大跨度曲线斜拉桥的地震响应分析

为了研究不对称双塔单索面大跨度曲线斜拉桥的地震响应,以工程实例为背景,通过MIDAS建立全桥的空间结构模型,运用多重Ritz向量法进行结构动力特性的计算,采用了反应谱分析的方法,对曲线斜拉桥在三向地震激励作用下响应进行研究.结果表明:该桥首阶振型为主梁竖向弯曲,而且主梁在三向地震作用下变形和内力响应均很大,说明塔梁固结,塔墩分离体系的曲线斜拉桥主梁的振动问题突出,应作为抗震设计的重点.基于地震响应对桥梁的不利影响,提出了一些抗震减震的措施,为实际桥梁工程中提供参考依据.     

大跨度公铁两用斜拉桥结构特性分析

在总结分析国内外已建大跨度铁路斜拉桥结构特征的基础上 ,针对我国拟建大跨度公铁两用斜拉桥的活载重和铁路设计车速高的特点 ,建立了大跨度公铁两用斜拉桥空间计算模型 ,并对其静、动力特性进行研究 .重点探讨了不同桥面体系对大跨度公铁两用斜拉桥静、动力受力特性的影响 ,并分析了结构几何非线性问题 .研究结果表明 :正交异性钢桥面板结合梁体系桥静、动力特性明显优于纵、横梁桥面体系桥 ,结构的几何非线性除对桥梁局部杆件的内力有一定影响外 ,对该桥大部分杆件内力影响较小     

大跨双层斜拉桥地震响应控制

以目前跨度最大的双层公路斜拉桥——闵浦大桥为例,基于Abaqus平台建立非线性动力分析模型,研究了非线性粘滞阻尼器、弹性/非弹性连接对该桥地震响应的减震控制效果.多组非线性时程分析研究表明:塔梁间的非线性粘滞阻尼器增大了下塔柱纵桥向弯矩和剪力,对上塔柱影响较小;阻尼指数一定的情况下,塔底纵桥向剪力和弯矩随阻尼系数的增加而增大.由于大跨斜拉桥的振动模态具有密集、低周期的特点,因而其地震响应受地震输入的影响较大;塔梁间增加弹性/非弹性连接会影响桥梁的纵漂振型,进而影响结构的地震响应,因此塔梁间增加弹性/非弹性连接的减震效果取决于输入地震特性以及塔梁间增加弹性/非弹性连接后的动力特性.文中提出采用非弹性连接参数的联合分布以分析其对地震响应的影响,非弹性的初始刚度和屈服位移联合作用对主梁地震响应的影响较为复杂,文中研究表明,其屈服位移对桥梁地震响应的影响较为明显.     

大跨度结合梁斜拉桥非线性动力特性研究

以大跨度半漂浮体系组合梁斜拉桥为例,首先运用有限元理论,并考虑结构几何刚度与非线性的影响,建立了三维空间动力分析模型,然后采用分块兰索斯法对桥梁进行动力特性研究。结果表明:几何刚度与非线性对结构动力特性影响明显,结构基本周期长,自振频率低,模态振型密集,空间性与耦合性显著。对大跨度组合梁斜拉桥进行动力特性研究时应考虑结构的几何刚度与非线性以及空间性,同时为研究抗震与抗风性能奠定了基础。     

矮塔斜拉桥的动力特性分析

矮塔斜拉桥是国际上一种新型的桥梁结构,具有跨越能力大、经济性好和造型美观等特点。以某实际工程矮塔斜拉桥为例,运用有限元软件MIDAS/CIVIL对该结构进行有限元建模,并对其进行动力特性分析,得到该结构的自振频率和振型,该研究可为矮塔斜拉桥的抗震设计提供参考。     

非一致地震激励下大跨斜拉桥的地震反应

为了研究非一致地震激励下大跨斜拉桥的地震响应规律,利用大型通用有限元分析软件ANSYS10.0建立该桥的动力计算模型,然后应用动力时程方法分析其地震反应,探讨波传播效应对非一致地震激励下大跨度双塔斜拉桥地震反应的影响规律.研究表明,对大跨度斜拉桥而言,一致地震激励不能控制其抗震设计,要对大跨度斜拉桥的地震反应进行准确分析,场地条件及行波效应必须予以考虑.     

纵向阻尼器对大跨度斜拉桥桥塔的抗震性能影响分析

为确定大跨度斜拉桥在阻尼器抗震约束体系作用下的减震性能,文章以某大跨度斜拉桥为研究对象,采用通用有限元软件SAP2000建立全桥有限元模型,采用非线性时程分析方法,研究主塔在有、无阻尼器的情况下内力变化情况。研究结果表明:该桥动力特性分析表明,第1阶周期为7.821 s,对应的振型为主梁纵漂+主塔纵向弯曲振动,远远大于结构的竖向、横向振动周期2.798、2.049 s,抗震需求明显;设置纵向阻尼器的方式能有效地减小主塔在地震荷载作用下的内力,达到内力重新分布的目的,尤其是对弯矩的减小最为明显,从而改善结构的受力性能。     

斜拉桥动力特性分析

以某大跨度斜拉桥为工程背景,利用大型通用有限元程序建立了该桥的三维空间有限元模型,计算分析了桥梁结构的自振频率和振型,文章结论可为该桥的设计、施工以及使用阶段的健康检测和维护提供技术参数和依据。     

大跨度四塔悬索桥动力特性参数敏感性分析

为了深入研究大跨度多塔悬索桥的动力特性,基于ANSYS软件建立了某大跨度四塔悬索桥的三维有限元模型,采用Block Lanczos法进行模态分析,以获得该桥的自振频率和振型,并分析了主缆矢跨比、恒载集度、主梁刚度以及中塔刚度等结构关键参数对其动力特性的影响.结果表明:该桥基频为0.071 71 Hz,对应振型为主梁一阶正对称侧弯;增大矢跨比有利于提高大桥颤振性能;随着恒载集度的增加,结构各阶自振频率均有不同程度的下降;增大主梁横向和扭转刚度可分别提高主梁侧弯和扭转频率,而增大主梁竖弯刚度对主梁竖弯频率影响较小;主梁一阶竖弯频率随着中塔纵向刚度的增大而显著提高.研究结果可为大跨度多塔悬索桥的结构设计与动力分析提供参考.     

基于一体化模型的斜拉桥地震反应分析方法

针对我国普遍采用的大跨度桩基桥梁,应用无限元-有限元土体边界、桩土面-面接触算法和显式求解技术,提出了场地-结构整体模型的地震反应分析方法.以一座主跨为202.5 m+300.0 m的独塔斜拉桥为工程实例,构建了河谷场地-桥梁整体有限元动力模型,研究了二维河谷场地对该斜拉桥纵向地震反应的影响,分析了基础附近扰动场地震动的特点.结果表明,场地中不同河岸高度和二维土层分布会对主塔处地震动的短周期分量产生一定影响,对结构短周期振型产生的地震力有较大影响;扰动场的地震动中接近基础振动频率的分量得到了加强,和自由场的地震动有显著区别,但长周期的分量变化较小.     

An Index mechanism for multi-scale view in spatial databases

There are numerous geometric objects stored in the spatial databases. An importance function in a spatial database is that users can browse the geometric objects as a map efficiently. Thus the spatial database should display the geometric objects users concern about swiftly onto the display window. This process includes two operations:retrieve data from database and then draw them onto screen. Accordingly, to improve the efficiency, we should try to reduce time of both retrieving object and displaying them. The former can be achieved with the aid of spatial index such as R-tree, the latter require to simplify the objects. Simplification means that objects are shown with sufficient but not with unnecessary detail which depend on the scale of browse. So the major problem is how to retrieve data at different detail level efficiently. This paper introduces the implementation of a multi-scale index in the spatial database SISP (Spatial Information Shared Platform) which is generalized from R-tree. The difference between the generalization and the R-tree lies on two facets: One is that every node and geometric object in the generalization is assigned with a importance value which denote the importance of them, and every vertex in the objects are assigned with a importance value,too. The importance value can be use to decide which data should be retrieve from disk in a query. The other difference is that geometric objects in the generalization are divided into one or more sub-blocks, and vertexes are total ordered by their importance value. With the help of the generalized R-tree, one can easily retrieve data at different detail levels.Some experiments are performed on real-life data to evaluate the performance of solutions that separately use normal spatial index and multi-scale spatial index. The results show that the solution using multi-scale index in SISP is satisfying.     

Characterization of Ordovician carbonate reservoirs, southeastern Saskatchewan, Canada

The discovery of the prolific Ordovician Red River reservoirs in 1995 in southeastern Saskatchewan was the catalyst for extensive exploration activity which resulted in the discovery of more than 15 new Red River pools. The best yields of Red River production to date have been from dolomite reservoirs. Understanding the processes of dolomitization is, therefore, crucial for the prediction of the connectivity, spatial distribution and heterogeneity of dolomite reservoirs.The Red River reservoirs in the Midale area consist of 3～4 thin dolomitized zones, with a total thickness of about 20 m, which occur at the top of the Yeoman Formation. Two types of replacement dolomite were recognized in the Red River reservoir: dolomitized burrow infills and dolomitized host matrix. The spatial distribution of dolomite suggests that burrowing organisms played an important role in facilitating the fluid flow in the backfilled sediments. This resulted in penecontemporaneous dolomitization of burrow infills by normal seawater. The dolomite in the host matrix is interpreted as having occurred at shallow burial by evaporitic seawater during precipitation of Lake Almar anhydrite that immediately overlies the Yeoman Formation. However, the low δ18O values of dolomited burrow infills (-5.9‰～ -7.8‰, PDB) and matrix dolomites (-6.6‰～ -8.1‰, avg. -7.4‰ PDB) compared to the estimated values for the late Ordovician marine dolomite could be attributed to modification and alteration of dolomite at higher temperatures during deeper burial, which could also be responsible for its 87Sr/86Sr ratios (0.7084～0.7088) that are higher than suggested for the late Ordovician seawaters (0.7078～0.7080). The trace amounts of saddle dolomite cement in the Red River carbonates are probably related to "cannibalization" of earlier replacement dolomite during the chemical compaction.     

A computer generator for randomly layered structures

AcomputergeneratorforrandomlylayeredstructuresYUJia shun1,2,HEZhen hua2(1.TheInstituteofGeologicalandNuclearSciences,NewZealand;2.StateKeyLaboratoryofOilandGasReservoirGeologyandExploitation,ChengduUniversityofTechnology,China)Abstract:Analgorithmisintrod…     

Perspherical Approaches for Electrons in Atoms and Charged Excitons in Quantum Wells

Instead of following Fock’s expansion,we solve the Schrodinger equation for some quantum mechanical manybody systems such as electrons in atoms and charged excitons in quantum wells in a similar way in hyperspherical coordinates by expanding the wave functions into orthonormal complete basis sets of the hyperspherical hannonics(HHs)of hyperangles and generalized Laguerre polynomials(GLPs)of the hyperradius.This leads the equation to     

Advances in broadband wireless communications under high-mobility scenarios

Future mobile communication systems aim at providing very high data transmission rates, even in high-mobility scenarios such as high-speed wheel-track trains, maglev trains, highway vehicles, airplanes, guided missiles or spacecraft. A particularly important commercial application is the strong and increasing worldwide demand for high- speed broadband wireless communications （up to 574.8 km/ h test speeds or 380 km/h commercial speeds） in railways, providing data, voice and video services for applications such as onboard entertainment services to passengers, train control, train dispatch, train sensor status handling and sur- veillance. In such high-mobility scenarios, there are a number of communication challenges, including fast hand- over, location updating, high-speed channel modeling, estimation and equalization, anti-Doppler spreading tech- niques, fast power control, and dedicated network architec- ture. Because signal transmission in very high-speed scenarios will inevitably experience serious deterioration, it is imperative to develop key broadband mobile communi- cation techniques for such high-speed vehicles.     

Wuhan University Journal of Natural Sciences TOTAL CONTENTS

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海南岛地体及其毗邻陆缘晚中生代—新生代古地磁研究和构造演化

本文叙述了对海南岛及其毗邻大陆边缘白垩纪到第四纪地层岩石进行古地磁研究的全部工作过程。通过分析岩石中剩余磁矢量的磁偏角及磁倾角的变化,提出海南岛白垩纪以来经历的构造演化模式如下:早期伴随顺时针旋转而向南迁移,后期伴随逆时针转动并向北运移。联系该地区及邻区的地质、地球物理资料,对海南岛上述的构造地体运动提出以下认识:北部湾内早期有一拉张作用,主要是该作用使湾内地壳显著伸长减薄,形成北部湾盆地。从而导致了海南岛的早期构造运动,而海南岛后期的构造运动则主要是受南海海底扩张的影响。海南地体运动规律的阐明对于了解北部湾油气盆地的形成演化有重要的理论和实际意义。     

Scale-based spatial data model for GIS

Being the primary media of geographical information and the elementary objects manipulated, almost all of maps adopt the layer-based model to represent geographic information in the existent GIS. However, it is difficult to extend the map represented in layer-based model. Furthermore, in Web-Based GIS, It is slow to transmit the spatial data for map viewing. In this paper, for solving the questions above, we have proposed a new method for representing the spatial data. That is scale-based model. In this model we represent maps in three levels: scale-view, block, and spatial object, and organize the maps in a set of map layers, named Scale-View, which associates some given scales.Lastly, a prototype Web-Based GIS using the proposed spatial data representation is described briefly.     

Exciton Seebeck in Molecular Systems

Various applications relevant to the exciton dynamics,such as the organic solar cell,the large-area organic light-emitting diodes and the thermoelectricity,are operating under temperature gradient.The potential abnormal behavior of the exicton dynamics driven by the temperature difference may affect the efficiency and performance of the corresponding devices.In the above situations,the exciton dynamics under temperature difference is mixed with     

Achieving Unusual States of Matter Under High Pressure

The elongation method,originally proposed by Imamura was further developed for many years in our group.As a method towards O(N)with high efficiency and high accuracy for any dimensional systems.This treatment designed for one-dimensional(ID)polymers is now available for three-dimensional(3D)systems,but geometry optimization is now possible only for 1D-systems.As an approach toward post-Hartree-Fock,it was also extended to