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CONTENTS
Volume 3, Number 6, December 2012
 

Abstract
Because of its large contribution to the environmental instability of the planet, the building industry will soon be subjected to a worldwide scrutiny. As a consequence, all professionals involved in the building industry will need to create a professional media in which their daily work adequately solves the technical issues involved in the conception, design and construction of concrete and steel buildings, and simultaneously convey care for the environment. This paper discusses, from the point of view of a structural engineer involved in earthquake-resistant design, some of the measures that can be taken to promote the consolidation of a building industry that is capable of actively contributing to the sustainable development of the world.

Key Words
displacement-based design; damage-tolerant structure; sustainable structural engineering; structural reuse; structural recycling

Address
Amador Teran Gilmore: Universidad Autonoma Metropolitana, Departamento de Materiales, Av. San Pablo 180, Col. Reynosa Tamaulipas, Mexico 02200, D.F.

Abstract
An enhanced and efficient methodology is proposed for evaluating the robustness of an uncertain structure with passive dampers. Although the structural performance for seismic loads is an important design criterion in earthquake-prone countries, the structural parameters such as storey stiffnesses and damping coefficients of passive dampers are uncertain due to various factors or sources, e.g. initial manufacturing errors, material deterioration, temperature dependence. The concept of robust building design under such uncertain structural-parameter environment may be one of the most challenging issues to be tackled recently. By applying the proposed method of interval analysis and robustness evaluation for predicting the response variability accurately, the robustness of a passively controlled structure can be evaluated efficiently in terms of the so-called robustness function. An application is presented of the robustness function to the design and evaluation of passive damper systems.

Key Words
robustness; earthquake response; passive damper; uncertain parameter; interval analysis; structural control

Address
Kohei Fujita: Department of Urban and Environmental Engineering, Kyoto University, Japan; Izuru Takewaki: Department of Architecture and Architectural Engineering, Kyoto University, Kyotodaigaku-Katsura, Nishikyo-ku, Kyoto 615-8540, Japan

Abstract
This paper proposes a new three-layer pillar-type hysteretic damper system for residential houses. The proposed vibration control system has braces, upper and lower frames and a damper unit including hysteretic dampers. The proposed vibration control system supplements the weaknesses of the previously proposed post-tensioning vibration control system in the damping efficiency and cumbersomeness of introducing a post-tension. The structural variables employed in the damper design are the stiffness ratio

Key Words
pillar-type hysteretic damper system; stiffness ratio; ductility ratio; damper

Address
Hyeong Gook Kim: Department of Urban and Environmental Engineering, Kyoto University, Japan; Shinta Yoshitomi, Masaaki Tsuji and Izuru Takewaki: Department of Architecture and Architectural Engineering, Graduate School of Engineering, Kyoto University, Kyotodaigaku-Katsura, Nishikyo-ku, Kyoto 615-8540, Japan

Abstract
Earthquake records are often analyzed in various earthquake engineering problems, making time-frequency analysis for such records of primary concern. The best tool for such analysis appears to be based on wavelet functions; selection of which is not an easy task and is commonly carried through trial and error process. Furthermore, often a particular wavelet is adopted for analysis of various earthquakes irrespective of record

Key Words
time-frequency analysis; wavelet function; continuous wavelet transform; multi-resolution analysis

Address
Amir Bazrafshan Moghaddam: Department of Civil Engineering,Shahrood University of Technology,Shahrood,Semnan, 36199, Iran; Mohammad H. Bagheripour: Faculty of Engineering, ShahidBahonar University of Kerman, Kerman, 76169, Iran

Abstract
In this paper, a new type of passive energy dissipating system similar to added damping and stiffness (ADAS) and triangular added damping and stiffness (TADAS) is proposed and implemented in the analytical model of a building with hybrid structural system in the structure

Key Words
telescopic columns; seismic behavior; nonlinear analysis; rubber isolator bearings; friction pendulum bearings

Address
Mahmood Hosseini and Ehsan Noroozinejad Farsangi: Structural Engineering Research Center, International Institute of Earthquake Engineering and Seismology (IIEES), Tehran, Iran

Abstract
Ground motion scaling techniques are actively debated in the earthquake engineering community. Considerations such as what amplitude, over what period range and to what target spectrum are amongst the questions of practical importance. In this paper, the effect of various ground motion scaling approaches are explored using three reinforced concrete prototypical building models of 8, 12 and 20 stories designed to respond nonlinearly under a design level earthquake event in the seismically active Southern California region. Twenty-one recorded earthquake motions are selected using a probabilistic seismic hazard analysis and subsequently scaled using four different strategies. These motions are subsequently compared to spectrally compatible motions. The nonlinear response of a planar frameidealized building is evaluated in terms of plasticity distribution, floor level acceleration and uncorrelated acceleration amplification ratio distributions; and interstory drift distributions. The most pronounced response variability observed in association with the scaling method is the extent of higher mode participation in the nonlinear demands.

Key Words
earthquake engineering; nonlinear analysis; ground motion scaling; geometric mean; spectrally compatible; structural engineering

Address
R.L. Wood and T.C. Hutchinson: Department of Structural Engineering, University of California, San Diego, La Jolla, CA, USA

Abstract
Because of the heavy demand of confining steel to restore the column ductility in seismic regions, it is more efficient to confine these columns by hollow steel tube to form concrete-filled-steeltube (CFST) column. Compared with transverse reinforcing steel, steel tube provides a stronger and more uniform confining pressure to the concrete core, and reduces the steel congestion problem for better concrete placing quality. However, a major shortcoming of CFST columns is the imperfect steel-concrete interface bonding occurred at the elastic stage as steel dilates more than concrete in compression. This adversely affects the confining effect and decrease the elastic modulus. To resolve the problem, it is proposed in this study to use external steel confinement in the forms of rings and ties to restrict the dilation of steel tube. For verification, a series of uni-axial compression test was performed on some CFST columns with external steel rings and ties. From the results, it was found that: (1) Both rings and ties improved the stiffness of the CFST columns and (2) the rings improve significantly the axial strength of the CFST columns while the ties did not improve the axial strength. Lastly, a theoretical model for predicting the axial strength of confined CFST columns will be developed.

Key Words
columns; concrete-filled-steel-tube; external confinement; normal-strength concrete; rings; ties

Address
J.C.M. Ho and L. Luo: Department of Civil Engineering, The University of Hong Kong, Hong Kong


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