scholarly journals A Tuned Mass Damper with Nonlinear Magnetic Force for Vibration Suppression with Wide Frequency Range of Offshore Platform under Earthquake Loads

2018 ◽  
Vol 2018 ◽  
pp. 1-18 ◽  
Author(s):  
Qiong Wu ◽  
Wei Zhao ◽  
Weiguo Zhu ◽  
Rencheng Zheng ◽  
Xilu Zhao
Keyword(s):  
High Speed ◽  
Permanent Magnets ◽  
Vibration Suppression ◽  
Wide Frequency Range ◽  
Offshore Platform ◽  
Offshore Platforms ◽  
Frequency Range ◽  
Response Characteristics ◽  
Narrow Frequency Band ◽  
Dynamic Performances

Tuned mass dampers (TMDs) are applied to ensure the safety and stability of offshore platforms; however, linear dampers are effective for a single resonance frequency, providing vibration suppression only within a narrow frequency band. Therefore, this paper proposed a magnetic TMD with two pairs of permanent magnets on both sides of the structures, which can generate a nonlinearly repulsive force, making the magnetic TMD reliable and robust in damping the oscillations of structures with wide frequency range under seismic excitations. A comprehensively numerical and experimental study was processed to investigate the dynamic performances of the proposed magnetic TMD, by application of a 1 : 200-scale prototype of the offshore platform. The results verified that the performance of the magnetic TMD can be significantly improved than that of the linear TMD, meanwhile maintaining high-speed response characteristics. The experimental results indicated that the displacement, acceleration, and frequency responses of the offshore platform can be significantly reduced; furthermore, the evaluation indices showed that the magnetic TMD system is credible in reducing the overall vibration levels and maximum peak values.

scholarly journals High Response Performance of a Tuned-Mass Damper for Vibration Suppression of Offshore Platform under Earthquake Loads

2016 ◽  
Vol 2016 ◽  
pp. 1-11 ◽  
Author(s):  
Qiong Wu ◽  
Xilu Zhao ◽  
Rencheng Zheng ◽  
Keisuke Minagawa
Keyword(s):  
Vibration Suppression ◽  
Initial Period ◽  
Offshore Platform ◽  
High Response ◽  
Experimental Investigations ◽  
Offshore Platforms ◽  
Earthquake Loads ◽  
Response Characteristics ◽  
Response Performance ◽  
The Stability

Currently, tuned-mass dampers (TMDs) are widely applied to maintain the stability of offshore platforms in hostile environments; however, the stability system of offshore platforms faces considerable challenges under critical earthquake loads of the initial period. Therefore, this study concentrated on the high response performance of a simple passive TMD system, and numerical and experimental investigations were performed using a 1 : 200-scale prototype. The obtained results indicated that the displacement, acceleration, and their power spectral density all decreased significantly for the offshore platform with the TMD system. By further analyses of its high response characteristics, it was validated that the TMD reactions can commence within the first 3 s of earthquake excitation, while the fundamental natural frequency was consistently tuned for the TMD system dependent on the dynamic magnification factor. The evaluation indices also confirmed that this method is effective in reducing the overall vibration level and the maximum peak values of the offshore platform exposed to earthquake excitations, mainly because of its high response characteristics.

scholarly journals A Bufferable Tuned-Mass Damper of an Offshore Platform against Stroke and Response Delay Problems under Earthquake Loads

2016 ◽  
Vol 2016 ◽  
pp. 1-12 ◽  
Author(s):  
Qiong Wu ◽  
Xilu Zhao ◽  
Shuai He ◽  
Wenxian Tang ◽  
Rencheng Zheng
Keyword(s):  
Seismic Waves ◽  
Large Earthquake ◽  
Tuned Mass Damper ◽  
Offshore Platform ◽  
Offshore Platforms ◽  
Response Delay ◽  
Earthquake Loads ◽  
Response Characteristics ◽  
Mass Damper ◽  
Dynamic Performances

A tuned-mass damper (TMD) is applied to ensure the safety and stability of an offshore platform in practice; however, damper stroke and response delay problems always result in intractable performances of vibration control while exposed to large earthquake loads. Therefore, this paper proposes a bufferable TMD, a passive TMD with buffers on both sides, to improve the performance of offshore platforms subjected to large seismic waves. A comprehensive simulation and experimental study was executed to investigate the dynamic performances of the bufferable TMD, by application of a 1 : 200-scale offshore platform prototype. It is verified that the bufferable TMD can be effective in absorbing the stroke energy, while the damper exceeds limitations of motion. Meanwhile, the bufferable TMD can maintain high-response characteristics. In conclusion, the experimental results indicate that the displacement, acceleration, and frequency performances of an offshore platform can be significantly decreased, and the evaluation indices show that the method is effective in reducing overall vibration levels and maximum peak values, with the application of the bufferable damper system.

scholarly journals THE INVESTIGATION OF VIBRO-ISOLATING FEATURES OF TRANSMISSIONS OF VEHICLES IN ELASTIC CENTRIFUGAL COUPLINGS USING THE METHOD OF IDENTIFICATION OF DYNAMIC PROCESSES IN HALF-COUPLINGS ON THE UNIVERSAL DYNAMIC TEST STAND

Transport ◽  
2002 ◽  
Vol 17 (3) ◽  
pp. 77-84
Author(s):  
Bronislovas Spruogis ◽  
Leonas Zubavičius
Keyword(s):  
Dynamic Characteristics ◽  
High Speed ◽  
Dynamic Test ◽  
Power Saving ◽  
Wide Frequency Range ◽  
Test Stand ◽  
Dynamic Processes ◽  
Frequency Range ◽  
Rotor Systems ◽  
Resonance Frequencies

The presented paper describes the investigation of vibro-isolating features of transmissions of vehicles using universal dynamic test stand. The stand is protected by copyright and distinguishes itself for many advantages in comparison with the existing stands: it is contactless, precise in a wide frequency range, power-saving, high-speed. Due to low exploitation expenses and wide possibilities it is fit for the investigation of dynamic characteristics of various vehicles. On the said stand using the method of the identification of experiment dynamic processes, the investigation of vibroisolating features of rotor systems has been performed. The errors caused by the unevenness of rotation of connecting shafts, the adequacy of the calculated models and the dangerous resonance frequencies have been determined.

VIBRATION CHARACTERISTICS OF THE DAMPER ELEMENT COMPOSED OF ANNULAR MAGNETS AND MAGNETIC FLUID

2005 ◽  
Vol 19 (07n09) ◽  
pp. 1520-1526 ◽  
Author(s):  
S. SUDO ◽  
A. NAKAGAWA
Keyword(s):  
Magnetic Fluid ◽  
Vibration Amplitude ◽  
Permanent Magnets ◽  
Wide Frequency Range ◽  
Vibration Characteristics ◽  
Testing System ◽  
Frequency Range ◽  
Vibration Testing ◽  
Fluid System ◽  
Optical Displacement

This paper is concerned with the development of a damper with excellent characteristics. The vibration characteristics of the damper element composed of two annular permanent magnets and magnetic fluid are studied experimentally using a vibration testing system. The vibration amplitude of the upper magnet-magnetic fluid system is measured with an optical displacement detector system. It was found that the element of two annular permanent magnets adsorbed magnetic fluid is very effective over the wide frequency range.

A Nonlinear Acoustic Resonator

2007 ◽  
Author(s):  
Umar Farooq ◽  
Shahin S. Nudehi
Keyword(s):  
Vibration Suppression ◽  
Perturbation Technique ◽  
Helmholtz Resonator ◽  
Acoustic Resonator ◽  
Wide Frequency Range ◽  
Frequency Range ◽  
Vibration Absorption ◽  
Membrane Attachment ◽  
Nonlinear Acoustic ◽  
System Frequency

An acoustic resonator of Helmholtz type with a membrane attached to one of its ends is studied in this work. A membrane possesses a geometric nonlinearity of cubic type. This work examines that when attached to the resonator, a membrane can be exploited to attenuate vibrations for a variable frequency range in an acoustical system. This can be viewed as a parallel to vibration absorption for the structural systems. The coupled nonlinear mathematical model of Helmholtz resonator with a membrane attachment is investigated by applying a perturbation technique to obtain a set of second order differential equations. These equations are then numerically solved. The simulations of system frequency response show that the vibration suppression could be achieved for a wide frequency range.

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