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Suzuki M.,Yamashita Sekkei Inc.
AIJ Journal of Technology and Design | Year: 2012

Velocity-dependent dampers have high ability to control responses for not only large but also small vibration. The direction of deformation in these dampers is generally limited to one direction. In the case that direction of damper's axis coincides with direction of excitation, damper dissipates energy most efficiently. However in practice it is relatively rare that the direction of damper's axis coincides with that of excitation. This paper presents that the energy dissipation of velocity-dependent dampers that have nonlinear relationships between velocity and damping force is greatly influenced by difference in excitation. Source


Matsushima S.,Kyoto University | Hirokawa T.,Yamashita Sekkei Inc. | De Martin F.,Bureau de Recherches Geologiques et Minieres | Kawase H.,Kyoto University | Sanchez-Sesma F.J.,National Autonomous University of Mexico
Bulletin of the Seismological Society of America | Year: 2014

Horizontal-to-vertical (H/V) spectral ratios of microtremors (HVRM) have been traditionally interpreted as representing either the S-wave amplification directly or the Rayleigh-wave ellipticity for a horizontally layered structure. However, based on the diffuse field theory, we have derived an alternative theoretical basis that HVRM corresponds to the square root of the ratio between the imaginary part of the horizontal Green's function and that of the vertical one. Under that condition, the 1D horizontal layering assumption is not needed to interpret HVRM. As observational evidence of such non-1D HVRM, we discovered significant directional dependency at a site on the Uji campus, Kyoto University, Japan. The observed microtremor north-south/vertical spectral ratios are quite stable and have only one peak around 0.5 Hz. On the other hand, the east-west/vertical spectral ratios are smaller in amplitude and have higher peak frequencies and sometimes two separated peaks. The directional dependency of observed HVRM is aligned to the axis of the 2D basin structure. We performed numerical analyses by spectral element method using a unit load on the surface to examine the effect of the 2D basin structure on the imaginary parts of the Green's functions. We found that the 2D basin structure clearly changes the characteristics of the H/V spectral ratios in both perpendicular and parallel directions relative to the basin axis. Thus, we succeeded in theoretically simulating the qualitative difference between the H/V spectral ratios for two orthogonal horizontal components of the HVRM observed on the Uji campus. Source


Suzuki M.,Yamashita Sekkei Inc. | Morihiro K.,Hokkaido DB | Mishio T.,Nihon Sekkei Inc. | Abe N.,Takenaka Corporation
AIJ Journal of Technology and Design | Year: 2010

The Hokkaido Toyako Summit was held in July 2008, and the international media center (IMC) was constructed. IMC was used in a short term for the Summit and dismantled afterwards. For reduction of environmental impact, non-waste of structural materials of IMC was aimed, and reuse and recycle were executed completely as a result. This paper describes a series of structural approach in designing, constructing, and dismantling of IMC. Source


Iguchi S.,Nippon Telegraph and Telephone | Hirashima T.,Chiba University | Matsudo M.,Fujita Corporation | Shinozuka W.,Chiba University | Kaneshiro R.,Yamashita Sekkei Inc.
Journal of Structural and Construction Engineering | Year: 2013

Mixed structures composed of R/C (Reinforced Concrete) columns and steel beams can accommodate larger building spaces, whereas the R/C columns may be subjected to severe thermal stresses due to the thermal elongation of long span steel beams in a fire. In previous paper, results of load-bearing fire tests of sub-frames of the mixed structure indicated that the fire resistance of R/C columns is reduced by covered concrete spalling and forced horizontal displacement at the top of the columns due to thermal elongation of steel beam. In this paper, results of thermal stress analysis of these tests are presented and the influence of the concrete spalling and the action from the beam on the fire resistance of R/C columns is discussed. Source


Bai Y.,Kyushu University | Kawano A.,Kyushu University | Odawara K.,Yamashita Sekkei Inc. | Matsuo S.,Kyushu University
Journal of Structural and Construction Engineering | Year: 2012

This paper studies the stress-strain models to simulate the strength deterioration of the confined concrete and various sectional steel tubes in hollow steel tubular (HST) columns and concrete filled steel tubular (CFT) columns. The stress-strain models for above components by considering strength deterioration are simplified as to analyze steel and CFT frames subjected to ground motions. The model consists of an elastic-plastic curve up to the peak and a bi-linear after the peak which expresses the strength deterioration by negative slopes. The characteristic parameters of the stress-strain models for in-filled concrete and steel tubes are calibrated by comparing the component test results and the corresponding analytical results, and the proposed formulae for the deteriorating models of HST and CFT columns can accurately simulate the strength, stiffness and deterioration after local-failures. Source

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