Tuned liquid dampers

Faculty of Engineering

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Tuned liquid dampers Abd Elrahman Abd Elbasst Elborolossy, Department of Civil Engineering,

Faculty of Engineering, Tanta University, Egypt

E-mail: [email protected]

Abstract - Current trends in construction industry demands taller and lighter structures, which are also more flexible and having quite low damping value. This increases failure possibilities and also, problems from serviceability point of view. Several techniques are available today to minimize the vibration of the structure, out of which concept of using of TLD is a newer one. This study was made to study the effectiveness of using TLD for controlling vibration of structure.

- A TLD (tuned liquid damper) is a passive control devise on top of a structure that dissipates the input excitation energy through the liquid boundary layer friction, the free surface contamination, and wave breaking. In order to design an efficient TLD, using an appropriate model to illustrate the liquid behavior as well as knowing optimum TLD parameters is of crucial importance. - In this study the accuracy of the existing models which are able to capture the liquid motion behavior are investigated and the effective range of important TLD parameters are introduced through real-time hybrid shaking table tests.


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History: Since 1950s liquid dampers have been used to stabilize marine vessels or to control wobbling motion of satellites. In the late 1970s TLD has started to be used in civil engineering to reduce structural motion; Vandiver and Mitome (1979) used TLD to reduce the wind vibration of a platform. Also, Mei (1978) and Yamamoto et al. (1982) looked into structure-wave interactions using numerical methods. In the early 1980s important parameters such as liquid height, mass, frequency, and damping for a TLD attached to offshore platforms were studied by Lee and Reddy (1982). Bauer (1984) introduced a rectangular tank full of two immiscible liquids to a building structure. Kareem and Sun (1987), Sato (1987), Toshiyuki and Tanaka, and Modi and Welt (1987) were among the first researchers who suggested using TLD in civil structures.Wakahara et al. (1992) and Tamamura et al. (1995) showed the effectiveness of TLDs installed in real structures such as Nagasaki airport tower, Yokohama Marine tower, and Shin Yokohama Prince (SYP) hotel to reduce the structural vibration.

Lateral load resistance :-

1- Structural modifications. 2- Aerodynamic modifications. 3- Base isolation techniques.

4- Damping sources.


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Damping sources :- 1- Structural.

2- Aerodynamic.

3- Soil.

4- Auxiliary " supplemental

Supplemental Damping Systems:-

Supplemental damping system can be categorized in three groups as passive, active and semi-active systems. These dampers are activated by the movement of structure and decrease the structural displacements by dissipating energy via different mechanisms

Active Systems. Active systems monitor the structural behavior, and after processing the information, in a short time, generate a

set of forces to modify the current state of the structure.

Generally, an active control system is made of three

components: a monitoring system that is able to perceive the

state of the structure and record the data using an electronic

data acquisition system; a control system that decides the

reaction forces to be applied to the structure based on the from

monitoring system and; an actuating system that applies the

physical forces to the structure. To accomplish all these, an

active control system needs continuous external power source.

The loss of power that might be experienced during a

catastrophic event may render these systems output data

ineffective.


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Semi-Active Systems.

Semi-active systems are similar to active systems except that compared to active ones they need less amount of external power. Instead of exerting additional forces to the structural systems, semi-active systems control the vibrations by modifying structural properties (for example damping modification by controlling the geometry of orifices in a fluid damper). The need for external power

Passive Mechanism. Seismic input energy without any need for external power source. Their properties are constant during the seismic motion of the structure and cannot be modified. Passive control devices have been shown to work efficiently; they are robust and cost-effective. As such, they are widely used in civil engineering structures. The main categories of the passive energy dissipation systems can be seen in Table (Christopoulos and Filiatrault 2006)


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Displacement-activated devices absorb energy through the relative displacement between the points they connect to the structure. Their behaviour is usually independent of the frequency of the motion and is in phase with the maximum internal forces generated at the end of each vibration cycle corresponding to the peak deformations of the structure. Metallic dampers, friction dampers, self-centering dampers, and viscoelastic dampers are the main devices in this group.

Velocity-activated

devices absorb energy through the relative velocity between their connection points. The behaviour of these dampers is usually dependent on the frequency of the motion and out-of-phase with the maximum internal forces generated at the end of each vibration cycle corresponding to the peak deformations of the structure. This causes a lower level of design forces for structural members and foundation. Viscous and viscoelastic dampers are the typical examples in this category.

Motion-activated dampers are secondary devices that absorb structural energy through their motion. They are tuned to resonate with the main structure, but, out-of-phase from it. These dampers absorb the input energy of the structure and dissipate it by introducing extra forces to the structure; therefore, they let less amount of energy to be experienced by the structure.


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Tuned mass dampers (TMDs) and tuned liquid dampers(TLDs)

are the examples in this category.

Tuned liquid damper types:

Tuned liquid dampers (TLDs) can be implemented as an active or passive device and are divided into two main categories: tuned sloshing dampers (TSD) and tuned liquid column dampers (TLCDs).

TSD: Tuned Sloshing Damper, TLCD: Tuned Liquid Column Damper, LCVA: Liquid Column Vibration Absorbers, DTLCD: Double Tuned Liquid Column Damper, HTLCD: Hybrid Tuned Liquid Column Damper, PTLCD: Pressurized Tuned Liquid Column Damper.


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Tuned Sloshing Damper:-

Tuned liquid column Damper :-


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Controllable Tuned Liquid Damper:


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Comparison

Type What it do How Main resistance

Structural modifications Resist the additional

straning actions form lateral loads.

By adding stiff elements (e.g.

shear wall, farm element, etc.)

Wind & Ground movement.

Aerodynamic modifications

Avoid the wind or enhancement of

it's behavior.

By making an Aerodynamicshap

e design for the overall building.

Wind.

Base isolation Avoid lateral loads (earth movement

)

By inserting a new elements under the foundations

and adding another

foundation under the base isolation

element.

Ground movement.

Damping Resist and reduce the relative lateral

movement between the

foundations and the super structure.

By adding a mass or a force acting

real time with the shake of the

building.

Wind & Ground movement.


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Tuned liquid damper

Type Force source Position Advantage T.S.D Water

sloshing force On the top of the building.

suited for small scale excitations

T.L.C.D Variance of mass while liquid motion

On the top or near top.

More advantageous and can be installed anywhere

C.T.L.D Structure & liquid mass

N.A efficiency, but costly

Structural vs Auxiliary:

Structural Auxiliary

Huge mass added. Less mass (about 2% of the hole structure mass )

Adds stiffness to the structure (less structure time period)

No stiffness or very small additional stiffness.

No lateral load force reduction

Reduce up to 50% of the forces.


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Analytical Models

In this chapter selected models that are considered in this study

are: introduced. Since the liquid behaviour is highly

1- nonlinear, considering nonlinearity of crucial importance

leads to the wave breaking

2-using shallow water in tanks occurrence under various excitation amplitude and frequency combinations where the

liquid surface is no longer continuous.

Therefore, the models presented in this chapter were selected

with the nonlinearity and wave breaking in mind for rectangular

tanks filled slopped bottom shape tanks (Olson and Reed 2001;

Xin et al. 2009

Gardarsson et al. 2001) and introduced models that are able to

account

3- for slopped bottom shapes, one of these models is also

included in this study There are two common approaches that

have been used to model the liquid-tank behaviour. In the first

one the dynamic equations of motion are solved, whereas in the

second approach the properties of the liquid

damper are presented by equivalent mass, stiffness and

damping ratio

essentially modeling the TLD as an equivalent TMD (Tuned Mass

Damper ) .


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Solving Liquid Equations of Motion

Several researchers have investigated the liquid behaviour

based on solving the liquid equations of motion

. The assumptions they made along with numerical methods

they used to solve the liquid equations of motion have a

significant effect on their prediction. Ohyama and Fujji (1989)

were among the first who introduced a numerical model for the

TLD.

Using among the first who introduced a numerical model for the

TLD .

Using potential flow theory their model was able to take care of

nonlinearity however, computational time was the main

problem with this model (Sun et al. 1992). Kaneko and Ishikawa

(1999) used an integrating scheme to solve continuity and

Navier-Stokes equations without any consideration for wave

breaking. Zang et al. (2000) used a linearized form of Navier -

Stokes equations

. Fediew et al. (1995) assumed that the derivative and higher

orders of the velocity and wave height can be neglected due to

small values of velocity and wave height; however, this

assumption works for weak excitations or when the frequency of

excitation is away from that of

the TLD (Lepelletier and Raichlen 1988). Ramaswamy et al.

(1986) solved nonlinear Navier -Stokes equations using Lagrang

ian description of fluid The model has some physical problems


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motion and finite element method involving sloshing dynamics

of inviscid and viscous fluids.

Although the amplitude excitations, they assumed a linear

behaviour of the liquid sloshing.

Yamamoto and Kawahara (1999) used arbitrary Lagrangian

Eulerian (ALE) form of Navier -Stokes equations to predict the

liquid motion .

The model tends to be unstable in the case of large amplitude

sloshing.

To solve the instability problem a smoothing factor is

considered and the accuracy is highly dependent to the value of

this factor that varies from zero to one with no clear outline for

the selection.

Siddique and Hamed (2005) presented a new numerical model

to solve Navier -Stokes and continuity equations. Although it is

indicated that the algorithm can accurately predict the sloshing

motion of the liquid under large excitations , the model is unable

to predict the deformations in the case of surface discontinuity

where screen exist or wave breaking occurs. Frandsen (2005)

developed a fully nonlinear 2- D -transformed finite difference

model based on inviscid flow equations in rec tangular tanks.

The model was not able to capture damping effects of liquid and

shallow water wave behaviour.


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Sun’s Model

Sun et al. (1992) introduced a model to solve nonlinear Navier -

Stokes and continuity equations.

A combination of boundary layer theory and shallow water

wave theory is employed and resulting equations were solved

using numerical methods . An important aspect of this model is

that it considers wave breaking under large excitations by means

of two emprical coefficients. In what follows, a summary of this

model will be provided.

The rigid rectangular tank shown in figure 3. 1 with the length

2𝑎 , width 𝑏

and the undisturbed water level ℎ is subjected to a lateral

displacement 𝑥 𝑠 .

The liquid motion is assumed to develop only in the − plane. It

is also assumed that the liquid is incompressible, irrotational

fluid, and the pressure is constant on the liquid free surface.


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Figure 3.1: Dimensions of the Rectangular TLD

The continuity and two- dimensional Navier -Stokes equations

that are employed to describe liquid sloshing are defined as

where 𝜕 (𝑥 , 𝑧 , 𝜕 ) and 𝜕 (𝑥 , 𝑧 , 𝜕 ) are the liquid velocities

relative to the tank in

the 𝑥 and 𝑧 direction, respectively, 𝑔 is the gravity

acceleration, 𝑝 is the pressure, 𝜌 denotes the density and 𝑣

represents the kinematic viscosity of the liquid Because of the

relatively small viscosity of the liquid, the friction is only

appreciable in the boundary layers near the solid boundaries of

the tank .

The liquid outside the boundary layers is considered as potential

flow and the velocity potential can be expressed as (Sun 1991)


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where 𝑘 is wave number and H is defined as (Sun 1991)

Based on the shallow water wave theory, potential is assumed

as (Shimisu and Hayama 1986)

𝛷 (𝑥 , 𝑧 , 𝜕 ) = 𝛷 (𝑥 , 𝜕 ). cosh 𝑘 (ℎ + 𝑧𝑧 ) (4 −

3)

The boundary conditions are described as

𝛷 ( , 𝜕 ) in equation (4- 3) can be determined by the boundary

conditions.

Then, using equation (4- 3) , 𝜕 and its differentials are expressed

in terms of 𝜕 .

Since the liquid depth is shallow, t he governing equations are

integrated with respect to z from bottom to free surface to

obtain :


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𝑘( = tanh 𝑔𝑇, ) ℎ𝑘( tanh ) / 𝜂+ ℎ( 𝑘= tanh 𝜙 ,) ℎ𝑘( = tanh 𝜎 Where

+ h )

𝜕 and are the independent variables of these equations . 𝜆

in equation (6) is a damping coefficient accounting for the

effects of bottom ,

side wall and free surface, and is determined as (Sun et al.

1989):

In which S stands for a surface contaminating factor and a value

of one corresponding to fully contaminated surface is used in

this model (Sun et. Al 1992). is the fundamental linear sloshing

frequency of the liquid and can be found as (Sun 1991)


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in equation (6) are employed to account for wave 𝑎𝑑and 𝑓𝐶

breaking when ( 𝜂 > ℎ ). These coefficients are initially equal to a

unit value, and when wave breaking occurs, takes a constant

𝑎𝑑𝐶value equal to 1.05 as suggested by Sun et al. (1992).

depends on 𝑚𝑎𝑥 that is the maximum displacement

experienced by the structure at the location of the TLD, when

there is no TLD attached; and it can be found as

Equations (5) and (6) are discretized in space by finite difference

method

and solved simultaneously using Runge- Kutta-Gill method to

find u and η.

Knowing η the force introduced at the walls of the TLD can be

described

as [29]:

are the free surface elevations at the right and 0𝜂and 𝑛𝜂where

left tank walls, respectively.

To consider TLD -Structure interaction, a single- degree-of-

freedom

(SDOF) structure with TLD is considered as shown in figure 3.2.

The

equation of motion of the TLD -structure system subjected to a

ground


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) is 𝑔𝑎acceleration (

are structural mass, damping 𝑠wand 𝑠𝜉, 𝑠𝑘, 𝑠𝑐, 𝑠𝑚where

stiffness, damping ratio and natural frequency coefficient,

structural relative displacement to represents 𝑠𝑥respectively,

displacement experienced the ground which is meanwhile the

is ground acceleration and F is TLD base shear 𝑔𝑎, by the TLD

due to sloshing force on the TLD wall that is given by equation

(10).

Equations (5), (6) and (12) must be solved simultaneously in

order to fin d the response of the SDOF structure equipped with

TLD. A step-by-step procedure is employed where knowing the

structural acceleration at each


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Figure 3.2: Schematic of SDOF System with a TLD Attached to It

step, equations (5) and (6) are solved using Runge- Kutta-Gill

method and F calculated on Then, F, SDOF is

calculated using Runge- Kutta-Gill method from equation (12)

and next step acceleration is found to be used in the next step

calculations.

Appendix A provides information on the discretization technique

and application of Runge-Kutta-Gill method.

Equivalent TMD Models

Another approach to investigate TLD behaviour is replacing the

TLD by its equivalent TMD and finding the effective TMD

properties such as stiffness , damping ratio , and mass that can

properly describe TLD characteristics.

These equivalent properties are found through experimental

procedures.

Sun et al. (1995) found equivalent TMD properties base on

nonlinear

Navier-Stokes equations and shallow water wave theory.

However, the experimental cases presented in this study are

limited.

Casciati et al. (2003) proposed a linear model which can

interpret frustum -conical TLDs behaviour for small. The

excitations model is not able to capture high amplitude

excitations and instability problems occur near resonance.


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Tait(2008) developed an equivalent linear mechanical model

that acc ounts for the energy dissipated by the damping screens

for both sinusoidal and random excitation.

Yu’s Model.

Yu (1997) and Yu et al. (1999) modeled the TLD as a solid mass

damper that can capture nonlinear stiffness and damping of the

liquid motion.

This mechanical model can capture the behaviour of the TLD in a

broad range of excitation amplitudes and can be a good TLD

design tool. An equivalent Nonlinear-Stiffness-Damping (NSD)

model is proposed through an energy matching procedure when

the dissipated energy by the equivalent NSD model is matched

by that of the TLD. Figure 3.3 shows the schematic of the

characterized SDOF model of the TLD; , 𝑐𝑑 , and 𝑚𝑑 refer to

the stiffness, damping coefficient , and mass of the NSD model,

respectively. A challenge in this model is the determination of

the NSD parameters to describe TLD behavior.

As it is shown in figure 3.3, the NSD model used in simulation is

based on introducing the interaction force made by liquid

sloshing inside the tank. Considering t he TLD as an equivalent

linear system, this force can be characterized by its amplitude

and phase.


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Energy dissipation per cycle is found by equation (13) and non-

Energy dissipation per cycle is found by equation (13) and non-

dimensionalized version is provided as equation (14).

Where, shows integration over the shaking table displacement

per cycle, 𝐹𝜕 is the force generated by the liquid sloshing

motion in the tank , 𝑚𝜕 refers to the mass of the liquid, w is the

excitation angular frequency of

Figure 3.3: Schematic of the a) TLD and b) Equivalent NSD Model

the shaking table (equation (8)), A is the amplitude of the

sinusoidal excitation and the denominator of (14) is the

maximum kinetic energy of the water mass treated as a solid

𝑑𝐸he NSD model dimensional energy dissipation of t-mass. Non

is determined based on NSD model behaviour when it is

subjected to harmonic base excitation with frequency ratio β.

The non-dimensionalized amplitude and phase 𝜙 that describe

the interaction force of the NSD model and are


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calculated as :

is the 𝑒𝑓⁄ is the excitation frequency ratio, 𝑑𝑓𝑒𝑓where =

excitation frequency is the natural frequency of the NSD,

frequency dissipation range of -over high w 𝐸is fitted to 𝑑𝐸

the frequency using least -squares method. In this procedure 𝑚𝑑

, the stiffness 𝑑𝑓and w𝑓 𝜉initial values for = , and assuming

and damping coefficients are determined .

The results are analyzed through two ratios; the first is

frequency shift ratio as defined by:


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stands for the linear fundamental frequency of the w𝑓where

liquid and is defined as :

where h is the undisturbed height of the water and a is the half

length of the tank. The second ratio is the stiffness hardening

ratio that is defined

The above matching scheme is applied to a set of experimental

tests in order to evaluate the equivalent stiffness and damping

ratio for the NSD model. The equivalent stiffness and damping

ratio are investigated as a function of the wave height, water

depth, amplitude of excitation and the tank size. Non-

dimensional value of the amplitude was found to be the most

suitable parameter to describe the stiffness and damping ratio.

This value is described as:

where 𝑤𝑤 is the amplitude of excitation and a is the half length

of the tank in the direction of motion . To calculate , as it is

shown in figure 3. 4, each time the displacement curve crosses

the time axis , the maximum displacement during the previous

half cycle x max, i-1 is calculated and the absolute value of that

is considered as 𝑤 for the its half cycle in order to find ᴧ .


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Figure 3.4: Displacement Time History to Calculate

After finding the corresponding values of and κ from

equations (18) and (20), they are plotted versus ᴧ and the best-

fitted curve is found in order to find the equations for damping

ratio and stiffness hardening ratio.

Yu (1997) and Yu et al. (1999) obtained the damping ratio as

As stiffness hardening ratio changes considerably before ᴧ =

0.03 (corresponding to weak wave breaking) and then starts to

grow up sharply after ᴧ = 0.03 (corresponding to strong wave

breaking), Yu (1997) and Yu et al. (1999) obtained the equation

for 𝜅𝜅 is obtained as

Finally, as it is shown in figure 3 .5, a two -degree-of-freedom

model is considered to investigate the interaction of TLD -

structure system when a TLD is attached to a SDOF structure. In

this model in equation (21) is found from the structural


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displacement where the TLD is attached (usually top floor). So,

each time the displacement curve crosses zero axis stiffness and

damping ratio of the NSD model are updated based on

equations (22), (23) and (24) corresponding to the top structural

displacement. Figure 3.6 illustrates the schematic for stiffness

and damping parameter updating of the NSD model. The

equations of motion are presented in matrix form as

are the mass, damping, 𝑠 𝑥and 𝑠 𝑥, 𝑠𝑥, 𝑠𝑘, 𝑠𝑐, 𝑠𝑚where

stiffness, relative displacement, velocity and acceleration of the

structure , respectively. The same parameters with the

, 𝑠𝑐, 𝑑𝑚parameters , subscripts d refer to the NSD model. The

are assumed to be given in this procedure. 𝑠𝑘and

Figure 3.5: 2-DOF System: a) Structure with TLD b) Structure with

NSD Model


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Figure 3.6: Schematic for Determining the NSD Parameters

𝑑𝑚, 𝑠𝑐, 𝑠𝑘Given Constants: ,

Sloped Bottom Models

There are studies on the effect of changing the tank bottom

shape from rectangular to sloped bottom pattern. Gardarsson

et al. (2001 ) investigated the performance of a sloped- bottom

TLD with an angle of 30° the tank base. It is observed that more

liquid mass participates in to sloshing force in the slopped-

bottom case leading to more energy dissipation. Olson and Reed

(2001) investigated the sloped- bottom TLDs el developed by

using non-linear stiffness and damping mod Yu (1999) . It is

shown that the sloped- bottom tank should be tuned slightly

higher than the fundamental frequency of the structure to

introduce the most effective damping. Tait and Deng (2009)


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showed that the normalized effective mass ratio for a sloped-

bottom tank with a sloping angle of 20° is larger than the

normalized effective mass ratio of flat-bottom tanks .

Xin’s Model

Xin (2006) and Xin et al. (2009) proposed a model that is capable

to investigate sloping - bottom TLD based on the linearized

shallow water wave equation ( Gardarsson 1997), using the

velocity potential function and wave height equation suggested

by Wang (1996) and liquid damping introduced by Sun et al.

(1995) and Sun (1991). As it is shown in figure an equivalent flat

- bottom TLD model is proposed to simulate the the sloped-

bottom case and the equivalent flat -bottom tank is kept equal

𝐿 ′ of the equivalent flat-bottom tank is equal to the total length

of the sloping bottom).

The maximum water depth H' remains the same when the

equivalent width of the flat - bottom tank 𝐵 ′ is decreased in

of the sloshing water the w𝑉to keep the total volume order

same as that of the sloped-bottom tank . 𝐵 ′ is defined as (Xin

2006):

floor of the ℎ𝑗 ) applied to the t( 𝑗𝐹The horizontal control force

building structure by a sloping - bottom TLD is equal to the

resultant of the fluid dynamic pressures on the left and right

walls of the flat - bottom TLD tank ; and is expressed as (Xin et

al. 2009)


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Figure 3.7: Equivalent Flat-Bottom Tank

) represents the relative t( 𝑗 𝑋is the water density, 𝜌where

building floor with respect to the base of ℎ𝑗the acceleration on

t the base the ground acceleration a ) refers tot( 𝑔𝑥the building,

of the building, and 𝑦 (t ) is the first modal acceleration of water

sloshing. The modal response of water

sloshing can be determined as :


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Where M , C , and K are the mass, damping coefficient, and

stiffness matrices of the structure ;

𝑋 , 𝑋 , and 𝑋'' represent the relative acceleration , velocity, and

displacement vectors with respect to the base of the building ; I

is the earthquake influence vector with unity for all elements;

is the TLD influence vector with zero elements except 𝑓I and

floor of the building ℎt𝑗he element corresponding to the for t

where the TLD is attached that is unity. Knowing the initial

condition, equation (28) is solved and the tank acceleration is

calculated and used in equation (27) to find the interface force.

Having the interface force and using equation (31) structural

displacement and acceleration are found for next step

calculations.


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In this study, since the experiments were done for a rectangular

tank , these equations are solved for the equivalent rectangular

tank in order to investigate this model’s accuracy. The Simulink

used to solve these equations is presented in Appendix B

Experimental Results and Analysis

Testing Method

In this study the real-time hybrid Pseudodynamic (PSD) testing

method has been employed to investigate the TLD behaviour

under a range of structural parameters and load cases.Hybrid

PSD testing method combines computer simulation with

physical by testing part of the structure physically (experimental

substructure) coupled with a numerical model of the remainder

of the structure (analytical substructure )

When the experimental substructure has load rate dependent

vibration characteristics as in the case of TLD, the hybrid PSD

test needs to be performed dynamically in real - time. By

employing real - time hybrid PSD interaction has been

investigated by test in this study, the structure- TLD only

physically testing the TLD as the experimental substructure and

a wide range of TLD - structure system properties were easily

investigated by modifying the parameters of the structure as the

analytical substructure As it is shown in figure 4.1 , the whole

system is divided into the experimental (TLD) and analytical

(structure) substructures . TLD is tested physically and the

interaction force is measured using a load cell. The response of


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the structure considering also the measured interaction force

from the TLD under the specified external loading is calculated

numerically using Simulink and Real -time Workshop. In this

study the analytical substructure is modeled as a single degree

of freedom oscillator. The displacement command generated by

the Simulink model is imposed on the shaker. The

software/hardware communication and synchronization issues

are taken care of by using the WinCon/Simulink interface.

Figure 4.1: Schematic of the Hybrid Testing Method

Test Setup

Figure 4.2 shows a picture of the test setup. The shaker table

consists of a 1 Hp brushless servo motor driving a 12.7 mm lead

screw. The lead screw drives a circulating ball nut which is

coupled to the 457x457 mm table. The table itself slides on low

friction linear ball bearings on 2 ground hardened shafts and has

76.2 mm stroke. The shaker comes with WinCon software, the

real-time control software that runs Simulink models in real -


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time. The built-in control laws are able to impose harmonic or

preset earthquake historical data under displacement control. In

this study a velocity feed forward component was added to

improve the tracking of the command displacements by the

shaker. The load cell is a 22.2 N ( 5 lb) load cell that can carry

compression and tension loads. The tank is made of plexi-glass

that has dimensions of 464 mm (length), 305 mm (width). A

water height of 40 mm which corresponds to 0.667 Hz of

sloshing frequency of the tank (based on equation (8)) was

selected there the weight of the TLD was 5.64 kg.

Figure 4.2: Experimental Setup

As it is shown in figures 4.1 and 4.2, the tank is placed on

greased ball bearings to eliminate friction. Special attention was

given to keep the tank in the perfectly horizontal position. Only

a few degrees out of horizontal position was observed to

introduce large amount of error in the measured restoring force.

Two rollers are also placed at the two sides of the tank in order

to keep its movement in one direction.


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TLD Subjected to Predefined Displacement

History

This section summarizes the results where the TLD was

subjected to displacement histories with amplitude of 20 mm

and various frequencies to cover a range of β from 0.5 to 1.5.

The frequency ratio β , as previously defined, is the ratio of the

frequency of loading to the sloshing frequency of the tank. By

considering the energy dissipated in each case (see figure 4.3),

the effective value for β was obtained. As can be seen in figure

4.3 energy dissipated by the TLD increases until β <1.2, and

starts to decrease for values of β >1.2, rendering β =1.2 as the

effective frequency in terms of energy dissipation. To shed some

light into the TLD energy dissipation behavior, another set of

experiments were performed. In these tests, the water inside

the TLD was replaced with an equivalent solid mass while the

TLD was imposed to the same predefined displacement

histories. The measured restoring forces in these tests

correspond to the inertia component of the interface force. By

subtracting the inertia component from the interface force, the

sloshing force was calculated for each frequency ratio. Figure

4.4a shows the inertia and sloshing force components of the

interface force for β=1.5.

It can be seen that these component s have a destructive

interface where they almost cancel each other resulting in very

little if not nonexistent


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Figure 4.3: Hysteresis Loops for Different β Values


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energy dissipation for this frequency (see figure 4.3). As it is

shown in figure 4.4b for β =1.2, on the other hand, the inertia

and sloshing force components have constructive interface

leading to an efficient energy dissipation as described earlier.

Figure 4.4a: Destructive Interface of Sloshing and Inertia Forces

at 𝛽𝛽 = 1.5

Figure 4.4b: Constructive Interface of Sloshing and Inertia Forces

at 𝛽𝛽 = 1.2


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TLD-Structure Subjected to Sinusoidal Force

In this section, using real -time hybrid PSD method, the TLD -

structure system was investigated under a series of sinusoidal

force. To be able to three different force observe weak and

strong wave breaking behavior amplitudes (i.e., 3 N, 5 N, and 8

N) were used while the forcing frequency adjusted to be the

same as the structural frequency (see table 4.1). In addition to

the forcing function amplitude, a range of structure to TLD

sloshing frequency ratio ( α ) from 0.5 to 1.5 was considered in

the hybrid simulations. The TLD properties were kept

unchanged; to obtain the aforementioned range of α , the

structural stiffness in the analytical the structure and the

substructure was adjusted. The mass of structural

Table 4.1: Parameters for experiments introduced in Chapter 4.4

Structural displacements in the form of deformations relate to

the damage of the structural members during seismic events. On

the other hand nonstructural components (ceiling - wall

attachments , experience considerable inertial forces due to

floor accelerations


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Figure4.5 present the displacement/ acceleration versus

frequency response graphs for 3 different force levels

considering the structure with and without the TLD.

Figure 4.5: Structural Displacement and Acceleration with and

Without TLD


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Figure 4.6 represents the data from figure 4.5 in terms of

percent reductions of displacements and accelerations. From

these figures it can be concluded that, for the forcing levels

considered corresponding to weak and strong wave breaking,

TLD is remarkably efficient in reducing the displacement and

acceleration response around the frequency ratio α near

Figure 4.6: Structural Displacement and Acceleration Reduction

one, where the tank is in resonance with the structure. The

results from the experiments with the sinusoidal forcing

function were also used to investigate the accuracy of the

models that were selected and presented in chapter 3. In each

case, the error between the experiment and model prediction

was quantified by:

represents 𝑝𝐹stands for measured values and 𝑚𝐹where

predicted values from the models.


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Figure 4.7: Comparison Between Experimental Results and

Analytical Predictions for 𝐹 = 3𝑁

Figure 4.7 presents the comparison between experiment and

numerical model predictions for the force level of = 3𝑁𝑁 Since

no wave breaking was observed, all the models were able to

capture the TLD behavior reasonable well. Considering the

entire range of α , the error quantified by equation (32) for Sun’s

and Xin’s models is around 2cm, and for Yu’s model it is 2.7 cm.

For the range of 𝛼𝛼 between 0.9 and 1.1, which is the range

where TLDs are tuned in the design practice, Yu’s and Xin’s

model


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introduce more accurate predictions with 0.7 and 0.6 cm error

while Sun’s model has 1.8 cm error in this range.



In the case of = 5𝑁𝑁 , where some wave braking near 𝛼𝛼 = 1

occurs, Yu’s and Xin’s models have a good prediction while Sun’s

model overestimates the displacement. For α smaller than 0.8

the models do not agree well with experimental results while

for α larger than 1.3 Sun’s model agrees well with experimental

results and Xin’s model overestimates the displacement.

Although Sun’s model has accounted for wave breaking in its

formulation, it is unable accurately liquid for values near one


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where some wave breaking is observed. Overall Xin’s model

generates more accurate results with 3 cm error in comparison

with Yu’s and Sun’s model with about 4.5 cm error. For

between 0.9 and 1.1, Yu’s and Xin’s model accumulate an error

of 0.8 and 0.6 cm, respectively; whereas Sun’s model has less

accurate predictions with 3.7 cm error.



For = 8𝑁𝑁 , where wave breaking was captured during almost

all frequency ratios, the accuracy of all the models suffer.


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Sun’s model overestimates the structural displacement for the

entire range of the frequency ratio. For α near one, Yu’s and

Xin’s models seem to match well with experiment results and

Yu’s model continues to have a good agreement with

experiment for α larger than one. Overall, Yu’s and Xin’s model

show more accurate results with 7 cm error and Sun’s model has

a less accurate prediction with an accumulated error of 8.5 cm.

For between 0.9 and 1.1, Xin presents a more accurate model

with 1.5 cm error in comparison with Yu’s and Sun’s model with

3 and 6 cm error, respectively. Considering all three load cases

and the ranges of the frequency ratios , Yu’s model provides

reasonable predictions in both weak and strong wave breaking

and in a broad range of frequency ratios. Xin’s model presents

good results near 𝛼 = 1 and overestimates the displacement for

α larger than 1.2. Sun’s model can predict the TLD behaviour in

the absence of wave breaking, i.e. 𝐹 = 3 , however

overestimates the displacements in the case of wave breaking.

Mass Ratio

The TLD efficiency under a range of mass ratios (the ratio of the

mass of water to that of the structure) has been investigated in

terms of structural displacement and acceleration reduction.


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Table 4.2: Parameters for Experiments Introduced in Chapter 4.5

As it is shown in table 4.2, t he structural stiffness, mass and

damping coefficient were changed in order to capture different

mass ratios varying from 0.5% to 5% while the damping ratio

remains constant as well as the structural frequency which is

equal to the tank and forcing frequency. The amplitude of the

applied sinusoidal force has been also changed in a way to reach

to the same steady state amplitude in the absence of TLD.

Figure 4.10: The Effect of Mass Ratio on TLD-Structure Behaviour


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Figure 4.11: Acceleration and Displacement Reduction for

Different Mass Ratios

It can be seen from figure 4.10 and 4.11 that the efficiency in

reducing the displacements and accelerations increase as the

mass ratio increases up to 3%. For larger mass ratios (i.e., up to 5

%), although the response of the structure with TLD is reduced in

comparison to the structure without TLD (see figure 4.10), there

is a reduction in the efficiency in comparison to the TLD’s with

mass ratio less than 3% (see figure 4.11). Noting that the

increasing the mass ratio from 1.5% to 3% increases the

efficiency in displacement acceleration reduction only by 10%

while considerably practical point of view 1.5% mass ratio can be

recommended as the optimum value.


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Figure 4.12a: Displacement Increase Due to Undesirable TLD

Forces for 5% Mass Ratio

Figure 4.12b: Displacement Time History for 3% Mass ratio

Another interesting phenomenon that was observed for the

mass ratio of5% was beating (see figure 4.12). Kareem and Yalla

(2000) concluded that the off -diagonal mass terms in the

coupled mass matrix of the damper-structure system was

responsible for this phenomenon.

Figure4.12b shows the TLD displacement in the absence of

beating.


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Structural Damping

Ratio

The effect of structural damping ratio on the TLD behaviour is

investigated here. Damping ratio was varied from 0.2% to 5% as

the typical range of damping for building structures.

Table 4.3: Parameters for Experiments Introduced in Chapter 4.6

As it is shown in Table 4.3, structural mass and stiffness w ere

kept constant in order to have the structural frequency constant

and equal to the tank and forcing frequency. The force

amplitude had constant amplitude equal to 9 N during all tests.

In figure 4.13, as the structural damping ration increases the

effectiveness of TLD in reducing the structural displacements

decreases. For the case considered, when the structure has 5%

inherent damping, its displacement response with and without

TLD is almost the same. It may be because, when the structural

damping is already high, the TLD - structure system does not go

through large displacements, where TLD does not get the chance

to dissipate energy.


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Figure 4.13: The Effect of Damping Ratio on TLD-Structure

Behaviour

In the case of acceleration, for the case considered, an increase

in the accelerations for the system with TLD was observed for

structural damping ratios more than 0.015. Therefore, it can be

concluded that TLD is more effective for structures with low

damping ratios. As the structural damping ratio increases TLD

not only ceases to become effective in reducing the

displacements, it can also amplify structural accelerations (see

figure 4.14). It needs to be pointed out that to establish

boundaries for the effective damping ratio ranges; an extensive

study with different force levels is required


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Figure 4.14: Acceleration and Displacement Reduction for

Different Damping Ratios

TLD-Structure Subjected to Ground Motions

Here the TLD-structure system is subjected to three well known

ground motions. The effectiveness of TLD and the accuracy of

the selected models in predicting the response under seismic

loading are investigated. El Centro, Kobe and Northridge

earthquakes have been used and due to the shaking table

displacement limitations, each record was scaled down by 0.3,

0.1 and 0.05 factors, respectively.

As can be seen in figures 4.15 to 4.17, the TLD is quite

effective in acceleration. However, it is noted that it takes a


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while for TLD to take effect (for the liquid to be set in motion

and dissipate energy) and the first peak displacement of the

time history remain unaffected by the existence of TLD for all

three earthquakes. This is expected as TLDs have been

considered ineffective under impulse type sudden loading

(Xin2009).

4.15: Structural Response with and Without TLD under El Centro

Earthquake


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4.16: Structural Response with and Without TLD under Kobe

Earthquake


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4.17: Structural Response with and Without TLD under

Northridge Earthquake

Additionally the accuracy of the selected models to predict TLD -

structure response under seismic loading was investigated and

shown in figures4.18 to 4.26. As it is shown in figure 4.18 to

4.20, Sun’s model prediction for Northridge ground motion

matches well with experimental results.

In the case of El Centro and Kobe ground motions Sun’s model

overestimates the displacements, but the model has a

reasonable prediction of the accelerations.


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4.18: Hybrid Test Results and Sun’s Model Predictions under El

Centro Earthquake


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4.19: Hybrid Test Results and Sun’s Model Predictions under

Kobe Earthquake


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Figure 4.21 to 4.23 indicate that, although on the conservative

side, Yu’s model have a better agreement (less error) compared

to the other two models under seismic loading. Also, the

acceleration of Yu’s model agrees very well with the real-time

hybrid test results.


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4.21: Hybrid Test Results and Yu’s Model Predictions under El

Centro Earthquake


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Kobe Earthquake


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4.23: Hybrid Test Results and Yu’s Model Predictions under


As can be seen from figures 4.24 to 4.26, Xin’s model is the least

accurate among the three selected models in predicting the

response under seismic loading. The displacement comparison

between Xin’s model and the real - time hybrid test result

reveals that this model underestimates the displacements in the

earlier times of the time history followed by overestimation.

Phase and amplitude inaccuracy in both displacement and

acceleration comparisons are apparent.


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4.24: Hybrid Test Results and Xin’s Model Predictions under El

Centro Earthquake


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4.25 :Hybrid Test Results and Xin’s Model Predictions under

Kobe Earthquake


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4.26 :Hybrid Test Results and Xin’s Model Predictions under


Investigating the accuracy of the three selected models in

comparison to the real -time hybrid testing results, Yu’s model

was found to be more accurate model in both displacement and

acceleration prediction. Sun’s model has also reasonable enough

answers especially in the case of low amplitude ground

accelerations and Xin’s model has the least accuracy among the

three models under seismic loading.


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Case of Study And Advantages

1. From this study, it has been found that the TLD can be

successfully used to control vibration of the structure.

2. The TLD is found to be more effective, when it is placed at the

top storey of the structure. In the study to access the effect of

TLD in structural damping placed at various floors, it has been

found that the amplitude of displacement at 10th storey of the

structure is 0.35mtr when the TLD is placed at the 10th storey,

which increases to 0.6mtr when TLD is placed at 5th floor. The

loading applied on the structure is sinusoidal loading at

resonance condition to fundamental frequency of the structure .

3. A study has been done to found the effect of mistuning of the

damper in damping effect of TLD. It has been found that, TLD is

most effective when it is tuned to the fundamental natural

frequency of structure. Under tuning or over tuning of TLD to

fundamental natural frequency of structure puts adverse

effect on the damping of the TLD. In the study to access the

effect of mistuning of TLD in structural damping, it has been

found that the amplitude of displacement at 10th storey of the

structure is 0.35mtr when the TLD is placed at the 10th storey,

which increases to 0.45mtr when TLD is both under tuned and

over tuned to 95.10% and 105.13% of fundamental natural

frequency of structure respectively


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TLD was most effective when the structure was excited at

resonance frequency of the structure, reducing the ratio

from 22 to 4 (80% reduction in vibration).

Case study

For the applications carried out in the scope of this paper, and

having in mind a specific building, the ground motion considered

was defined only along one horizontal direction. The building

chosen for this study is representative of the modern Portuguese

architecture and was designed and built in the 1950s, when

earthquake design was not contemplated in the national

standards. This building has nine-storeys. The option for this

case-study is justified by the moderate to high local seismic

hazard of the Lisbon region and by the significant number of

buildings with this typology designed and built in Southern

European cities in that period.

The block plan is rectangular with 11.10m width and 47.40m

length. The building has the height of 8 habitation storeys plus

the pilotis height at the ground floor. The “free plan” is also a

reference because the house was conceived in a way of

flexibility in use. But, the 12 structural plane frames define the

architectural plan of the floor type, with 6 duplex apartments.

The distance between frame’s axes is 3.80m. Each frame is

supported by two columns and has one cantilever beam on each

side with 2.80m span, resulting in 13 modules.

The building geometry and dimensions of the RC elements and

infill walls were given in the original project (1950–1956), and

were confirmed in the technical. The structure is mainly


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composed by twelve plane frames oriented in the transversal

direction (direction Y, as represented in Fig. 2).

The twelve transversal plane frames have the same geometric

characteristics for all beams and columns. A peculiar structural

characteristic of the type of buildings, with direct influence in

the global structural behaviour, is the ground storey without

infill masonry walls. Furthermore, at the ground storey the

columns are 5.5m height. All the upper storeys have an inter-

storey height of 3.0m. A detailed definition of the existing infill

panels were considered in the structural models.

For the numerical analyses, constant vertical loads distributed

on beams were considered in order to simulate the dead load of

the self-weight including RC elements, and infill walls, finishing,

and the correspondent quasi-permanent value of the live loads,

.20kN/m.totalising a value of 8

Fig. 2 Case study: a general views of the building block under

analyses; b structural system (plan)

The mass of the structure was assumed concentrated at storey

levels. Each storey has a mass, including the self-weight of the

structure, infill walls and finishings, and the quasipermanent

value of the live loads, of about 4M tons. For the dynamic

analysis, the storey mass is assumed to be uniformly distributed

on the floors


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Design of a TLD for the case study

The procedure adopted for the design of the tuned liquid

dampers for the studied building was as follows. The procedure

adopted for the design of the tuned liquid dampers for the

studied building was as follows. From previous analysis

(Rodrigues et al. 2010), it was found that the most flexible

direction of the building corresponds to the longitudinal

direction. Also, in this case study, the absence of infill’s in the

ground story induces a dynamic behaviour mainly governed by

the first mode. In this numerical analysis, intending to show the

efficiency of the TLDs in the seismic protection of building

structures, it was considered the design of the TLDs only

relatively to the longitudinal direction and ignoring the upper

modes influence. However, it is recalled that, in most building

structures, the influence of various modes should be taken in to

account.

The building first natural frequency in the longitudinal

direction measured in-situ (Rodrigues et al. 2010) was f = 1.08Hz.

The sloshing frequency of the fluid is equalled to the first natural

frequency of the building:

where T is the natural period of the structure and ω is the

corresponding angular frequency.


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In terms of linear frequency (in Hz) the equation of sloshing

frequency of the fluid (Eq. 3), can be rewritten as follows

, and the ,fh Imposing a ratio between the height of the fluid,

length of the tank, L, equal to 0.15, as suggested by Fujino et al.

(1992), and substituting the values for the structure under

analysis in Eq. (5), the following non-linear system of equations

. Land fhcan be obtained as a function of

0441m..0= fh 3000m and.0= L Therefore, on the present case,

In the scope of this work, it was assumed that the width b of the

TLD is equal to its length

L, leading to a quadrangular geometry in plan. This geometry

guarantees that the TLD will behave equally on both horizontal

directions, as opposed to a rectangular tank. From the literature

review, no rule or proposal was found for the height limitation

of the TLDs.


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Summary And Conclusions

- Current trends in construction industry demands taller and

lighter structures, which are also more flexible and having quite

low damping value. This increases failure possibilities and also,

problems from serviceability point of view. Several techniques

are available today to minimize the vibration of the structure,

out of which concept of using of TLD is a newer one. This study is

made to study the effectiveness of using TLD for controlling

vibration of structure.

- In this study a series of experiments have been conducted with

a TLD to investigate the effects of some of the design

parameters of the TLD structure system and also to check the

accuracy of selected models in predicting TLD response. These

models have been compared against experimental data when

they were first published. Unlike these

studies which provided the comparisons for only a few selected

cases, this study considers a broad range of frequency ration,

load amplitude and types; which also enabled the investigation

for determination of effective frequency ratio, mass ratio, and

structural damping ratio. A part of the experiments were

conducted by imposing predefined sinusoidal displacements to

the TLD by using a shake table. The TLD -structure interaction

was investigated by employing real-time hybrid PSD testing

method where the structure was modeled analytically and the

TLD was tested physically in coupled experiment -simulation

mode Frequency Ratio. Subjecting the TLD to predefined


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displacement with various frequencies, it is observ ed that to

design an effective TLD, the ratio of the structural frequency to

that of the TLD should be between 1 and 1.2 when larger

frequency ratios frequency ratios, as the inertia and sloshing

large amount of energy dissipation can be obtained . For

analytical

components of the TLD interface force start canceling each

other, the TLD was observed to be ineffective in dissipating the

energy.

- In the case of three ground motions consider ed (El Centro,

Kobe and Northridge), Yu was observed to be more accurate in

both displacement and acceleration predictions. Having some

overestimations, Sun’s model had also reasonable enough

predictions especially in the case of low amplitude ground

accelerations and Xin’s model predict ed structural response

with some inaccuracy in the response amplitude and phase.

From the results of this study, it can be con cluded that properly

designed TLD is an effective damper to reduce both structural

displacement and acceleration in the case of ground

accelerations and harmonic loads. It is also economical in

comparison with other common kind of dampers. Investigating

the analytical models, it can be concluded that more accurate

models that are able to have a better consideration for wave

breaking occurrence during high amplitude of excitations are

required. Also a more comprehensive experimental/analytical

study is necessary to understand the behavior of TLD under

higher mode and structural nonlinearity effects.


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FURTHER SCOPE FOR STUDY:

1. Both the structure and Damper model considered in this study are linear one; this provides a further scope to study this problem using a nonlinear model for liquid as well as for structure. 2. The structure and Damper model considered here is two-dimensional, which can be further studied to include 3-dimensional structure model as well as damper liquid model. 3. Response of Liquid model can be studied by Mess free methods. 4. This study can be done by introducing obstacles like baffles, screens and floating particles, and the change efficiency in the TLD model can be compared. 5. Further scope, also includes studying the possibility of

constructing Active TLD using controllable baffles and screens.


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MY

Experiment


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Introduction Seismic isolation and energy dissipation technologies have found an

increasing number of applications over the last decade and

particularly over the last few years. The increase in the use of these

technologies may be attributed to the development of analysis and

design guidelines and specifications and the availability of computer

programs for dynamic analysis.

So that in our research we will discuss one of these analysis.

We used models made us able to investigate the liquid motion

behavior, effective range and important TLD parameters through the

El Centro Earthquake .

El Centro Earthquake


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Results Model (1): [S.D.F]

Model shape

Deformed shape


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↳ By considering the behavior of two identical points on the two

model structures we managed to have some relations with time

such as displacement and acceleration as shown.

Displacement is decreased dramatically in the case of using T.L.D

as predicted but what about the acceleration? Let us see ..

Displacement-time relationship

relationship

relationshiprelationshiprelationshipre

lationshiprelationship


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As we can see the acceleration is also effected slightly .

Acceleration-time relationship

relationship

relationshiprelationshiprelationshipre

lationshiprelationship


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After that we tried another model to work with, a new structure

with more degrees of freedom.

We used 5 identical structures except of the T.L.D's

Model shape

Deformed shape

1 2 3 4 5

1 2 3 4 5

Case 1: no T.L.D.

Case 2: 1 T.L.D in the last floor.

Case 3: 5 T.L.D s alternately.

Case 4: 2 T.L.D s in the last floor

and in the medial.

Case 5: T.L.D s in all floors.


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And the same with the S.D.F we got out some relations as the

following.

displacement-time relations:

`

Case1 VS Case2


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Case1 VS Case3

Case1 VS Case4


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Case1 VS Case5


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• Acceleration-time relations:

Case1 VS Case2


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Case1 VS Case3

Case1 VS Case4


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Case1 VS Case5


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Conclusion - The acceleration is reduced but not as greatly as the

displacement did.

- The displacement in the M.D.F is effected more than the

S.D.F.

- Adding more T.L.D s in the structure doesn't give us the result

we hoped and it may make the system less efficiency just like

case5 when we used T.L.D s all over the structure.

- The availability of combining another lateral load resisting

system because the T.L.D does not required any special base

treatment or floor constructions.

- When using T.L.D on the M.D.F systems we can get a benefit

in the response with is the decay of the motion faster with

the earthquake age.


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References

1- BHARADWAJ NANDA - APPLICATION OF TUNED LIQUID DAMPER

FOR CONTROLLING STRUCTURAL VIBRATION

2- Emili Bhattacharjee , Lipika Halder * and Richi Prasad Sharma - An

experimental study on tuned liquid damper for mitigation of structural response

3- Pradipta Banerji1, Avik Samanta2 and Sachin A. Chavan3 -

EARTHQUAKE VIBRATION CONTROL OF STRUCTURES USING

TUNED LIQUID DAMPERS: EXPERIMENTAL STUDIES

4- Hadi Malekghasemi - Experimental and Analytical Investigations of

Rectangular Tuned Liquid Dampers (TLDs)

5- T. Novo · H. Varum · F. Teixeira-Dias · H. Rodrigues ·

M. Falcao Silva · A. Campos Costa · L. Guerreiro

- Tuned liquid dampers simulation for earthquake response control of buildings

6- A. A. El Damatty, Ph.D., P. Eng. - Studies on the Application of Tuned Liquid

Dampers (TLD) to Up-Grade the Seismic Resistance of Structures

7- Sun Limin - Semi- Analytical Modelling of Tuned Liquid Damper

(TLD ) with Emphasis on Damping of liquid Sloshing

8- Abe, M., Fujino, Y., and Kimura, Sh., “Active Tuned Liquid Damper (TLD)

with Magnetic Fluid”,

9- Banerji, P., Murudi, M., Shah, A. H., and Popplewell, N., “Tuned liquid

dampers for controlling earthquake response of structures”,

10- Bauer, H. F., ''Oscillations of Immiscible Liquids in a Rectangular

Container ''

11- Biswal, K.C., Bhattacharyya, S.K., and Sinha, P.K, ''Free-Vibration

Analysis of Liquid-Filled Tank with Bafflesc''


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12- Biswal, K.C., Bhattacharyya, S.K., and Sinha, P.K., “Dynamic response

analysis of a liquid-filled cylindrical tank with annular baffle”,

13- Casciati, Fabio, De Stefano, Alessandro, Matta, Emiliano, “Simulating a

conical tuned liquid damper”,

14- Cassolato, M. R., Love, J. S., and Tait, M. J., “Modelling of a Tuned Liquid

Damper with Inclined Damping Screens”

15- Chang, C.C., and Gu, M., “Suppression of Vortex-Excited Vibration of Tall

Buildings using Tuned Liquid Damper”,

16- Chen, Y., and Ko, C., “Active Tuned Liquid Column Damper with

Propellers”,

17- Fediw A.A., Isyumov N., and Vickery B.J., “Performance of a tuned sloshing

water damper,”

18- Kaneko S., and Mizota Y., “Dynamical Modeling of Deepwater-Type

Cylindrical Tuned Liquid Damper with a Submerged Net,”

19- Tait M.J., Damatty A.A. El, Isyumov N., and Siddique M.R., “Numerical

flow models to simulate tuned liquid dampers (TLD) with slat screens,”

20- Tait M.J., “Modeling and preliminary design of a structure-TLD system,”

21- Gardarsson S., Yeh H., and Reed D., “Behavior of Sloped-Bottom Tuned

Liquid Dampers,”

22- Reed D. and Olson D.E., “A nonlinear numerical model for sloped-bottom

Tuned Liquid Damper,”

23- Modi V.J. and Akinturk A., “An efficient liquid sloshing damper for control

of wind-induced instabilities,”

.

24- Casciati F., Stefano A.D., and Matta E., “Simulating a conical tuned liquid

damper,”

25- Ueda T., Nakagaki R., and Koshida K., “Supression of wind induced

vibration by dynamic dampers in tower-like structures,”

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