Cyclic tests on steel and concrete‐filled tube frames with Slit Walls     

Toko Hitaka  Chiaki Matsui  Jun'ichi Sakai 《地震工程与结构动力学》2007,36(6):707-727

Cyclic loading tests were performed on three one‐storey steel frames and four three‐storey concrete‐filled tube (CFT) moment frames reinforced with a new type of earthquake‐resisting element consisting of a steel plate shear wall with vertical slits. In this shear wall system, the steel plate segments between the slits behave as a series of flexural links, which provide fairly ductile response without the need for heavy stiffening of the wall. The steel shear walls and the moment frames behaved in a ductile manner up to more than 4% drift without abrupt strength degradation or loss of axial resistance. Results of these tests and complementary analysis provide a basis for an equivalent brace model to be employed in commercially available frame analysis programs. Test and analytical results suggest that the horizontal force is carried by the bolts in the middle portion of the wall–frame connection, while the vertical forces coupled with the moment in the connection are resisted by the bolts in the edge portion of the connection, for which the friction bolts in the connection should be designed. When sufficient transverse stiffening is provided, full plastic strength and non‐degrading hysteretic behaviour can be achieved for this new type of shear wall. Copyright © 2006 John Wiley & Sons, Ltd.  相似文献   

Semi-brittle behavior of wet olivine aggregates: the role of aqueous fluid in faulting at upper mantle pressures     

Tomohiro?OhuchiEmail author  Xinglin?Lei  Yuji?Higo  Yoshinori?Tange  Takeshi?Sakai  Kiyoshi?Fujino 《Contributions to Mineralogy and Petrology》2018,173(10):88

The role of aqueous fluid in fracturing in subducting slabs was investigated through a series of deformation experiments on dunite that was undersaturated (i.e., fluid-free) or saturated with water (i.e., aqueous-fluid bearing) at pressures of 1.0–1.8 GPa and temperatures of 670–1250 K, corresponding to the conditions of the shallower regions of the double seismic zone in slabs. In situ X-ray diffraction, radiography, and acoustic emissions (AEs) monitoring demonstrated that semi-brittle flow associated with AEs was dominant and the creep/failure strength of dunite was insensitive to the dissolved water content in olivine. In contrast, aqueous fluid drastically decreased the creep/failure strength of dunite (up to ~?1 GPa of weakening) over a wide range of temperatures in the semi-brittle regime. Weakening of the dunite by the aqueous fluid resulted in the reduction of the number of AE events (i.e., suppression of microcracking) and shortening of time to failure. The AE hypocenters were located at the margin of the deforming sample while the interior of the faulted sample was aseismic (i.e., aseismic semi-brittle flow) under water-saturated conditions. A faulting (slip rate of ~?10^?3 to 10^?4 s^?1) associated with a large drop of stress (Δσ?~?0.5 to 1 GPa) and/or pressure (ΔP?~?0.5 GPa) was dominant in fluid-free dunite, while a slow faulting (slip rate?<?8?×?10^?5 s^?1) without any stress/pressure drop was common in water-saturated dunite. Aseismic semi-brittle flow may mimic silent ductile flow under water-saturated conditions in subducting slabs.  相似文献   

Hitoshi Sakai (1930–2008)     

Ken Sakai 《Applied Geochemistry》2012

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Fe–Mg partitioning between post-perovskite and ferropericlase in the lowermost mantle     

Takeshi Sakai  Eiji Ohtani  Hidenori Terasaki  Masaaki Miyahara  Masahiko Nishijima  Naohisa Hirao  Yasuo Ohishi  Nagayoshi Sata 《Physics and Chemistry of Minerals》2010,37(7):487-496

Fe–Mg partitioning between post-perovskite and ferropericlase has been studied using a laser-heated diamond anvil cell at pressures up to 154 GPa and 2,010 K which corresponds to the conditions in the lowermost mantle. The composition of the phases in the recovered samples was determined using analytical transmission electron microscopy. Our results reveal that the Fe–Mg partition coefficient between post-perovskite and ferropericlase (K _D^PPv/Fp) increases with decreasing bulk iron content. The compositional dependence of K _D^PPv/Fp on the bulk iron content explains the inconsistency in previous studies, and the effect of the bulk iron content is the most dominant factor compared to other factors, such as temperature and aluminum content. Iron prefers ferropericlase compared to post-perovskite over a wide compositional range, whereas the iron content of post-perovskite (X _Fe^PPv, the mole fraction) does not exceed a value of 0.10. The iron-rich ferropericlase phase may have significant influence on the physical properties, such as the seismic velocity and electrical conductivity at the core–mantle boundary region.  相似文献   

Tropospheric delay correction with dense GPS network in L1-SAIF augmentation   总被引：2，自引：0，他引：2  

Noboru Takeichi  Takeyasu Sakai  Sounosuke Fukushima  Ken Ito 《GPS Solutions》2010,14(2):185-192

The L1-SAIF (L1 Submeter-class Augmentation with Integrity Function) signal is one of the Quasi-Zenith Satellite System (QZSS) navigation signals, which provides an augmentation function for mobile users in Japan. The tropospheric delay correction in the L1-SAIF augmentation is discussed in detail. Because the topographical features in Japan are complicated, the correction information is generated from GPS observation data collected at 200 GPS stations which are densely distributed over Japan. A total of 210 Tropospheric Grid Points (TGPs) are arranged to fully cover Japan. The TGPs that provide the correction information are selected adaptively to achieve the expected correction accuracy. This selection of TGPs is provided by the TGP mask message. Mobile users acquire the zenith tropospheric delay (ZTD) value at neighboring TGPs from the correction messages, and can estimate the local ZTD value accurately by using a suitable ZTD model. Only up to seven L1-SAIF messages are sufficient to provide the full correction information. Accuracy evaluations have proven that it is possible to achieve a correction accuracy of 13.4 mm RMS. The strategy presented here has been implemented into the augmentation system using the L1-SAIF signal, and its application guidance is presented in the QZSS interface specification.  相似文献