Analysis on Influencing Factors of the Moment that Slider Begins to Slide for Sliding Base-Isolated System

2012 ◽  
Vol 166-169 ◽  
pp. 2713-2717
Author(s):  
Min Sun ◽  
Yu Guo Zhang ◽  
Yong Niu
Keyword(s):  
Friction Coefficient ◽  
Natural Vibration ◽  
Damping Ratio ◽  
Harmonic Excitation ◽  
Design Parameters ◽  
External Excitation ◽  
Vibration Period ◽  
Isolation Layer ◽  
The Moment ◽  
System Characteristics

The moment that isolation layer slider begins to slide has great effects on the whole system characteristics for sliding base-isolated system,and the moment plays a crucial role for the analysis of system energy and the confirmation of energy spectrum.Change rules of the moment that isolation layer slider begins to slide under the influence of the acting parameters and system’s design parameters,Taking two particle of plain sliding base-isolated system of building structure under harmonic excitation as the research object,are studied by using the numerical analysis method.The results show that the moment will be delayed if the friction coefficient of isolation layer or the natural vibration period of superstructure will be increased,and the moment will be advanced under the condition that the damping ratio of superstructure or external excitation which is exerted on structure being increased,while the mass ratio of isolation layer slider and superstructure has a very complex effect on the moment that isolation layer slider begins to slide,and the influence law relates to friction coefficient.

The Dynamic Characteristics Analysis of Liaocheng Guangyue Tower

2015 ◽  
Vol 744-746 ◽  
pp. 920-923
Author(s):  
Zhao Bo Meng ◽  
Yu Cao ◽  
Jie Jin
Keyword(s):  
Numerical Analysis ◽  
Dynamic Characteristics ◽  
Natural Vibration ◽  
Damping Ratio ◽  
Analysis Method ◽  
Vibration Period ◽  
Incentive Effect ◽  
First Order ◽  
Characteristics Analysis ◽  
Dynamic Characteristics Analysis

Taking Liaocheng Guangyue tower as an example, based on the on-site measurements, to determine its dynamic characteristics and provide a basis by numerical analysis method for determining traffic incentive effect on the ancient timber buildings. From the research, we can conclude that the first-order self-vibration frequency of Guangyue tower can be taken as 1.638Hz, the corresponding natural vibration period is 0.61s,the damping ratio is 1.098.

Ratio between peak inelastic and elastic responses with uncertain structural properties

2004 ◽  
Vol 31 (4) ◽  
pp. 703-711 ◽  
Author(s):  
H P Hong ◽  
J Jiang
Keyword(s):  
Structural Properties ◽  
Natural Vibration ◽  
Damping Ratio ◽  
Elastic Displacement ◽  
Vibration Period ◽  
Peak Displacement ◽  
Linear Elastic ◽  
Inelastic Displacement ◽  
The Mean ◽  
The Impact

A systematical assessment of the impact of the uncertainty in the natural vibration period and damping ratio on the peak displacement of linear elastic and elastoplastic single-degree-of-freedom systems is carried out using more than 200 strong ground-motion records. The assessment is based on the ratio of the peak inelastic displacement with uncertain structural properties to the peak linear elastic displacement and, the ratio of the peak linear elastic displacement to the yield displacement. Statistical analysis for the ratios obtained is presented. The analysis results indicate that the impact of the uncertainty in the damping ratio on these ratios is less significant than that of the uncertainty in the natural vibration period. The results also show that the consideration of uncertainty in the natural vibration period slightly alters the average peak displacement of the linear or elastoplastic systems. However, the coefficients of variation of these ratios change significantly, especially, if the mean of the natural vibration period is less than about 0.1 s. Simple to use empirical equations, based on the results obtained, are suggested in evaluating the mean and the coefficient of variation of the ratios considering the uncertainty in structural properties. Key words: seismic excitation, uncertainty, peak elastic displacement, peak inelastic displacement.

scholarly journals Field Test for a Base Isolation Structure on Condition of Horizontal and Initial Displacement

2021 ◽  
Vol 12 (1) ◽  
pp. 232
Author(s):  
Ying-Xiong Wu ◽  
Xin-Jun Dong ◽  
You-Qin Lin ◽  
Hao-De Cheng
Keyword(s):  
Dynamic Response ◽  
Dynamic Characteristics ◽  
Natural Vibration ◽  
Base Isolation ◽  
Seismic Structure ◽  
Control Effect ◽  
Initial Displacement ◽  
Pump System ◽  
Vibration Period ◽  
Isolation Layer

There are a few isolated structures that have been subjected to seismic testing. An isolated structure is incapable of tracking, adjusting, and controlling its dynamic characteristics. As a result, field evaluations of solitary structures’ dynamic characteristics are important. The horizontal initial displacement of a base isolation kindergarten made of 46 isolation bearings is 75 mm. The method for creating the horizontal initial displacement condition is illustrated, as are the primary test findings. Horizontal initial displacement is accomplished with the assistance of a reaction wall, rods, and hydraulic pump system. To begin, we removed the building using hydraulic jacks to produce horizontal displacement of the isolation layer and then attached rods to support the building. The rods were then shot and unloaded, causing the building to shake freely, and its dynamic response and other parameters were tested. The results indicate that the natural vibration period of an isolated structure is much greater than the natural vibration period of a seismic structure. The isolation layer’s hysteretic curve as completely filled; upon unloading, the isolation layer as promptly reset; the dynamic response control effect of each was visible, but the top floor’s acceleration was magnified by approximately 1.27 times.

scholarly journals Design, modeling, and demonstration of a new dual-mode back-assist exosuit with extension mechanism

2021 ◽  
Vol 2 ◽  
Author(s):  
Erik P. Lamers ◽  
Karl E. Zelik
Keyword(s):  
Biomechanical Model ◽  
Mode Switching ◽  
Design Parameters ◽  
Dual Mode ◽  
Extension Mechanism ◽  
Body Forces ◽  
Low Profile ◽  
Military Healthcare ◽  
The Moment ◽  
Practical Factors

Abstract Occupational exoskeletons and exosuits have been shown to reduce muscle demands and fatigue for physical tasks relevant to a variety of industries (e.g., logistics, construction, manufacturing, military, healthcare). However, adoption of these devices into the workforce has been slowed by practical factors related to comfort, form-factor, weight, and not interfering with movement or posture. We previously introduced a low-profile, dual-mode exosuit comprised of textile and elastic materials to address these adoption barriers. Here we build upon this prior work by introducing an extension mechanism that increases the moment arm of the exosuit while in engaged mode, then collapses in disengaged mode to retain key benefits related to being lightweight, low-profile, and unobstructive. Here we demonstrate both analytically and empirically how this extensible exosuit concept can (a) reduce device-to-body forces (which can improve comfort for some users and situations), or (b) increase the magnitude of torque assistance about the low back (which may be valuable for heavy-lifting jobs) without increasing shoulder or leg forces relative to the prior form-fitting exosuit. We also introduce a novel mode-switching mechanism, as well as a human-exosuit biomechanical model to elucidate how individual design parameters affect exosuit assistance torque and device-to-body forces. The proof-of-concept prototype, case study, and modeling work provide a foundation for understanding and implementing extensible exosuits for a broad range of applications. We envision promising opportunities to apply this new dual-mode extensible exosuit concept to assist heavy-lifting, to further enhance user comfort, and to address the unique needs of last-mile and other delivery workers.

scholarly journals Estimation of Additional Equivalent Damping Ratio of the Damped Structure Based on Energy Dissipation

2019 ◽  
Vol 2019 ◽  
pp. 1-14
Author(s):  
Xiuyan Hu ◽  
Qingjun Chen ◽  
Dagen Weng ◽  
Ruifu Zhang ◽  
Xiaosong Ren
Keyword(s):  
Energy Dissipation ◽  
Damping Ratio ◽  
Theoretical Concept ◽  
Estimation Methods ◽  
External Excitation ◽  
Single Degree Of Freedom ◽  
Equivalent Damping ◽  
Seismic Motion ◽  
Practical Engineering ◽  
Energy Dissipation Capacity

In the design of damped structures, the additional equivalent damping ratio (EDR) is an important factor in the evaluation of the energy dissipation effect. However, previous additional EDR estimation methods are complicated and not easy to be applied in practical engineering. Therefore, in this study, a method based on energy dissipation is developed to simplify the estimation of the additional EDR. First, an energy governing equation is established to calculate the structural energy dissipation. By means of dynamic analysis, the ratio of the energy consumed by dampers to that consumed by structural inherent damping is obtained under external excitation. Because the energy dissipation capacity of the installed dampers is reflected by the additional EDR, the abovementioned ratio can be used to estimate the additional EDR of the damped structure. Energy dissipation varies with time, which indicates that the ratio is related to the duration of ground motion. Hence, the energy dissipation during the most intensive period in the entire seismic motion duration is used to calculate the additional EDR. Accordingly, the procedure of the proposed method is presented. The feasibility of this method is verified by using a single-degree-of-freedom system. Then, a benchmark structure with dampers is adopted to illustrate the usefulness of this method in practical engineering applications. In conclusion, the proposed method is not only explicit in the theoretical concept and convenient in application but also reflects the time-varying characteristic of additional EDR, which possesses the value in practical engineering.

On the Analysis of Hopf Bifurcation Associated with a Two-Fold Zero Eigenvalue, Part 2: Nonautonomous System

1999 ◽  
Vol 121 (1) ◽  
pp. 105-109 ◽  
Author(s):  
M. Moh’d ◽  
K. Huseyin
Keyword(s):  
Stability Analysis ◽  
Hopf Bifurcation ◽  
Autonomous System ◽  
Critical Value ◽  
Harmonic Excitation ◽  
Nonautonomous System ◽  
External Excitation ◽  
Zero Eigenvalue ◽  
Bifurcation And Stability

This paper extends the bifurcation and stability analysis of the autonomous system considered in Part 1 to the case of a corresponding nonautonomous system. The effect of an external harmonic excitation on the Hopf bifurcation is studied via a modified Intrinsic Harmonic Balancing technique. It is observed that a shift in the critical value of the parameter occurs due to the external excitation. The analysis is carried out with the aid of MAPLE which is also instrumental in verifying the consistency of the approximations conveniently.

The Dynamic Behaviour of Passively Compensated, Hydrostatic Journal Bearings with Various Numbers of Recesses

1976 ◽  
Vol 18 (6) ◽  
pp. 292-302 ◽  
Author(s):  
P. B. Davies
Keyword(s):  
Dynamic Behaviour ◽  
Damping Ratio ◽  
Equations Of Motion ◽  
Steady State Solution ◽  
Flow Equation ◽  
External Excitation ◽  
Signal Flow Graphs ◽  
Flow Compensation ◽  
Circular Functions ◽  
Flow Graphs

A previously established small-perturbation analysis is developed to express the unsteady-state continuity-of-flow equation for an isolated recess in a passively compensated, multirecess, hydrostatic journal bearing in terms of generalized co-ordinates. The concise form of this equation enables motion of the shaft about the concentric position to be described by equations which are derived in closed form for bearings with orifice, capillary or constant flow compensation and any number of recesses. These equations of motion, and hence the expressions for the receptances which describe the response of a bearing to external excitation, are shown to be of exactly the same form for all bearings of the type considered. Furthermore, the damping ratio and natural frequency in any particular case are determined by a single dynamic constant which is shown to be equal to a linear combination of circular functions and a limited number of coefficients which may be found explicitly by routine use of signal flow graphs. The results of the analysis, which is exact within the stated assumptions, are compared with those of other workers and the steady-state solution of the equations of motion is shown to give an expression for static stiffness which is useful for design purposes. Numerical values of the dynamic constant for bearings with between 3 and 20 recesses are given graphically.

Optimal Design of Vibration Absorber Systems Supported by Elastic Base

1991 ◽  
Author(s):  
Hashem Ashrafiuon
Keyword(s):  
Dynamic Models ◽  
Damping Ratio ◽  
Equations Of Motion ◽  
Elastic Base ◽  
Design Parameters ◽  
Primary System ◽  
Vibration Absorbers ◽  
Equivalent Damping ◽  
System Equations ◽  
Different Levels

Abstract This paper presents the effect of foundation flexibility on the optimum design of vibration absorbers. Flexibility of the base is incorporated into the absorber system equations of motion through an equivalent damping ratio and stiffness value in the direction of motion at the connection point. The optimum values of the uncoupled natural frequency and damping ratio of the absorber are determined over a range of excitation frequencies and the primary system damping ratio. The design parameters are computed and compared for the rigid, static, and dynamic models of the base as well as different levels of base flexibility.

Simplified characteristics of active magnetic bearings

2002 ◽  
Vol 216 (5) ◽  
pp. 623-628 ◽  
Author(s):  
D J Peel ◽  
C M Bingham ◽  
Y Wu ◽  
D Howe
Keyword(s):  
Natural Vibration ◽  
Magnetic Bearing ◽  
Active Magnetic Bearing ◽  
Viscous Damping ◽  
Vibration Frequencies ◽  
Active Magnetic Bearings ◽  
Complex Dynamic ◽  
Speed Range ◽  
Constant Coefficients ◽  
System Characteristics

Traditionally, active magnetic bearing (AMB) systems are designed as an integral component of machines having generally complex dynamic characteristics. An AMB supported rotor has been tested over a speed range that included system natural vibration frequencies. A linear stiffness and viscous damping AMB characteristic with constant coefficients was identified which was independent of the overall system characteristics and which can thus provide simple and transferable data for a machine designer.

scholarly journals Simulation model of a pulsed spiral hydro-mechanical energy converter in the heat supply system of a building

2020 ◽  
Vol 10 (3) ◽  
pp. 388-397
Author(s):  
Anton A. Golyanin ◽  
◽  
Aleksey P. Levtsev ◽  
Anton V. Vdovin ◽  
◽  
...  
Keyword(s):  
Simulation Model ◽  
Water Pressure ◽  
Mechanical Energy ◽  
Heat Supply System ◽  
Design Parameters ◽  
Energy Converter ◽  
Electric Generator ◽  
Flow Energy ◽  
The Moment ◽  
Experimental Values

The objective was to develop a mathematical simulation model of a pulsed spiral hydro-mechanical flow energy converter with a variable speed operating in a pulsed mode. This simulation model can be used for calculating the optimal parameters of such devices. The mechanical energy generated by pulsed liquid can be applied in the driving gear of mini-hydroelectric generators working without drops in water pressure, pumping stations and heat networks providing pressure reduction, as well as in heater fans operating in damp or explosion-hazardous facilities. Pulsed spiral hydro-mechanical energy converters can be used for converting the energy of a liquid flow into rotational motion, which can be further transferred to an electric generator or capacitor. In this study, using the example of a hydro-mechanical converter with a cone-shaped coil, the equations of torque depending on the change in the frequency of flow interruption, the moment of inertia and the resistance in the supports were obtained. Design charts were built for the torque of a hydro-mechanical converter with a cone-shaped coil for a number of coil turns equal to 4 pcs., square tube section 0.00011 m2, and the length of the initial round 0.176 m. The validity of the equations was confirmed by a physical experiment with sufficient accuracy. The conducted comparison of simulated and experimental values showed their agreement with an error of less than 5%. According to the simulation results, design parameters for different models have their own characteristics.

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