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1.
Waterfront retaining walls supporting dry backfill are subjected to hydrostatic pressure on upstream face and earth pressure on the downstream face. Under seismic conditions, if such a wall retains a submerged backfill, additional hydrodynamic pressures are generated. This paper pertains to a study in which the effect of earthquakes along with the hydrodynamic pressure including inertial forces on such a retaining wall is observed. The hydrodynamic pressure is calculated using Westergaard's approach, while the earth pressure is calculated using Mononobe-Okabe's pseudo-static analysis. It is observed that when the horizontal seismic acceleration coefficient is increased from 0 to 0.2, there is a 57% decrease in the factor of safety of the retaining wall in sliding mode. For investigating the effect of different parameters, a parametric study is also done. It is observed that if φ is increased from 30° to 35°, there is an increase in the factor of safety in the sliding mode by 20.4%. Similar observations were made for other parameters as well. Comparison of results obtained from the present approach with [Ebeling, R.M., Morrison Jr, E.E., 1992. The seismic design of waterfront retaining structures. US Army Technical Report ITL-92-11. Washington DC] reveal that the factor of safety for static condition (kh=0), calculated by both the approaches, is 1.60 while for an earthquake with kh=0.2, they differ by 22.5% due to the consideration of wall inertia in the present study. 相似文献
2.
Most of the existing relevant materials have been obtained from experiments, in which evaluating the added mass at the resonant frequency corresponding to the peak of a frequency-response curve obtained from the “forced” vibration analysis is the most popular technique. In this paper, a simple experimental method was presented where the “free” vibration responses instead of the “forced” ones were used to determine the values of mah and Iap. The main part of the experimental system is composed of a floating body (model) and a spring–shaft shaker. The “free” vibration of this main part was induced by imposing on it an initial displacement (and/or an initial velocity), and from the time histories of displacements information such as the “damped” natural frequencies, damping ratios, sectional added mass coefficients (CV and CP) were obtained. Since the displacements of the spring–shaft shaker are “translational” and those of the floating body due to pitch motions are “angular”, a technique for the transformation between the associated parameters of the two components of the main part was presented. 相似文献
3.
MTMD对建筑结构多模态控制的减震分析 总被引:5,自引:1,他引:5
本文研究了MTMD对建筑结构多模态减震控制。将主结构简化为多自由度模型,MTMD对结构的反力与地震荷载共同作为结构的荷载输入进行分析;基于主结构多模态耦合进行推导分析,阐述了MTMD与结构之间的相互作用关系,提出MTMD的复惯性质量。提出MTMD的控制类型是加速度相关型的无源被动控制。从频域传递函数,白噪声、宽带和窄带地震激励下的结构相对位移和绝对加速度谱密度,以及El-centro地震波作用下结构的地震响应三个方面,分析了MTMD对顶部带有结构附属物的结构的控制效果。并且给出TMD的控制效果加以比较验证。算例说明MTMD多模态控制对结构的相对位移和绝对加速度均有较好的控制效果,并且优于TMD控制效果。 相似文献
4.
热惯量法在监测土壤表层水分变化中的研究 总被引:95,自引:2,他引:95
利用遥感方法监测一定层水深土壤水分变化,关键是建立卫星数据与地表水热变化关系,该文地遥感定量反演土壤水热变化的数值模拟系统及热惯量在其边界,初始条件确定中所起的作用进行的简述,并介绍了热惯量法求解表层水分含量的发展概况,为进一步提高定量化监测方法的地必琢计算精度,该文发展了地表能量平均方程的一种新的化简方法,经过这样的处理,可从遥感图象数据直接得到真实热惯量值,进而得到土壤水分含量分布,通过野外实 相似文献
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6.
A Possible Detection of the 26 December 2004 Great Sumatra-Andaman Islands Earthquake with Solution Products of the International GNSS Service 总被引:1,自引:0,他引:1
J. Kouba 《Studia Geophysica et Geodaetica》2005,49(4):463-483
The main goal of this work is to critically review the IGS solution products and Precise Point Positioning (PPP) in order
to demonstrate their potential to contribute to studies of large earthquakes such as the one that devastated Southeast Asia
on December 26th, 2004. In view of a possible detection of the Mw 9.0 Sumatra-Andaman Islands Earthquake of December 26, 2004,
position solutions, ranging from intervals of years to one second, of four International GNSS Service (IGS) stations within
3000 km of the epicenter were examined. The IGS combined, cumulative solution product (IGS04P51), consisting of epoch and
station velocity solutions and based on data spans of several years prior to the earthquake, was used as a reference. Four
IGS combined weekly position solutions (igs04P1301-4), two weeks before and after the earthquake, were utilized for the weekly
solution resolution. PPP static and kinematic solutions with IGS Final combined orbits and clocks were used for the mean daily
and instantaneous 5-min and 1-sec epoch solutions, respectively. The most significant changes, detected by both weekly and
daily solutions occurred in longitude. The nearest IGS station ntus, about 1000 km east of the epicenter, moved westward about
15 mm, while the more distant Indian station iisc (∼ 2300 km NW from the epicenter), shifted about 15 mm eastward. In spite
of position errors caused by interpolation of the 5-min IGS clocks, the 1-sec solutions, based on separate data sets, available
only for two stations (iisc, dgar), still showed seismic surface waves, in particular at the Indian station iisc. Precise
daily IGS combined polar motion and length-of-day products, after correcting for the atmospheric effects, also likely detected,
statistically significant, anomalistic excitations on December 26, 2004 that could be caused by this great earthquake. 相似文献
7.
8.
9.
Wang Xingbao 《Acta Meteorologica Sinica》1995,9(4):488-500
Effects of topography on the propagation and development of inertia gravity waves areinvestigated by means of WKBJ method.The equation of wave action conservation is obtained.It isfound that the inertia gravity wave tends to propagate to the higher elevation area,meanwhile theamplitudes of the waves increase.While the inertia gravity waves propagate to a lower elevation area,their amplitudes decrease. 相似文献
10.