A model of triple friction pendulum bearing for general geometric and frictional parameters          下载免费PDF全文

Michael C. Constantinou 《地震工程与结构动力学》2016,45(11):1837-1853

Current models describing the behavior for the triple friction pendulum (TFP) bearing are based on the assumption that the resultant force of the contact pressure acts at the center of each sliding surface. Accordingly, these models only rely on equilibrium in the horizontal direction to arrive at the equations describing its behavior. This is sufficient for most practical applications where certain constraints on the friction coefficient values apply as a direct consequence of equilibrium. This paper presents a revised model of behavior of the TFP bearing in which no assumptions are made on the location of the resultant forces at each sliding surface and no constraints on the values of the coefficient of friction are required, provided that all sliding surfaces are in full contact. To accomplish this, the number of degrees of freedom describing the behavior of the bearing is increased to include the location of the resultant force at each sliding surface and equations of moment equilibrium are introduced to relate these degrees of freedom to forces. Moreover, the inertia effects of each of the moving parts of the bearing are accounted for in the derivation of the equations describing its behavior. The model explicitly calculates the motion of each of the components of friction pendulum bearings so that any dependence of the coefficient of friction on the sliding velocity and temperature can be explicitly accounted for and calculations of heat flux and temperature increase at each sliding surface can be made. This paper presents (a) the development of the revised TFP bearing model, (b) the analytic solution for the force–displacement relations of two configurations of the TFP bearing, (c) a model that incorporates inertia effects of the TFP bearing components and other effects that are useful in advanced response history analysis, and (d) examples of implementation of the features of the presented model. Copyright © 2016 John Wiley & Sons, Ltd.  相似文献   

Spherical gauges for improving the accuracy of rainfall measurements     

Mingteh Chang  Lee A. Flannery 《水文研究》2001,15(4):643-654

Rain‐gauge catch efficiencies are affected by wind. Wind makes raindrops fall at an angle of inclination and the effective diameter of the rain gauge orifice smaller than if raindrops fall into the gauge vertically. Two spherical and two semi‐spherical orifices were designed to modify standard gauges and others in use today. The two spherical orifices catch rain with an effective diameter always equal to the actual diameter regardless of wind speed and direction. The semi‐spherical orifices, used side‐by‐side with a standard gauge, correct 50% of catch deficiencies made by the standard gauge. Tests based on 115 storms show that the four new gauges caught more rainfall than the standard gauge, with an average catch increase ranging from 8% to 16%. Compared with the pit gauge, average deficiency in catch ranged from ?1% (spherical rain gauge orifice with cylinders) to 4%, whereas the deficiency for the standard gauge was ?10%. Percentage deficiencies of the new gauges were positively affected by wind speed, raindrop inclination and rainfall intensity. Although the new gauges tended to underestimate the standard gauge in small storms (<0·25 cm) and overestimated the pit gauge under strong winds, their deviations are small. Underestimates for small storms could be improved by using gauge materials that reduce surface temperature, evaporation and water retention. The gauges are simple in design, easy to operate and inexpensive. In order to maintain a historically consistent set of rainfall data, a dual‐gauge (standard gauge + spherical gauge) is recommended for existing rainfall stations. The new rain gauge orifices are suitable for large‐scale applications. Copyright © 2001 John Wiley & Sons, Ltd.  相似文献   

Spherical harmonic analysis of the CRUST 2.0 global crustal model     

D. Tsoulis 《Journal of Geodesy》2004,78(1-2):7-11

The spherical harmonic analysis of the 2×2 density and stratification information contained in the global crustal model CRUST 2.0 is presented from the viewpoint of gravity field recovery and interpretation. Using a standard Airy/Heiskanen (A/H) isostatic hypothesis and a radially distributed compensation mechanism, two models of topographic/isostatic (t/i) potential harmonic coefficients are obtained up to degree and order 90. The CRUST-derived coefficients are compared with the spectrum of uncompensated topography, with the EGM96 observed gravity field, and with the t/i spectrum based on an A/H hypothesis with a constant compensation depth of 30 km. The signal degree variances of both CRUST models decrease quite smoothly towards degree 90, while the seven-layer model approaches the EGM96 spectrum for degrees 80–90. The significant deviation of the CRUST spectra from the A/H combined spectrum may prove of relevance to local and regional applications investigating the validity of current isostatic hypotheses.Acknowledgments. Sincere thanks go to Nikolaos Pavlis and three unknown referees for their thoughtful comments. Figure 1 has been produced using the mapping package m_map by R. Pawlowicz, which is a MATLAB toolbox that can be freely downloaded from http://www2.ocgy.ubc.ca/~rich/map.html  相似文献   

Derivations of the equation for the field lines of an axisymmetric multipole     

Bertha Jeffreys 《Geophysical Journal International》1988,92(2):355-356

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位移矢量的矢量球函数表达     

高锡铭 《大地测量与地球动力学》1994,(3)

本文给出了位移矢量的矢量球函数表达及其有关的公式。使用这种表达对球形形变问题，无论是理论研究还是实际计算，都会起到重要的作用，并且十分方便。  相似文献   

一种通用球面等积离散网格生成算法   总被引：5，自引：0，他引：5  

贲进  童晓冲张衡 李勇 《测绘学院学报》2005,22(4):252-255,258

球面离散网格模型是管理海量数据的有效途径,如何构建球面网格是这类模型的基础问题.文中利用Snyder等积多面体投影建立了平面与球面的对应关系,设计了球面等积三角形和四边形离散网格的生成算法.结合实验分析了两种网格的最大/最小边长比和单元周长均方差两项指标,结果表明全部网格的指标均收敛,适合用作多分辨率地理空间信息的管理.  相似文献   

内核地球自转动力学理论的研究进展(Ⅰ)          下载免费PDF全文

张捍卫    许厚泽  王爱生 《地球物理学进展》2005,20(2):507-512

地球固体内核（SIC）和地球其余部分之间的引力和压力的耦合作用引起了一个力矩，从而对地球的章动运动产生影响.由于SIC的转动惯量和整体地球转动惯量相比是非常小的，因此可以认为SIC的动力学效应只是导致一个新的章动本征模，其频率与自由核章动（FCN）相差不太远，且对地球章动产生了一个微弱的共振影响.本文在文献〔1〕理论的基础上，对内核地球自转动力学理论进行了更加深入和详细的研究，顾及到高阶引潮力位的影响，介绍了研究内核地球自转的基本假设和定义，引潮力位的复数球函数表示，复数矢量球函数的基本理论等.  相似文献   

地震道空间分辨力研究   总被引：2，自引：7，他引：2       下载免费PDF全文

云美厚  丁伟  杨凯 《地球物理学进展》2005,20(3):741-746

在高分辨率地震勘探中，除了了解子波特性对分辨力的影响外，研究地震道在空间任意方向的分辨力变化规律同样是非常重要的.受分辨力估算方法的局限性，除垂直分辨力和水平分辨力外，目前对于空间任意空间方向分辨力变化的研究很少.本文分析了微分法分辨力和广义空间分辨力估算公式的异同.并利用广义空间分辨力公式分析了分辨力随炮检距、观测点位置、深度的变化规律及其内在本质.与此同时，对广义空间分辨力概念进行了图形解释，揭示了其实质.这对于更好地理解和运用广义空间分辨力计算公式具有重要的意义.  相似文献   

虚拟球谐方法逼近市级大地水准面计算分析     

王建强  孙云龙 《大地测量与地球动力学》2022,42(2):115-118

研究了构建市级大地水准面的虚拟球谐方法。首先,选择构建区域的中心点和区域半径对观测值进行数据预处理,并统计分析数值范围和位置信息;然后,将观测值由地理坐标系转换到球冠坐标系,再转换到虚拟球坐标系中;最后,根据虚拟球谐方法构建市级大地水准面。以南昌市为例构建采样点,采用多项式拟合和神经网络方法与本文虚拟球谐方法进行比较分析,结果表明,虚拟球谐方法的RMS值为0.308 cm,拟合效果最好。  相似文献   

基于移去-恢复法的区域大气负荷影响精化——以滇西地区为例     

申龙杰  章传银  徐鹏飞  杨康 《大地测量与地球动力学》2022,42(6):631-636

传统的大气负荷改正根据全球大气压模型计算获取,但全球大气压模型中、长波信号占优,缺乏突显区域特征信息的短波信号,而在研究高精度的区域大气负荷影响时,空间信息中的短波信号不可忽视。为此,根据地球重力场理论,引入移去-恢复思想,结合ECMWF提供的全球大气压变化数据和区域高分辨率大气压变化数据（CLDAS-V2.0）,基于负荷球谐系数和区域负荷格林函数方法得到大气压变化对滇西地区的负荷影响。结果表明,得到的大气负荷形变场在空间和时间分变率上均有一定提高。利用移去-恢复法计算区域大气压负荷影响,可为固体地球形变和CORS站时序分析提供参考。  相似文献