Equivalent mechanical models of tuned liquid dampers with different tank geometries

2008 ◽  
Vol 35 (10) ◽  
pp. 1088-1101 ◽  
Author(s):  
X. Deng ◽  
M. J. Tait
Keyword(s):  
Mechanical Properties ◽  
Effective Mass ◽  
Virtual Work ◽  
Damping Ratio ◽  
Tuned Liquid Damper ◽  
Equivalent Viscous Damping ◽  
Tuned Liquid Dampers ◽  
Mechanical Models ◽  
Sloshing Mode ◽  
Liquid Dampers

This paper focuses on the development of equivalent mechanical models for tuned liquid dampers (TLDs) with rectangular, vertical-cylindrical, horizontal-cylindrical, and hyperboloid (conical) tank shapes under external excitation in the transverse direction. Potential flow theory is utilized to obtain the free-surface response amplitude and the corresponding velocity of the sloshing liquid and Lagrange’s equations are used to determine the generalized properties. Morison’s equation and the virtual work method are used to estimate an equivalent viscous damping ratio based on the screen loss coefficient. The equivalent mechanical properties derived in this paper model the fundamental sloshing mode only and are restricted to small response amplitudes. Subsequently, the equivalent mechanical properties including effective mass, natural frequency, and damping ratio of the TLDs, having different tank geometries, are compared. It is found that the effective mass values for horizontal-cylindrical and hyperboloid TLDs are larger than the effective mass values for vertical-cylindrical and rectangular TLDs. The increased effective mass values for horizontal-cylindrical and hyperboloid TLDs can result in improved tuned liquid damper performance given the same total liquid mass as that of rectangular or vertical-cylindrical TLDs.

Linearized sloshing model for 2D tuned liquid dampers with modified bottom geometries

2014 ◽  
Vol 41 (2) ◽  
pp. 106-117 ◽  
Author(s):  
J.S. Love ◽  
M.J. Tait
Keyword(s):  
Mechanical Properties ◽  
Closed Form ◽  
Cost Savings ◽  
Mode Shapes ◽  
Tuned Liquid Damper ◽  
Flat Bottom ◽  
Tuned Liquid Dampers ◽  
Proposed Model ◽  
Sloshing Mode ◽  
Liquid Dampers

This study presents a new model for predicting the response of a two-dimensional tuned liquid damper (TLD) tank with a variable fluid depth. A simple finite element method is presented, which is used to calculate the sloshing mode shapes. From the mode shapes, the equivalent mechanical properties of the sloshing fluid are estimated. Three tanks (flat-bottom, triangular-bottom, and circular-bottom), which have closed-form expressions for their equivalent mechanical properties are used to evaluate the model. The proposed model is in agreement with the closed-form expressions. Subsequently, a parametric study is conducted on tanks with a chamfered-bottom, boxed-bottom, and ramped-bottom to assess how their properties change as the shape of the tank bottom is altered. The model provides TLD designers with greater flexibility when selecting a tank shape. Moreover, the model could be used to optimize the shape of a TLD tank to maximize its performance for a given liquid mass, allowing construction cost savings to be realized.

Tuned Liquid Damper Experiment Using Shaking Table

2013 ◽  
Vol 421 ◽  
pp. 772-777 ◽  
Author(s):  
Ki Pyo You ◽  
Young Moon Kim ◽  
Jang Youl You
Keyword(s):  
Natural Frequency ◽  
Damping Ratio ◽  
Tall Buildings ◽  
Excitation Amplitude ◽  
Shaking Table ◽  
Tuned Liquid Damper ◽  
Tuned Liquid Dampers ◽  
Liquid Dampers ◽  
Water Tanks ◽  
Wind Induced Vibration

The present study examines the characteristics of rectangular and circular tuned liquid dampers, which control wind-induced vibration in tall buildings, according to the natural frequency. The tuned liquid dampers (TLD) were of frequencies: 0.44Hz, 0.55Hz, 0.64Hz and 0.73Hz. The tuning feature of TLD water tanks was better in circular water tanks than in rectangular water tanks. Excitation amplitude affected the damping ratio based on energy dissipation capacity. At low excitation (below 5mm) and low natural frequency (0.44Hz), circular water tanks were advantageous over rectangular water tanks. However, at high excitation (over 5mm) and high natural frequency (over 0.55Hz), rectangular water tanks were advantageous over circular water tanks.

Theoretical Modeling of TLD With Different Tank Geometries Using Linear Long Wave Theory

2009 ◽  
Vol 131 (4) ◽  
Author(s):  
X. Deng ◽  
M. J. Tait
Keyword(s):  
Effective Mass ◽  
Virtual Work ◽  
Damping Ratio ◽  
Wave Theory ◽  
Mass Ratio ◽  
Flat Bottom ◽  
Tuned Liquid Dampers ◽  
Long Wave ◽  
Effective Mass Ratio ◽  
Energy Dissipated

This study focuses on the modeling of tuned liquid dampers (TLDs) with triangular-bottom, sloped-bottom, parabolic-bottom, and flat-bottom tanks using the linear long wave theory. The energy dissipated by damping screens is modeled theoretically utilizing the method of virtual work. In this proposed model, only the fundamental sloshing mode is considered, and the assumption of small free surface fluid response amplitude is made. Subsequently, the equivalent mechanical properties including effective mass, natural frequency, and damping ratio of the TLDs, having different tank geometries, are compared. It is found that the normalized effective mass ratio values for a parabolic-bottom tank and a sloped-bottom tank with a sloping angle of 20 deg are larger than the normalized effective mass ratio values for triangular-bottom and flat-bottom tanks. An increase in the normalized effective mass ratio indicates that a greater portion of the water inside the tank participates in the sloshing motion. The derived equivalent mechanical models for the TLD tank geometries considered in this study can be used for the preliminary design of structural-TLD systems.

Reduced Equivalent Static Wind Loads for Tall Buildings with Tuned Liquid Dampers

2012 ◽  
Vol 226-228 ◽  
pp. 1218-1227
Author(s):  
Andrew S. Ross ◽  
Ashraf A. El Damatty ◽  
Ayman M. El Ansary
Keyword(s):  
Boundary Layer ◽  
Wind Tunnel ◽  
Tall Buildings ◽  
Wind Loading ◽  
Tuned Liquid Damper ◽  
Dynamic Component ◽  
Tuned Liquid Dampers ◽  
Liquid Dampers ◽  
Equivalent Static Wind Load ◽  
Auxiliary Device

The tuned liquid damper (TLD) is a proven and an increasingly popular auxiliary device for mitigating the dynamic effects induced by wind loading on tall buildings. As buildings become taller, lighter, and more flexible, there is a greater contribution from the dynamic component. The most reliable tool for assessing the dynamic component is wind tunnel testing. A boundary layer wind tunnel is capable of accurately calculating an equivalent static wind load (ESWL) acting on a building. The current study investigates the reduction in the ESWL of a lateral-torsional coupled building with a TLD system installed. The building is sensitive to torsion in the first two vibration modes. The current investigation uses three unique multi-modal TLD systems designed specifically for a lateral-torsional coupled building. The building ESWL is evaluated with the TLD systems using measurements from tests conducted at the Boundary Layer Wind Tunnel Laboratory at Western University.

scholarly journals Study on the Aging Time Variation Law of Mechanical Properties of the Laminated Rubber Bearing in Coastal Bridges considering Frictional Slip

2021 ◽  
Vol 2021 ◽  
pp. 1-12
Author(s):  
Yue Li ◽  
Chongming Gao ◽  
Chong Li ◽  
Qian Li
Keyword(s):  
Mechanical Properties ◽  
Aging Time ◽  
Damping Ratio ◽  
Viscous Damping ◽  
Equivalent Viscous Damping ◽  
Coastal Bridges ◽  
Shape Coefficient ◽  
Rubber Bearings ◽  
Frictional Slip ◽  
Equivalent Viscous Damping Ratio

As an important support member in the structural system of coastal bridges, the frictional slip and the rubber aging of laminated rubber bearings will affect the service safety of the overall structure in earthquakes. In order to investigate the mechanical properties aging law of the rubber bearings considering frictional slip in the coastal bridges, a frictional slip experiment was carried out on the laminated rubber bearings. Moreover, the influence of rubber aging on the mechanical properties of the bearings with various shape coefficients was analyzed by the finite element method during the 100 years of service life of bridges. The results indicate that (1) the horizontal and vertical stiffness of the bearing increase linearly with the aging time of the rubber. The amplification of the bearing stiffness also grows with the shape coefficient of the bearing. (2) The frictional slip initiation displacement of the bearing grows with the rubber aging time. Furthermore, the larger the shape coefficient of the bearing is, the more the frictional slip initiation displacement of the bearing increases. (3) With the increase of the aging time, the equivalent viscous damping ratio of the bearing continues to increase and more energy is consumed by frictional slip. For the bearing with the shape coefficient of 16.38, the equivalent viscous damping ratio at 100 years of rubber aging time is 1.17 times higher than that of the initial state of the bearing, and 33.21% more energy is consumed through frictional slip. Given that the marine environment accelerates rubber aging and changes the mechanical properties, the effects of the frictional slip and rubber aging properties of the laminated rubber bearings on the seismic dynamic response of bridges should be considered in the seismic design of coastal bridges.

Experimental Test and Numerical Analysis of a Structure Equipped with a Multi-Tuned Liquid Damper Subjected to Dynamic Loading

2020 ◽  
Vol 20 (07) ◽  
pp. 2050075
Author(s):  
Bui Pham Duc Tuong ◽  
Phan Duc Huynh
Keyword(s):  
Shaking Table ◽  
Tuned Liquid Damper ◽  
Lumped Mass ◽  
Tuned Liquid Dampers ◽  
Lumped Mass Method ◽  
Dynamic Loadings ◽  
Coupling Equations ◽  
Liquid Dampers ◽  
Volume Method ◽  
Simplified Calculation

Tuned liquid dampers (TLDs) have many advantages in controlling building vibrations, among which multi-tuned liquid dampers (MTLDs) appear to have better stability and effectiveness. However, the tank wall was assumed to be rigid in the past by ignoring the fluid-structure interaction (FSI) at the interface, resulting in simplified calculation for the design of the TLDs. Moreover, the fluid in the tank was considered to be separate from the structure. This paper presents two numerical methods to control the responses of the frame under the dynamic loadings: (1) the lumped mass method for quickly designing the TLDs, and (2) the finite volume method/finite element method (FVM/FEM) for analyzing the fluid and solid domains of the TLDs in a single computational 3D model. In addition, the multi-field interaction between the structure-fluid-tank walls is considered by solving the coupling equations at the interfaces. A steel frame is fitted with an MTLD and tested experimentally on a shaking table to investigate its dynamic response. Numerical results are verified with the experimental ones, which show good agreement.

scholarly journals Numerical Analysis of the Dynamic Responses of Multistory Structures Equipped with Tuned Liquid Dampers Considering Fluid-Structure Interactions

2019 ◽  
Vol 13 (1) ◽  
pp. 289-300 ◽  
Author(s):  
Bui Pham Duc Tuong ◽  
Phan Duc Huynh ◽  
Tan-Trung Bui ◽  
Vasilis Sarhosis
Keyword(s):  
Fluid Structure Interaction ◽  
Fluid Pressure ◽  
Dynamic Responses ◽  
Water Tank ◽  
Tank Wall ◽  
Tuned Liquid Damper ◽  
Fluid Structure ◽  
Structure Interaction ◽  
Tuned Liquid Dampers ◽  
Liquid Dampers

Aims: The paper analyzes the effectiveness of tuned liquid damper in controlling the vibration of high rise building. The new contribution is considering the fluid-structure interaction of a water tank as a Tuned Liquid Dampers (TLD). Background: Currently, buildings are being built higher and higher, which requires TLDs to be larger as well. Therefore, the fluid pressure acting on the tank wall is more significant. In previous studies of liquid sloshing in TLDs, researchers simply ignored the effect of liquid pressure acting on the tank walls by making the assumption that the tanks are rigid. Currently, the failure of a tank because of FSI occurs regularly, so this phenomenon cannot be ignored when designing the tanks in general and TLDs in particular. Objective: To investigate the thickness of the tank wall affect to the TLD mechanism. Method: Numerical method was used for this research. Results: A TLD could be easy to design; however one could not bypass the fluid-structure interaction by assuming the tank wall is rigid. Conclusion: This kind of damper is very good to mitigate the dynamic response of structrure.

scholarly journals Effective Mass of Tuned Mass Dampers

Vibration ◽  
2018 ◽  
Vol 1 (1) ◽  
pp. 192-206 ◽  
Author(s):  
Laust Tophøj ◽  
Nikolaj Grathwol ◽  
Svend Hansen
Keyword(s):  
Effective Mass ◽  
Mechanical Systems ◽  
Added Mass ◽  
Tuned Mass Dampers ◽  
Traditional Methods ◽  
Engineering Structures ◽  
Tuned Liquid Dampers ◽  
Internal Motions ◽  
Liquid Dampers ◽  
Traditional Representation

Tuned Mass Dampers (TMDs) are widely used for the control and mitigation of vibrations in engineering structures, including buildings, towers, bridges and wind turbines. The traditional representation of a TMD is a point mass connected to the structure by a spring and a dashpot. However, many TMDs differ from this model by having multiple mass components with motions of different magnitudes and directions. We say that such TMDs have added mass. Added mass is rarely introduced intentionally, but often arises as a by-product of the TMD suspension system or the damping mechanism. Examples include tuned pendulum dampers, tuned liquid dampers and other composite mechanical systems. In this paper, we show how a TMD with added mass can be analyzed using traditional methods for simple TMDs by introducing equivalent simple TMD parameters, including the effective TMD mass, the mass of the equivalent simple TMD. The presence of added mass always reduces the effective TMD mass. This effect is explained as a consequence of smaller internal motions of the TMD due to the increased inertia associated with the added mass. The effective TMD mass must be correctly calculated in order to predict the TMD efficiency and in order to properly tune the TMD. The developed framework is easy to apply to any given general linear TMD system with a known motion. Here, we demonstrate the approach for a number of well-known examples, including tuned liquid dampers, which are shown to use only a small fraction of the total liquid mass effectively.

scholarly journals Multipoint Wave Measurement in Tuned Liquid Damper Using Laser Doppler Vibrometer and Stepwise Rotating Galvanometer Scanner

Sensors ◽  
2021 ◽  
Vol 21 (24) ◽  
pp. 8211
Author(s):  
Yoon-Soo Shin ◽  
Junhee Kim
Keyword(s):  
Natural Frequency ◽  
Vibration Suppression ◽  
Laser Doppler Vibrometer ◽  
Laser Doppler ◽  
Liquid Level ◽  
Tuned Liquid Damper ◽  
Tuned Liquid Dampers ◽  
Liquid Dampers ◽  
Tuning Frequency ◽  
Galvanometer Scanner

Liquid dampers, such as tuned liquid dampers (TLDs), are employed to improve serviceability by reducing wind-affected building vibrations. In order to maximize the vibration suppression efficiency of the liquid damper, the tuning frequency of the liquid damper should match the natural frequency of the building. Experimental evaluation of the tuning frequency of a liquid damper performed in a factory prior to installation in a building is a critical task to ensure correct performance, and for this, multipoint measurement of the TLD is required. In this study, a novel liquid level measurement system combining Laser Doppler Vibrometer (LDV) and a stepwise rotating galvanometer scanner was developed to observe liquid sloshing in TLD. The proposed system can measure the liquid level at multiple points simultaneously with a single laser point. In the experimental phase, the liquid damper’s natural frequency and mode shape are experimentally evaluated utilizing the developed system. The performance of the proposed system was verified by comparison with the video sensing system.

Development of a novel tuned liquid damper with floating base for converting deep tanks into effective vibration control devices

2020 ◽  
pp. 136943322095353
Author(s):  
Tanmoy Konar ◽  
Aparna (Dey) Ghosh
Keyword(s):  
Vibration Control ◽  
Structural Response ◽  
Liquid Level ◽  
Water Level Fluctuations ◽  
Tuned Liquid Damper ◽  
Water Storage Tank ◽  
Tuned Liquid Dampers ◽  
Floating Base ◽  
Tank System ◽  
Liquid Dampers

Despite the proven effectiveness of tuned liquid dampers (TLDs), readily available liquid storage tanks are rarely utilized for vibration control of laterally-excited structures, as these are deep tanks with low inherent damping. Further, the fluctuation in liquid level in these tanks also causes variation in the fundamental sloshing frequency, leading to detuning. To overcome these problems, a novel TLD with floating base (TLD-FB) is proposed, in which a constant and shallow liquid level is maintained between the free liquid surface and the floating base. The liquid above the floating base acts as a conventional shallow TLD that always remains tuned to the structural frequency. The paper demonstrates how the TLD-FB can be incorporated into a water storage tank system on an example building without disturbing its functionality and achieves structural response reduction, despite water level fluctuations in the tanks.

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