scholarly journals Methodologies for predicting natural frequency variation of a suspension bridge

2014 ◽  
Vol 80 ◽  
pp. 211-221 ◽  
Author(s):  
Irwanda Laory ◽  
Thanh N. Trinh ◽  
Ian F.C. Smith ◽  
James M.W. Brownjohn
Keyword(s):  
Natural Frequency ◽  
Suspension Bridge ◽  
Frequency Variation ◽  
Natural Frequency Variation

Effect of Residual Stress in Ductile Iron Component on its Natural Frequency

2011 ◽  
Vol 308-310 ◽  
pp. 967-972 ◽  
Author(s):  
Xue Wu Dong ◽  
Dai Ren ◽  
Dong Qiang Wang ◽  
Ya Fei Zhai
Keyword(s):  
Residual Stress ◽  
Natural Frequency ◽  
Ductile Iron ◽  
Diffraction Method ◽  
Stress Relief ◽  
Quantitative Relation ◽  
Frequency Variation ◽  
Natural Stress ◽  
The Status ◽  
Natural Frequency Variation

In the paper four components of ductile iron cast in different stress status, including the cast status, the status of vibratory stress relief and the status of thermal stress relief with 3 months of the natural stress relief and 10 years of the natural stress relief, are selected.X-ray diffraction method is used to measure residual stress and experimental modal analysis is for measuring natural frequency. A quantitative relation between residual stress in ductile iron cast component and its natural frequency variation is obtained. Thus we provide a reference for using natural frequency to evaluate the macroscopic residual stress of ductile iron material component. The results show that the peak value variation of macro residual stress in ductile iron component have a logarithmic relation to its natural frequency variation, and same as the mean value variation in macro-residual stress and its natural frequency variation.

Effect on Vibroengineering of Material Deterioration in a Scale-Down Reinforced Concrete Containment Vessel Specimen

2013 ◽  
Vol 479-480 ◽  
pp. 13-19
Author(s):  
Wei Ting Lin ◽  
Yuan Chieh Wu ◽  
Tung Liang Chu ◽  
An Cheng
Keyword(s):  
Reinforced Concrete ◽  
Corrosion Rate ◽  
Natural Frequency ◽  
Natural Frequencies ◽  
Frequency Variation ◽  
Accelerated Corrosion ◽  
Containment Vessel ◽  
Scale Down ◽  
Concrete Resistivity ◽  
Natural Frequency Variation

This study is aim to evaluate the natural frequency variation of the scale-down reinforced concrete containment vessel specimen under accelerated corrosion conditions. A plastic ring was sealed around the perimeter of the cylindrical vessel bottom with the 3.5 % NaCl solution to achieve the accelerated corrosion test. Concrete resistivity, open circuit potential, corrosion rate and natural frequencies were tested and discussed in this study. Test results presented that the accelerated corrosion method with a direct 60 voltage applied was a suitable method for estimating and accelerating the concrete vessel specimen. Therefore, the changes in natural frequencies were consistent with the material degradation of the concrete vessel specimen. The natural frequencies decreased with the increasing corrosion rate or decreasing resistivities for the specimen at higher mode, but would be no change for the specimen at the natural frequency of 1stmode.

Robust, Adaptive Q-Parameterization for Feedback Control of Vibro-Acoustic Systems

2003 ◽  
Author(s):  
Mark A. McEver ◽  
Daniel G. Cole ◽  
Robert L. Clark
Keyword(s):  
Natural Frequency ◽  
Closed Loop ◽  
Single Mode ◽  
Feedback Controller ◽  
Frequency Variation ◽  
Third Order ◽  
Order Of Magnitude ◽  
Robust Adaptive ◽  
And Performance ◽  
Natural Frequency Variation

An adaptive, single-mode feedback controller for vibroacoustic applications is developed based on the IMC form Q-parameterization. By structuring the Q-parameter as a third-order filter with fixed dynamics and an adaptable gain, the resulting controller is robust to changes in plant natural frequency variation. Analysis shows the advantages of using a highly-damped plant model in terms of increased stability and performance robustness, and was proven by closed-loop simulations on a single-mode plant with a time-varying natural frequency. Even with a natural frequency variation of ±50%, the adaptive-Q controller was able to decrease the squared plant output response to white noise disturbance by an order of magnitude, outperforming an optimally-tuned positive position feedback controller.

scholarly journals Detection of Broken Strands of Transmission Line Conductors Using Fiber Bragg Grating Sensors

Sensors ◽  
2018 ◽  
Vol 18 (7) ◽  
pp. 2397 ◽  
Author(s):  
Long Zhao ◽  
Xinbo Huang ◽  
Jianyuan Jia ◽  
Yongcan Zhu ◽  
Wen Cao
Keyword(s):  
Wind Speed ◽  
Transmission Line ◽  
Fiber Bragg Grating ◽  
Natural Frequency ◽  
Monitoring System ◽  
Natural Frequencies ◽  
Modal Identification ◽  
Bragg Grating ◽  
Frequency Variation ◽  
Natural Frequency Variation

Transmission lines are affected by Aeolian vibration, which causes strands to break and eventually causes an entire line to break. In this paper, a method for monitoring strand breaking based on modal identification is proposed. First, the natural frequency variation of a conductor caused by strand breakage is analyzed, and a modal experiment of the LGJ-95/15 conductor is conducted. The measurement results show that the natural frequencies of the conductor decrease with an increasing number of broken strands. Next, a monitoring system incorporating a fiber Bragg grating (FBG)-based accelerometer is designed in detail. The FBG sensor is mounted on the conductor to measure the vibration signal. A wind speed sensor is used to measure the wind speed signal and is installed on the tower. An analyzer is also installed on the tower to calculate the natural frequencies, and the data are sent to the monitoring center via 3G. Finally, a monitoring system is tested on a 110 kV experimental transmission line, and the short-time Fourier transform (STFT) method and stochastic subspace identification (SSI) method are used to identify the natural frequencies of the conductor vibration. The experimental results show that SSI analysis provides a higher precision than does STFT and can extract the natural frequency under various wind speeds as an effective basis for discriminating between broken strands.

Detection of Machine and Structure Assemblies With Bolt Looseness

2000 ◽  
Author(s):  
J. H. Yeh ◽  
F. W. Liou
Keyword(s):  
Natural Frequency ◽  
Spring Constant ◽  
Structural Safety ◽  
Frequency Variation ◽  
Bolted Joint ◽  
Element Analysis ◽  
Safety And Reliability ◽  
Natural Frequency Variation ◽  
The Relationship ◽  
Causes Of Failure

Abstract Machine and structural safety and reliability are important issues in engineering. Since self-looseness is one of the most frequent causes of failure in bolted joint structures, it is highly desirable to detect bolted joint looseness early. The focus of this study is to model the structure natural frequency variation as the bolted joint is loosened. A virtual spring approach, incorporating finite element analysis, is proposed to model bolted structure assemblies. The spring constant estimation based on the Hertz theory is addressed, and the relationship between the spring constant and structure natural frequency is presented. An experimental study is used to verify the analytical model. A load bolt is used to measure the existing force in a bolted joint. The changes in the natural frequency of fixed-fixed beams due to the presence of joint looseness were investigated both analytically and experimentally.

Reduction of Residual Vibrations in Positioning Control Mechanism

1985 ◽  
Vol 107 (1) ◽  
pp. 47-52 ◽  
Author(s):  
I. Yamada ◽  
M. Nakagawa
Keyword(s):  
Natural Frequency ◽  
High Speed ◽  
Control Mechanism ◽  
Frequency Variation ◽  
Vibratory System ◽  
Positioning Control ◽  
Design Point ◽  
Wide Range ◽  
Parameter Variations ◽  
Natural Frequency Variation

This paper clarifies numerically and experimentally the characteristics of residual vibrations caused by the natural frequency variation for a positioning mechanism, such that a load modeled as a one-degree-of-freedom vibratory system is driven by a servomotor. Moreover, a multi-design-point method is proposed, which can reduce residual vibrations over a comparatively wide range of parameter variations. It is also shown that this method enables high-speed and accurate positioning for a serial printer carriage.

Multi-Tower Effect Analysis of Long-Span Suspension Bridge

2010 ◽  
Vol 163-167 ◽  
pp. 1940-1944
Author(s):  
Xiao Yan Zheng ◽  
Zhuo De Feng ◽  
Yue Xu
Keyword(s):  
Finite Element ◽  
Natural Frequency ◽  
Bending Moment ◽  
Suspension Bridge ◽  
Finite Element Models ◽  
Performance Difference ◽  
Displacement Effect ◽  
Effect Analysis ◽  
Long Span ◽  
Behavior Study

As a new bridge system, mechanics behavior study on long-span multi-tower suspension is also very deficiency. The existence of center towers is the origin of performance difference between multi-tower suspension bridge and the traditional one. Based on the Midas/Civil platform, the paper takes a three tower suspension bridge as project reference, establishes finite element models of suspension bridge, which the main span is longer than one kilometer and towers from two to seven. Moreover, the structural property is analyzed separately, which bending moment and displacement effect of girder and tower along with the tower number changes is considered. Natural frequency differences of the model bridges are also paid attention on.

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