Multiple Tuned Liquid Column Dampers Research Articles

Tuned Liquid Column Damper based Reduction of Dynamic Responses of Scaled Offshore Platforms in Different Ocean Wave Basins

Control of dynamic responses of renewable energy device platforms is important for their performance, safe operation and efficiency over their lifetime under regular and extreme wave conditions. Tuned Liquid Column Dampers (TLCDs) have been recently considered as a viable passive control mechanism in this regard but limited information is available in relation to their experimental performance. This paper compares scaled experiments conducted in two different ocean wave basins where floating offshore platforms were retrofitted with multiple TLCDs (MTLCDs). Performance of such MTLCDs in these scaled ocean wave basins are evaluated and compared considering control of dynamic responses for a specific objective. This paper shows the potential of MTLCDs to reduce motions in offshore platforms for different designs and platforms of MTLCDs and provides a comparison of the levels of reduction of dynamic responses achieved. The performance of MTLCDs in different wave basins create an experimental evidence base behind the potential use of such solutions, the objectives of such use and highlight related challenges and limitations.

Dynamic response mitigation of floating wind turbine platforms using tuned liquid column dampers.

In this paper, we experimentally study and compare the effects of three combinations of multiple tuned liquid column dampers (MTLCDs) on the dynamic performance of a model floating tension-leg platform (TLP) structure in a wave basin. The structural stability and safety of the floating structure during operation and maintenance is of concern for the performance of a renewable energy device that it might be supporting. The dynamic responses of the structure should thus be limited for these renewable energy devices to perform as intended. This issue is particularly important during the operation of a TLP in extreme weather conditions. Tuned liquid column dampers (TLCDs) can use the power of sloshing water to reduce surge motions of a floating TLP exposed to wind and waves. This paper demonstrates the potential of MTLCDs in reducing dynamic responses of a scaled TLP model through an experimental study. The potential of using output-only statistical markers for monitoring changes in structural conditions is also investigated through the application of a delay vector variance (DVV) marker for different conditions of control for the experiments.

Optimal Design of Multiple Tuned Liquid Column Dampers for Seismic Vibration Control of MDOF Structures

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 dierent 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 eectiveness 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.

Using Optimal Multiple Tuned Liquid Column Dampers for Mitigating the Seismic Response of Structures

Tuned liquid column damper (TLCD) has been used extensively to improve the seismic behavior of structures, and different methods have been proposed for optimal design of TLCDs on linear structures. For improving the effectiveness of TLCDs, multiple tuned liquid column dampers (MTLCDs) have been proposed, and each TLCD has different dynamic parameters. In this paper designing optimal MTLCDs and assessment of its effectiveness in mitigating the response of structures under earthquake excitations have been studied. The parameters of TLCDs have been determined based on minimizing the maximum displacement of structure through solving an optimization problem. Genetic algorithm (GA) has been used for solving the optimization problem. For illustration, the method has been used for designing optimal MTLCDs for a ten-storey linear shear frame subjected to a white noise excitation. According to the results of numerical simulations it could be said that the proposed method for designing optimal MTLCDs has been effective regarding the simplicity and convergence behavior of the method. Based on designing MTLCDs for different values of MTLCDs total mass ratio, it has been concluded that MTLCDs total mass affects significantly the performance of MTMDs where its increasing has led to improve MTLCDs performance. Also, testing the optimal MTLCDs structure under different testing excitations has shown that the performance of MTLCDs depends on the characteristics of earthquakes.

Multiple tuned liquid column dampers for reducing coupled lateral and torsional vibration of structures

This paper presents a theoretical investigation on the performance of multiple tuned liquid column dampers (MTLCD) for mitigating the coupled lateral and torsional vibration of a long span bridge which can be modelled as a two degrees-of-freedom structure. The cross section of the bridge has a vertical axis of symmetry but with the vertical offset between the elastic centre and the mass centre of the bridge. The external dynamic force and moment are applied at the elastic centre of the bridge. The proposed MTLCD consists of two sets of liquid column dampers with one tuned to the lateral frequency of the bridge and the other tuned to the torsional frequency of the bridge. The equations of motion for the coupled lateral and torsional vibration of the bridge with MTLCD are first presented. The nonlinear damping property of MTLCD is linearized using the equivalent linearisation technique. Extensive parametric studies are then carried out in the frequency domain to find beneficial parameters of the MTLCD for achieving maximum reduction of coupled lateral and torsional vibration of the bridge. The parameters investigated herein include water mass distribution between the two dampers, distance from the centre line of the MTLCD to the rotational axis of the bridge, ratio of horizontal length to total length of liquid column, head loss coefficient, and frequency tuning ratio. The performance of the MTLCD in reducing buffeting response of the bridge due to turbulent wind is finally investigated. This study shows that the performance of MTLCD in reducing the lateral and torsional displacements of the bridge depends on the head-loss coefficient and the frequency-tuning ratio significantly. It is also demonstrated that the aeroelastic effects due to the interaction between turbulent wind and bridge motion is a crucial factor affecting the performance of MTLCD in reducing buffeting responses of the bridge.

Multiple‐tuned liquid column dampers for torsional vibration control of structures: theoretical investigation

AbstractThis paper presents a theoretical investigation on the performance of multiple‐tuned liquid column dampers (MTLCD) for reducing torsional vibration of structures in comparison with single‐tuned liquid column dampers (STLCD). The analytical model is first developed for torsional vibration of a structure with an MTLCD under either harmonic excitation or white noise excitation. The experimental results are then used to verify the analytical model for coupled MTLCD‐structure systems under harmonic excitation. The performance of an MTLCD and its beneficial parameters for achieving the maximum torsional response reduction to white noise excitation are finally investigated through an extensive parametric study in terms of the distance from the centre line of the MTLCD to the rotational axis of the structure, the ratio of the horizontal length to the total length of liquid column, frequency bandwidth, head‐loss coefficient, the number of TLCD units in an MTLCD, frequency‐turning ratio and the spectral level of excitation moment. The results show that there is an optimal head‐loss coefficient and an optimal frequency bandwidth for an MTLCD to achieve the maximum torsional response reduction. It is also demonstrated that the sensitivity of an optimized MTLCD to the frequency‐tuning ratio is less than that of an optimized STLCD, and it can be further improved by increasing the bandwidth but at the cost of less torsional vibration reduction. Copyright © 2002 John Wiley & Sons, Ltd.

Multiple-tuned liquid column dampers for torsional vibration control of structures: experimental investigation

Multiple-tuned liquid column dampers for torsional vibration control of structures: experimental investigation

Multiple‐tuned liquid column dampers for torsional vibration control of structures: experimental investigation

AbstractThis paper presents an experimental investigation on the performance of multiple‐tuned liquid column dampers (MTLCD) for reducing torsional vibration of structures in comparison with single‐tuned liquid column dampers (STLCD). A large structure model simulating its torsional vibration and several STLCDs and MTLCDs of different configurations are designed and constructed. A series of harmonically forced vibration tests are conducted to evaluate the effectiveness of MTLCDs in reducing torsional vibration of the structure and to assess the performance effects of various design parameters, which include the number of TLCD units in a MTLCD, the bandwidth of a MTLCD, the frequency tuning ratio and the moment excitation amplitude. An averaging method is also used to identify the head loss coefficients of STLCDs and MTLCDs in conjunction with the free vibration test technique. The experimental results show that the performance of a MTLCD is better than a STLCD with the same water volume in reducing the torsional vibration of structure. The performance sensitivity to frequency tuning ratio can be improved by using MTLCDs. Copyright © 2002 John Wiley & Sons, Ltd.

Characteristics of multiple tuned liquid column dampers in suppressing structural vibration

The characteristics of multiple tuned liquid column dampers (MTLCD) in suppressing structural vibration are investigated. A parametric study involving the effects of frequency range, coefficient of head loss, number of TLCDs and central frequency on the performance of MTLCD is carried out through a numerical procedure which reflects the non-linear character of the liquid motion. The advantages and disadvantage of MTLCD are discussed. It was found that the frequency range and the coefficient of head loss have significant effects on the performance of a MTLCD; increasing the number of TLCDs can enhance the efficiency of the MTLCD, but no further significant enhancement is observed when the number of TLCDs is over five. The investigation also confirmed that the sensitivity of an optimised MTLCD to its central frequency ratio is not much less than that of an optimised single TLCD to its frequency ratio, and an optimised MTLCD is even more sensitive to the coefficient of head loss (or damping). However, to maintain the same level of efficiency as an optimised single TLCD, a MTLCD offers much wider choices in both frequency ratio and coefficient of head loss. In this sense, a MTLCD is more robust than a single TLCD.

Single- and multiple-tuned liquid column dampers for seismic applications

Design parameters for single- and multiple-tuned liquid column dampers for reducing the response of structures to seismic excitations are presented. A deterministic analysis is carried out using 72 earthquake ground motion records to determine the tuning ratio, tube width to liquid length ratio, and head loss coefficient corresponding to a given mass ratio for single-tuned liquid column dampers. A similar analysis is performed to determine the central tuning ratio, tuning bandwidth, and grouping of dampers for multiple-tuned liquid column dampers. The study indicates that by properly selecting the design parameters, single- and multiple-tuned liquid column dampers can reduce the response of structures to seismic excitation by up to 45 per cent. Design examples using single- and multiple-tuned liquid column dampers in a bridge and a ten-storey building are presented to illustrate how the parameters are selected and to demonstrate the performance of the devices under different ground excitations. The response of several structures with tuned liquid column dampers is compared with that using tuned mass dampers where it is shown that both devices result in comparable reductions in the response. © 1998 John Wiley & Sons, Ltd. This paper was produced under the auspices of the U.S. Government and it is therefore not subject to copyright in the U.S.

Control of buildings using single and multiple tuned liquid column dampers

Some design formulas and design procedures for single and multiple tuned liquid column dampers (TLCDs) are proposed in this study. Previous studies show that if the properties of the TLCD system are properly selected then the TLCD could be as effective as the traditional tuned mass dampers. In addition, the TLCD system offers advantages such as flexibility in terms of installation, little maintenance required, and potentials for multiple usage, etc., which are incomparable by other mechanical types of dampers. In this paper, a set of optimal properties such as length and head loss of a TLCD system are derived under the assumption that the building vibrates in a dominate mode and is subjected to Gaussian white noise excitation. A design procedure for a single TLCD system will be illustrated and discussed. Due to the nonlinearity in the damping term, the TLCD system is sensitive to the loading intensity. This loading sensitivity could limit the application range of the TLCD system. It will be shown in this paper that such a nonlinear effect can be reduced by using multiple TLCDs. As a demonstrative example, the control effects on a flexible building modeled as a single degree-of-freedom system subjected to white noise excitation will be analyzed and discussed using single or multiple TLCDs.