Probabilistic critical excitation for MDOF elastic–plastic structures on compliant ground     

Izuru Takewaki 《地震工程与结构动力学》2001,30(9):1345-1360

Earthquake ground motions and their effects on structural responses are very uncertain even with the present knowledge. It is therefore desirable to develop a robust structural design method taking into account these uncertainties. Critical excitation approaches are promising and a new random critical excitation method is proposed for MDOF elastic–plastic shear‐building structures on compliant ground. The power (area of power spectral density (PSD) function) and the intensity (magnitude of PSD function) are fixed and the critical excitation is found under these restrictions. In contrast to linear elastic structures, transfer functions and simple expressions for response evaluation cannot be defined in elastic–plastic structures and difficulties arise in describing the peak responses except by laborious elastic–plastic time‐history response analysis. Statistical equivalent linearization is used to estimate the elastic–plastic stochastic peak responses approximately. The critical excitation responses are obtained for several examples and compared with those of the corresponding recorded earthquake ground motion. Copyright © 2001 John Wiley & Sons, Ltd.  相似文献   

伪权现象及抗差估计   总被引：1，自引：0，他引：1  

靳奉祥  王同孝 《测绘工程》1997,6(4):16-20

讨论了权与平差结果的关系，指出了残差向量与权之间不一定存在的一一对应的关系，对现行常用抗差估计方案用实例进行了研究，并建议抗差方案设计应对权函数的取值加以限制，以保证平差系统的稳健性。  相似文献   

Nonlinear surface ground analysis via statistical approach     

Izuru Takewaki  Nobuyoshi Fujii  Koji Uetani 《Soil Dynamics and Earthquake Engineering》2002,22(6)

A statistical approach is proposed for nonlinear surface ground analysis. In contrast to the conventional method which deals with only a single ground motion for equivalent linearization of soil properties, a design response spectrum defined at the upper level (bottom of the surface ground) of an engineering bedrock can be handled as the target design earthquake in the present paper. The effective shear strain in each soil layer is evaluated by means of a statistical procedure in which the mean peak shear strain is computed in terms of its standard deviation and the corresponding peak factor. The stiffness and damping ratio of each soil layer are obtained iteratively from the nonlinear relation of stiffness reduction factors and damping ratios with respect to the strain level. After the evaluation of the equivalent stiffness and damping ratio of every soil layer, the ground surface response spectrum is transformed from the design response spectrum defined at the upper level of the engineering bedrock via the one-dimensional wave propagation theory. The reliability and accuracy of the proposed analysis method is examined through the comparison with the results by the conventional method (represented by the program) for many simulated spectrum-compatible ground motions.  相似文献   

亚欧及北太平洋相当正压层高度的分析及数值模拟     

欧阳首承  兰伟 《高原气象》1990,9(3):277-283

本文利用相当正压层方法,分析了亚欧及北太平洋中纬度地区47个站点的相当正压层高度,其结果与文献[1]类似。计算表明:亚欧及北太平洋的相当正压层高度平均位于359hPa,略去高原站点后,平原地区的平均高度为374hPa。相当正压层是一个波动很大的不同气压的曲面,并随地区和季节变化较大。高原和西风急流的强弱可能都是其影响因子,尤其是高原的作用值得进一步探讨。数值模拟也证实了300hPa上Rossby波比500hPa效果好。  相似文献   

Electromagnetic response of a buried cylindrical conductor for sheet and line current sources     

S. O. Ogunade 《Pure and Applied Geophysics》1982,120(1):136-150

A major problem in electromagnetic induction studies in regions of localized source fields, such as the auroral and equatorial electrojet regions, is the source effect. Using an analytical model, the electromagnetic response of a buried conducting cylinder to sheet current and line current excitations has been studied for the period rangeT=5 s to 24 h. The validity of the numerical results obtained from the analytical model are compared with the numerical results obtained from a finite difference model. The results show that for periods less than 30 min, there is no significant difference in the response of the cylinder to both source fields. However, significant differences are observed at longer periods. It was also observed that the equivalent height at which a uniform sheet current at 100 km above the earth's surface can be approximated by a line current varies as a function of the source period.  相似文献   

抗差卡尔曼滤波模型及其在GPS监测网中的应用   总被引：16，自引：0，他引：16  

余学祥  吕伟才 《测绘学报》2001,30(1):27-31

根据量测向量中的粗差对状态向量滤波值的影响规律，导出了抗差卡尔曼滤波模型，该模型对观测空间和设计空间均具有良好的抗差性。通过对含有粗差的模拟GPS监测网的计算，与标准卡尔曼滤波模型相比较，利用该抗差滤波模型，可获得可靠的变形分析结果。  相似文献   

常速叠加－DMO－叠后偏移等效叠前偏移   总被引：1，自引：0，他引：1       下载免费PDF全文

王振华 《地球物理学报》1994,(6)

常速叠加是根据给定的速度将炮检距空间的地震数据映射到叠加速度空间，在实际叠加速度位置形成叠加能量；速度变换是将叠加速度空间的能量数据映射到均方根速度空间，消除地层倾角对速度的影响，这实际上是一种ＤＭＯ方法；常速偏移是在每个均方根速度剖面上独立地进行波场归位，消除反射点位置对速度的影响．经过这三步处理获得最终叠前偏移结果．  相似文献   

成都粘土孔隙性的微观研究   总被引：4，自引：0，他引：4  

朱春润索.  BH 《地质灾害与环境保护》1994,5(3):37-47

孔隙是土结构的重要标志之一,其特征对土的工程地质性质有很大影响。本文介绍了应用结构图象定量分析系统对成都粘土孔隙性的微观研究成果并对孔隙的大小、数量、形状、类型和定向程度等形态和几何特征进行了讨论。  相似文献   

卫星磁异常的理论模型   总被引：3，自引：3，他引：0  

安振昌 《地球物理学进展》2000,15(2):54-62

本文介绍了计算卫星磁异常理论模型的数学方法 ,即球谐分析方法、冠谐分析方法、矩谐分析方法和等效源方法 .根据相同的 MAGSAT资料 ,计算的卫星磁异常冠谐模型、矩谐模型和等效源模型都能很好地表示卫星磁异常的分布 .由于在整个研究区域 ( 1 0°N～60°N,70°E～ 1 40°E)都有卫星资料 ,所以这些理论模型没有所谓的“边界效应”.这一结论对计算地磁场的区域模型是很有意义的 .  相似文献   

我国中低纬度地区S_q焦点的分析与研究   总被引：1，自引：0，他引：1  

熊先宝  钱家栋  徐文耀 《地震工程学报》1993,15(4):12-22

本文利用１９８８年３月－１９８９年３月几次大的太阳活动期间我国９个台站的地磁资料，采用无穷大平板电流的等效电流体系方法，分析了我国中低纬度地区Ｓｑ焦点位置的变化特征，并对照ＫｐＤｓｔ，Ａｐ等指数给出了Ｓｑ焦点位置变化的合理解释。结构表明：（１）在不同的Ｋｐ指数段Ｓｑ焦点有不同的规律性，当Ｋｐ＜４时，随着Ｋｐ指数增大，Ｓｑ焦点向高纬方向移动；当Ｋｐ在４和６之间时，随着Ｋｐ指数增大，Ｓｑ焦点向低纬方向  相似文献