A tuned liquid column damper (TLCD) is widely used in offshore structures as a passive energy dissipation device to reduce the harm of wind, wave, and current loads to the safety of offshore platforms. This investigation explores the dynamic response and interaction mechanism of a photovoltaic support structural platform (SSP) equipped with a TLCD by experimental and numerical analysis. The vibration mitigation performance of the TLCD under varying liquid depth ratios, external excitation frequencies, and amplitudes is systematically evaluated. The experiments focus on assessing the structural dynamic response and wall pressure to determine the vibration reduction efficiency of the TLCD for structures with fundamental frequencies more than 2 Hz. The experimental results indicate that the TLCD can reduce the structural response maximally near the natural frequency (2.52 Hz) of the structure, with vibration reduction effectiveness ranging from 42.0% to 85.1%. Additionally, one develops a two-way fluid-structure interaction (FSI) model to investigate further the impact of hydrodynamic pressure caused by sloshing inside the TLCD on the SSP motion response, which providing a more detailed explanation for the different phenomena observed in the experimental results.

Event-triggered semi-active TLCD for ground motion-induced vibration control

One potential drawback of tuned liquid column dampers (TLCDs) is their relatively low control efficiency during the initial stage of structural vibration caused by external excitations. This is because satisfactory control effects can only be achieved when the liquid inside TLCD is fully oscillating, which is not the case during the initial stage. To solve this problem, in this study, an event-triggered semi-active technique is creatively proposed to improve the vibration reduction efficiency of TLCDs during the initial stage. The fundamental idea of the proposed approach is to provide an initial displacement to the liquid column via baffles, and then release the constraints on the initial liquid displacement at an appropriate time to achieve the rapid activation of TLCDs. A strategy from the standpoint of phase difference between liquid column motion and structural motion is proposed to determine the triggering conditions (i.e. when to release the constraints). The effectiveness of the proposed semi-active system is examined under both harmonic and stochastic excitations. The results show that the proposed strategy successfully improves the vibration suppression performance of TLCDs in the early stage of structural vibration.

Nonlinear analysis of a wind turbine tower with a tuned liquid column damper (TLCD)

Nonlinear analysis of a wind turbine tower with a tuned liquid column damper (TLCD)

Vertical vibration control of structures with tuned liquid column dampers

Conventional tuned liquid column dampers (TLCDs) can only be used to suppress structural vibrations in horizontal directions. However, in reality, the vibration-induced motion of civil engineering structures normally consists of both vertical and horizontal components. In this study, a TLCD-based vibration control system, which is composed of a pair of inclined U-shaped containers, springs, dashpots, as well as supporting slopes, is proposed to control the vertical vibration of an engineering structure. The proposed control system (denoted as vertical TLCD) successfully extends the application of TLCD-type devices to vertical vibration reduction. First, the general configuration and operating principle of the proposed vertical TLCD are illustrated in detail. Second, the equations of motion are derived based on the Lagrange dynamic equations and further verified by two-way fluid–structure coupling numerical simulations using finite element method and finite volume method. Subsequently, the closed-form solution is derived for the optimized design of the vertical TLCD in the frequency domain. The dynamic characteristics of an optimized vertical TLCD-structure system are revealed. The effects of mass ratio, excitation amplitude and structural damping ratio on the optimization results are elaborated, respectively. Under the same optimized parameters, the vertical TLCD is found to be superior, compared to the vertical tuned mass damper (TMD). Finally, the effectiveness of the proposed system is demonstrated by applying it to the control of a bridge experiencing vertical vibrations under seismic loads. The findings of this study provide a comprehensive understanding of TLCD’s capabilities and identify its potential for vertical vibration control, which contributes to the development of more effective and versatile vibration mitigation strategies for a wide range of structures under different engineering scenarios.

Comparison of the Dynamic Characteristics of Tuned Liquid Column Dampers with Different Elbow Forms

Comparison of the Dynamic Characteristics of Tuned Liquid Column Dampers with Different Elbow Forms

Hedge-Algebras-based hybrid control of earthquake-induced buildings using upgraded tuned liquid column dampers

Upgraded Tuned Liquid Column Damper (UTLCD) is an interesting variant of Tuned Liquid Column Damper, which was developed recently. UTLCD consists of a conventional Tuned Liquid Column Damper (TLCD) integrated into an undamped Tuned Mass Damper (TMD). Based on this device, a hybrid type of UTLCD (HUTLCD) is developed to minimize the vibration response of earthquake-induced buildings. HUTLCD is constituted of two independent components, including an active UTLCD (AUTLCD) and a passive UTLCD (PUTLCD). These individual components are connected in parallel to a high-rise building. In this research, the Hedge-Algebras theory (HA) is utilized to design controllers for AUTLCD. This study also uses a new algorithm, Balancing Composite Motion Optimization (BCMO), which has recently been introduced to solve optimization problems. The performance of HUTLCD is compared with that of a pure AUTLCD or a pure PUTLCD, which have the same weight as the HUTLCD. The results achieved from the present work confirm that the HUTLCD is more effective than the pure PUTLCD for the vibration reduction capacity and is better than the pure AUTLCD for both aspects of the vibrational control capacity (for most cases compared with) and saving control energy (for all cases considered). Moreover, the HUTLCD is not more robust than the AUTLCD as the structural stiffness rises, but the HUTLCD still offers higher control effectiveness compared with the AUTLCD or PUTLCD when the structural stiffness decreases. In addition, although the data used to design the optimum HA-based controller is the El Centro earthquake, this controller maintains a high efficiency level for numerous other earthquakes.

Vibration controlling effect of tuned liquid column damper (TLCD) on support structural platform (SSP)

A bidirectional fluid-structure coupling model between tuned liquid column damper (TLCD) and support structural platform (SSP) was developed to study effects of TLCD-SSP mass ratio and tuning ratio on reducing SSP vibration. Laboratory experiments of TLCD interaction with SSP were conducted to validate TLCD-SSP coupling model. Good agreements between numerical results and experimental data are obtained. TLCD/SSP mass ratio increases from 1% to 3%, the maximum amplitude of SSP upper displacement decreases from 43.77% to 78.32%, and the upper acceleration damping rate increases from 43.26% to 77.88%. There is a phase differences between dynamic water pressure offered by sloshing inside TLCD and upper displacement curves, and the damping energy dissipation effect is maximized when the hysteresis phase difference reaches π/2. The larger mass ratio is more effective in suppressing the structural vibration. But it also brings about a fundamental frequency drift. It is advised that the mass ratio of water in TLCD to SSP should be 1.5%, the total mass of water and shell of TLCD should be about 2.5% of the mass of SSP, and the intrinsic frequencies of TLCD and SSP should be tuned the same so that the vibration controlling performance of TLCD can be improved maximally.

Combined Tuned Mass Dampers for structural vibration control

A Combined Tuned Mass Damper (CTMD), including a Tuned Liquid Column Damper (TLCD) integrated on the top of a traditional Tuned Mass Damper (TMD), is proposed to control vibrations of a Single Degree-Of-Freedom (SDOF) structure. This device can also be considered as a new hybrid type of tuned mass damper. The gained results from the parametric study indicate that the mass ratio between the TLCD and the TMD significantly affects the CTMD's effectiveness. In order to assess the structural vibration absorption capacity of this device, the effectiveness and robustness of an optimized CTMD are compared with those of optimum TMD and TLCD with the same weight as the CTMD. The numerical simulations show that the proposed CTMD provides a higher performance over a broader excitation frequency domain compared with both a conventional TMD and TLCD in mitigating structural vibration. Furthermore, the frequency response curve of the structure using the CTMD is relatively flat, whereas the frequency response curves of the structure with the TMD and TLCD remain a two-peak characteristic on the same frequency range considered. In another aspect, although the optimum CTMD is not more robust than the TMD or TLCD in resisting the change of the structural stiffness, it offers a wider range for choosing the frequency and damping ratio to aim at remaining similar efficiency to that of the optimized TMD (or TLCD). Therefore, a CTMD is much more robust than a single TMD or TLCD having equal weight to the CTMD. For parameters of the CTMD, the present research also indicates that the damping ratio of the TMD does not display an essential role in the CTMD. In contrast, although the TLCD mass is much smaller than the TMD mass, the appearance of the TLCD is very important in this device.

Development of a Water Supplement System for a Tuned Liquid Damper under Excitation

Integrating existing liquid storage and supply tanks in buildings with tuned liquid dampers (TLDs) are significant for reducing the effective cost of TLDs. However, existing water supplement devices for fire-suppression liquid tanks may overfill with water, which leads to TLD mistuning. To overcome this problem, a passive liquid control system named TLD with a stable replenishment sub-tank system (TLD-SRS) is proposed. The system, which consists of an additional sub-tank connected to the main tank and a floating ball, replenishes liquid in the TLD automatically. The system can avoid vibration interference and maintain the normal operation of the passive replenishment system under usual wind loads. According to the studies of tuned liquid column dampers (TLCD), the proposed TLD with a stable replenishment sub-tank system (TLD-SRS) uses simple devices to ensure that the liquid level in the TLD is steady at the target liquid level with a floating ball. The TLD-SRS is verified on a large-scale TLD shaking table experiment. The overshoot, which is the percentage of liquid that exceeds the target volume of TLD is calculated during sloshing with wind loads. Compared with TLD installed with a regular liquid replenishment device, the proposed TLD-SRS significantly reduces the overshoot of liquid and acceleration on the roof of the building.

Optimum TLCD for Mitigation of Offshore Wind Turbine Dynamic Response Considering Soil–Structure Interaction

The paper presents a parametric optimization of Tuned Liquid Column Damper (TLCD) to control the structural vibration of 5MW NREL offshore wind turbine (OWT) subject to the wind and waves random forces. In this work, the fluid–structure interaction of monopile with seawater are modeled as an added mass and the soil-structure interaction of monopile foundation is considered through simplified model of discrete coupled springs model. Using a proprietary genetic algorithm, the TLCD on nacelle has its parameters optimized to reduce the standard deviation or roots mean square (RMS) dynamic response on tower top. The displacement results are compared to the ones obtained by exhaustive search methods via a response map. From the stochastic analysis of the structure response, the ideal tuning ratio and damping ratio are determined for the liquid column damper to present its highest efficiency, i.e. the lowest RMS displacement at the tower top. The damper parameters achieved by both optimization methods show a significant agreement between them. In addition, the use of the genetic algorithm, a parametric optimization of the TLCD installed in OWT is carried out considering the random excitation of the wind, wave, and rotor forces (Kaimal, JONSWAP, and rotational spectra, respectively). In possession of the TLCD optimal parameters determined by the parametric study, the mitigation of displacements at the standard wind turbine top is analyzed. The fore-aft vibration at tower top with a TLCD attached shows a significant reduction for actions dynamic components. Finally, TLDC optimal parameters have a direct relation with the considered force spectrum and the turbine transfer function, and both must be considered for the damper optimization process.

Nontraditional configuration of tuned liquid column damper inerter for base-isolated structures

In this paper, the concept of a novel passive control device, namely the Nontraditional Tuned Liquid Column Damper Inerter (NT-TLCDI), is investigated in combination with seismic base isolation (BI), to control lateral displacement demands in base-isolated structures during seismic events. The considered NT-TLCDI is a revision of the ordinary configuration of the recently proposed Tuned Liquid Column Damper Inerter (TLCDI). Unlike the traditional TLCDI layout, which involves a secondary liquid mass in a U-shaped tank coupled with a grounded inerter and connected to the isolation system by a spring-dashpot system, in the NT-TLCDI configuration, the damper is in parallel with the inerter rather than the spring. The optimal design, including the determination of the tuning frequency and damping ratios of the NT-TLCDI, is discussed with the purpose to reduce the base displacement variance of the BI system assuming a white noise base excitation. Under the optimal tuning condition, it is found that the proposed NT-TLCDI provides a larger suppression of vibration amplitude of the BI system than the traditional TLCDI in both the frequency domain and time domain. A more interesting aspect is the reduction of the device displacement achieved by the NT-TLCDI, which may be beneficial in practice when the space for housing the device is limited.

Design Optimization of a Hybrid Vibration Control System for Buildings

Control of high-rise structures under seismic excitations was investigated using a passive hybrid control system consisting of a base-isolation (BI) subsystem and a passive tuned liquid column damper (TLCD) system. Both of the systems were optimized considering using the other system in the same structure. An optimization method was developed, and a computer code was written based on dynamic analysis of the structure and metaheuristic optimization methods. Within the scope of the study, a general solution was found by using many earthquake records during the optimization process. Moreover, one of the most suitable and successful metaheuristic algorithms was used in this study. In addition, numerical simulations were performed on a benchmark high-rise building structure to investigate the effectiveness of the optimized hybrid control system in controlling the seismic response of the building. The performance of the base-isolated TLCD-controlled structure was examined when the TLCD was placed on the base floor by using a set of 44 recorded ground motions as base excitations. Based on the results obtained from this study, the use of a base-isolation subsystem decoupling the superstructure from the ground motions by lowering the structure’s fundamental natural frequency reduces the structural responses of the building in most cases. The responses of the base-isolation subsystem were not too large since the parameters of the BI subsystem were optimized specifically for the investigated structure. Nevertheless, displacements of BI might exceed the maximum limit to undesirable values in some cases. The TLCD system appears to be quite effective in protecting the base-isolation subsystem by reducing its displacements to the maximum allowable limit or below when attached to it. Moreover, the proposed passive hybrid control system can effectively reduce the structural responses under seismic excitations.

Roll motion mitigation of a barge-type floating wind turbine under random excitation using a tuned liquid column damper

ABSTRACT This paper aims to numerically evaluate the performance of tuned liquid column damper (TLCD) on mitigating roll motion of a barge-type floating wind turbine system subjected to random excitation. The governing equations for modeling the interaction between the roll motion of the floating system and liquid sloshing in the TLCD were derived using a Lagrangian approach. Random excitation based on wave spectrum was generated to simulate applied moment. Then, under the constraints of barge dimension and vertical liquid column movement, Den Hartog’s method was used to obtain optimum TLCD parameters. The results show that the optimally designed TLCD can efficiently mitigate the roll motion of the floating wind turbine.

A study of TLCD parameters for structural vibration mitigation

In this article, the efficiency of the tuned liquid column damper (TLCD) in reducing structural vibration is analyzed. The analysis by numerical methods and by analytical methods is adopted in the search for the ideal parameters for the liquid column. The equivalent linear model is considered for the U-shaped liquid column equation of motion with damping resulting from an orifice. Thus, variation of TLCD parameters for different loads is investigated. Initially, for the numerical study in conjunction with the analytical formulation, a sinusoidal forcing is adopted. Subsequently, the action of an earthquake through the recorded ground accelerations is considered in the case study. Optimal TLCD parameters are presented via response map for reducing the structure's maximum permanent response to harmonic excitation and for reducing the structure's rms response to seismic excitation with wide frequency and various amplitude. The variation of the TLCD parameters presented by the response map is directly related to the force acting on the structure. However, it is verified that regardless of the acting force, there is an ideal frequency range to tune the TLCD where the greatest reductions in the primary system response are found. It appears that reducing the aspect ratio of the liquid column makes this range narrower, making the damper more sensitive to parameter variations, as well as its performance. It is also observed that the increase in the attenuator mass ratio combined with the correct tuning and damping ratios present greater reductions in structural vibration. Also, the frequency ratio is reduced with the increase of the mass ratio, while the damping rate of the liquid column increases. From the ideal liquid column parameters determined by the parametric analysis, structural response reductions of approximately 60% were achieved.

Influence of Liquid Sloshing in the Vertical Limbs of Tuned Liquid Column Dampers on Structural Response Reduction

Influence of Liquid Sloshing in the Vertical Limbs of Tuned Liquid Column Dampers on Structural Response Reduction

Active Control Based on Hedge-Algebras Theory of Seismic-Excited Buildings with Upgraded Tuned Liquid Column Damper

Active Control Based on Hedge-Algebras Theory of Seismic-Excited Buildings with Upgraded Tuned Liquid Column Damper

On the Bidirectional Decoupling Characteristics of Toroidal Tuned Liquid Column Dampers

ABSTRACT The current theoretical model of toroidal-tuned liquid column dampers (TTLCDs) is developed only for unidirectional excitation. For the bidirectional design, it is necessary to verify whether the liquid responses can be effectively decoupled in two principal directions. This article analyzes the dynamic response of TTLCDs under unidirectional and bidirectional excitation scenarios. The results reveal that the liquid responses of TTLCDs excited unidirectionally provide a good prediction for those excited bidirectionally, and the bidirectional response of TTLCDs can be simplified as the linear superposition of the response in two principal directions.

MR Tuned Liquid Colum Damper (MR-TLCD) for Seismic Vibration Control

Seismic vibration control of flexible structure is an important aspect which mostly involves reduction of structure displacement via application of passive damper or mass dampers. Present study focuses on the seismic vibration control of flexible structure against random earthquake, through modified (using MR fluid) tuned liquid column damper (TLCD), known as the MR-TLCD. To this end, stochastic structural response analysis has been performed and results (structure displacement ratio and liquid displacement) are compared with conventional the TLCD. To establish the superior control efficiency of MR-TLCD over conventional TLCD, parametric study has been performed considering wide range of damper, structure, and earthquake loading parameters. Study results shows the existence of optimal value of tuning ratio, head loss coefficient, and yield shear strength of MR fluid of MR-TLCD which minimizes the structure displacement ratio, i.e. maximizes the control efficiency. Another important observation is that, for similar level of control efficiency MR-TLCD requires much less value of mass ratio than that of TLCD, and also at same time it keeps the liquid displacement much less compared to the TLCD, for same value of mass ratio. This aspect increases the applicability of MR-TLCD over TLCD for vibration control of the flexible structure. In comparison to the TLCD, MR-TLCD provides 17 % to 43 % higher structural displacement control efficiency and reduces liquid displacement by 14 % to 45 %.