Summary of Activities

Structural vibration control, as an innovative technology in structural engineering, is to implement energy dissipation devices or control systems into buildings and structures to reduce excessive structural vibration, enhance human comfort, and prevent catastrophic structural failure due to strong winds and earthquakes. Structural vibration control technology can also be used for the retrofitting of historic buildings and structures against strong winds and earthquakes. Systematic investigations have been carried out by the Center on passive, semi-active, hybrid, and active control devices for a variety of buildings and structures. The Center has been also involved in the real application of this advanced technology for construction industry.

• Vibration measurement and assessment of buildings and structures
• Development of innovative control devices
• Model or full-scale tests of buildings and structures with control devices
• Advanced analysis and design of buildings and structures with control devices
• Real-time monitoring of buildings and structures with control devices
• Smart vibration isolation technology for automation and precision equipment
• Optimal design of number and locations of actuators in active vibration control of a space truss

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Representative Projects

• Smart vibration isolation technology for automation and precision equipment
  Supported by the Innovation and Technology Commission - Innovation and Technology Fund-University-Industry Collaboration Program-Matching Grant for Joint Research
  To develop a smart vibration isolation system for use in automation and precision equipment. First, the vibration behavior of equipment due to the dynamics of moving parts will be studied, and appropriate smart materials for vibration isolation will be tailored. Based on the results, a modular-typed vibration isolation system consisting of sensors and smart material-based isolation devices interfaced to an intelligent control unit will be developed. Finally, the smart system will be integrated with the equipment, and its performance will be evaluated in-situ.
  
• Vibration measurement of gantries at Ting Kau Bridge, Tsing Ma Bridge and Kwai Chung Viaduct
  Commissioned by the General Electric Company of Hong Kong Limited
  To assess dynamic response and fatigue damage of the gantries and the lane use signals at the Ting Kau Bridge, the Tsing Ma Bridge, and the Kwai Chung Viaduct due to the dynamic interaction between the gantries and long span bridges.
• Vibration mitigation of adjacent buildings using passive, semi-active, or active dampers Supported by the Hong Kong Polytechnic University and collaborated with Southeast University and Tongji Univrsity
  To carry out a systematic investigation of using various dampers to connect adjacent buildings or a podium structure to a tall building to enhance the safety of the buildings under earthquake. The investigation includes the development and manufacture of damper devices, large-scale laboratory tests, and advanced analysis of the buildings implemented with dampers.
• Mitigation of wind-rain-induced cable vibration in cable-stayed bridges Supported by the Hong Kong Research Grants Council
  To establish an analytical model of wind-rain-induced cable vibration and predict the minimum damping ratio required for mitigating excessive vibration of a stay cable. To develop a hybrid numerical method for evaluating the increased damping ratio in a stay sag cable provided by attached fluid dampers. The combination of the above two phases of the research leads to an engineering approach for designing fluid dampers to mitigate wind-rain-induced cable vibration.
  
• Control of wind-rain-induced cable vibration of Dongting Lake Bridge using magnetorheological dampers Supported by the Hong Kong Polytechnic University and collaborated with Central South University
  To implement semi-active magnetorheological dampers (MR) for cable vibration control in the cable-stayed Dongting Lake Bridge. A total of 312 MR dampers have been installed on the bridge, which completely suppress wind-rain-induced cable vibration originally occurring in the bridge. This is the world's first time implementation of MR-based smart damping technique in bridge structures.
  
• Human comfort enhancement of wind-excited buildings and towers using piezoelectric friction dampers Supported by the National Natural Science Foundation of China and collaborated with Wuhan University of Technology
  To explore the possibility of incorporating piezoelectric friction dampers into wind-excited buildings and towers with semi-active control to abate excessive vibration and enhance human comfort. Compared with passive friction dampers, the semiactive piezoelectric friction dampers are more robust and versatile to copy with harsh environment.
  
• Semi-active tuned liquid column dampers using magnetorheological fluids (MR-TLCDs) for vibration control of tall buildings Supported by the Hong Kong Polytechnic University and collaborated with Zhejiang University and UIUC
  To devise semi-active tuned liquid column dampers using magnetorheological fluids (MR-TLCDs) for wind-induced vibration mitigation of high-rise buildings. The devised MR-TLCDs exhibit alterable fluid viscosity and adjustable damping force when exposed to a magnetic field. With the aid of a proper feedback control law, they are able to implement real-time structural vibration control.
  
• Intelligent platform for micro-vibration control of high tech equipment in a large building subject to ground motion Supported by the Hong Kong Research Grants Council
  Very small vibration of building floors is not acceptable in modern high tech facilities. This project explores the possibility of using intelligent platform to mitigate microvibration of a batch of high tech equipment installed inside a building subject to nearby traffic-induced ground motion to ensure the high quality of ultra-precision products.

Wind-rain-induced vibration control of stay cables in the Dongting Lake Bridge
	Calibration of linear viscous fluid damper
Experimental investigation of vibration mitigation of inclined cable using fluid damper
	Large scale shaking table test of adjacent buildings linked by fluid dampers
Multiple tuned liquid column dampers for torsional vibration suppression of structures
	Experimental investigation of intelligent floor systems for high tech facility

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Major Facilities

• MTS 3m x 3m seismic simulation table
• dSPACE DS1005 control system
• Servo-loop controlled MTS actuators
• Electric-magnetic shakers
• A set of field measurement instrument including displacement transducers, laser transducers, accelerometers, amplifiers, and signal conditioners.

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Selected Publications

• Y.Y. Li, L.H. Yam, K.T. Chen and T.P. Leung (2000) "Robust synthesis of active controller for uncertain vibration systems", pp. 609-617, Vol. 75, No. 6 Computers and Structures.
• Y.Y. Li, L.H. Yam and T.P. Leung (2000) "A design of active vibration controller for thin plate systems", Control Theory and Application, pp. 353-357. 17, No.3.
• Y.Y. Li and L.H. Yam (2001) "A robust design method of active controller for uncertain vibration systems", Journal of Vibration and Control, Vol. 7, No. 3, pp453-466.
• Y.Y. Li and L.H. Yam (2001) "Robust vibration control of uncertain systems using variable parameter feedback and model-based fuzzy strategies", Computers and Structures, Vol.79, No. 11, pp.1109-1119.
• Y.J. Yan and L.H. Yam (2001) "A synthesis analysis on design of optimum control for an optimized intelligent structure", Journal of Sound and Vibration, Vol. 249, No. 4, pp. 775-784.
• Y. J. Yan and L. H. Yam (2002) "Optimal design of number and locations of actuators in active vibration control of a space truss" Smart Materials and Structures, Vol. 11 (4) pp. 496-503.
• Y.J. Yan and L.H. Yam (2003) "Mechanical Interaction Issues in Piezoelectric Composite Structures", Composite Structures, Vol. 59, No. 1, pp. 61-65.
• Xu, Y.L., Samali, B. and Kwok, K.C.S. (1992)  'Control of along-wind response of structures by mass and liquid dampers', Journal of Engineering Mechanics, ASCE, Vol. 118, No. 1, 20-39. 
• Xu, Y.L., Kwok, K.C.S. and Samali, B. (1992)  'Control of wind-induced tall building response by tuned mass dampers', Journal of Wind Engineering and Industrial Aerodynamics, Vol. 40, 1-32. 
• Xu, Y.L., Kwok, K.C.S. and Samali, B. (1992)  'The effect of tuned mass dampers and liquid dampers on cross-wind response of tall/slender structures', Journal of Wind Engineering and Industrial Aerodynamics, Vol. 40, 33-54.
• Xu, Y.L. and Kwok, K.C.S. (1992)  'Wind-induced response of soil-structure-mass damper systems', Journal of Wind Engineering and Industrial Aerodynamics, Vol. 43, 2057-2068. 
• Xu, Y.L., Kwok, K.C.S. and Samali, B. (1992)  'Torsion response and vibration suppression of wind-excited buildings', Journal of Wind Engineering and Industrial Aerodynamics, Vol. 43, 1997-2008. 
• Zhang, X.T., Zhang, R.C. and Xu, Y.L. (1993) 'Analysis of control of flow-induced vibration by tuned liquid damper with crossed tube-like containers', Journal of Wind Engineering and Industrial Aerodynamics, Vol. 50, 351-360.
•  Xu, Y.L. and Kwok, K.C.S. (1994) 'Semianalytical method for parametric study of tuned mass dampers', Journal of Structural Engineering, ASCE, Vol.12, No.3, March, 747-764. 
• Xu, Y.L. (1996) 'Parametric study of active mass dampers for wind-excited tall buildings', Engineering Structures, Vol.18, No.1, 64-76.
• Xu, Y.L., Yu, Z. and Ko, J.M. (1998) "Forced vibration studies of sagged cables with oil damper using a hybrid method", Engineering Structures, Vol.20, No.8, 692-705.
• Yu, Z. and Xu, Y.L. (1998) "Mitigation of three-dimensional vibration of inclined sag cable using discrete oil dampers, Part I: formulation", Journal of Sound and Vibration, July, 214(4), 659-673.
• Xu, Y.L. and Yu, Z. (1998) "Mitigation of three-dimensional vibration of inclined sag cable using discrete oil dampers, Part II: application", Journal of Sound and Vibration, July, 214(4), 675-693.
• Xu, Y.L. and Yu, Z. (1998) "Vibration of inclined sag cables with oil damper in cable-stayed bridges", Journal of Bridge Engineering, ASCE, No. 4, Vol.3. 194-203.
• Xu, Y.L., Zhan, S., Ko, J.M. and Zhang, W.S. (1999) "Experimental investigation of adjacent buildings connected by fluid dampers", Journal of Earthquake Engineering and Structural Dynamics, Vol.28, 609-631.
• Xu, Y.L., Zhan, S, J.M. Ko and Z.Yu (1999) "Experimental investigation of vibration mitigation of bridge stay cables using oil dampers", Journal of Structural Engineering, ASCE, Vol.125, No.9, 977-986.
• Yu, Z. and Xu, Y.L. (1999) "Nonlinear vibration of cable-damper systems, part I: formulation",  Journal of Sound and Vibration, Vol.225, No.3, 447-463.
• Xu, Y.L. and Yu, Z. (1999) "Nonlinear vibration of cable-damper systems, part II: application and verification",  Journal of Sound and Vibration, Vol.225, No.3, 465-481.
• Zhang, W.S. and Xu, Y.L. (1999) "Dynamic characteristics and seismic response of adjacent buildings linked by discrete dampers", Journal of Earthquake Engineering and Structural Dynamics, Vol.28, 1163-1185.
• Xue, S.D., Ko, J.M. and Xu, Y.L. (1999) "Experimental study on performance of tuned liquid column damper in suppressing pitching vibration of structures", Journal of Intelligent Material Systems and Structures, Vol. 10, 386-396.
• Ni, Y.Q., Ko, J.M., Wong, C.W. and Zhan, S. (1999), "Modelling and Identification of a wire-cable vibration isolator via cyclic loading test", Journal of Systems and Control Engineering, IMechE, Vol. 213, No. 3, 163-171.
• Ni, Y.Q., Ko, J.M. and Wong, C.W. (1999), "Nonparametric identification of nonlinear hysteretic systems", Journal of Engineering Mechanics, ASCE, Vol. 125, No. 2, 206-215.
• Xue, S.D, Ko, J.M.,. and Xu, Y.L. (2000) " Suppression of structural pitching motion by tuned liquid column damper", Engineering Structures, Vol.23, No.11, 1538-1551.
• Xu, Y.L., Qu, W.L. and J.M. Ko, (2000) "Seismic response control of frame structures using magnetorheological/electrorheological dampers,' Earthquake Engineering and Structural Dynamics, Vol. 29, 557-575.
• Zhang, W.S. and Xu, Y.L.(2000) "Vibration analysis of two buildings linked by Maxwell model-defined fluid dampers,' Journal of Sound and Vibration, Vol. 233, No.5, 775-796. 
• Xu, Y.L. and Zhang, W.S, (2001) "Modal analysis and seismic response of steel frames with connection dampers," Engineering Structures, Vol. 23, No.4, 385-396.
• Xu, Y.L., Qu, W.L. and Chen, Z.H. (2001) "Control of wind-excited truss tower using semi-active friction dampers", Journal of Structural Engineering, ASCE, Vol. 127, No.8, 861-868.
• Qu, W.L. and Xu, Y.L. (2001) "Semi-active control of seismic response of tall buildings with podium structures using ER/MR dampers", The Structural Design of Tall Buildings, Vol.10, No.3, 179-192. 
• Zhang, W.S. and Xu, Y.L. (2001) " Closed form solution for alongwind response of actively controlled tall buildings with LQG controllers", Journal of Wind Engineering and Industrial Aerodynamics, Vol. 89, No.9, 785-807.
• Qu, W.L., Chen, Z.H. and Xu, Y.L. (2001) "Dynamic analysis of wind-excited truss tower with friction dampers", Computers & Structures, Vol. 79, No.32, 2817-2831.
• Ni, Y.Q., Ko, J.M. and Ying, Z.G. (2001), "Random seismic response analysis of adjacent buildings coupled with non-linear hysteretic dampers", Journal of Sound and Vibration, Vol. 246, No. 3, 403-417. 
• Xu,Y.L. and Zhang, W.S. (2002) "Closed form solution for seismic response of adjacent buildings with LQG controllers",  Earthquake Engineering and Structural Dynamics, Vol.31, No.2, 235-259. 
• Xu, Y.L., Guo, A.X. and Wu, B. (2002) " Seismic reliability analysis of hysteretic structure with viscoelastic dampers", Engineering Structures, Vol. 24, No.3, 373-383.
• Qu, W.L., Xu, Y.L. and Lv, M.Y. (2002) " Seismic response control of large span machinary building on top of ship lift towers using ER/MR moment controllers", Engineering Structures, Vol.24, No.4, 517-527.
• Xu, Y.L. and Teng, J. (2002) "Optimum design of active/passive control devices for tall buildings under earthquake excitation", The Structural Design of Tall Buildings, Vol.11, No.2, 109-127.
• Shum, K.M and Xu, Y.L. (2002) "Multiple tuned liquid column dampers for torsional vibration control of structures: experimental investigation", Journal of Earthquake Engineering and Structural Dynamics, Vol.31, No.4, 977-991.
• Ni, Y.Q., Ying, Z.G. and Ko, J.M. (2002), "Random response analysis of Preisach hysteretic systems with symmetric weight distribution", Journal of Applied Mechanics, ASME, Vol. 69, No. 2, 171-178.
• Ni, Y.Q., Chen, Y., Ko, J.M. and Cao, D.Q. (2002), "Neuro-control of cable vibration using semi-active magneto-rheological dampers", Engineering Structures, Vol. 24, No. 3, 295-307.

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Contact Information

Contact Person

Prof. Y.L. Xu
Department of Civil & Structural Engineering
The Hong Kong Polytechnic University
Kowloon, Hong Kong
Fax:     + 852 - 2334 6389
Phone:   + 852 - 2766 6050
E-mail:  ceylxu@polyu.edu.hk

Other Investigators

Prof. J.M. Ko (cejmko@polyu.edu.hk)
Prof. H.L.W. Chan (apahlcha@polyu.edu.hk)
Dr. Y.Q. Ni (ceyqni@polyu.edu.hk)
Dr. L.H. Yam (mmlhyam@polyu.edu.hk)