Comparative study of the inelastic response of base isolated buildings

This article presents a numeric comparative study of the inelastic structural response of base isolated buildings. The comparative study includes the following isolation systems: laminated rubber bearings, New Zealand one, pure friction and the frictional pendulum ones. The study is based on obtaining non‐linear response spectra for various design parameters using six earthquake records. Usually the base isolation of a new building seeks to maintain the structure in the linear elastic range. The response of old weak buildings or the response of new ones subjected to extreme earthquakes may not be, necessarily, in the aforementioned ideal elastic range. Consequently, it is important to characterize the response of isolated buildings responding inelastically. A conclusion from this research is that the isolators affect significantly the structural response of weak systems. Rubber isolators seem slightly less sensitive to plastification that may occur in the structure compared to friction isolators. Ductility demands in the structure are affected significantly by friction and neoprene protected systems, in particular sliding ones where larger demands are obtained. Copyright © 2002 John Wiley & Sons, Ltd.     

Geoid determination using adapted reference field, seismic Moho depths and variable density contrast

 The traditional remove-restore technique for geoid computation suffers from two main drawbacks. The first is the assumption of an isostatic hypothesis to compute the compensation masses. The second is the double consideration of the effect of the topographic–isostatic masses within the data window through removing the reference field and the terrain reduction process. To overcome the first disadvantage, the seismic Moho depths, representing, more or less, the actual compensating masses, have been used with variable density anomalies computed by employing the topographic–isostatic mass balance principle. In order to avoid the double consideration of the effect of the topographic–isostatic masses within the data window, the effect of these masses for the used fixed data window, in terms of potential coefficients, has been subtracted from the reference field, yielding an adapted reference field. This adapted reference field has been used for the remove–restore technique. The necessary harmonic analysis of the topographic–isostatic potential using seismic Moho depths with variable density anomalies is given. A wide comparison among geoids computed by the adapted reference field with both the Airy–Heiskanen isostatic model and seismic Moho depths with variable density anomaly and a geoid computed by the traditional remove–restore technique is made. The results show that using seismic Moho depths with variable density anomaly along with the adapted reference field gives the best relative geoid accuracy compared to the GPS/levelling geoid. Received: 3 October 2001 / Accepted: 20 September 2002 Correspondence to: H.A. Abd-Elmotaal     

一个中尺度流复合体的环境场、云场的特征分析

利用常规天气图、物理量诊断分析、逐时红外云图、单站资料等,对2003年4月12日影响鹰潭市的强对流、暴雨天气过程进行分析,认为该过程是在一定的大尺度环流背景下,由不同层次的天气系统共同作用下产生的;其触发机制是冷空气从近地层楔入暖空气中,在高、低空急流、层结不稳定等诸多有利条件下,由几个小尺度对流云团合并发展成1个中尺度对流复合体(MCC).     

Helmholtz算子逆的多方向分裂

Fourier有限差分(FFD)方法是一个重要的波场深度延拓方法，它需要用到包括Taylor展开、连分式晨开、迭代展开等一系列数学展开，将FFD方法从二维推广到三维时，需要解决二维Helmholtz算子的求逆问题。本文利用多方向分裂方法导出了二维Helmholtz算子逆的近似公式，可以应用于三维波场深度延拓问题的研究。     

The spacetime gravitational field of a deformable body

The high-resolution analysis of orbit perturbations of terrestrial artificial satellites has documented that the eigengravitation of a massive body like the Earth changes in time, namely with periodic and aperiodic constituents. For the space-time variation of the gravitational field the action of internal and external volume as well as surface forces on a deformable massive body are responsible. Free of any assumption on the symmetry of the constitution of the deformable body we review the incremental spatial (“Eulerian”) and material (“Lagrangean”) gravitational field equations, in particular the source terms (two constituents: the divergence of the displacement field as well as the projection of the displacement field onto the gradient of the reference mass density function) and the `jump conditions' at the boundary surface of the body as well as at internal interfaces both in linear approximation. A spherical harmonic expansion in terms of multipoles of the incremental Eulerian gravitational potential is presented. Three types of spherical multipoles are identified, namely the dilatation multipoles, the transport displacement multipoles and those multipoles which are generated by mass condensation onto the boundary reference surface or internal interfaces. The degree-one term has been identified as non-zero, thus as a “dipole moment” being responsible for the varying position of the deformable body's mass centre. Finally, for those deformable bodies which enjoy a spherically symmetric constitution, emphasis is on the functional relation between Green functions, namely between Fourier-/ Laplace-transformed volume versus surface Love-Shida functions (h(r),l(r) versus h ^′(r),l ^′(r)) and Love functions k(r) versus k ^′(r). The functional relation is numerically tested for an active tidal force/potential and an active loading force/potential, proving an excellent agreement with experimental results. Received: December 1995 / Accepted: 1 February 1997     

丽江7.0级地震地下流体异常特征

通过对１９９６年２月３日云南丽江Ｍｓ７．０地震前震中周围水位、水氡、水汞、泉点宏观等地下流体共７１个台项观测资料的异常及综合特征分析，初步认为震前异常数量较多，异常时间分布具有整体性、同步性、集中性的特点，但异常主要集中在短期阶段，临震异常不突出；突间分布具有集中性和非均匀性，孕震区至远场影响区的异常比例最高，震源区内为相对“盲区”，且突出而肯定的宏观异常极少；异常的时空演变特征复杂，总体没有规律     

平面图形演化方法在地震预报中的应用

“平面图形演化方法”是利用无量刚的异常信息量来反映震前异常空间分布及其随时间的演化，从而预报发震时间和地点的一种方法，这种方法μ值等值线图法，μ值异常平面图法组成，它是通过绘制不同的时间上述二种平面图，通过分析水位，水化异常于震前在时间上，空间上的演化规律，寻找μ值异常集中区或高值区，异常丛集图像分布区，条带图像分布带及条带交叉图像地区，并考虑异常分布图像与活动构造带和地震带的关系，从而对强震发生     

水库地震主震发生时间的预测

水利工程对水库地震的抗震设防要求事先对水为地震进行预测。预测内容包括蓄水后诱发地震的危险性（可能性、）最大震级、最大震的地占紧及不库地震对场址地震动参数的影响。除主震时间的预测外，本文第一作者都曾提出过初步的预测方法。本文认为，水库地震前震波速比异常、非线性灰色模型以及前震系列回归等方法，是预测主震时间的有前途的方法。     

强地震地点预报方法─—交汇法

利用小震调制比法、动态空区法、震群链式活动轨迹交汇法和短期震中迁移带交汇法这4种地震活动时空图像动态监测方法，结合震源模式中震源和其它单元之间的差异性以及各调整单元、调整层、深浅构造之间的差异性对若干震例进行研究，发现应用不同时段多个异常区边界或空区边界或条带交汇可求得未来强震的位置。交汇法使地震的预报范围大大缩小，这对防震减灾有一定的现实意义。另外，交汇法不仅具有明确的物理基础，而且具有可操作性和普适性。只要异常边界比较正确，采用的又是动态监测方法，这种预测强震位置的思路和方法还可推广到其它各种地震活动性参数和前兆场的分析中。     

科学计算可视化技术的研究与应用

本文介绍了科学计算可视化技术的发展和应用情况，论述了这一新技术的特点及其在油气藏描述，工程设计ＣＡＤ等学科的应用和发展趋势。阐述了目前国际国内计算机图形学领域具体的研究方向和方法及图形软件、图形硬件的发展概况。