Tuned Liquid Column Gas Damper Research Articles

Vibration control of floating offshore wind turbine using semi-active liquid column gas damper

Floating offshore wind turbines (FOWTs) are becoming an essential instrument for energy generation worldwide. Specific environmental conditions at sea have led to unwanted vibrations and excessive displacement in floating wind turbines, which reduce the performance of these systems. This study aimed to evaluate the effect of semi active liquid column gas damper (SALCGD) on controlling the vibrations of a FOWT under different loads with wave and wind. Variable hydraulic head loss coefficient and variable frequency were used in this study, as well as DBG, VBG, and Bang-Bang algorithms. An analytical model was developed to analyze the dynamic response of the joint wind turbine and damper system, and a time history analysis was performed in the SIMULINK/MATLAB simulation environment. The results indicated that the SALCGD could reduce the displacement response of the pitch degree of freedom in platform in both semi-activation methods. In addition, the performance of each control algorithm varied according to the loading conditions. The effect of SALCGD and TLCGD (tuned liquid column gas damper) was compared in controlling the vibrations of the wind turbine system. According to the results, the superiority of using a semi-active damper was revealed in control.

Development of a novel tuned liquid multiple columns gas damper under wave and earthquake incidence

A developed tuned liquid multiple columns gas damper, introduced as a TLMCGD damper, is proposed in this study and its capability is assessed on an offshore jacket platform under regular and irregular waves and also earthquake incidence. The proposed damping system includes a combination of performance of both tuned liquid multiple columns damper (TLMCD) and tuned liquid column gas damper (TLCGD). The number of multiple columns and gas pressure are defined as of the main parameters of the damper and their performance are investigated through various values under earthquake. According to the results, a passive optimum TLMCGD system can decrease the structural response of the system up to 22, 60, and 55 percent under regular wave, irregular wave, and earthquake, respectively. The whole structural response of the system reduces as the number of columns and the value of gas pressure increases up to a certain amount. To investigate the effectiveness of gas pressure in performance of the damper, various gas pressure values are considered for different 4 to 10-column TLMCGD dampers. By increasing the value of the gas, the displacement RMS reduces significantly. The highest decrement occurs as 50 to 100 bar gas pressure is specified for the gas springs of the dampers. Still more investigation is required to evaluate other key parameter of the system within an experimental study which is left for future studies.

Adaptive control of damaged structures by using smart tunable liquid column gas damper considering dynamic soil–structure interaction

Liquid column dampers are adjusted based on the characteristics of the host structure and the type of external forces. It is assumed in most studies that the structure is rigidly connected to the ground, and the characteristics of the structure are invariant during external excitations. The performance of passive dampers may lose, or structural displacements may be increased by changing these conditions. This study presented a new method to find the optimal control forces for structures equipped with smart tuned liquid column gas damper (TLCGDs), considering variable characteristics of the structure and the soil–structure interaction. The proposed method calculates the gas pressure inside the columns by regularly adjusting and updating the frequency and damping of the TLCGD. The unknown or changed soil–structure characteristics are estimated by a system identification method, and damper parameters are determined through an optimization algorithm. The method was tested on 3- 9- and 10-story shear buildings under harmonic and earthquake excitation. According to the results, the smart damper more effectively reduced the structural displacement.

An innovative approach for bias correction of a passive controlled offshore structure using experimental non-contact measurements

Abstract The discrepancy between the theoretical and experimental results is defined as one of the main reasons for updating the analytical models of the structures based on experimental data sets. Although various updating methods have been proposed in the literature, the capability of the approaches on controlled systems is yet to be investigated. In this paper, a numerical model updating method is proposed considering both parametric and structural uncertainties on a passive controlled complex structural system. The method is applied on a three-dimensional offshore jacket platform model including an attached Tuned Liquid Column Gas Damper (TLCGD) damping system. The effect of the damper parameters on updating the numerical model is investigated for the first time using a Laser Doppler Vibrometer (LDV) as a non-contact measuring system. The maximum decrement is occurred using a sine function which seems to be because of the sinusoidal nature of the experimental data. According to the results, the discrepancy between the numerical and experimental data can be decreased by 75 percent utilizing non-contact measurements and discrepancy functions. The results also indicate that by calibrating the gas pressure and the total liquid column length of the TLCGD damping system, as the most important parameters of the damper, the discrepancy is decreased almost 66 percent. The proposed method of updating the FE model for the controlled systems is beneficial for the old sophisticated controlled practical systems that increasing their life time span is essential.

Upgrading the Seismic Capacity of Pile-Supported Wharfs Using Semi-Active Liquid Column Gas Damper

One of the most important structures in the ports is the wharf. The most common one is the pile-supported wharf. This type of wharf is consisted of a number of piles and one deck which placed on the piles. In addition to the conventional loads that this structure should withstand, in seismic areas, pile-supported wharfs should have the necessary capacity and strength against seismic excitations. There are some approaches to increase the seismic capacity of the berth. One of these methods is to control the vibrations of the pile-supported wharf against earthquake loads using a damper. In this research, for the first time, a new semi-active damper called the semi active liquid column gas damper (SALCGD), was used to reduce the response of pile supported wharf under seismic loads. In the first step by applying different records of the earthquake, the most important parameter of this damper - the optimal opening ratio of the horizontal column- was obtained for this particular structure. In the following, the performances of this damper and its comparison with the tuned liquid column gas damper (TLCGD) were discussed. This study showed that the use of this semi-active damper (SALCGD) reduces the displacement of the pile-supported wharf by 35% and reduces the acceleration of the structure by 50% on average. In contrast, the passive damper (TLCGD) reduces the displacement of about 20 percent and the acceleration of about 30 percent. Therefore, it was observed that the semi-activation of the damper (SALCGD) had a significant improvement in its performance in controlling the vibrations of pile-supported wharf.

Structural control of a fixed offshore structure using a new developed tuned liquid column ball gas damper (TLCBGD)

Structural control of a system can be achieved by employing different control methods. The effectiveness of a control technique straightly depends on the performance of the control device. Among control devices, the tuned liquid column gas damper (TLCGD) has shown high vibration control capabilities. In this study, a newly developed damping system as a tuned liquid column ball gas damper (TLCBGD) system is introduced. The developed system is a combined version of a tuned liquid column ball damper (TLCBD) and a TLCGD system. The new damper is utilized on an offshore jacket platform and its qualification is studied under both regular and irregular wave incidences. The efficiency of the TLCBGD system is investigated numerically by implementing ball-tube ratio and gas pressure parameters. The effects of the ball-tube ratios and the gas pressure values on the vibration suppression capacity of the system are assessed through a parametric study. In comparison to a passive TLCGD system, the results revealed that the utilizing a TLCBGD system in the jacket platform improves the structural vibration suppression capability.

Suppressing structural vibration of a jacket-type platform employing a novel Magneto-Rheological Tuned Liquid Column Gas Damper (MR-TLCGD)

Structural vibration is one of the main engineering concerns in recent decades especially in offshore structures due to the dynamic environment and accessibility. Among different methods, applying a device within the primary system for mitigating the vibration through system damping increment is one of the most promising methods. In this study, a combined novel Magneto-Rheological Tuned Liquid Column Gas Damper (MR-TLCGD) as a damping system is introduced for the first time in structural control field and the efficiency of the system is investigated on a three dimensional fixed offshore jacket platform under both wave and earthquake excitation. The performance of the system is studied through considering different values of yield stress and gas pressure as of the main parameters of MR fluid and gas damper. The results are compared to a previously studied Tuned Liquid Column Gas Damper (TLCGD) system. Based on the results, utilizing an MR-TLCGD system in an offshore structure can be defined as a proper choice for reducing structural vibration. It can be concluded that considering an appropriate value for yield stress and gas pressure, regardless of the results limitation for this case study, is of great importance in practical cases.

Application of Soft Computing in the Design and Optimization of Tuned Liquid Column–Gas Damper for Use in Offshore Wind Turbines

Application of Soft Computing in the Design and Optimization of Tuned Liquid Column–Gas Damper for Use in Offshore Wind Turbines

Design of coupled tuned liquid column gas dampers for multi-mode reduction in vibrating structures

Tuned liquid column gas dampers (TLCGD) show excellent energy and vibration absorbing capabilities appropriate for earthquake engineering. The objective of this work is to introduce a new concept of coupled tuned liquid column gas dampers which allow an extended field of applications. In the proposed configuration, several absorbers are connected in a spatial chain generating a multi-degree of freedom damper system which can be tuned to a selected number of structural modes. Because all absorbers vibrate at different natural frequencies simultaneously, the proposed design represents an improvement over conventional TLCGD which can only be tuned to a single structural mode. Another benefit of multi-mode tuning is the significant increase in active liquid mass compared to other damping devices. For a most effective vibration reduction, a numerical tuning process in state space will deliver the free system natural frequency and damping ratio of all absorbers. The capabilities of the new damping device are demonstrated on a simple laboratory structure that is investigated numerically and experimentally. The results illustrate the excellent energy dissipating properties of the proposed setup and emphasize the adequacy of coupled TLGCD for base-isolated structures. A notable benefit of such types of dampers lies in their lack of moving mechanical parts, their cheap and easy implementation into civil engineering structures and low maintenance costs. Possible modifications with respect to natural frequency and even of the damping properties can be performed with little additional expenses, and the additional weight due to the liquid mass may be used as a possible reservoir, e.g., for fire fighting. Apart from that, they exhibit a performance that is comparable to tuned mass dampers.

Contribution of tuned liquid column gas dampers to the performance of offshore wind turbines under wind, wave, and seismic excitations

The main intention of the present study is to reduce wind, wave, and seismic induced vibrations of jackettype offshore wind turbines (JOWTs) through a newly developed vibration absorber, called tuned liquid column gas damper (TLCGD). Using a Simulink-based model, an analytical model is developed to simulate global behavior of JOWTs under different dynamic excitations. The study is followed by a parametric study to explore efficiency of the TLCGD in terms of nacelle acceleration reduction under wind, wave, and earthquake loads. Study results indicate that optimum frequency of the TLCGD is rather insensitive to excitation type. In addition, while the gain in vibration control from TLCGDs with higher mass ratios is generally more pronounced, heavy TLCGDs are more sensitive to their tuned frequency such that ill-regulated TLCGD with high mass ratio can lead to destructive results. It is revealed that a well regulated TLCGD has noticeable contribution to the dynamic response of the JOWT under any excitation.

Control of wind/wave-induced vibrations of jacket-type offshore wind turbines through tuned liquid column gas dampers

Wind/wave-induced vibrations of jacket-type offshore wind turbines (JOWTs) are suppressed by placing a passive vibration absorber, called tuned liquid column gas damper (TLCGD), on the turbine nacelle. Adopting an ensemble of 75 wind/wave combinations, three different JOWTs and a SimuLink-based nonlinear model in time domain, main parameters of the TLCGD are optimised to reach the minimum standard deviation of nacelle displacement. Obtained results indicate that contribution of the proposed TLCGD is more pronounced in the case of regular excitations such as those from sea waves and less turbulent winds. Depending on the wind/wave combination, TLCGD can result in reductions up to 45% and 51% in nacelle displacement standard deviation and maximum acceleration, respectively. As a result, TLCGD deemed to be well suited to protect fatigue critical JOWTs as well as acceleration-sensitive devices of the nacelle.

A novel aseismic foundation system for multipurpose asymmetric buildings

The vulnerability of civil engineering structures with fundamental frequency, say roughly above 1 Hz, (or buildings having less than ten stories), when exposed to the strong motion phase of an earthquake is considerably reduced by means of base isolation. The low-pass filter for isolating horizontal vibrations is redesigned where the classical elastomeric bearings are substituted by a number of prestressed helical steel springs with pivoted columns along their vertical axes carrying a fraction of the dead weight and guiding the remaining horizontal motion. The base-isolated building in its fundamental mode is considered to be rigid and low-cost tuned liquid column gas dampers (TLCGDs), in optimal arrangement within the plan of the basement of the building, supply the effective damping of the remaining horizontal vibrations. TLCGD-tuning in a first step is performed by a simple transformation of the well-documented optimal parameters of the tuned mass damper (TMD) followed by fine-tuning in state space. The action of the passive damping device is commonly considered to be sufficient. Since the gas-spring effect somewhat counter acts changes in fluid mass, the absorber can be used as a water reservoir. Compatible sliding elements are innovatively designed to resist the motion of the building relative to the ground for sufficiently small disturbances by static friction, thus complete the isolation system. However, during seismic excitation, the frictional contact is released over much of the time to avoid excessive wear.

Active TLCGD control of plane asymmetric buildings under earthquake excitation

The sealed, tuned liquid column gas damper (TLCGD) with gas-spring effect extends the frequency range of application and efficiently increases the modal structural damping. Active tuned liquid column gas damper (ATLCGD) is developed for the vibration control of plane asymmetric buildings subjected to earthquake excitation, improving the performance of the passive control scheme. The active behaviour is obtained by adjusting the pressure at the end of the liquid column using a pressurised reservoir. The classical linear quadratic regulator (LQR) design is presented as a straightforward approach to optimal control. Numerical simulations indicate a significant vibration reduction of plane asymmetric buildings by active control within the strong motion of the dynamic response.

Vibration Control of Plan-Asymmetric Buildings Using Active TLCGD

This paper examines the effectiveness of the Active Tuned Liquid Column Gas Damper (ATLCGD) when equipped on the plan-asymmetric structures subjected to earthquake excitation. The active behaviour is obtained by adjusting the pressure at the end of the liquid column using a pressurised reservoir. The classical linear quadratic regulator (LQR) control strategy is applied to determine optimal control force of the ATLCGDs. A case study of a four-storey asymmetric structure is conducted to illustate excellent control efficacy of the proposed active TLCGD control system.

Passive vibration control of plan-asymmetric buildings using tuned liquid column gas dampers

The sealed, tuned liquid column gas damper (TLCGD) with gas-spring effect extends the frequency range of application up to about 5 Hz and efficiently increases the modal structural damping. In this paper the influence of several TLCGDs to reduce coupled translational and rotational vibrations of plan-asymmetric buildings under wind or seismic loads is investigated. The locations of the modal centers of velocity of rigidly assumed floors are crucial to select the design and the optimal position of the liquid absorbers. TLCGD`s dynamics can be derived in detail using the extended non-stationary Bernoulli`s equation for moving reference systems. Modal tuning of the TLCGD renders the optimal parameters by means of a geometrical transformation and in analogy to the classical tuned mass damper (TMD). Subsequently, fine-tuning is conveniently performed in the state space domain. Numerical simulations illustrate a significant reduction of the vibrations of plan-asymmetric buildings by the proposed TLCGDs.