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996.
Hilbert-Huang Transform(HHT)是一种新的适用于非线性、非平稳信号,且具有自适应性的数据处理方法．本文简要介绍了一座45层钢筋混凝土框架结构及其振动台试验模型概况. 利用HHT分析了模型结构在不同烈度地震中的反应记录,得到了Hilbert时频幅值三维分布和Hilbert边际谱．Hilbert谱得到记录能量集中分布的频段与时间范围,捕捉到信号变化的主要特征. Hilbert边际谱曲线形状和峰值频率值随着地震烈度的升级而发生了相应变化,而且所有的结果图形体现出相同的规律性,预示着Hilbert边际谱在土木工程结构安全评价中的应用前景． 相似文献
997.
Study on the failure process of high concrete dams subjected to strong earthquakes is crucial to reasonable evaluation of their seismic safety. Numerical simulation in this aspect involves dynamic failure analysis of big bulk concrete dam subjected to cyclic loading. The Rock Failure Process Analysis (RFPA) proposed by C.A. Tang, with successful applications to failure modeling of rock and concrete specimens mainly subjected to static loading, is extended for this purpose. For using the proposed model, no knowledge on the cracking route needs to be known beforehand, and no remeshing is required. Simulation of the whole process of elastic deformation, initiation and propagation of microcracks, severe damage and ultimate failure of concrete dams in earthquakes with a unified model is enabled. The model is verified through a shaking table test of an arch dam. Finally a practical gravity dam is employed as a numerical example. Considering the uncertainty in ground motion input and concrete material, typical failure process and failure modes of gravity dam are presented. Several small cracks may occur due to tension particularly at dam neck, dam faces and dam heel, and a few of them evolve into dominant ones. Relatively smaller earthquake may cause damage to the dam neck while a bigger one may bring on cracks at lower parts of the dams. Cracking at the dam bottom may incline to a direction almost perpendicular to the downstream face after propagating horizontally for a certain distance when the shaking is strong enough. 相似文献
998.
This paper deals with geochemical features of gas emitted from the Hubin Springs.The Hubin Springs zone,a strong thermal emission zone,is are locatedd at the north edge of the Tianchi caldera lake.Very young deposits with uncertain eruption date are found on the top area of the Tianwenfeng,which might have been formed in one of the recent eruptions or the Millennium Eruption.It is of significance to study the geochemistry features of the emitting gas from the Hubin Springs to understand the activities of the Tianchi Volcano.This paper systematically sampled and analyzed the gases emitted from the Hubin Springs and discussed their geochemistry features.The results show that there is a high content of deep derived gases,such as CO2,He,CH4 and Ar in Hubin Springs zone.The isotopic ratio of He lies between 4.18 and 5.95 Ra.The averaged mantle derived gas content calculated from the 4He/20Ne ratio and He content reaches 67.1%.All these show that the Hubin Springs are located on a special belt of deep gases released in high intensity and large scale.The spatial distribution of Helium isotope is characterized by concavity,showing that this special area may be related to the volcanic edifice.It is highly possible that the released gases represent the residual gas samples of the latest eruptions from the Tianchi Volcano.However more detailed studies are demanded. 相似文献
999.
Recognition of natural deformation during the excavation of ancient remains and tombs is important for tracing or enriching historic and prehistoric deformation records. Recently, the earthquake agencies,in cooperation with the cultural relics and archaeological institutions, conducted a special excavation investigation to the Gaixia remains archaeological scene in Guzhen,Anhui Province. Faults and fissures were discovered there, which,as demonstrated by the preliminary study,are the traces of two stratum d... 相似文献
1000.
By using the finite element method and viscoelastic artificial boundary,a soil-structure interaction system is established to simulate the influence of surface buildings on the seismic response of subway structures.The conditions of different relative positions between ground building and subway structure are analyzed.The results indicate that when considering the existence of surface buildings,the relative story displacements and internal forces of subway structures are changed greatly.Further the influence of surface buildings on subway structure changes as the distance increases. 相似文献