火山射气岩浆喷发作用研究进展   总被引：5，自引：2，他引：5  

孙谦  樊祺诚 《岩石学报》2005,21(6):1709-1718

射气岩浆喷发是一种特殊类型的火山活动，水在这类火山活动中起到至关重要的作用，且其喷发产物——低平火山口和基浪堆积物在我国乃至全世界都有广泛的分布。国际上对射气岩浆喷发的研究始于1921年，迄今为止已有80余年的历史。国内外许多学者运用火山地质学、岩石学、沉积学、物理火山学及数值模拟等多学科研究手段，对射气岩浆喷发作用及其产物进行详细的野外观测描述，并探讨其成因机制。本文在前人研究基础上，以我国南方北部湾周边第四纪火山区大量存在的射气岩浆喷发成因的低平火山口和基浪堆积物为研究对象，深入讨论了基浪堆积物的地质特征、射气岩浆喷发形成的基本条件、喷发过程的动力学机制以及基浪流的搬运过程等几方面重要问题，并对已有的研究成果进行了概括和总结，提出有待解决的难点，揭示了这类火山活动特有的属性。  相似文献   

房产测绘平面图系统的实现研究   总被引：1，自引：0，他引：1  

陈洋  张宏  蒋文明  乔延春  温永宁 《现代测绘》2005,28(3):15-16,19

随着城市规划管理的不断发展．使得城市房产测绘单位采用大型空间数据库管理测绘平面图资料成为必然。通过建立房产测绘平面图系统，可以有效地解决数据标准不一致．图数不能互访，测绘各部门无法协调一致等问题，充分发挥网络功能，提升整个城市的房产管理水平．达到房产管理和房产服务一体化的目标。本文详细论述了房产测绘平面图系统的概念、设计原则和系统功能．在南京数字房产共享平台的建设中得到了实现．并取得了良好的效果。  相似文献   

Selective controlled base isolation system with magnetorheological dampers     

Y. Ribakov  J. Gluck 《地震工程与结构动力学》2002,31(6):1301-1324

A base isolation system composed of low‐damping isolation bearings and magnetorheological (MR) fluid dampers is described. The MR fluid changes its properties under the influence of a magnetic field resulting in a damper with characteristics that may be modified in real time. This feature enables optimal control under changing excitations in a stable and cost‐effective manner. The voltage is applied according to a selective control strategy. According to the proposed approach the dampers are activated only within a given range of the base displacements. The selective control improves the efficiency of the system and significantly reduces the control forces required for an optimal structural behaviour. Models of five‐ and eight‐storey buildings are used to study the efficiency of the proposed system. Copyright © 2002 John Wiley & Sons, Ltd.  相似文献   

Pseudodynamic tests on rubber base isolators with numerical substructuring of the superstructure and strain‐rate effect compensation     

F. J. Molina  G. Verzeletti  G. Magonette  Ph. Buchet  V. Renda  M. Geradin  A. Parducci  M. Mezzi  A. Pacchiarotti  L. Federici  S. Mascelloni 《地震工程与结构动力学》2002,31(8):1563-1582

A pseudodynamic testing procedure has been applied by which the seismic response of a base‐isolated building is obtained by using as specimen the isolators, while the superstructure is numerically simulated. The procedure also takes advantage of the continuous pseudodynamic testing capabilities of the ELSA laboratory, which increase the accuracy of the results and reduce the strain‐rate effect of the rubber bearings. A simple proportional correction of the measured forces compensates the remaining strain‐rate effect due to the unrealistic speed of the test. The correction factor is obtained by means of a characterizing test on the specific rubber isolators. The developed method has been successfully applied to the prediction of the seismic response of a base‐isolated four‐storey building submitted to several specified accelerograms. The results for those earthquakes as well as the effects of some changes of the parameters of the system are discussed. Copyright © 2002 John Wiley & Sons, Ltd.  相似文献   

Study on effects of damping in laminated rubber bearings on seismic responses for a ⅛ scale isolated test structure     

Bong Yoo  Yang‐Hann Kim 《地震工程与结构动力学》2002,31(10):1777-1792

The effects of damping in various laminated rubber bearings (LRB) on the seismic response of a ?‐scale isolated test structure are investigated by shaking table tests and seismic response analyses. A series of shaking table tests of the structure were performed for a fixed base design and for a base isolation design. Two different types of LRB were used: natural rubber bearings (NRB) and lead rubber bearings (LLRB). Three different designs for the LLRB were tested; each design had a different diameter of lead plug, and thus, different damping values. Artificial time histories of peak ground acceleration 0.4g were used in both the tests and the analyses. In both shaking table tests and analyses, as expected, the acceleration responses of the seismically isolated test structure were considerably reduced. However, the shear displacement at the isolators was increased. To reduce the shear displacement in the isolators, the diameter of the lead plug in the LLRB had to be enlarged to increase isolator damping by more than 24%. This caused the isolator stiffness to increase, and resulted in amplifying the floor acceleration response spectra of the isolated test structure in the higher frequency ranges with a monotonic reduction of isolator shear displacement. Copyright © 2002 John Wiley & Sons, Ltd.  相似文献   

Approximate analysis methods for asymmetric plan base‐isolated buildings     

Keri L. Ryan  Anil K. Chopra 《地震工程与结构动力学》2002,31(1):33-54

An approximate method for linear analysis of asymmetric‐plan, multistorey buildings is specialized for a single‐storey, base‐isolated structure. To find the mode shapes of the torsionally coupled system, the Rayleigh–Ritz procedure is applied using the torsionally uncoupled modes as Ritz vectors. This approach reduces to analysis of two single‐storey systems, each with vibration properties and eccentricities (labelled ‘effective eccentricities’) similar to corresponding properties of the isolation system or the fixed‐base structure. With certain assumptions, the vibration properties of the coupled system can be expressed explicitly in terms of these single‐storey system properties. Three different methods are developed: the first is a direct application of the Rayleigh–Ritz procedure; the second and third use simplifications for the effective eccentricities, assuming a relatively stiff superstructure. The accuracy of these proposed methods and the rigid structure method in determining responses are assessed for a range of system parameters including eccentricity and structure flexibility. For a subset of systems with equal isolation and structural eccentricities, two of the methods are exact and the third is sufficiently accurate; all three are preferred to the rigid structure method. For systems with zero isolation eccentricity, however, all approximate methods considered are inconsistent and should be applied with caution, only to systems with small structural eccentricities or stiff structures. Copyright © 2001 John Wiley & Sons, Ltd.  相似文献   

鄂尔多斯盆地上古生界高分辨率层序地层分析   总被引：35，自引：1，他引：35  

郑荣才  文华国  梁西文 《矿物岩石》2002,22(4):66-74

按基准面旋回原理，将鄂尔多斯盆地上古生界本溪组（C2b)、太原组（P1t）、山西组(P1s)和下石盒子组（P1xs)划分为3个超长期、8个长期、19个中期和62个短期旋回层序：较为详细地介绍了各级别层序的结构类型、叠加样式和沉积演化序列；建立以长期旋回层序为年代地层框架，中期旋回层序为等时地层对比单元的层序的地层格架；并讨论高分辨率层序地层与天然气藏的关系。  相似文献   

Principal axes of m-DOF structures PartⅠ:Static loading     

Zack Liang  George C.Lee 《地震工程与工程振动(英文版)》2002,1(2)

This paper is the first in a two-part series that discusses the principal axes of M-DOF structures subjected to static and dynamic loads. The primary purpose of this series is to understand the magnitude of the dynamic response of structures to enable better design of structures and control modification devices/systems. Under idealized design conditions, the structural responses are obtained by using single direction input ground motions in the direction of the intended control devices/systems,and by assuming that the responses of the structure is decoupleable in three mutually perpendicular directions. This standard practice has been applied to both new and retrofitted structures using various seismic protective systems. Very limited information is available on the effects of neglecting the impact of directional couplings (cross effects - of which torsion is a component) of the dynamic response of structures. In order to quantify such effects, it is necessary to examine the principal axes of structures under both static and dynamic loading.This first paper deals with quantitative definitions of principal axes and "cross effects" of three-dimensional structures under static load by using linear algebra. It shows theoretically that, for three-dimensional structures, such principal axes rarely exist. Under static loading conditions, the cross effect is typically small and negligible from the viewpoint of engineering applications. However, it provides the theoretical base for subsequent quantification of the response couplings under dynamic loads, which is reported in part Ⅱ of this series.  相似文献   

Recent developments in seismically isolated buildings in Japan     

Shin Okamoto  Nagahide Kani  Masahiko Higashino  Norihide Koshika  Masayuki Kimizuka  Mitsumasa Midorikawa  Masanori Iiba 《地震工程与工程振动(英文版)》2002,1(2):213-225

The Building Standard Law of Japan and related Enforcement Order and Notifications have been substantially revised since the year 2000 to introduce a performance-based regulatory and deregulation system for building control systems. Up to then, time-history analyses were mandatory for isolated buildings and had to be specially approved by the Minster of the Ministry of Construction (MOC). Simplified design procedures based on the equivalent linear method for seismically isolated buildings have been issued as “Notification 2009 — Structural calculation procedure for buildings with seismic isolation” from MOC, and are now integrated into the Ministry of Land, Infrastructure, and Transportation (MLIT). Along with Notification 2009, “Notification 1446 of year 2000 — Standard for specifications and test methods for seismic isolation devices” was also issued. Buildings with heights equal to or less than 60m and that are designed according to these Notifications, including base isolated buildings, only need approval from local building officials, and no longer require the special approval of the Minister of MLIT. This paper summarizes: 1) some statistics related to buildings with seismic isolation completed up to the end of 2001; 2) simplified design procedures required by Notification 2009 of year 2000; and 3) performance of seismic isolation devices required by Notification 1446 of year 2000.  相似文献   

旱地紫色土团聚体特征的指标比较   总被引：5，自引：1，他引：5  

骆东奇  侯春霞  魏朝富  谢德体  朱波 《山地学报》2003,21(3):348-353

土壤团聚体是土壤肥力的基础，团聚体结构对土壤肥力有重要的影响。用团聚体几何平均直径(GMD)、平均重量直径(MWD)、粒径分布分形维(D)和表面分形维(P)分别对紫色土团聚体及水稳性团聚体进行分析：几何平均直径(GMD)、平均重量直径(MWD)、粒径分布分形维(D)和表面分形维(P)从不同角度反映紫色土团聚体特征；几何平均直径(GMD)、平均重量直径(MWD)对团聚体和水稳性团聚体分布均能较好地反映；粒径分布分形维(D)和表面分形维(P)能更好地反映团聚体的水稳性和抗蚀性，是描述土壤团聚体水稳性和抗蚀性的新指标和新方法。  相似文献