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261.
262.
We consider the problem of the applicability of KAM theorem to a realistic problem of three bodies. In the framework of the averaged dynamics over the fast angles for the Sun–Jupiter–Saturn system we can prove the perpetual stability of the orbit. The proof is based on semi-numerical algorithms requiring both explicit algebraic manipulations of series and analytical estimates. The proof is made rigorous by using interval arithmetics in order to control the numerical errors. 相似文献
263.
地震安全性评价和高层建筑的地震动输入 总被引:4,自引:1,他引:3
本文根据现行的中国地震烈度区划图中烈度的含义,指出在使用现行“建筑抗震设计规范”时存在的一些问题和与《中华人民共和国防震减灾法》的不协调之处。根据多年参加工程场地地震安全性评价的经验,总结了目前进行地震安全性评价过程中存在的一些问题。文中建议:针对高层建筑进行新的场地分类方法的研究;对高层建筑工程场地作地震安全性评价时,可根据高度的不同,适当简化安全性评价过程。 相似文献
264.
The effect of the long‐period filter cut‐off, Tc, on elastic spectral displacements is investigated using a strong ground‐motion database from Europe and the Middle East. The relation between the filter and oscillator responses is considered to observe the influence of Tc for both analogue and digital records, and the variations with site classification, magnitude, filter order and viscous damping. Robust statistics are derived using the re‐processed European data to generalize the effects of the long‐period filter cut‐off on maximum oscillator deformation demands as a function of these seismological and structural features. Statistics with a 95% confidence interval are derived to suggest usable period ranges for spectral displacement computations as a function of Tc. The results indicate that the maximum period at which spectral displacements can be confidently calculated depend strongly on the site class, magnitude and filter order. The period range where reliable long‐period information can be extracted from digital accelerograms is twice that of analogue records. Copyright © 2006 John Wiley & Sons, Ltd. 相似文献
265.
2004年9月2—6日四川盆地中东部发生了一次持续性强暴雨过程。利用时间平均合成分析方法对强暴雨维持期间 (9月3日20:00—5日08:00, 北京时) 的探测资料进行合成平均, 再对合成平均资料做诊断分析, 以揭示持续性强暴雨过程持续期的平均特征。诊断分析显示, 台风西进导致稳定的环流以及中低层大量的水汽输送为暴雨持续提供了背景条件。在时间平均流场上, 与暴雨相联系的中尺度系统十分显著, 它在对流层中低层表现为准东西向的中尺度辐合带, 在对流层高层表现为中尺度辐散带, 两者垂直耦合为深厚系统。此外, 在暴雨持续期间, 对流层低层大气运动表现出强烈的非平衡特征, 这种非平衡的动力强迫作用支撑着低层强辐合的维持。 相似文献
266.
267.
The correlation between ground motion intensity measures (IM) and single-degree-of-freedom (SDOF) deformation demands is described in this study. Peak ground acceleration (APG), peak ground velocity (VPG), peak ground displacement (DPG), spectral acceleration at the first-mode period of vibration [As(T1)] and ratio of VPG to APG are used as IM parameters, and the correlation is characterized by correlation coefficients p. The numerical results obtained by nonlinear dynamic analyses have shown good correlation between As(T1) or VPG and deformation demands. Furthermore, the effect of As(T1) and VPG as IM on the dispersion of the mean value of deformation demands is also investigated for SDOF systems with three different periods T=0.3 s, 1.0 s, 3.0 s respectively. 相似文献
268.
Artificial ground motion compatible with specified peak velocity and target spectrum 总被引:1,自引:0,他引:1
In this paper, a method, which synthesizes the artificial ground motion compatible with the specified peak velocity as well as the target acceleration response spectrum, was proposed. In this method, firstly, an initial acceleration time history α8^(0) (t), which satisfies the prescribed peak ground acceleration, the target spectral acceleration ST(ω, ζ),and the specified intensity envelope, is generated by the traditional method that generates the requency domain; secondly,α8^(0) (t)is further modulated by superimposing narrow-band time histories upon it in the time domain to make its peak velocity, approach the target peak ground velocity, and at the same time to improve its fitting precision to the target spectrum. Numerical examples show that this algorithm boasts high calculation precisions. 相似文献
269.
Introduction Scattering of incident waves by local topographies is one of the most attractive topics in the field of engineering seismology. They can be resolved by either a numerical method or an analyti-cal method. The numerical methods include finite difference method, finite element method, boundary element method, etc. The analytical method is the wave function expansion method. Al-though numerical methods can be used for arbitrary-shaped topographies, the analytical solutions are still … 相似文献
270.
Arthur Rodgers Hrvoje Tkalcic David McCallen Shawn Larsen Catherine Snelson 《Pure and Applied Geophysics》2006,163(1):55-80
We report site response in Las Vegas Valley (LVV) from historical recordings of Nevada Test Site (NTS) nuclear explosions
and earthquake recordings from permanent and temporary seismic stations. Our data set significantly improves the spatial coverage
of LVV over previous studies, especially in the northern, deeper parts of the basin. Site response at stations in LVV was
measured for frequencies in the range 0.2–5.0 Hz using Standard Spectral Ratios (SSR) and Horizontal-Vertical Spectral Ratios
(HVR). For the SSR measurements we used a reference site (approximately NEHRP B ``rock' classification) located on Frenchman
Mountain outside the basin. Site response at sedimentary sites is variable in LVV with average amplifications approaching
a factor of 10 at some frequencies. We observed peaks in the site response curves at frequencies clustered near 0.6, 1.2 and
2.0 Hz, with some sites showing additional lower amplitude peaks at higher frequencies. The spatial pattern of site response
is strongly correlated with the reported depth to basement for frequencies between 0.2 and 3.0 Hz, although the frequency
of peak amplification does not show a similar correlation. For a few sites where we have geotechnical shear velocities, the
amplification shows a correlation with the average upper 30-meter shear velocities, V30. We performed two-dimensional finite difference simulations and reproduced the observed peak site amplifications at 0.6 and
1.2 Hz with a low velocity near-surface layer with shear velocities 600–750 m/s and a thickness of 100–200 m. These modeling
results indicate that the amplitude and frequencies of site response peaks in LVV are strongly controlled by shallow velocity
structure. 相似文献