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CONTENTS
Volume 4, Number 1, January 2013
 

Abstract
The present investigation deals with the analysis of wave motion in the layer of an anisotropic, initially stressed, fiber reinforced thermoelastic medium. Secular equations for symmetric and skewsymmetric modes of wave propagation in completely separate terms are derived. The amplitudes of displacements and temperature distribution were also obtained. Finally, the numerical solution was carried out for Cobalt and the dispersion curves, amplitudes of displacements and temperature distribution for symmetric and skew-symmetric wave modes are presented to evince the effect of anisotropy. Some particular cases are also deduced.

Key Words
wave propagation; initially stressed; fiber-reinforced; transversely isotropic; amplitudes

Address
Raj Rani Gupta and Rajani Rani Gupta: Department of Mathematics, M. M. University, Mullana, Ambala, Haryana, India-133203

Abstract
Since slender structures such as utility poles, radio masts, and chimneys, are essentially statically determinate structures, they often collapse during earthquakes. Although vibration control is the most logical method for improving the earthquake resistance of such structures, there are many practical problems with its implementation due to their very long natural vibration period. This paper proposes a new vibration control device to effectively prevent the collapse of slender structures subjected to strong earthquakes. The device consists of a pendulum, an elastic restraint and a lever, and is designed such that when it is attached to a slender structure, the second vibration mode of the structure corresponds to the first vibration mode of the same structure without the device attached. This is highly effective in causing the transverse motions of the device and the structure to oppose each other and so reduce the overall transverse vibration during an earthquake. In the present paper, the effectiveness of the vibration control device is first evaluated based on laboratory experiments and numerical studies. An example of applying the device to a tall chimney is then simulated. A new dynamic analytical method for slender structures with abrupt rigidity variations is then proposed.

Key Words
slender structure; vibration control; vibration control device; long period; pendulum type; earthquake resistance; dynamic analyses; abrupt variation of rigidity.

Address
Hideo Takakbatake and Fumiya Ikarashi: Department of Architecture, Kanazawa Institute of Technology, Institute of Disaster and Environmental Science 3-1, Yatsukaho, Hakusan City, Ishikawa 924-0838, Japan

Abstract
A comprehensive experimental program of cyclic tests on 1:3-scale models of bridge piers is going to be carried out at the Laboratory of Structures and Materials of the University of Basilicata. The testing models include eight RC single shaft piers with hollow circular cross section. Four piers have been realised using corroded steel rebars. In this paper, the results of preliminary numerical simulation analyses of the cyclic behaviour of the piers, carried out with Opensees using fiber-based models, are presented. Pull-out and lap-splice effects of steel rebars have been taken into account in the numerical analyses. First, the experimental specimens and the test set up are presented. Next, the results of the numerical analyses are discussed. In the numerical analyses, different configurations and levels of corrosion have been considered. The effective stiffness and equivalent damping of the piers is reported as a function of pier ductility and pier drift.

Key Words
RC piers; nonlinear cyclic behavior; numerical simulation analyses; corrosion of steel rebars

Address
D. Cardone, G. Perrone and S. Sofia: DiSGG, Dipartimento di Strutture Geotecnica e Geologia, Universita degli studi della Basilicata, Via Dell

Abstract
A semi-active mass damping (SMD) system with magnetorheological (MR) dampers focusing on low- and mid-rise buildings is proposed in this paper. The main purpose of this study is to integrate the reliable characteristics of the traditional tuned mass damper (TMD) and the superior performance of the active mass damper (AMD) to the new system. In addition, the commonly seen solution of deploying dense seismic dampers throughout the structure nowadays to protect the main structure is also expected to switch to the developed SMD system on the roof with a similar reduction performance. In order to demonstrate this concept, a full-size three-story steel building representing a typical mid-rise building was used as the benchmark structure to verify its performance in real life. A numerical model with the interpolation technique integrated was first established to accurately predict the behavior of the MR dampers. The success of the method was proven through a performance test of the designated MR damper used in this research. With the support of the MR damper model, a specific control algorithm using a continuous-optimal control concept was then developed to protect the main structure while the response of the semi-active mass damper is discarded. The theoretical analysis and the experimental verification from a shaking table test both demonstrated the superior mitigation ability of the method. The proposed SMD system has been demonstrated to be readily implemented in practice.

Key Words
tuned mass damper; hybrid control; MR damper

Address
Pei-Yang Lin: National Center for Research on Earthquake Engineering, Taipei, Taiwan; Tzu-Kang Lin: Department of Civil Engineering, National Chiao Tung University, Hsin-Chu, Taiwan; Jenn-Shin Hwang: Department of Construction Engineering, National Taiwan University of Science and Technology, Taipei, Taiwan

Abstract
The research presented in this paper deals with the seismic protection of existing frame structures by means of passive energy dissipation. A displacement-based procedure to design dissipative bracings for the seismic protection of frame structures is proposed and some applications are discussed. The procedure is based on the displacement based design using the capacity spectrum method, no dynamic non linear analyses are needed. Two performance objective have been considered developing the procedure: protect the structure against structural damage or collapse and avoid non structural damage as well as excessive base shear. The compliance is obtained dimensioning dissipative braces to limit global displacements and interstorey drifts. Reference is made to BRB braces, but the procedure can easily be extended to any typology of dissipative brace. The procedure has been validated through a comparison with nonlinear dynamic response of two 2D r.c. frames, one bare and one infilled. Finally a real application, on an existing 3D building where dissipative braces available on market are used, is discussed.

Key Words
infilled frames; passive damping; dissipative braces; seismic retrofitting

Address
A.V. Bergami and C. Nuti: University of Roma Tre, Department of Structures, Rome, Italy

Abstract
Current codes incorporate simplified methods for the prediction of acceleration demands on secondary structural and non-structural elements at different levels of a building. While the use of simple analysis methods should be advocated, damage to both secondary structural and non-structural elements in recent earthquakes have highlighted the need for improved design procedures for such elements. In order to take a step towards the formation of accurate but simplified methods of predicting floor spectra, this work examines the floor spectra on elastic and inelastic single-degree of freedom systems subject to accelerograms of varying seismic intensity. After identifying the factors that appear to affect the shape and intensity of acceleration demands on secondary structural and non-structural elements, a new series of calibrated equations are proposed to predict floor spectra on single degree of freedom supporting structures. The approach uses concepts of dynamics and inelasticity to define the shape and intensity of the floor spectra at different levels of damping. The results of non-linear time-history analyses of a series of singledegree of freedom supporting structures indicate that the new methodology is very promising. Future research will aim to extend the methodology to multi-degree of freedom supporting structures and run additional verification studies.

Key Words
floor spectra; non-structural elements; secondary structural elements

Address
Timothy J Sullivan: Department of Civil Engineering and Architecture, Universita degli Studi di Pavia, Via Ferrata 1, Pavia, 27100, Italy; Paolo M Calvi and Roberto Nascimbene: Department of Structural Mechanics, Universita degli Studi di Pavia, Via Ferrata 1, Pavia, 27100, Italy


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