Tuned Sloshing Damper Research Articles

Investigating the Vibration Mitigation Efficiency of Tuned Sloshing Dampers Using a Two-Fluid CFD Approach

The efficiency of a Tuned Sloshing Damper (TSD) when mitigating wind-induced structural vibrations is investigated. We assessed the performance in terms of peak structural displacements and accelerations, compared to that of the Tuned Mass Damper (TMD). One load scenario considers oncoming gusts due to natural turbulence, whereas the other assumes predominant vortex shedding at a low turbulence intensity. The known optimum tuning rules for TSDs and TMDs were adopted. We combined numerical models for fluids and structures to simulate the dynamic effects caused by wind loading. A two-fluid Computational Fluid Dynamics (CFD) approach was used for the realistic simulation of the TSD. The interaction between the flow, the structural behavior and the added devices was captured. All of these computational methods and respective models represent the necessary components of a modular and flexible simulation environment. The study demonstrates that this workflow is suited to model the inclusion of TSDs and TMDs, as well as to capture the effect of transient wind at full scale. We specifically used it to quantify the efficiency of added dampers. The process highlights challenges in properly tuning a TSD and its reduced efficiency compared to that of a TMD. Such an outcome is attributed to the water mass and potential added damping only being partially activated. The computational framework promises the ability to improve such designs by enabling numerical optimization for better efficiency.

Characterization of Liquid Oscillation and Sloshing Properties of Toroidal TLCDs for Multidirectional Vibration Control

The toroidal tuned liquid column damper (TTLCD) has been known so far only for its multidirectional vibration control capabilities. The details of its liquid motion characteristics and energy dissipation capacity have been missing. To cover this gap, in this paper, experimental studies are carried out by shaking table tests and an effective three-dimensional computational fluid dynamics model of the TTLCD is developed. All parametric effects and the characteristics of the liquid motion in the TTLCD are addressed. The findings of the paper now clearly reveal that the TTLCD encompasses both an oscillatory liquid deflection as the first mode and a sloshing motion as the second mode vibration response. Accordingly, the results prove that the TTLCD operates not only multidirectionally but also as a unique multimodal device, which unites the properties of tuned liquid dampers (TLDs)/tuned sloshing dampers (TSDs) with tuned liquid column dampers (TLCDs).

Enhanced energy dissipation through 3D printed bottom geometry in Tuned Sloshing Dampers

This paper presents an experimental investigation about the dissipation properties of Tuned Sloshing Dampers (TSDs) characterized by different bottom geometries. An experimental campaign on sloped and rounded shaped TSDs is carried out considering a uni-directional harmonic base motion, by varying the water level and the excitation characteristics, i.e. amplitude and frequency. Results are compared with those obtained on a rectangular flat bottom TSD and benchmarked against a classic Tuned Mass Damper (TMD). The present study demonstrates that a TSD with a suitably modified bottom shape can significantly outperform a traditional flat-bottom TSD in terms of maximum amount of dissipated energy and robustness against frequency mistuning.

Tuned Sloshing Dampers in Tall Buildings: A Practical Performance-Based Design Approach

AbstractIt is becoming increasingly common to employ tuned sloshing damper (TSD) systems to reduce the wind-induced motion of tall buildings due to their affordability and apparent simplicity. Howe...

Hybrid simulation of a tall building with a double‐decker tuned sloshing damper system under wind loads

SummaryThis study presents an advanced experimental system, hardware‐in‐the‐loop (HIL), recently referred to as hybrid testing, to validate the effectiveness of a double‐decker tuned sloshing damper (TSD) system with screens applied to a recently constructed tall building. The HIL simulation facilitates a performance analysis of a combined structure‐damper system in which the nonlinear behavior of liquid motion in a TSD is physically modeled, whereas a building system under wind loads that behaves linearly is embedded virtually utilizing a computer model. The scaled model of the TSD is composed of a computer‐controlled system with a shaking table, sensors, and a real‐time communication link. The virtual building system on the computer communicates in real time with the hardware, that is, the physical model of TSD to evaluate on‐the‐fly the performance of a combined building‐TSD system. External excitation including random loading characteristics of winds, waves, or earthquakes can be implemented in HIL to observe the dynamics of the building‐damper system under a host of loading scenarios. An example of a recently completed tall reinforced concrete building with multiple TSDs placed side by side in double‐decker configuration under a suite of external loads and the proposed damping estimation procedure to evaluate the amount of auxiliary damping with TSD for ensuring the TSD design is presented. It examines the habitability of the building in winds and evaluates the effectiveness of the TSD system as well as the efficacy of the first HIL simulation for an actual tall building‐TSD system equipped with screens inside.

Tuned Sloshing Dampers With Large Rectangular Core Penetrations

Abstract Space restrictions at the top of tall buildings may necessitate using tuned sloshing dampers (TSD) tanks with large rectangular penetrations to accommodate the structural core of the tower. A finite element model is employed to predict the natural sloshing frequencies and mode shapes of liquid sloshing in a rectangular tank with a rectangular core. Equivalent mechanical properties are determined to predict the sloshing response. Frequency response predictions of wave heights, sloshing forces, and energy-dissipation per cycle agree with results from shake table testing conducted on a rectangular tank with a rectangular core. Energy dissipation due to flow around the core adds considerable damping to the liquid and is proportional to the response velocity-squared. Nonlinear coupling among sloshing modes results in multiple peaks in the frequency response plots near the fundamental resonant frequency. An interior core with a broad dimension in one direction substantially reduces the fundamental sloshing frequency and equivalent mechanical mass in the perpendicular direction; however, the fundamental sloshing frequency and equivalent mechanical mass in the parallel direction are only influenced marginally. Large rectangular cores reduce the proportion of the total water mass that is effective in controlling tower motion. A TSD with a rectangular penetrating core may enable a TSD option to be considered for the control of a tall building in cases where a traditional rectangular TSD is infeasible.

Series-Type Pendulum Tuned Mass Damper-Tuned Sloshing Damper

Abstract A pendulum-type tuned mass damper (TMD)-tuned sloshing damper (TSD) system is proposed as a cost-effective device to reduce wind-induced structural motion. Lagrange's principle is employed to develop an equivalent mechanical model for the system. The sloshing liquid provides additional gravitational restoring force to the pendulum TMD but does not provide a corresponding increase to its inertia. As a result, the natural frequency of the pendulum TMD is increased due to the TSD degree-of-freedom. Shake table testing is conducted on several pendulum TMD-TSD systems that are subjected to harmonic base excitation at discrete frequencies near the natural frequency of the pendulum TMD. The modeled and experimental results are in reasonable agreement when the liquid is not shallow or the response amplitude is not large. The pendulum TMD-TSD is coupled to a linear structure, and it is demonstrated through an analytical study that the device provides performance that is comparable to a traditional TMD. The proposed system is advantageous because it does not require a viscous damping system that is often one of the most costly components of traditional TMDs.

A method to generate dynamic vibration absorber load combinations

Dynamic vibration absorbers (DVAs) in the form of tuned mass dampers (TMDs) and tuned sloshing dampers (TSDs) are commonly employed to reduce structural accelerations during common wind events. Since the loads are applied in multiple directions, and may be produced by multiple DVAs, the generation of load combinations that envelop all expected DVA loads applied to the structure is a challenging task. A method is presented that employs principal component analysis to transform the DVA loading time series into M orthogonal principal components (PCs). By normalizing the PC time series, the loading envelop can be represented as an M-sphere (M-dimensional hypersphere). M-dimensional geometric objects (polytopes) are required to envelop the M-sphere. The coordinates of the polytope’s vertices, when converted back into the original loading coordinates, represent the load combinations. The method is applied to wind tunnel test data as well as monitoring data collected from two anonymous buildings equipped with multiple DVAs. The method reduces the dimensionality of the problem by eliminating PCs that do not contribute significantly to the response. The results demonstrate that if efficient polytopes are chosen, the conservatism associated with the load combinations can be reduced by employing a larger number of load combinations.

On the nonlinear performance of a tuned sloshing damper under small amplitude excitation

This paper explores the potential of a tuned sloshing damper (TSD) in the control of small amplitude vibrations, which is often important from serviceability considerations, through the use of a relatively small mass ratio of the damper liquid. To investigate the nonlinear behavior of the TSD, real-time hybrid testing is conducted in which a single rectangular tank containing water constitutes the prototype TSD. The structure is modeled as a multi-degree-of-freedom system. Two different base input motions, namely harmonic and synthetically generated broad-banded input, are considered. The sensitivity of the TSD performance to tuning ratio vis-à-vis low mass ratio is studied. The experimental results are compared with those obtained from a numerical study carried out using the shallow water wave theory-based nonlinear, semi-empirical model, for the simulation of the sloshing motion of the TSD liquid (water). Results indicate that in the tuned condition, even with a low mass ratio, the TSD is highly effective in the suppression of the small amplitude vibrations, which is underestimated by the simulation model.

A New Hybrid SPH–FEM Model to Evaluate Seismic Response of TSD Equipped-Structures

Tuned Sloshing Dampers (TSD) are passive devices, working based on shallow liquid sloshing in a rigid tank to suppress the horizontal structural vibrations induced by wind loading or earthquake excitations. The key parameters in design of a TSD could be referred to the natural frequency of the liquid sloshing motion and the inherent damping of the TSD during the excitation. Due to the highly nonlinear behavior of the liquid free-surface occurring in TSDs, accurate prediction of the TSD-structure’s behavior during strong excitations is highly desirable. In the current paper, Weakly Compressible form of Smoothed Particle Hydrodynamic (SPH) method is used to simulate the flow within rectangular TSDs during large movements. Characteristics of the flow such as wave height and sloshing forces acting on the container’s walls are calculated and compared with the existing experimental and numerical data. A hybrid SPH-Finite Element Method (FEM) was developed to investigate the seismic response of MDOF structures equipped with multiple TSDs. The proposed model was employed to evaluate the dynamic response of MDOF structures under severe seismic excitations with different frequency contents. The results showed that depending on the frequency content of the ground motion, having the TSDs tuned to a frequency close to the natural frequency of the structure could significantly alter the seismic response of the structures. The effectiveness of TSD is also related to the higher modes effect for MDOF structures and location of TSDs placed on the structural floors.

Nonlinear Series-Type Tuned Mass Damper-Tuned Sloshing Damper for Improved Structural Control

A novel type of dynamic vibration absorber (DVA) is proposed, which consists of a tuned mass damper (TMD) and tuned sloshing damper (TSD) connected in series to the structure. The system enables the expensive viscous damping devices (VDDs) associated with traditional TMDs to be omitted from the design. A linearized equivalent mechanical model and a nonlinear multimodal model are developed to investigate the proposed system. A TMD–TSD is nonlinear due to the quadratic damping associated with liquid drag, which ensures the system performance is amplitude-dependent. Simple expressions for the optimal TSD–TMD mass ratio, tuning, and damping ratios are employed to design a TMD–TSD coupled to a single degree-of-freedom (SDOF) structure. Frequency response curves for the structure, TMD, and TSD degrees-of-freedom are created for several excitation amplitudes, and the nonlinear behavior of the system response is evident. The performance of the TMD–TSD is evaluated against traditional TMD and TSD systems—with the same total mass—by computing the effective damping produced by each system. The proposed system is found to provide a superior acceleration reduction performance and superior robustness against changes to the frequency of the primary structure. The proposed system is, therefore, an effective and affordable means to reduce the resonant response of tall buildings.

Effectiveness of dynamic vibration absorbers implemented in tall buildings

In recent decades, dynamic vibration absorbers (DVAs), such as tuned sloshing dampers (TSDs) and tuned mass dampers (TMDs) have been increasingly used to enhance the serviceability performance of tall buildings subjected to wind excitation. While the fundamental theory of ideal structure-DVA systems is well developed, there is a lack of available literature documenting the performance of DVA systems that have been installed in tall buildings. Moreover, it is challenging to directly quantify the effectiveness of DVAs installed in buildings due to the uncertainties associated with the applied wind loading. In particular, traditional methods are generally unable to directly calculate the effective damping that a DVA adds to the building.This study presents the results of full-scale structural monitoring conducted on two tall buildings that have been equipped with DVAs to reduce wind-induced motion. The responses of the building and the DVA were monitored during significant wind events. The performance of the DVAs is directly determined by using the building and DVA responses, and the structure-DVA mass ratio, to calculate the added effective damping. The theoretical added effective damping of an ideal structure-DVA system is compared to the measured value, revealing that nonlinear effects that are typically neglected, such as friction, can significantly alter the theoretical added effective damping from its measured value at low response amplitudes. The DVAs studied have significantly decreased the wind-induced motions of the tall buildings monitored.

Nonlinear modelling of tuned sloshing dampers with large internal obstructions: Damping and frequency effects

Internal obstructions are commonly employed in tuned sloshing damper (TSD) tanks to increase the inherent damping of the sloshing liquid closer to its optimal value for the targeted excitation amplitude. However, these obstructions also produce added mass, which acts to decrease the natural sloshing frequency of the tank. Using potential flow theory, this study develops both a linearized equivalent mechanical model and a fourth-order nonlinear multimodal model that are capable of accommodating the fluid drag and added mass that are generated by the paddles. The linearized equivalent mechanical model represents the sloshing liquid as an equivalent spring–mass–dashpot system with amplitude-dependent damping. The fourth-order nonlinear multimodal model captures the nonlinear coupling that occurs among the first four sloshing modes. Shake table tests are then conducted on a scale model TSD tank equipped with vertical paddles of cruciform plan section. The sloshing forces predicted by the linearized and nonlinear models are in reasonable agreement with the experimental results. The nonlinear model is generally in good agreement with the experimental wave heights, whereas the linearized model often underestimates the peak wave heights considerably. A plot is created which shows the frequency shift produced by the paddles as a function of the width of the paddles. If the paddles’ widths are greater than approximately 5% of the tank width, the effect on the natural sloshing frequency is noticeable.

Tuned Sloshing Damper in Response Control of Tall Building Structure

The paucity of space and requirements of building infrastructure has driven us to explore for taller building systems. Also a large number of construction materials has emerged and are being used extensively in buildings. The usage of light weight high strength materials reduces the space requirement and also becomes economical. However, such structures have structurally become susceptible to the lateral loading generated due to wind or earthquake. Attempts are made to control the response of tall building systems by introducing control mechanisms in the form of active, passive or hybrid system. Usage of liquid storage tanks in tall building system in the form of a passive control device proves effective. Several works have been carried out in the past to understand the efficacy of such system, which popularly is known as tuned liquid dampers or tuned sloshing dampers (TSD). The present paper deals with the development of a numerical code to demonstrate the efficacy of such tuned sloshing damper considering fluid structure interaction effect.

Vibration control in wind turbines for performance enhancement: A comparative study

The need for a more affordable, reliable, clean and secure energy has led to explorations in non-traditional sources, particularly renewable energies. Wind is one of the cleanest energy sources that plays a significant role in augmenting sustainability. Wind turbines, as energy convertors, are usually tall and slender structures, and depending on their location (inland or offshore), they can be subject to high wind and/or strong wave loadings. These loads can cause severe vibrations with detrimental effects on energy production, structural lifecycle and initial cost. A dissipativity analysis study was carried out to know whether wind turbine towers require damping enhancement or rigidity modifications for vibration suppression. The results suggest that wind turbines are lightly damped structures and damping enhancement is a potential solution for vibration lessening. Accordingly, the paper investigates different damping enhancement techniques for vibration mitigation. The efficacy of tuned mass damper (TMD), tuned liquid column damper (TLCD), tuned sloshing damper (TSD), and viscous damper (VD) to reduce vibrations is investigated. A comparison among these devices, in terms of robustness and effectiveness, is conducted. The VD can reduce both displacement and acceleration responses of the tower, better than other types of dampers, for the same control effort, followed by TMD, TSD, and finally TLCD. Nevertheless, the use of VDs raises concerns about where they should be located in the structure, and their application may require additional design considerations.

A design procedure of two-way liquid dampers for attenuation of wind-induced responses of tall buildings

A new design procedure of a two-way liquid damper which reduces wind-induced responses of a tall building is presented as a quick guide for structural engineers. The two-way liquid damper combines the (1) Tuned Liquid Column Damper (TLCD) in which liquid moves through a U-shape tube and the (2) Tuned Sloshing Damper (TSD) in which liquid sloshes within a container, respectively for two orthogonal directions. Dimensions of the damper, such as horizontal liquid column length and the thickness of the TLCD, the width of the TSD, and liquid height are determined given the condition of tuning the natural frequencies of liquid motion in the damper to those of the building. The design procedure is a trial and error process of satisfying geometrical constraints (i.e., maximum space where the damper is installed) and varying controlled response factors (i.e., performance of vibration attenuation). A design example of the damper is illustrated in the paper for its installation at a 64-story reinforced-concrete residential building.

Effectiveness of Distributed Mass Damper Systems for Lightweight Superstructures

AbstractDistributed mass damper (DMD) systems are discussed as a method of suppressing lateral motions of superstructures during wind storms and earthquakes. Potentially, DMD systems are a technology that is economical enough for widespread application to buildings or other structures. Focus is placed on lightweight superstructures as a reflection of the trend toward the use of ultra-lightweight floor slabs in high-rise buildings. Results of model-scale experiments are presented that show that tuned mass damper (TMD) systems that add between 1.3 and 2% to the total superstructure gravitational mass are effective methods of increasing damping in superstructures and reducing peak lateral accelerations during forced vibration events. In those experiments, tuned sloshing dampers (TSDs) were employed in conjunction with floor and roof plates that simulated ultra-lightweight slabs constructed from cross-laminated timber (CLT), which is a new material option in North America. The use of TSDs was a surrogate for ...

Reducing Acceleration Response of a SDOF Structure with a Bi-Directional Liquid Damper

This study deals with the design of a bi-directional liquid damper for a SDOF structure. Two dampers are usually needed to reduce wind-induced responses of tall structures since they are along and across wind ones. The proposed damper has the advantage of controlling both responses with a single damper. The damper shows dynamic behavior of both tuned liquid column damper (TLCD) and tuned sloshing damper (TSD) in the direction of two axes perpendicular with each other. This paper presents experimental verification to confirm its control performance. First, shaking table test is carried out to investigate reducing responses of a SDOF structure by the damper. Control performance of the damper is expressed by the transfer function from shaking table accelerations to SDOF structure ones. Testing results show that the damper reduced bi-directional responses of a SDOF structure. Also, it reduced torsion responses. It was confirmed from system identification results that damping ratio of a SDOF structure increased by the bi-directional liquid damper.

TLCD와 TSD를 이용한 새로운 형태의 양방향 감쇠기 설계변수

A new type bi-directional damper using a tuned liquid column damper(TLCD) and a tuned sloshing damper(TSD) is introduced in this study. Two dampers are usually needed to reduce wind-induced responses of tall buildings since they are along and across wind ones. The proposed damper has the advantage of controlling both responses with one damper. One of objectives of this study is to derive analytical dynamics to investigate coupled effects due to TLCD and TSD. Another objective is to address the effect of coupled control force due to TLCD and TSD on the dynamic characteristic of the damper based on analytical dynamics. Shaking table test is undertaken to experimentally grasp dynamic characteristics of the damper under white noise excitation. Its dynamic characteristic is expressed by the transfer function from the shaking table acceleration to the control force generated from the damper. Finally, its design parameters are identified based on the coupled dynamics, which include the mass ratio of horizontal liquid column to total liquid for a TLCD, the participation factor of the fundamental liquid sloshing for a TSD and damping ratio for both cases.

Tunedsloshing damper using electro-rheological fluid

A tuned sloshing damper (TSD) utilizing an electro-rheological(ER) fluid as a sloshing liquid (ER-TSD) is proposed. The sloshingfrequency of the TSD depends on the sloshing stroke length of the liquidcontained in the tank. In this paper, the ER-TSD is used in the form of arectangular tank with electrodes. The ER-TSD sloshing frequency can becontrolled by applying an electric field to the ER fluid. We have studiedthe vibrations of a structure which had two natural frequencies. Theforced and free vibration tests were carried out with and without theER-TSD. By controlling the electric field, the ER-TSD can suppress thevibrations of the structure even when the natural frequency of thestructure changes. The free vibration responses of the structure with theER-TSD were analytically obtained by using a tuned mass damper model basedon the Housner theory. The simulated results appeared to be in reasonableagreement with experiments.