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201.
A new efficient method is developed for the analysis of pile-group effects on the seismic stiffness and strength design of buildings with pile foundations. An efficient continuum model consisting of a dynamic Winkler-type soil element and a pile is used to express the dynamic behavior of the structure-pile-soil system with only a small numerical error. The pile-group effect is taken into account through the influence coefficients among piles which are defined for interstory drifts and pile-head bending moments. It is shown that, while the pile-group effect reduces the interstory drift of buildings in general, it may increase the bending moment of piles at the head. This means that the treatment without the pile-group effect results in the conservative design for super-structures and requires a revised member design for piles. 相似文献
202.
C. J. Hapke 《地球表面变化过程与地形》2005,30(6):679-697
High‐resolution historical (1942) and recent (1994) digital terrain models were derived from aerial photographs along the Big Sur coastline in central California to measure the long‐term volume of material that enters the nearshore environment. During the 52‐year measurement time period, an average of 21 000 ± 3100 m3 km?1 a?1 of material was eroded from nine study sections distributed along the coast, with a low yield of 1000 ± 240 m3 km?1 a?1 and a high of 46 700 ± 7300 m3 km?1 a?1. The results compare well with known volumes from several deep‐seated landslides in the area and suggest that the processes by which material is delivered to the coast are episodic in nature. In addition, a number of parameters are investigated to determine what influences the substantial variation in yield along the coast. It is found that the magnitude of regional coastal landslide sediment yield is primarily related to the physical strength of the slope‐forming material. Coastal Highway 1 runs along the lower portion of the slope along this stretch of coastline, and winter storms frequently damage the highway. The California Department of Transportation is responsible for maintaining this scenic highway while minimizing the impacts to the coastal ecosystems that are part of the Monterey Bay National Marine Sanctuary. This study provides environmental managers with critical background data on the volumes of material that historically enter the nearshore from landslides, as well as demonstrating the application of deriving historical digital terrain data to model landscape evolution. Published in 2005 by John Wiley & Sons, Ltd. 相似文献
203.
S. Chakraverty 《地震工程与结构动力学》2005,34(6):543-554
A procedure has been presented in this paper to identify the structural parameters, viz. mass and stiffness matrices, from modal test data for multistorey shear buildings. The first two orders of modal data have been used by other researchers to estimate the global matrices where they depend only on measurable points which are less than the total number of structural degrees of freedom. The above method has been refined here by using Holzer criteria along with other numerical methods to estimate the global mass and stiffness matrices of the structure. This shows the methodology to be more efficient and accurate. The reliability of the procedure has been shown by examples of multistorey buildings. Copyright © 2004 John Wiley & Sons, Ltd. 相似文献
204.
Introduction The anisotropy of the Earth crust medium is a common phenomenon(Crampin,1984).More and more observation materials and study results have proved that on most of the Earth′s upper crust is spread fluid-filled cracks and microcracks,which are aligned according to the contempo-rary stress-field.Such distributions of aligned cracks show effectively anisotropy to seismic wave and the phenomenon is called extensive-dilatancy anisotropy(EDA)(Crampin et al,1984).At the same time,it is … 相似文献
205.
On the basis of about 300 earthquake wave forms observed in the Shidian M
S=5.9 sequences on April 12, 2001 recorded in Kunming Digital Seismic Network, the spectra of shear wave have been used to
estimate the focal parameters of these earthquake sequences. The results show that within the magnitude range of 1.5–5.3,
the seismic moments are 1010–1016 N·m, the corner frequencies are 0.2–0.8 Hz, radii of the focal rupture are 200–2 500 m and the stress drops are 0.1×105–20×105Pa. Through the statistical analyses of variation of corner frequency f
c and stress drop Δσ with time, it is discovered that the average corner frequency of the foreshock sequences is obviously
lower than that of the aftershock sequences. Contrarily, the average stress drops Δσ of the foreshock sequences are clearly
higher than that of the aftershocks. It is considered that these variation characteristics of average corner frequency and
stress drops before and after the main shock have index significance to the precursory information before a strong earthquake.
The higher stress drops for the foreshock sequences show that the higher shear stresses have been stored in the area of main
shock. After the main shock, most of the stresses have been released, so the aftershock sequences show a rupture process of
lower stresses.
Foundation item: Scientific and Technological Key Project of Yunnan Province (2001NG46) 相似文献
206.
Zhao Cuiping 《中国地震研究》2005,19(4):381-390
INTRODUCTIONThe study of source parameters is usually based oninversionfromobservational seismic waveformdata.Seismic wave affected bygeometric spreading,inelastic attenuation,scatteringandsite effects ofthe mediumontheir way fromsource to station.Therefo… 相似文献
207.
208.
209.
We have measured P- and S-wave velocities on two amphibolite and two gneiss samples from the Kola superdeep borehole as a function of pressure (up to 600 MPa) and temperature (up to 600 °C). The velocity measurements include compressional (Vp) and shear wave velocities (Vs1, Vs2) propagating in three orthogonal directions which were in general not parallel to inherent rock symmetry axes or planes. The measurements are accompanied by 3D-velocities calculations based on lattice preferred orientation (LPO) obtained by TOF (Time Of Flight) neutron diffraction analysis which allows the investigation of bulk volumes up to several cubic centimetres due to the high penetration depth of neutrons. The LPO-based numerical velocity calculations give important information on the different contribution of the various rock-forming minerals to bulk elastic anisotropy and on the relations of seismic anisotropy, shear wave splitting, and shear wave polarization to the structural reference frame (foliation and lineation). Comparison with measured velocities obtained for the three propagation directions that were not in accordance with the structural frame of the rocks (foliation and lineation) demonstrate that for shear waves propagating through anisotropic rocks the vibration directions are as important as the propagation directions. The study demonstrates that proper measurement of shear wave splitting by means of two orthogonal polarized sending and receiving shear wave transducers is only possible when their propagation and polarization directions are parallel and normal to foliation and lineation, respectively. 相似文献
210.
Basil Tikoff Matthew R. Davis Christian Teyssier Michel de St. Blanquat Guillaume Habert Sven Morgan 《Tectonophysics》2005,400(1-4):209-226
The Cascade Lake shear zone occurs on the eastern margin of the Tuolumne Intrusive Suite, Sierra Nevada Batholith, California. Foliation in the zone is NNW trending and subvertical, and lineation is moderately south plunging. Deformation is syn-tectonic with emplacement of the Cathedral Peak granodiorite. A deformation gradient exists toward the NE margin of this pluton, with higher strains and lower temperatures of deformation found near the contact. We compare fabric data collected very densely in this shear zone using several techniques: field fabrics, 3D orientation of K-feldspar megacrysts, and AMS (anisotropy of magnetic susceptibility) analysis. In general, the results from the three different methods are in agreement. Deformation in this shear zone is part of a larger pattern of deformation within the Cathedral Peak granodiorite, as recorded by AMS analysis, and dextral shearing associated within the last stage of plutonism within the Sierra Nevada magmatic arc. 相似文献