我国现行抗震设计规范中场地评定方法的比较和评述   总被引：1，自引：0，他引：1  

刘曾武  魏培恒 《地震工程与工程振动》1995,15(4):118-130

目前，我国抗震设计规范中采用的场地评定方法主要有两种：一是建筑抗震设计规范（ＧＢＪ１１－８９）采用的场地分类的方法，一是构筑物抗震设计规范（ＧＢ５０１９１－９３）和电力设施抗震设计规范采用的场地指数法。前者是把场地影响按照场地分类指标划分成若干场地类别，因此，确定的地震荷载是不连续的，跳跃变化的。后者是一种以模糊推论的综合评判方法导出的场地指数为指标进行连续评定的新方法，在这种方法里，场地性质的差  相似文献   

探讨渤海及周边地区海洋平台抗震设防水准   总被引：3，自引：0，他引：3       下载免费PDF全文

彭艳菊  吕悦军  唐荣余  沙海军 《地震学报》2005,27(6):647-655

介绍了美国API规范的内容，并将南加利福尼亚和中国渤海海域地震活动特征与地震危险性进行对比. 对比结果表明，无论在地震活动的频度与强度还是地震危险性分析结果上，渤海都比南加州弱. API规范指出，对于南加利福尼亚地区的永久性建筑， 强度设计水准取重现期200 a，变形设计水准取几百至几千年. 我国相关规范规定的海洋平台强度设计和变形设计水准分别取500 a和10 000 a，过于保守. 同时，与其它建构筑物的抗震水平相比较，甲类建筑变形设计水准取设计基准期100 a内超越概率2%~3%，乙、丙类取50 a内2%~3%，考虑海洋平台易于引起严重的次生灾害，变形设计水准取设计基准期30 a内1%（相当于重现期3 000 a）应是安全的. 基于上述对比分析， 同时考虑到经济承受能力以及与现行标准的连贯性， 建议我国海洋石油平台的强度设计水准和变形设计水准分别取200 a和3 000 a.   相似文献   

Integral inversion of SST data of type GRACE     

P. Novák 《Studia Geophysica et Geodaetica》2007,51(3):351-367

Satellite missions CHAMP and GRACE dedicated to global mapping of the Earth’s gravity field yield accurate satellite-to-satellite tracking (SST) data used for recovery of global geopotential models usually in a form of a finite set of Stokes’s coefficients. The US-German Gravity Recovery And Climate Experiment (GRACE) yields SST data in both the high-low and low-low mode. Observed satellite positions and changes in the intersatellite range can be inverted through the Newtonian equation of motion into values of the unknown geopotential. The geopotential is usually approximated in observation equations by a truncated harmonic series with unknown coefficients. An alternative approach based on integral inversion of the SST data of type GRACE into discrete values of the geopotential at a geocentric sphere is discussed in this article. In this approach, observation equations have a form of Green’s surface integrals with scalar-valued integral kernels. Despite their higher complexity, the kernel functions exhibit features typical for other integral kernels used in geodesy for inversion of gravity field data. The two approaches are discussed and compared based on their relative advantages and intended applications. The combination of heterogeneous gravity data through integral equations is also outlined in the article. panovak@kma.zcu.cz  相似文献   

Approaches for modeling longitudinal dispersion in pore-networks     

R.C. Acharya  S.E.A.T.M. Van der Zee  A. Leijnse 《Advances in water resources》2007

The purpose of this study is to quantify the dispersivity in the longitudinal direction by upscaling pore scale mixing over a network domain and to verify the dispersivity with that obtained through the more rigorous upscaling technique, the Brownian particle tracking model (BPTM). We model a porous medium with a network of pore-units that are comprised of pore bodies and bonds of finite volume. Such a pore-unit is assumed to be a mixing cell with the steady state flow condition for a single fluid. Dispersivity can be obtained by solving the mixing cell model (MCM) for the concentration in each pore-unit and by averaging the concentrations for a large number of pore units (as a function of time and space). A minimal size of network that ascertains an asymptotic value of dispersivity was determined and verified with large size pore networks. This numerically computed dispersivity is compared with the results from the BPTM for the same porous medium and flow conditions. We show that the dispersivity obtained from the MCM is equally reliable for the heterogeneous pore-networks and can be estimated as a function of pore size heterogeneity. For homogeneous networks with the MCM, the iteration time step plays an important role. On the other hand, for networks with the BPTM, the assumption of intra-bond velocity profile affects the results.  相似文献   

Stability and accuracy analysis of outer loop dynamics in real‐time pseudodynamic testing of SDOF systems     

Oya Mercan  James M. Ricles 《地震工程与结构动力学》2007,36(11):1523-1543

Real‐time pseudodynamic (PSD) testing is an experimental technique for evaluating the dynamic behaviour of a complex structure. During the test, when the targeted command displacements are not achieved by the test structure, or a delay in the measured restoring forces from the test structure exists, the reliability of the testing method is impaired. The stability and accuracy of real‐time PSD testing in the presence of amplitude error and a time delay in the restoring force is presented. Systems consisting of an elastic single degree of freedom (SDOF) structure with load‐rate independent and dependent restoring forces are considered. Bode plots are used to assess the effects of amplitude error and a time delay on the steady‐state accuracy of the system. A method called the pseudodelay technique is used to derive the exact solution to the delay differential equation for the critical time delay that causes instability of the system. The solution is expressed in terms of the test structure parameters (mass, damping, stiffness). An error in the restoring force amplitude is shown to degrade the accuracy of a real‐time PSD test but not destabilize the system, while a time delay can lead to instability. Example calculations are performed for determining the critical time delay, and numerical simulations with both a constant delay and variable delay in the restoring force are shown to agree well with the stability limit for the system based on the critical time delay solution. The simulation models are also used to investigate the effects of a time delay in the PSD test of an inelastic SDOF system. The effect of energy dissipation in an inelastic structure increases the limit for the critical time delay, due to the energy removed from the system by the energy dissipation. Copyright © 2007 John Wiley & Sons, Ltd.  相似文献   

有限区域变分四维同化系统的设计和试验     

徐国强  沈桐立  覃丹宇 《南京气象学院学报》2002,25(6):764-771

使用共轭码技术，构造了中尺度模式的伴随模式，研究了模式侧边界条件。基于伴随模式技术的原理，设计了伴随同化和Derber同化方法两套方案；下降算法采用共轭梯度法，使用准真实资料，进行子同化数值试验和预报试验。结果表明，两套同化方案都取得了一定的同化效果，Derber同化方法比伴随同化更令人满意。证明了变分同化是提高预报准确率的一种非常有效的手段。  相似文献   

PWM驱动电机的电流环设计   总被引：4，自引：0，他引：4  

郑舒 《华东地质学院学报》2002,25(2):174-177

总结了PWM驱动电机电流环的设计及提取反馈电流的方法，提出了一种无超调的电流环设计方法－－积分反馈校正方法，并探讨了小电流时电流环的设计各种获取电流的方法。  相似文献   

上行气象报文监控和自动转发系统     

薛双青  刘川生等 《山西气象》2001,(3):33-36

本文针对目前我省上行报文发送情况的现状，说明了建立上行气象报文监控和转发系统的关键技术，包括：使用三层模式、三层模式中各个层次的功能、接收和转发报文的过程、监控系统的运行状态，如何统一处理气象报文等。  相似文献   

多层电流片中双撕裂模耦合的压强效应          下载免费PDF全文

王传兵  王水 《地球物理学报》2001,44(2):145-153

应用边界层理论研究了等离子体压强对多层电流片中m≥2的双撕裂模耦合的线性和非线性发展行为的影响.考虑等离子体的压强效应，在一阶近似下，解析求得了环位形中双撕裂模的外区匹配参数Δ′.结果表明，当等离子体β<<1时，等离子体压强对双撕裂模的两有理面模之间通过撕裂模外区发生耦合作用的线性行为没有定性影响.虽然等离子体压强将影响双撕裂模耦合的非线性行为，但是主要表现在对其单模项的影响，而对由于两有理面模之间的耦合作用产生的耦合项的影响却很小.  相似文献   

Rundle模式地震滞后环和突变现象研究   总被引：2，自引：0，他引：2       下载免费PDF全文

李丁一 《地震工程学报》2001,23(4):354-358

基于耗散结构理论详细研究了地震活动的主要特征。研究结果表明，地震活动呈现双稳态及尖拐突变现象，主要表现是：发生在应力临界值区间[-pc,pc]内的滞后现象和发生在临界值pc和-pc处的突变现象，前对应系统变能积累过程，后（即强震过程）地该系统能量的主要耗散机制。  相似文献