Coupling behavior of shear deformation and end rotation of elastomeric seismic isolation bearings          下载免费PDF全文

Ken Ishii  Masaru Kikuchi  Takuya Nishimura  Cameron J. Black 《地震工程与结构动力学》2017,46(4):677-694

This paper presents a mechanical model for predicting the behavior of elastomeric seismic isolation bearings subject to combined end rotations and shear deformation. The mechanical model consists of a series of axial springs at the top, mid‐height and bottom of the bearing to vertically reproduce asymmetric bending moment distribution in the bearings. The model can take into account end rotations of the bearing, and the overall rotational stiffness includes the effect of the variation of vertical load on the bearing and the imposed shear deformation. Static bending tests under various combinations of vertical load and shear deformation were performed to identify the mechanical characteristics of bearings. The test results indicate that bearing rotational stiffness increases with increasing vertical load but decreases with increasing shear deformation. Simulation analyses were conducted to validate the new mechanical model. The results of analyses using the new model show very good agreement with experimental observations. A series of seismic response analyses were performed to demonstrate the dynamic behavior of top‐of‐column isolated structures, a configuration where the end rotations of isolation bearings are typically expected to be larger. The results suggest that the end rotations of elastomeric bearings used in practical top‐of‐column isolated structures do not reduce the stability limit of isolation system. Copyright © 2016 John Wiley & Sons, Ltd.  相似文献   

Distributions of Water Masses and Currents in Tachibana Bay, West of Ari-ake Sound, Kyushu, Japan     

T. Matsuno  M. Shigeoka  A. Tamaki  T. Nagata  K. Nishimura 《Journal of Oceanography》1999,55(4):515-529

We have investigated the water mass distribution and circulation in Tachibana Bay, which is located in the junction area between Ari-ake Sound and Amakusa-Nada in western Kyushu, Japan. This was done to clarify the mechanism by which ghost shrimp larvae, originating from a sandflat of Amakusa-Shimoshima Island, are transported. Temperature and salinity data repeatedly obtained over the area of Tachibana Bay show that relatively low salinity water lies over northern part of the bay, while high salinity water lies over southern part of the bay. The location of the low salinity water margin tends to depend on the amount of rainfall several days before the observation. A large amount of rainfall makes a clear boundary between low and high salinity waters. Current velocity data indicate an eastward mean flow just north of Tomioka, northern tip of Amakusa-Shimoshima Island, and a clockwise mean flow approaching the Tomioka Bay sandflat, which should be suitable for the on-shore transport of the ghost shrimp postlarvae. Current measurements with shipboard ADCP just west of Hayasaki Strait, at the entrance of Ari-ake Sound, show that a westward tidal residual current tends to incline to the north, with evidence of a density current in the northern part of the western Hayasaki Strait.  相似文献   

Estimation of crustal structure from observed group velocities ofPL-waves in Japan     

Masayuki Fujita  Keiichi Nishimura 《Pure and Applied Geophysics》1991,137(3):233-249

Forward modelling of the crustal structure of the eastern Honshu Island, Japan, was made based on the group velocities ofPL-waves in the period range of 20–30 s. The observed values of group velocity were obtained by appling the multiple filter technique to the seismograms for earthquakes with the epicentral distance ranging from 500 to 1000 km. The theoretical values were calculated using Oliver and Major's method to find the best fit dispersion curve in the least-squares sense. The obtained structural model has considerably high crustal velocities compared to other previous models. It was shown that thePL-wave group velocity in the period range of interest was most sensitive to seismic velocities of the center of the crust. Numerical experiments confirmed the applicability of the approximation methods employed to obtain both observed and theoretical group velocities.  相似文献   

Estimation of crustal structure in central and west Japan from waveform modeling of regionalPL waves     

Masayuki Fujita  Keiichi Nishimura 《Pure and Applied Geophysics》1993,140(4):569-592

An inverse method of modeling the regionalPL waveform with the predominant period of about 20 s was developed to estimate the averageS-velocity structure of the upper crust. Applicability of the waveform modeling was confirmed by the results of the numerical experiments: thePL waveform is most sensitive to theS velocity in the upper crust, whereas it is not affected significantly by errors involved in the focal mechanism solution and focal depth determination when thePL wave is well developed. The method was applied to the observed seismograms recorded in central Japan from the earthquakes with epicentral distances 300–500 km. As a result, distinct regional differences were found in the upper crustalS velocity; in particular, between the southern Shikoku district, west Japan, and the southern Chubu district, central Japan, and between the mountainous and the coastal areas in the southern Chubu district. These differences are in agreement with the general features ofP-velocity structures obtained by explosion experiments and by analyses of natural earthquakes. Our method is effective to the extent that the crustal structure along the propagation path can be assumed a horizontally layered structure; it is not applicable when the sensitivity of thePL waveform to the error in the focal mechanism solution is exceptionally high.  相似文献   

The anisotropic structure of the upper mantle in the Pacific   总被引：4，自引：0，他引：4  

Clyde E. Nishimura  Donald W. Forsyth 《Geophysical Journal International》1989,96(2):203-229

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A possible Caledonide arm through the Barents Sea imaged by OBS data     

Asbjrn Johan Breivik  Rolf Mjelde  Paul Grogan  Hideki Shimamura  Yoshio Murai  Yuichi Nishimura  Asako Kuwano 《Tectonophysics》2002,355(1-4)

The assembly of the crystalline basement of the western Barents Sea is related to the Caledonian orogeny during the Silurian. However, the development southeast of Svalbard is not well understood, as conventional seismic reflection data does not provide reliable mapping below the Permian sequence. A wide-angle seismic survey from 1998, conducted with ocean bottom seismometers in the northwestern Barents Sea, provides data that enables the identification and mapping of the depths to crystalline basement and Moho by ray tracing and inversion. The four profiles modeled show pre-Permian basins and highs with a configuration distinct from later Mesozoic structural elements. Several strong reflections from within the crystalline crust indicate an inhomogeneous basement terrain. Refractions from the top of the basement together with reflections from the Moho constrain the basement velocity to increase from 6.3 km s⁻¹ at the top to 6.6 km s⁻¹ at the base of the crust. On two profiles, the Moho deepens locally into root structures, which are associated with high top mantle velocities of 8.5 km s⁻¹. Combined P- and S-wave data indicate a mixed sand/clay/carbonate lithology for the sedimentary section, and a predominantly felsic to intermediate crystalline crust. In general, the top basement and Moho surfaces exhibit poor correlation with the observed gravity field, and the gravity models required high-density bodies in the basement and upper mantle to account for the positive gravity anomalies in the area. Comparisons with the Ural suture zone suggest that the Barents Sea data may be interpreted in terms of a proto-Caledonian subduction zone dipping to the southeast, with a crustal root representing remnant of the continental collision, and high mantle velocities and densities representing eclogitized oceanic crust. High-density bodies within the crystalline crust may be accreted island arc or oceanic terrain. The mapped trend of the suture resembles a previously published model of the Caledonian orogeny. This model postulates a separate branch extending into central parts of the Barents Sea coupled with the northerly trending Svalbard Caledonides, and a microcontinent consisting of Svalbard and northern parts of the Barents Sea independent of Laurentia and Baltica at the time. Later, compressional faulting within the suture zone apparently formed the Sentralbanken High.  相似文献   

Vibration characteristics of rigid body placed on sand ground     

Y. -S. Kim  K. Miura  S. Miura  M. Nishimura 《Soil Dynamics and Earthquake Engineering》2001,21(1)

This study aims to investigate experimentally the vibration properties of rigid body placed on sand ground surface. The rigid body models with circular or rectangular base with variable mass, inertial moment and base sizes, were prepared, and the vibration behavior was observed in some series of free vibration tests and forced vibration tests. The observed behavior was analyzed and the vibration mode, vibration period and damping ratio were examined. It was found that the natural vibration period depends not only on the mechanical properties of rigid body and ground, but also on the magnitude of vibration amplitude. This suggested the notable effect of nonlinear strain dependent stiffness of ground material. A physical model with distributed spring–dashpot element was used to model the interactive mechanical behavior between rigid body and ground. The stiffness of the spring–dashpot element was evaluated through the modal analysis of the observed vibration behaviors. The effects of base shape, base size and base pressure on the stiffness of spring–dashpot element are discussed. The spring–dashpot model was verified with the behavior observed in forced vibration tests.  相似文献   

The absence of apparent correlations between iras and optical spectral features of late-type stars     

M. Othman  K. Ishida  S. Okamura  S. Nishimura 《Astrophysics and Space Science》1988,148(2):191-198

The spectral signatures of circumstellar dust shells (CS) of late-type stars cannot be tied in a simple manner to their optical spectral features. The spectral indices of featureless low-resolution spectrometer (LRS) spectra of K and early-M (M0-M5) stars are consistent with that of the Rayleigh-Jeans law and those of late-M (M6 and later) stars tend to have lower values showing CS radiation. There is no correlation observed between the optical sub-type and the 10 m emission strength for M stars. The absence of a simple relationship is also evident for C stars where the temperature and abundance indices show no correlation with the 11 m emission strength. The sample is confined to the IRC stars identified with accurate spectra observed by the LRS of IRAS. The IRC stars are the whole sky survey done with the 2 m band, where late-type stars are bright and interstellar extinction is one-tenth of the visual colour band.  相似文献   

人工岛周围的波生流计算方法     

包四林  西村仁嗣  陈沈良 《海洋学报》2006,28(2):140-145

针对Hardy-Cross法的基本原理建立的一种波生流计算的数值模型在计算处理人工岛周围区域方面还存在的问题,提出了解决处理方法,并通过算例验证了该模型能够运用于人工岛等岛状非水面区域附近的波生流计算,从而消除了Hardy-Cross法实用化中的一个障碍.  相似文献   

Regeneration of silicate in the ocean     

Katsutoshi Kido  Masakichi Nishimura 《Journal of Oceanography》1973,29(5):185-192

Regeneration of silicate in the Japan Sea, an example of semi-closed sea, was studied. In the Japan Sea Proper Water the apparent regenerative ratio of the nutrients was determined to be:O C N P Si=–289 (116)14.3181.It was assumed that the dissolved silicate present in sea water is grouped into three fractions; 1)preformed silicate of conservative nature, 2)oxidative silicate which dissolves in oxidation process of organisms with consumption of oxygen, and 3)non-oxidative silicate which dissolves without oxygen consumption. The dissolution rate ofnon-oxidative silicate in the Japan Sea Proper Water was estimated to be 0.07g-at. Si/l/yr from the data ofAOU values and assumed rates of oxygen consumption. This dissolution rate ofnon-oxidative silicate agreed with that obtained in the deep Pacific by the vertical advection diffusion model byKido andNishimura (1972).  相似文献