Abstract
Idea of using piezoelectric materials with flexible structures made of rubber-like materials is quite novel. In this study a non-linear finite element model based on updated Lagrangian (UL) approach has been developed for dynamic response and its control of rubber-elastic material with surface-bonded PVDF patches/layers. A compressible stain energy density function has been used for the modeling of the rubber component. The results obtained are compared with available analytical solutions and other published results in some cases. Some results are reported as new results which will be useful for future references since the number of published results is not sufficient.
Key Words
nonlinear finite element; compressible strain energy function; hyperelastic material; piezoelectric material; dynamic response; smart rubber beam.
Address
M.C. Manna: Department of Aerospace Engineering and Applied Mechanics, Bengal Engineering and Science University, Shibpur, Howrah - 711 103, India
R. Bhattacharyya: Department of Mechanical Engineering, Indian Institute of Technology, Kharagpur - 721 302, India
A.H. Sheikh: Department of Civil, Environmental and Mining Engineering, University of Adelaide, SA - 5005, Australia
Abstract
Changes in temperature, loads and boundary conditions may have effects on the dynamic properties of large civil structures. Taking the Run Yang Suspension Bridge as an example, modal properties obtained from ambient vibration tests and from the structural health monitoring system of the bridge are used to identify and evaluate the modal parameter variability. Comparisons of these modal parameters reveal that several low-order modes experience a significant change in frequency from the completion of the bridge to its operation. However, the correlation analysis between measured modal parameters and the temperature shows that temperature has a slight influence on the low-order modal frequencies. Therefore, this paper focuses on the effects of the boundary conditions on the dynamic behaviors of the suspension bridge. An analytical model is proposed to perform a sensitivity analysis on modal parameters of the bridge concerning the stiffness of expansion joints located at two ends of bridge girders. It is concluded that the boundary conditions have a significant influence on the low-order modal parameters of the suspension bridge. In addition, the influence of vehicle load on modal parameters is also investigated based on the proposed model.
Key Words
suspension bridge; ambient vibration test; structural health monitoring system; boundary condition; expansion joints.
Address
Zhijun Li and Aiqun Li: College of Civil Engineering, Southeast University, Nanjing 210096, P.R. China
Jian Zhang: Department of Civil Engineering, National University of Singapore, Singapore 117576
Abstract
Most of studies on control of beams containing piezoelectric sensors and actuators have been based on linear quadratic regulator (LQR) with state feedback or output feedback law. The aim of this study is to develop velocity-acceleration feedback law in the optimal control of smart piezoelectric beams. A new controller which is an optimal control system with velocity-acceleration feedback is presented. In finite element modeling of the beam, the variation of mechanical displacement through the thickness is modeled by a sinus model that ensures inter-laminar continuity of shear stress at the layer interfaces as well as the boundary conditions on the upper and lower surfaces of the beam. In addition to mechanical degrees of freedom, one electric potential degree of freedom is considered for each piezoelectric element layer. The efficiency of this control strategy is evaluated by applying to an aluminum cantilever beam under different loading conditions. Numerical simulations show that this new control scheme is almost as efficient as an optimal control system with state feedback. However, inclusion of the acceleration in the control algorithm increases practical value of a system due to easier and more accurate measurement of accelerations.
Key Words
active structural control; smart piezoelectric beam; velocity-acceleration feedback.
Address
Department of Civil Engineering, Khajeh Nasir Toosi University of Technology (KNTU), Tehran, Iran
Abstract
A low-cost wireless sensor network (WSN) solution with highly expandable super and simple nodes was developed. The super node was designed as a sensing unit as well as a receiving terminal with low energy consumption. The simple node was designed to serve as a cheaper alternative for large-scale deployment. A 12-bit ADC inputs and DAC outputs were reserved for sensor boards to ease the sensing integration. Vibration and thermal field tests of the Chi-Lu Bridge were conducted to evaluate the WSN
Key Words
wireless sensor network (WSN); ZigBee; structural health monitoring (SHM); Chi-Lu cable-stayed bridge.
Address
H.R. Lin: Institute of Applied Mechanics, National Taiwan University, Taipei, Taiwan
C.S. Chen: Department of Civil Engineering, National Taiwan University, Taipei, Taiwan
P.Y. Chen: Department of Engineering Science and Ocean Engineering, National Taiwan University, Taipei, Taiwan
F.J. Tsai and J.D. Huang: Institute of Applied Mechanics, National Taiwan University, Taipei, Taiwan
J.F. Li: Department of Civil Engineering, National Taiwan University, Taipei, Taiwan
C.T. Lin: Graduate Institute of Electronics Engineering, National Taiwan University, Taipei, Taiwan
W.J. Wu: Department of Engineering Science and Ocean Engineering, National Taiwan University, Taipei, Taiwan
Abstract
The performance of variable dampers for seismic protection of the benchmark highway bridge (phase I) under six real earthquake ground motions is presented. A simplified lumped mass finite-element model of the 91/5 highway bridge in Southern California is used for the investigation. A variable damper, developed from magnetorheological (MR) damper is used as a semi-active control device and its effectiveness with friction force schemes is investigated. A velocity-dependent damping model of variable damper is used. The effects of friction damping of the variable damper on the seismic response of the bridge are examined by taking different values of friction force, step-coefficient and transitional velocity of the damper. The seismic responses with variable dampers are compared with the corresponding uncontrolled case, and controlled by alternate sample control strategies. The results of investigation clearly indicate that the base shear, base moment and mid-span displacement are substantially reduced. In particular, the reduction in the bearing displacement is quite significant. The friction and the two-step friction force schemes of variable damper are found to be quite effective in reducing the peak response quantities of the bridge to a level similar to or better than that of the sample passive, semi-active and active controllers.
Key Words
benchmark highway bridge; MR damper; variable damper; friction force scheme; two-step friction force scheme.
Address
Department of Civil Engineering, Indian Institute of Technology Bombay, Powai, Mumbai - 400 076, India
Abstract
Based on the theory of piezo-elasticity, the paper obtains the exact solutions of functionally graded piezoelectric hollow cylinders with different piezoelectric parameter g31. Two kinds of piezoelectric hollow cylinders are considered herein. One is a multi-layered cylinder with different parameter g31 in different layers; the other is a continuously graded cylinder with arbitrarily variable g31. By using the Airy stress function method with plane strain assumptions, the exact solutions of the mechanic and electrical components of both cylinders are obtained when they are subjected to external voltage (actuator) and pressure (sensor), simultaneously. Furthermore, good agreement is achieved between the theoretical and numerical results, and useful conclusions are given.
Key Words
functionally graded material (FGM); ring actuator; multi-layered; piezoelectric material.
Address
Taotao Zhang: School of Transportation Science and Engineering, Beihang University, Beijing, 100191, P.R. China
Zhifei Shi: School of Civil Engineering, Beijing Jiaotong University, Beijing, 100044, P.R. China
