Passive Vibration Control of Structures Subjected to Random Ground Excitation Utilizing Sloshing in Rectangular Tanks

2013 ◽  
Vol 136 (1) ◽  
Author(s):  
Takashi Ikeda ◽  
Raouf A. Ibrahim
Keyword(s):  
Vibration Control ◽  
Natural Frequency ◽  
Equations Of Motion ◽  
Correlation Coefficients ◽  
Liquid Sloshing ◽  
Center Frequency ◽  
System Response ◽  
Mean Square ◽  
Passive Vibration Control ◽  
Tuned Liquid Dampers

Passive vibration control of an elastic structure carrying a rectangular tank, partially filled with liquid, is investigated when the structure is subjected to horizontal, narrowband, random ground excitation. The modal equations of motion for liquid sloshing are derived using Galerkin's method, considering the nonlinearity of sloshing. The system response statistics including mean square values, correlation coefficients, and probability density functions (PDFs) are numerically estimated from the time histories using the Monte Carlo simulation when the natural frequency of the structure is close to that of liquid sloshing. The influences of the excitation center frequency, its bandwidth, and the liquid level on the system responses are examined. As a result, it is found that the mean square responses of the structure decrease when the center frequency is close to the natural frequency of the structure due to sloshing. Tuned liquid dampers (TLDs) are found to be most effective for comparatively low liquid levels.

Horizontal Ground Random Excitation of Structures Carrying a Rigid Container Partially Filled With Liquid

2006 ◽  
Author(s):  
Takashi Ikeda ◽  
Raouf A. Ibrahim
Keyword(s):  
Natural Frequency ◽  
Vibration Suppression ◽  
Hydrodynamic Force ◽  
Equations Of Motion ◽  
Random Excitation ◽  
Center Frequency ◽  
System Response ◽  
Structure Response ◽  
Mean Square Response ◽  
The Mean

Nonlinear random interaction of an elastic structure carrying a container, partially filled with liquid, under horizontal narrowband random excitation is investigated. The modal equations of motion are derived by using Galerkin’s method, taking into account the nonlinearity of the hydrodynamic force when the natural frequency of the structure is close to the natural frequency of liquid sloshing. The system response statistics are numerically estimated using Monte Carlo simulation. The influences of the excitation center frequency, its bandwidth and liquid level on the system response are studied. As a result, it is found that the mean square response of the structure decreases as the center frequency approaches to the natural frequency of the structure, and that the sloshing in the container has an effect on the vibration suppression of the structure response.

Random Excitation of a Structure Interacting With Liquid Sloshing Dynamics

2002 ◽  
Author(s):  
Takashi Ikeda ◽  
Raouf A. Ibrahim
Keyword(s):  
Free Surface ◽  
Natural Frequency ◽  
Internal Resonance ◽  
Gaussian White Noise ◽  
Liquid Sloshing ◽  
Elastic Structure ◽  
Center Frequency ◽  
System Response ◽  
Liquid Free Surface ◽  
Sloshing Dynamics

The nonlinear random interaction of an elastic structure with liquid sloshing dynamics in a cylindrical tank is investigated in the neighborhood of 1:2 internal resonance. Such internal resonance takes place when the natural frequency of the elastic structure is close to twice the natural frequency of the antisymmetric sloshing mode (1,1). The excitation is generated from the response of a linear shaping filter subjected to a Gaussian white noise. The analytical model involves three sloshing modes; (1,1), (0,1) and (2,1). The system response statistics and stability boundaries are numerically estimated using Monte Carlo simulation. The influence of the excitation center frequency, its bandwidth, and the liquid level on the system responses is studied. It is found that there is an irregular energy exchange between the structure and the liquid free surface motion when the center frequency is close to the structure natural frequency. Depending on the excitation power spectral density, the liquid free surface experiences zero motion, uncertain motion (intermittency), partially developed motion, and fully developed random motion. The structure response probability density function is almost Gaussian, while the liquid elevation deviates from normality. The unstable region, where the liquid motion occurs, becomes wider as the excitation intensity increases or as the bandwidth decreases. As the liquid depth decreases, the region of nonlinear interaction shrinks which is associated with a shift of the peak of the structure mean square response toward the left side of the frequency axis.

Vibration Control of Buildings Using Series Rolling-Pendulum Tuned Mass Dampers

2019 ◽  
Author(s):  
Jer-Fu Wang ◽  
Chun-Hung Chen ◽  
Chang-Ching Chang ◽  
Chi-Chang Lin
Keyword(s):  
Vibration Control ◽  
Natural Frequency ◽  
Structural Control ◽  
Degrees Of Freedom ◽  
Equations Of Motion ◽  
Control Device ◽  
Tuned Mass Dampers ◽  
High Rise ◽  
Mass Damper ◽  
In Series

Abstract This paper proposes a passive vibration control device, series rolling-pendulum tuned mass damper (SRPTMD), with a “ball-in-ball” configuration. A conventional pendulum TMD (PTMD) generally requires a long cable length that usually exceeds one-story height for high-rise buildings. A rolling-pendulum TMD (RPTMD) is a mass that can roll on a base with a curvature instead of swaying with a cable, significantly reducing the requirement of vertical rooms. In addition, a ball-in-ball SRPTMD is equivalent to a system with two degrees of freedom in series. This study aimed to derive equations of motion of the primary building-SRPTMD system, conduct a parametric study for SRPTMD, and investigate the structural control performance of an SRPTMD. Results showed that an SRPTMD performed similarly to an RPTMD. One advantage of an SRPTMD is that the fundamental natural frequency of an SRPTMD can be altered to a certain extent by changing the radius ratio of the inner ball to the outer ball, whereas the natural frequency of an RPTMD can only be altered by changing the curvature of its base, which is far more difficult. Another advantage is that the two modal frequencies of an SRPTMD can be manipulated by selecting a specific set of radius ratios between the base, the outer ball, and the inner ball, which means that an SRPTMD has higher potential on multiple modes control.

Rain-Wind-Induced Vibration Control for Long Span Transmission Tower

2012 ◽  
Vol 160 ◽  
pp. 240-244 ◽  
Author(s):  
Li Tian ◽  
Shu Jin ◽  
Zi Long Wang
Keyword(s):  
Vibration Control ◽  
Equations Of Motion ◽  
Time History ◽  
Induced Response ◽  
Tuned Liquid Damper ◽  
Transmission Tower ◽  
Long Span ◽  
Tuned Liquid Dampers ◽  
Liquid Dampers ◽  
Wind Induced Vibration

In this paper, multiple tuned liquid dampers control for rain-wind-induced response of long span transmission tower is investigated. Equations of motion for a structure-TLD system are derived. According to the mechanism of vibration control, rain-wind-induced vibration control for tower model with multiple tuned liquid dampers is carried out by using numerical simulation. Three-dimensional finite element model of tower based on a real project is established. Rain-wind load time history is simulated based on wind and rain theory. Time history curves and the maximum responses without and with tuned liquid damper under rain-wind excitation are analyzed and discussed. The results show that the tuned liquid damper could decrease the rain-wind-induced response of long span transmission tower, and the device could be installed in tower when the response too large.

scholarly journals A Variable Parameter Ambient Vibration Control Method Based on Quasi-Zero Stiffness in Robotic Drilling Systems

Machines ◽  
2021 ◽  
Vol 9 (3) ◽  
pp. 67
Author(s):  
Laixi Zhang ◽  
Chenming Zhao ◽  
Feng Qian ◽  
Jaspreet Singh Dhupia ◽  
Mingliang Wu
Keyword(s):  
Vibration Control ◽  
Vibration Isolation ◽  
Control Method ◽  
Control Strategies ◽  
Equations Of Motion ◽  
Variable Parameter ◽  
Harmonic Balance Method ◽  
Variable Stiffness ◽  
Ambient Vibration ◽  
Robotic Drilling

Vibrations in the aircraft assembly building will affect the precision of the robotic drilling system. A variable stiffness and damping semiactive vibration control mechanism with quasi-zero stiffness characteristics is developed. The quasi-zero stiffness of the mechanism is realized by the parallel connection of four vertically arranged bearing springs and two symmetrical horizontally arranged negative stiffness elements. Firstly, the quasi-zero stiffness parameters of the mechanism at the static equilibrium position are obtained through analysis. Secondly, the harmonic balance method is used to deal with the differential equations of motion. The effects of every parameter on the displacement transmissibility are analyzed, and the variable parameter control strategies are proposed. Finally, the system responses of the passive and semiactive vibration isolation mechanisms to the segmental variable frequency excitations are compared through virtual prototype experiments. The results show that the frequency range of vibration isolation is widened, and the stability of the vibration control system is effectively improved without resonance through the semiactive vibration control method. It is of innovative significance for ambient vibration control in robotic drilling systems.

Segmenting Star Images with Complex Backgrounds Based on Correlation between Objects and 1D Gaussian Morphology

2021 ◽  
Vol 11 (9) ◽  
pp. 3763
Author(s):  
Yunlong Zou ◽  
Jinyu Zhao ◽  
Yuanhao Wu ◽  
Bin Wang
Keyword(s):  
Mean Square Error ◽  
Selection Process ◽  
Minimum Mean Square Error ◽  
Correlation Coefficients ◽  
False Alarms ◽  
Mean Square ◽  
Segmentation Method ◽  
Space Objects ◽  
High Earth Orbits ◽  
Star Images

Space object recognition in high Earth orbits (between 2000 km and 36,000 km) is affected by moonlight and clouds, resulting in some bright or saturated image areas and uneven image backgrounds. It is difficult to separate dim objects from complex backgrounds with gray thresholding methods alone. In this paper, we present a segmentation method of star images with complex backgrounds based on correlation between space objects and one-dimensional (1D) Gaussian morphology, and the focus is shifted from gray thresholding to correlation thresholding. We build 1D Gaussian functions with five consecutive column data of an image as a group based on minimum mean square error rules, and the correlation coefficients between the column data and functions are used to extract objects and stars. Then, lateral correlation is repeated around the identified objects and stars to ensure their complete outlines, and false alarms are removed by setting two values, the standard deviation and the ratio of mean square error and variance. We analyze the selection process of each thresholding, and experimental results demonstrate that our proposed correlation segmentation method has obvious advantages in complex backgrounds, which is attractive for object detection and tracking on a cloudy and bright moonlit night.

scholarly journals Vibration analysis of a sandwich cylindrical shell in hygrothermal environment

2021 ◽  
Vol 10 (1) ◽  
pp. 414-430
Author(s):  
Chunwei Zhang ◽  
Qiao Jin ◽  
Yansheng Song ◽  
Jingli Wang ◽  
Li Sun ◽  
...  
Keyword(s):  
Cylindrical Shell ◽  
Natural Frequency ◽  
Equations Of Motion ◽  
Single Layer ◽  
Functionally Graded ◽  
Sandwich Shell ◽  
Continuous Change ◽  
Multilayered Structures ◽  
Cylindrical Sandwich Shell ◽  
Vibrational Behavior

Abstract The sandwich structures are three- or multilayered structures such that their mechanical properties are better than each single layer. In the current research, a three-layered cylindrical shell including a functionally graded porous core and two reinforced nanocomposite face sheets resting on the Pasternak foundation is used as model to provide a comprehensive understanding of vibrational behavior of such structures. The core is made of limestone, while the epoxy is utilized as the top and bottom layers’ matrix phase and also it is reinforced by the graphene nanoplatelets (GNPs). The pattern of the GNPs dispersion and the pores distribution play a crucial role at the continuous change of the layers’ properties. The sinusoidal shear deformation shells theory and the Hamilton’s principle are employed to derive the equations of motion for the mentioned cylindrical sandwich shell. Ultimately, the impacts of the model’s geometry, foundation moduli, mode number, and deviatory radius on the vibrational behavior are investigated and discussed. It is revealed that the natural frequency and rotation angle of the sandwich shell are directly related. Moreover, mid-radius to thickness ratio enhancement results in the natural frequency reduction. The results of this study can be helpful for the future investigations in such a broad context. Furthermore, for the pipe factories current study can be effective at their designing procedure.

Intersession reliability of GPS-based and accelerometer-based physical variables in small-sided games with and without the offside rule

2021 ◽  
pp. 175433712098764
Author(s):  
Igor Junio de Oliveira Custódio ◽  
Gibson Moreira Praça ◽  
Leandro Vinhas de Paula ◽  
Sarah da Glória Teles Bredt ◽  
Fabio Yuzo Nakamura ◽  
...  
Keyword(s):  
Root Mean Square ◽  
Global Positioning System ◽  
Intraclass Correlation ◽  
Correlation Coefficients ◽  
Mean Square ◽  
Physical Demands ◽  
Intraclass Correlation Coefficients ◽  
Total Distance ◽  
Global Positioning ◽  
High Level

This study aimed to analyze the intersession reliability of global positioning system (GPS-based) distances and accelerometer-based (acceleration) variables in small-sided soccer games (SSG) with and without the offside rule, as well as compare variables between the tasks. Twenty-four high-level U-17 soccer athletes played 3 versus 3 (plus goalkeepers) SSG in two formats (with and without the offside rule). SSG were performed on eight consecutive weeks (4 weeks for each group), twice a week. The physical demands were recorded using a GPS with an embedded triaxial accelerometer. GPS-based variables (total distance, average speed, and distances covered at different speeds) and accelerometer-based variables (Player Load™, root mean square of the acceleration recorded in each movement axis, and the root mean square of resultant acceleration) were calculated. Results showed that the inclusion of the offside rule reduced the total distance covered (large effect) and the distances covered at moderate speed zones (7–12.9 km/h – moderate effect; 13–17.9 km/h – large effect). In both SSG formats, GPS-based variables presented good to excellent reliability (intraclass correlation coefficients – ICC > 0.62) and accelerometer-based variables presented excellent reliability (ICC values > 0.89). Based on the results of this study, the offside rule decreases the physical demand of 3 versus 3 SSG and the physical demands required in these SSG present high intersession reliability.

Sign in / Sign up

Export Citation Format

Share Document