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CONTENTS
Volume 6, Number 3, March 2014
 

Abstract
This paper experimentally investigates the seismic performance of RC columns retrofitted with Super Reinforcement with Flexibility (SRF), which is a polyester fiber reinforced polymer. A total of three specimens with a scale factor of 1/2 were constructed and tested in order to assess the structural behavior of the retrofitted RC columns. One specimen was a non-seismically designed column without any retrofit, while others were retrofitted with either one or two layers of the polyester belt with urethane as the adhesive. Static cyclic testing with a constant axial load was conducted to assess the seismic performance of the retrofitted RC columns. It is concluded that the SRF retrofitting method increases the strength and ductility of the RC columns and can also impact on the failure mode of the columns.

Key Words
seismic retrofit; reinforced concrete column; SRF(Super Reinforcement with Flexibility); shear failure

Address
Chunho Chang, Dongbyung Park and Sunghun Choi:
Department of Civil Engineering, Keimyung University, Dalseo, Daegu, 704-701, Korea
Sung Jig Kim: Department of Architectural Engineering, Keimyung University, Dalseo, Daegu, 704-701, Korea

Abstract
Dynamic analyses for a suite of ground of motions were conducted on concrete gravity dam sections to examine the earthquake induced stresses and effective damping. For this purpose, frequency domain methods that rigorously incorporate dam-reservoir-foundation interaction and time domain methods with approximate hydrodynamic foundation interaction effects were employed. The maximum principal tensile stresses and their distribution at the dam base, which are important parameters for concrete dam design, were obtained using the frequency domain approach. Prediction equations were proposed for these stresses and their distribution at the dam base. Comparisons of the stress results obtained using frequency and time domain methods revealed that the dam height and ratio of modulus of elasticity of foundation rock to concrete are significant parameters that may influence earthquake induced stresses. A new effective damping prediction equation was proposed in order to estimate earthquake stresses accurately with the approximate time domain approach.

Key Words
concrete gravity dams; stress estimation; damping; numerical simulation; linear dynamic analysis; dam-reservoir-foundation interaction

Address
Ugur Akpinar, Baris Binici and Yalin Arici: Department of Civil Engineering, Middle East Technical University, Ankara, Turkey

Abstract
Shape Memory Alloy (SMA) braces can be used to reduce seismic residual deformations observed in steel braced Reinforced Concrete (RC) frames. To further enhance the seismic performance of these frames, the use of SMA bars to reinforce their beams is investigated in this paper. Three-story and nine-story SMA-braced RC frames are designed utilizing regular steel reinforcing bars. Their seismic performance is examined using twenty seismic ground motions. The frames are then re-designed using SMA reinforcing bars. Different design alternatives representing different locations for the SMA reinforcing bars are considered. The optimum locations for the SMA bars are identified after analysing the design alternatives. The seismic performance of these frames has indicated better deformability when SMA bars are used in the beams.

Key Words
SMA; residual deformations; braced frames; seismic performance; reinforced concrete; design alternatives

Address
Mohamed E. Meshaly: Department of Civil and Environmental Engineering, Western University, London, Ontario, Canada, N6A 5B9
Department of Structural Engineering, Alexandria University, Alexandria, Egypt
Maged A. Youssef: Department of Civil and Environmental Engineering, Western University, London, Ontario, Canada, N6A 5B9
Hamdy M. Abou Elfath: Department of Structural Engineering, Alexandria University, Alexandria, Egypt

Abstract
This study proposes a scheme to design control parameters for a data center facility with a vibration controller on its top floor and a secondary isolation device with its own vibration controller designed to protect vibration-sensitive computer equipment. The aim is to reduce the effects of acceleration and drift from an earthquake on computer servers placed on the isolation device that must operate during a seismic event. A linear elastic model is constructed and the evaluation function of the linear quadratic Gaussian (LQG) control is formulated. The relationship between the control parameters and the responses is examined, and based on the observations, a control parameter design scheme is constructed to reduce the responses of both the building and the computer server effectively.

Key Words
vibration control; isolation floor; computer center; function maintenance

Address
Masayuki Kohiyama: Department of System Design Engineering, Keio University, Yokohama, Japan
Minako Yoshida: Formerly, Graduate School of Science and Technology, Keio University, Yokohama, Japan

Abstract
This paper is devoted to investigate the effects of SSI on strength reduction factor of multistory buildings. A new formula is proposed to estimate strength reduction factors for MDOF structure-soil systems. It is concluded that SSI reduces the strength reduction factor of MDOF systems. The amount of this reduction is relevant to the fundamental period of structure, soil flexibility, aspect ratio and ductility of structure, and could be significantly different from corresponding fixed-base value. Using this formula, measuring the amount of this error could be done with acceptable accuracy. For some practical cases, the error attains up to 50%.

Key Words
dynamic analysis; soil-structure interaction; strength reduction factor; multi-story building

Address
Farhad Abedi Nik: Department of Civil Engineering, SADRA Institute of Higher Education, Tehran, Iran
Faramarz Khoshnoudian: Department of Civil Engineering, Amirkabir University of Technology, Tehran, Iran

Abstract
The work is concerned with an investigation of the advantages stemming from the use of lightweight aggregate concrete in earthquake-resistant reinforced concrete construction. As the aseismic clauses of current codes make no reference to lightweight aggregate concrete beams made of lightweight aggregate concrete but designed in accordance with the code specifications for normal weight aggregate concrete, together with beams made from the latter material, are tested under load mimicking seismic action. The results obtained show that beam behaviour is essentially independent of the design method adopted, with the use of lightweight aggregate concrete being found to slightly improve the post-peak structural behaviour. When considering the significant reduction in deadweight resulting from the use of lightweight aggregate concrete, the results demonstrate that the use of this material will lead to significant savings without compromising the structural performance requirements of current codes.

Key Words
beams; earthquake-resistant design; lightweight aggregate concrete; cyclic tests

Address
E.G. Badogiannis and M.D. Kotsovos: Civil Engineering Department, National Technical University of Athens, Athens 15773, Greece


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