scholarly journals Effect of Base Shape on Dynamic Characteristics of Rocking of Rigid Body (Amplitude Dependency of Natural Frequency and Damping Ratio)

2011 ◽  
Vol 77 (783) ◽  
pp. 4043-4057
Author(s):  
Nozomu IMASNISH ◽  
Yoshio INOUE ◽  
Kyoko SHIBATA ◽  
Koji IWAGO
Keyword(s):  
Rigid Body ◽  
Natural Frequency ◽  
Dynamic Characteristics ◽  
Damping Ratio ◽  
Amplitude Dependency

Dynamic Characteristics of Planar Compliant Parallel-Guiding Mechanisms

2008 ◽  
Author(s):  
Wenjing Wang ◽  
Yueqing Yu
Keyword(s):  
Numerical Methods ◽  
Rigid Body ◽  
Natural Frequency ◽  
Dynamic Modeling ◽  
Dynamic Characteristics ◽  
Compliant Mechanisms ◽  
Design Parameters ◽  
Dynamic Effects ◽  
Body Model ◽  
Rigid Body Model

Dynamic effects are very important to improving the design of compliant mechanisms. An investigation on the dynamic characteristics of planar compliant parallel-guiding mechanism is presented. Based on the pseudo-rigid-body model, the dynamic model of planar compliant parallel-guiding mechanisms is developed using the numerical methods at first. The natural frequency is then calculated, and frequency characteristics of this mechanism are studied. The numerical results show the accuracy of the proposed method for dynamic modeling of compliant mechanisms, and the relationships between the natural frequency and design parameters are analyzed clearly.

Dynamic Characteristics of Structure With Bolted Joint Considering Some Factors

2004 ◽  
Author(s):  
Shigeru Aoki
Keyword(s):  
Natural Frequency ◽  
Dynamic Characteristics ◽  
Damping Ratio ◽  
Random Excitation ◽  
Pressure Vessels ◽  
Bolted Joints ◽  
Piping System ◽  
Bolted Joint ◽  
Earthquake Excitation ◽  
Applied Torque

Bolted joints are widely used for pressure vessels and piping system. Many studies on strength and stiffness of bolted joint are carried out. However, few studies on the dynamic characteristics of structure with bolted joint are carried out. The dynamic characteristics are important for design of structure subjected to earthquake excitations. In this paper, the effect of bolted joints on dynamic characteristics of structure is examined. First, the damping ratio and the natural frequency of specimens with some types of bolted joints are measured. Those are obtained for some factors, amplitude of excitation, applied torque. Obtained results are compared with those for the specimen without bolted joint. It is found that the damping ratio increases and the natural frequency becomes lower. Next, modeling of the bolted joint is presented. The bolted joint is modeled using additional mass, stiffness and damping elements. Finally, using model of bolted joint, response of the structure with bolted joint subjected to earthquake excitation is examined. Earthquake excitation is modeled as stationary random excitation. Mean square values of the response are obtained. Standard deviation of the acceleration response of the structure with bolted joint are lower than those without bolted joint.

Study on Dynamic Characteristics and Dynamic Response of Woodworking Four-Side Planer

2011 ◽  
Vol 291-294 ◽  
pp. 1970-1976
Author(s):  
Shao Qun Zhang ◽  
Jun Hua ◽  
Wei Xu
Keyword(s):  
Mathematical Model ◽  
Dynamic Response ◽  
Natural Frequency ◽  
Dynamic Characteristics ◽  
Feed Rate ◽  
Reference Data ◽  
Damping Ratio ◽  
Vibration Test ◽  
Vibration Magnitude ◽  
The Mathematical Model

Through woodworking four-side planer vibration test, this article studiesits dynamic characteristics and dynamic response to identify the vibration magnitudes law of each feed roll shafts of the four-side feed beam; then finds the natural frequency and damping ratio of the feed beam and lathe bed; obtains the mathematical model of feed roll shaft vibration magnitude changing with the feed rate U under different process thicknesses. The analysis of feeding quantity and the rationality of lathe bed from the perspective of vibration design supplies the designs and operation staff with reference data.

Integrated Dynamic Characteristics and Application in Semi-Active Dynamic Absorber of Magneto-Rheological Fluids

2012 ◽  
Vol 220-223 ◽  
pp. 601-606
Author(s):  
Shi Zhen Li ◽  
Gong Yu Li ◽  
Xiao Wu Kong ◽  
Jian Hua Wei
Keyword(s):  
Natural Frequency ◽  
Dynamic Characteristics ◽  
Damping Ratio ◽  
Dynamic Test ◽  
Shear Mode ◽  
Vibration Absorption ◽  
New Type ◽  
Dynamic Absorber ◽  
Magneto Rheological ◽  
Squeeze Effect

As a new type of controllable rheological smart material, Magneto-rheological Fluids (MRF) are widely used in the field of vibration control. This article investigated their integrated dynamic characteristics in squeeze mode and shear mode. Two prototypes were designed and fabricated. The dynamic test for the two prototypes was performed on a simply supported beam vibrating device with the methods of drop-hammering and sweep-frequency measuring. The experimental results demonstrate that the damping ratio of the prototype in squeeze effect presents linearly and widely controllable from 0.0948 to 0.2268 with the increase of the coils’ excitation current, behaving as a variable MR damper. However, its natural frequency remains unchanged. It is also shown that the natural frequency of the prototype in shear effect increases significantly from 18Hz to 24 Hz, acting as a semi-active dynamic vibration (SDVA) absorber with broadband vibration absorption for the maximum attenuation of up to 74.3%. This study provides guidance for engineering applications of MRF.

The Dynamic Characteristics of a Couple System by Pedestrian Bridge and Walking Persons

2011 ◽  
Vol 71-78 ◽  
pp. 1499-1506 ◽  
Author(s):  
Dong Wang ◽  
Shi Qiao Gao ◽  
Michael Kasperski ◽  
Hai Peng Liu ◽  
Lei Jin
Keyword(s):  
Natural Frequency ◽  
Dynamic Characteristics ◽  
Dynamic Properties ◽  
Damping Ratio ◽  
Couple System ◽  
Damping Capacity ◽  
Single Beam ◽  
Simplified Approach ◽  
Beam Experiment ◽  
External Loads

The human body forms a complex dynamic system with more than one natural frequency and provides considerable damping capacities. In a simplified approach active persons can be modeled as external loads. While this approach may be sufficient for an activity like jumping, it has been shown already that for a bobbing person some interaction effects may occur. The question arises if also pedestrians are able to influence the dynamic characteristics of the structure they are actually crossing. Observations during a mass event with several thousand persons crossing a 66 m long bridge indicate that the damping capacity of the coupled structure may have increased. In this paper a single beam experiment was operated. The basic idea is to use a known background excitation induced by a shaker. It can be seen that both natural frequency and damping ratio have been changed comparing with empty structure. The change with passive person is stronger that an active person. Meanwhile, the linear sweep method which was used in measurement provides a good result for the analysis of dynamic properties of a structure.

scholarly journals Study On The Vibration Amplitudes Of Reinforced Concrete Bridge Piers Using ABAQUS Software

2021 ◽  
Vol 28 (2) ◽  
pp. 37-45
Author(s):  
Mais Ghassoun ◽  
Ali Algharrash ◽  
Reem Alsehnawi
Keyword(s):  
Dynamic Analysis ◽  
Natural Frequency ◽  
Dynamic Characteristics ◽  
Vibration Amplitude ◽  
Dynamic Properties ◽  
Damping Ratio ◽  
Response Amplitude ◽  
Experimental Results ◽  
Important Indicator ◽  
Design Values

The Dynamic characteristics such as damping ratio and natural frequency are an important indicator for predicting the dynamic behavior of bridges, but it is customary during the design that the designer assess the dynamic properties of the dynamic analysis because it is very difficult to determine the damping of the origin before construction and damping is taken as a predetermined constant value independent of the response amplitude and frequency of the structure. In the dynamic analysis of constructions design some experimental research has been concerned with the determination of dynamic structural properties and their relationship with the response amplitude experimentally, but the changes in dynamic properties with vibration amplitude has never been taken During dynamic analysis, further analytical treatments and computer modeling were required to study different cases based on the experimental results available by simulating them with a computer model. Dynamic characteristics are very essential to accurately determine the dynamic response, and it is necessary to study the effect of changes of the actual dynamic characteristics of bridges, which were determined by measuring their vibration in the results of dynamic analysis and comparing them with results that do not take into account the changes of dynamic properties and with laboratory results in order to assess the role of. Dynamic analysis inputs in simulating vibrations by monitoring their responses. As a result, it was found that the dynamic properties are independent of the shape of the external exactions. Also, it was concluded that relationships express the change of dynamic properties in terms of vibration amplitudes. And Similar reliance of the dynamic characteristics to the vibration amplitude is confirmed for the pier model, where the increase of the amplitude of the acceleration is accompanied by a decrease in the natural frequency, and an increase in the damping ratio is obvious. Before choosing design values when considering the dynamic characteristics of a structure, we need to give unique concentration to the predictable vibration amplitudes. Dynamic characteristics changes during dynamic analysis should be considered to produce analytical results that simulate experimental results and are closer to reality.

An experimental study of static and dynamic responses of prestressed concrete box irder bridges

1990 ◽  
Vol 17 (3) ◽  
pp. 481-493 ◽  
Author(s):  
M. Saeed Mirza ◽  
O. Ferdjani ◽  
A. Hadj-Arab ◽  
K. Joucdar ◽  
A. Khaled ◽  
...  
Keyword(s):  
Natural Frequency ◽  
Dynamic Characteristics ◽  
Prestressed Concrete ◽  
Damping Ratio ◽  
Physical Models ◽  
Dynamic Responses ◽  
Box Girder Bridges ◽  
Box Girder ◽  
Girder Bridges ◽  
Bridge Models

Experimental data from static and dynamic tests on [Formula: see text] direct models of simply supported, one- and two-cell, box girder bridges are presented. Variation of flexural and torsional stiffnesses and dynamic characteristics, such as the natural frequency of vibrations and damping ratios of the bridge models at different levels of cracking damage, are examined; in turn, these dynamic characteristics can be used to estimate the cracking damage in the bridge. The physical model proved to be an adequate tool for the study of static and dynamic responses of box girder bridges at all load levels. Key words: box girder bridges, direct physical models, damping ratio, flexural and torsional stiffnesses, level of cracking damage, load–deformation response, load distribution characteristics, longitudinal and transverse strains, natural frequency of vibrations, simulated OHBDC truck.

Dynamic Characteristics of Structures With Bolted Joint

2002 ◽  
Author(s):  
Shigeru Aoki
Keyword(s):  
Natural Frequency ◽  
Dynamic Characteristics ◽  
Random Vibration ◽  
Damping Ratio ◽  
Pressure Vessels ◽  
Bolted Joints ◽  
Simplified Model ◽  
Piping System ◽  
Bolted Joint ◽  
Acceleration Response

Bolted joints are widely used for pressure vessels and piping system. Many studies on strength of bolted joint are carried out. However, few studies on dynamic characteristics of structure with bolted joint are carried out. In this paper, the effect of bolted joints on dynamic characteristics of structure is examined. First, the damping ratio and the natural frequency of specimens with some types of bolted joints are measured. Obtained results are compared with those for the specimen without bolted joint. It is found that damping ratio increases and the natural frequency becomes lower. Next, the effect of bolted joint on random vibration response of structure using simplified model is examined. Standard deviation of acceleration response of structure with bolted joint is lower than that of structure without bolted joint.

Long-term monitoring of dynamic characteristics of high-rise and super high-rise buildings using strong motion records

2021 ◽  
Vol 13 (12) ◽  
pp. 168781402110672
Author(s):  
Yinfeng Dong ◽  
Hui Tian ◽  
Man Zhang ◽  
Lejun Wei
Keyword(s):  
Natural Frequency ◽  
Dynamic Characteristics ◽  
Dynamic Properties ◽  
Epicentral Distance ◽  
Damping Ratio ◽  
Focal Depth ◽  
High Rise ◽  
Fundamental Natural Frequency ◽  
Term Monitoring

Seismic behavior of a structure is directly related to its dynamic characteristics, which include natural frequency, damping ratio, and mode shape. This study focuses on the long-term monitoring of dynamic characteristics of six selected target structures. The covariance-driven stochastic subspace identification (SSI) approach is used to estimate the fundamental natural frequency and damping ratio of target buildings based on long-term motion records in order to examine the temporal variation of dynamic properties. The fundamental natural frequency and damping ratio variations over time are first discussed. It is found that the fundamental natural frequency of some structures reduces dramatically after the 2011 Tohoku Earthquake, accompanied by a rise in damping ratio. Then, regression analysis is used to assess the relationship between dynamic characteristics and ground motion parameters (Peak ground acceleration (PGA), magnitude, focal depth, and epicentral distance) and structural response (root mean square acceleration, maximum response amplitude). It is discovered that the identified natural frequency has no clear correlation with the focal depth, a slight negative correlation with the epicentral distance, and a strong negative correlation with the magnitude and PGA. The root mean square acceleration and the maximum response amplitude are negatively correlated to the target buildings’ natural frequencies. Finally, the influence of environmental factors on dynamic properties is investigated.

Dynamic tests and analysis of a massive pier subjected to ice forces

1980 ◽  
Vol 7 (3) ◽  
pp. 432-441 ◽  
Author(s):  
C. James Montgomery ◽  
A. William Lipsett
Keyword(s):  
Natural Frequency ◽  
Short Duration ◽  
Dynamic Characteristics ◽  
Fundamental Mode ◽  
Damping Ratio ◽  
Field Tests ◽  
Bridge Pier ◽  
Dynamic Tests ◽  
Ice Forces

This paper describes the field tests and analysis of a massive bridge pier that is subjected to the action of dynamic ice forces. The field results indicate that the pier has a natural frequency of 8.9 Hz and a damping ratio of 0.19 in the fundamental mode of vibration. By using these dynamic characteristics, the response of the pier to dynamic ice forces was analyzed. This analysis confirms that the pier is capable of responding in full to short duration peak ice forces.

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