Tendency of Damping Ratio of Floating Artificial Base by Experiment and Measurement

2005 ◽  
Author(s):  
Koichi Maruyoshi ◽  
Osamu Saijo
Keyword(s):  
Vibration Mode ◽  
Damping Ratio ◽  
Experimental Models ◽  
Radiation Damping ◽  
Elastic Behavior ◽  
Structural Damping ◽  
Floating Structure ◽  
Vibration Data ◽  
Random Decrement Technique ◽  
Random Decrement

It is important to estimate both added mass and radiation damping of floating artificial base, which is floating structure, in fluid-structure interaction problem. When a floating artificial base shows elastic behavior, its damping contains both structural damping and radiation damping. Therefore it is difficult to estimate the damping. We aimed to grasp tendencies of damping, when a floating artificial base shows elastic behavior, by both experiment and field measurement. The experimental modal analysis using elastic plate models was carried out and tendencies of damping ratio of experimental models were grasped. Besides, damping ratio of an existent floating artificial base was calculated from measured vibration data by the Random Decrement Technique (RDT). In our experimental results, the damping ratio became larger value in lower vibration mode, and then it decreased in higher vibration mode. In higher vibration mode, we could not confirm radiation damping. It is thought that structural damping accounts for nearly all of obtained damping ratio. Consequently, it is appropriate that damping ratio of the floating artificial base is evaluated as Rayleigh type damping.

scholarly journals Structural Responses of a Supertall Building Subjected to a Severe Typhoon at Landfall

2020 ◽  
Vol 10 (8) ◽  
pp. 2965 ◽  
Author(s):  
Zhi Li ◽  
Jiyang Fu ◽  
Yuncheng He ◽  
Zhen Liu ◽  
Jiurong Wu ◽  
...  
Keyword(s):  
Dynamic Properties ◽  
Damping Ratio ◽  
Field Measurements ◽  
Amplitude Dependence ◽  
Modal Shape ◽  
Stochastic Subspace Identification ◽  
Random Decrement Technique ◽  
Random Decrement ◽  
Combined Use ◽  
Structural Responses

Typhoon Mangkhut (1822) was one of the strongest tropical cyclones that ever impacted the south coast of China in past decades. During the passage of this typhoon, the structural health monitoring (SHM) system installed on a 303 m high building in this region worked effectively, and high-quality field measurements at nine height levels of the building were collected successfully, which provides a valuable opportunity to explore the dynamic properties of the building and the associated wind effects. In this study, the typhoon wind characteristics are presented first based on in-situ measurements at two sites. Acceleration responses of the building is then investigated, and the building’s serviceability is assessed against several comfort criteria. This study further focuses on the identification of modal parameters (i.e., natural frequency, damping ratio, and modal shape) via two methods: stochastic subspace identification (SSI) method and a method based on combined use of spectral analysis and random decrement technique (RDT). The good agreement between the two results demonstrates the effectiveness and the accuracy of the adopted methods. The obtained results are further compared with the stipulations in several technical codes as well as simulation results via finite element method to examine their performances in this real case. The amplitude dependence of natural frequencies and damping ratios of the studied building are also stressed.

Using a Single-DOF Test Vehicle to Simultaneously Retrieve the First Few Frequencies and Damping Ratios of the Bridge

2021 ◽  
pp. 2150108
Author(s):  
Y. B. Yang ◽  
K. Shi ◽  
Z. L. Wang ◽  
H. Xu ◽  
B. Zhang ◽  
...  
Keyword(s):  
Damping Ratio ◽  
Contact Point ◽  
Vehicle Speed ◽  
Test Vehicle ◽  
Closed Form Solutions ◽  
Random Decrement Technique ◽  
Mode Decomposition ◽  
Random Decrement ◽  
Contact Response ◽  
The Hilbert Transform

Bridge damping ratios are extracted via the skillful use of the single-degree-of-freedom (DOF) test vehicle for the first time in this paper. Central to the simultaneous retrieval of the first few frequencies and damping ratios from the contact (point) response of the bridge is the use of the variational mode decomposition (VMD) and random-decrement technique (RDT). Closed-form solutions are newly derived for the vehicle and contact responses of the damped bridge and validated later numerically. Using the proposed method, one calculates first the mono-component from the contact response by the VMD; then extracts the free-decay response for each mode by the RDT; and finally identifies the frequency and damping ratio by the Hilbert transform. The parametric study confirms that: (1) the contact response outperforms vehicle’s response in retrieving bridge frequencies and damping ratios; (2) the first few frequencies can be identified with robustness for reasonable levels of road roughness, vehicle speed, bridge damping and noise; (1) good result is obtained for the first damping ratio, in spite of the traditional uncertainty existing with damping; and (2) ongoing traffic can enhance the proposed method for bridge identification.

Random Decrement Technique Based on the Sampling Methods

2011 ◽  
Vol 243-249 ◽  
pp. 5413-5419
Author(s):  
Chuan Xiong Zhang ◽  
Wen Hai Shi ◽  
Zheng Nong Li
Keyword(s):  
Sampling Method ◽  
Sampling Methods ◽  
Dynamic Properties ◽  
Damping Ratio ◽  
Structural System ◽  
Random Decrement Technique ◽  
Linear Dynamic ◽  
Random Decrement ◽  
Effective Use

This paper presents the random decrement (RD) technique based on the sampling method for parameter identification of linear dynamic system. The development of RD technique was elaborated briefly in the aspects of identifying the dynamic properties, and then this paper summarized the corresponding parameters recognition problems due to the quantity and quality of measured sampling segments. Detailed analysis of two kinds of sampling method (the probability-proportional-to-size and two-stage sampling) is conducted to investigate its adaptation range in extracting RD signatures. The results of two simulated examples indicates that in view of the different vibration parameter recognition situation, the above provided RD technique based on different sampling methods could improve the quality of RD signature obviously, and lead to a quite accurate frequency and the damping ratio of structural system under the effective use of all measured sampling segments.

Effect of guy cable constraint on structural damping of open lattice antenna towers

1980 ◽  
Vol 7 (4) ◽  
pp. 614-620
Author(s):  
J. S. Kennedy ◽  
D. J. Wilson ◽  
P. F. Adams ◽  
M. Perlynn
Keyword(s):  
Natural Frequencies ◽  
Damping Ratio ◽  
Field Tests ◽  
Full Scale ◽  
Structural Damping ◽  
Scale Field ◽  
Modes Of Vibration

This paper presents the results of full-scale field tests on two steel guyed latticed towers. The towers were approximately 83 m in height, were guyed at three levels, and were of bolted angle construction. The observed results consist of the natural frequencies of the first two modes of vibration as well as the damping ratio for the first mode. The observed results are compared with analytical predictions and observations made concerning the contributions of structural and cable action to the damping ratio.

Preparation and Vibration Damping Characteristics of Wide Frequency Domain PVMQ/IIR Foam Materials

2012 ◽  
Vol 538-541 ◽  
pp. 2298-2303
Author(s):  
Shi Kai Luo ◽  
Guo Fang Ding ◽  
Jing Li Li ◽  
Yan Song Sha ◽  
Qing Min Cheng ◽  
...  
Keyword(s):  
Frequency Domain ◽  
Wide Temperature Range ◽  
Damping Ratio ◽  
Vibration Damping ◽  
Simple Equation ◽  
Structural Damping ◽  
Damping Characteristics ◽  
Damping Materials ◽  
Foaming Technology ◽  
Isoprene Rubber

In this paper, we prepared foaming silicon rubber (PVMQ) /isobutylene-isoprene rubber (IIR) composites with chemical foaming technology. The DMA tests results showed that these foaming materials have effective damping characteristics in a wide temperature range. With the special vibrator, we found that the PVMQ/IIR foams that we prepared were the damping materials which has wide frequency domain, because they can keep high damping ratio in a wide frequency domain. When the preloading was between 1.0 mm and 1.7 mm, the structural damping did not change obviously. According to tests, we found that the damping ratio of these foams was fit to the simple equation .

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