Structural behaviour of water sloshing damper with embossments subject to random excitation

2004 ◽  
Vol 31 (1) ◽  
pp. 120-132 ◽  
Author(s):  
Young-Kyu Ju
Keyword(s):  
Standard Deviation ◽  
Vibration Control ◽  
Structural Model ◽  
Structural Characteristics ◽  
Damping Ratio ◽  
Tall Buildings ◽  
Random Excitation ◽  
Water Tank ◽  
Structural Behaviour ◽  
Peak Displacement

To improve the serviceability of tall buildings, several types of vibration control systems have been developed. The tuned liquid damper (TLD) has advantages, such as simple adjustment of natural frequency, easy installation, and low maintenance. Since water tanks at the top of tall buildings can be directly modeled as a TLD system, it is more practical than any other vibration control system in Korea. Since most of the tanks in Korea have embossments on the wall, the structural characteristics are different from those of tanks used in other countries. As the damping ratio of the TLD depends on several factors, such as the magnitude and frequency of applied load, the shape of the tank, wall roughness, and so forth, it is difficult to evaluate the control performance of the tank exactly. In this study, the characteristics of the water sloshing damper with embossments (WSDE) are evaluated and the equation for equivalent damping ratio is proposed. To clarify the damping effect of a high-rise building with a damping device subject to random excitation, an experiment of a coupled structural model with a water tank was conducted. The parameters were mass ratio of water to model structure, number of wire screens, and shape factor of the water tank. The peak displacement, acceleration response, and standard deviation of the experimental results are analyzed. The coupled structural model with a water tank shows lower maximum and standard deviation responses than those of the structural model alone.Key words: water sloshing damper with embossment, vibration control, structural test, tall buildings.

Increasing Damping Ratios in a Tuned Liquid Damper Using Damping Bars

2007 ◽  
Vol 353-358 ◽  
pp. 2652-2655 ◽  
Author(s):  
Ki Pyo You ◽  
Young Moon Kim ◽  
Cheol Min Yang ◽  
Dong Pyo Hong
Keyword(s):  
Passive Control ◽  
Damping Ratio ◽  
Tall Buildings ◽  
Shaking Table ◽  
Water Tank ◽  
Tuned Liquid Damper ◽  
Structural Vibrations ◽  
Existing Structures ◽  
Long Time ◽  
Wind Induced Vibration

Wind-induced vibration of tall buildings have been of interest in engineering for a long time. Wind-induced vibration of a tall building can be most effectively controlled by using passive control devices. The tuned liquid damper(TLD) is kind of a passive mechanical damper, which relies on the sloshing liquid in a rigid tank. TLD has been successfully employed in practical mitigation of undesirable structural vibrations because it has several potential advantages: low costs, easy installation in existing structures, and effectiveness even against small-amplitude vibrations. Shaking table experiments were conducted to investigate the characteristics of the shallow water sloshing motion in a rectangular tank. To increase the damping ratio of the rectangular water tank, triangle sticks were installed at the bottom of water tank. This installation increased the damping ratio by amaximum of 40-70%.

Study on the influence of structural nonlinearity on the performance of multiunit impact damper

2020 ◽  
pp. 107754632092562
Author(s):  
Zheng Lu ◽  
Naiyin Ma ◽  
Hengrui Zhang
Keyword(s):  
Vibration Control ◽  
Damping Ratio ◽  
Mean Square Displacement ◽  
Random Excitation ◽  
Frame Structure ◽  
Control Effect ◽  
Momentum Exchange ◽  
Impact Damper ◽  
Structural Nonlinearity ◽  
Steel Frame Structure

In this article, the vibration control effect of the multiunit impact damper under stationary random excitation and seismic excitation is studied, based on both the elastic and nonlinear benchmark structures. The benchmark structure is a nonlinear steel frame structure, which can calculate the nonlinear response by considering the material nonlinearity at the ends of the beam and column. To analyze the influence of various system parameters on the performance of the multiunit impact damper, such as the number of units, mass ratio, damping ratio, and gap clearance, a great number of parameter studies are carried out. In addition, the control effects of the multiunit impact damper on elastic and nonlinear structures are compared to analyze the influence of structural nonlinearity on the performance of the multiunit impact damper. The results show that a lightweight multiunit impact damper with reasonable parameters can significantly reduce the root mean square displacement response of the benchmark structure. Furthermore, the structural nonlinearity will lead to a decrease in the vibration control performance of the multiunit impact damper. The reasons for this phenomenon are that the effective momentum exchange and energy dissipation of the multiunit impact damper will decrease when the benchmark structure responds in a nonlinear state.

A Family of Efficient Sloshing Liquid Dampers for Suppression of Wind-Induced Instabilities

2003 ◽  
Vol 9 (3-4) ◽  
pp. 361-386 ◽  
Author(s):  
V. J. Modi ◽  
A. Akinturk ◽  
W. Tse
Keyword(s):  
Energy Dissipation ◽  
High Efficiency ◽  
Damping Ratio ◽  
Real Life ◽  
Wind Tunnel Test ◽  
Tall Buildings ◽  
Two Phases ◽  
Liquid Dampers ◽  
Obstacle Geometry ◽  
Floating Particles

Bluff structures in the form of tall buildings, smokestacks, control towers, bridges, etc., are susceptible to vortex resonance and galloping type of instabilities. One approach to vibration control of such systems is through energy dissipation using sloshing liquid dampers. In this paper we focus on enhancing the energy dissipation efficiency of a rectangular liquid damper through the introduction of two-dimensional obstacles as well as floating particles. The investigation has two phases. To begin with, a parametric free vibration study aimed at the optimization of the obstacle geometry is undertaken to arrive at configurations promising increased damping ratio and hence higher energy dissipation. The study is complemented by an extensive wind tunnel test program, which substantiates the effectiveness of this class of damper in suppressing both vortex resonance and galloping type of instabilities. Simplicity of design, ease of implementation, minimal maintenance, reliability as well as high efficiency make such liquid dampers quite attractive for real-life applications.

Uvula Dynamic Characteristics

2013 ◽  
Author(s):  
A. M. Al-Jumaily ◽  
S. Ashaat ◽  
B. A. Martin ◽  
R. Heinzer ◽  
J. Haba Rubio ◽  
...  
Keyword(s):  
Dynamic Characteristics ◽  
Structural Model ◽  
Fluid Layer ◽  
Structural Characteristics ◽  
Upper Airway ◽  
Mode Shapes ◽  
Tissue Elasticity ◽  
Upper Airways ◽  
Obstructive Sleep ◽  
Mri Scans

The airway binary fluid layer and the structural characteristics of the upper airways have significant influence on the activity of the airway muscles by changing airway compliance and collapsibility during obstructive sleep apnea trauma. The uvula plays an important role in the collapse process. Using MRI scans, this paper develops a structural model for the uvula and determines its dynamic characteristics in terms of natural frequencies and mode shapes as a preliminary process to determine optimum conditions to therapeutically relieve upper airway obstruction. The effect of the variation of tissue elasticity due to water content is elaborated on.

scholarly journals Wind-Induced Vibration Control of High-Rise Structures Using Compound Damping Cables

2021 ◽  
Vol 2021 ◽  
pp. 1-9
Author(s):  
Jianda Yu ◽  
Zhibo Duan ◽  
Xiangqi Zhang ◽  
Jian Peng
Keyword(s):  
Vibration Control ◽  
Damping Ratio ◽  
Viscosity Coefficient ◽  
Structural Vibration ◽  
Vibration Displacement ◽  
High Rise ◽  
Main Cable ◽  
Small Vortex ◽  
Wind Induced Vibration ◽  
Fluctuating Wind

Based on the vibration reduction mechanism of compound damping cables, this study focuses on the wind-induced vibration control of high-rise structures with additional mass at the top. The differential equation of motion of the system under the action of the composite damping cable is established, and the analytical solution of the additional damping ratio of the structure is deduced, which is verified by model tests. The vibration response of the structure under the action of simple harmonic vortex excitation and randomly fluctuating wind loads is studied, and the effect of different viscous coefficients of the dampers in the composite damping cable and different installation heights of the damping cable on the vibration control is analyzed. The results show that a small vortex excitation force will cause large vibrations of low-dampened towering structures, and the structure will undergo buffeting under the action of wind load pulse force. The damping cable can greatly reduce the amplitude of structural vibration. The root means square of structural vibration displacement varies with damping. The viscosity coefficient of the device and the installation height of the main cable of the damping cable are greatly reduced.

Vibration Control of Tall Buildings under Seismic and Wind Loads

1996 ◽  
Vol 122 (8) ◽  
pp. 948-957 ◽  
Author(s):  
Lih-Shing Fur ◽  
Henry T. Y. Yang ◽  
Seshasayee Ankireddi
Keyword(s):  
Vibration Control ◽  
Tall Buildings ◽  
Wind Loads

Active Vibration Control of a Triple Flexible Structures Combined With Actuators

1995 ◽  
Author(s):  
Kazuto Seto ◽  
Yoshihiro Toba ◽  
Fumio Doi
Keyword(s):  
Vibration Control ◽  
Large Scale ◽  
Active Vibration Control ◽  
Flexible Structures ◽  
Low Frequency ◽  
Tall Buildings ◽  
Control Force ◽  
Active Vibration ◽  
Strong Winds ◽  
Lq Control

Abstract In order to realize living comfort of tall buildings by reducing the vibration of higher floors by strong winds, this paper proposes a new method of vibration control for flexible structures with a large scale. The higher a tall building the lower its natural frequency. Since obtaining sufficient force to control the lower frequency vibrations of tall buildings is a difficult task, controlling the vibration of ultra-tall buildings using active dynamic absorbers is nearly impossible. This problem can be overcome by placing actuators between a pair of two or three ultra-tall buildings and using the vibrational force of each building to offset the vibrational movement of its paired mate. Therefore, it is able to obtain enough control force under the low frequency when the proposed method is used. In this paper, a reduced-order model expressed by 2DOF system under taking into consideration for preventing spillover instability is applied to control each flexible structure. The LQ control theory is applied to the design of such a control system. The effectiveness of this method is demonstrated theoretically as well as experimentally.

Wavelet Transform Modulus Maxima Decay Lines

2015 ◽  
pp. 48-68
Author(s):  
Andreas Kyprianou ◽  
Andreas Tjirkallis
Keyword(s):  
Experimental Data ◽  
Wavelet Transform ◽  
Damage Detection ◽  
Environmental Conditions ◽  
Simulated Data ◽  
Random Excitation ◽  
Operating Conditions ◽  
Structural Behaviour ◽  
Operational Conditions ◽  
Three Degree Of Freedom

An important task in structural health monitoring (SHM) is that of damage detection under varying environmental and operational conditions. Structures, under varying environmental conditions, change their mass, elasticity and damping properties whereas changing operational conditions cause changes to excitations. A damage detection methodology implemented in these circumstances faces serious challenges since changes to structural behaviour imparted by environmental or operational conditions could be wrongly attributed to damage. The part of a damage detection decision algorithm that removes environmental and operational effects is called normalization. In this chapter a normalization methodology that is based on the similarity between continuous wavelet transform maxima decay lines is presented. This methodology is implemented on both simulated and experimental data. Simulated data were obtained from a three degree of freedom system. Varying environmental conditions were simulated by temperature dependent stiffness parameters and operating conditions by changing the colour of random excitation. Experimental data were obtained from damaged cantilever beams that were subjected to random excitations of different colour and varying temperatures.

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