桥梁多次重撞击动力学响应的瞬态波效应法

为精确计算地震过程中桥梁的瞬态波响应,研究了多次重撞击现象对桥梁地震响应和安全性能的影响。针对剧烈竖向地震作用下梁可能偏离支座的双跨单墩连续梁桥,采用Ber-noulli-Euler梁模型描述上部结构和St.VENANT杆理论模拟桥墩结构。将竖向地震动以正弦激励形式的人工地震激励代替,应用瞬态波传播理论研究地震过程中上部结构和桥墩之间的多次重撞击现象。提出了计算桥梁多次重撞击瞬态动力学响应的瞬态波效应法。该方法避免了求解耦合重撞击力的强非线性方程,能够较精确地计算多次重撞击过程和分离过程中的瞬态波响应,准确描述结构中的撞击波传播现象。研究结果表明:重撞击力数值巨大;随着桥墩弹性模量的增大,最大重撞击力逐渐增大,而最大墩顶位移逐渐减小;竖向地震动引起的多次重撞击对桥梁的地震响应有较大影响,应当在连续梁桥的抗震设计中予以考虑。     

竖向地震作用下桥梁碰撞响应的动态子结构方法

该文研究了竖向地震作用下桥梁结构的碰撞响应问题。考虑多次碰撞和多次分离过程以及桥梁支座的影响,针对多跨连续桥梁建立动态子结构模型,导出了模态坐标表示的碰撞动力学方程,并将动态子结构方法应用于竖向地震作用下桥梁结构的碰撞响应问题。采用Newmark隐式积分法对动力学控制方程进行数值求解,研究了竖向地震作用下桥梁与桥墩的碰撞动力学响应。数值收敛性结果和理论解的对比分析表明,该动态子结构方法具有良好的数值收敛性和较高的计算精度,可有效地分析竖向地震作用下桥梁的碰撞响应。     

近场地震作用下高速铁路简支梁桥的碰撞行为

近场地面运动有显著的改变结构响应的特点,使结构产生较大的内力和位移,高速铁路简支梁桥与普通铁路简支梁一样存在着梁缝,在近场地震作用下由于相邻两跨梁之间或是梁与桥台之间运动的不协调导致发生碰撞,这种碰撞现象可能会造成梁体的脱落.本文研究了碰撞现象对桥梁结构产生的不利影响,认为对固定铰支座的影响很大,在支座设计时应该给予重视.     

考虑支座失效的基础隔震结构振动台试验研究

为研究隔震结构在多向动力耦合激励下的动力响应和荷载传递路径,进行了一个缩尺比例为1∶4的三层平面不规则RC隔震框架结构振动台试验. 通过研究结构的加速度响应、位移响应、隔震支座内力响应、损伤跨梁混凝土和钢筋应变等,揭示了多向动力耦合激励下的抗倒塌性能. 进一步利用OpenSees有限元软件,分析了损伤跨梁内力和支座损伤指数分布规律. 研究结果表明：在双向水平地震和单个隔震支座突然失效引起的竖向不平衡荷载耦合激励下,失效点位置处结构的竖向动力响应显著增大,并发生明显的竖向变形;支座瞬时失效产生的动力效应对各支座内力均有影响,特别是对相邻支座的内力影响更加明显;支座瞬时失效产生的竖向不平衡荷载由空腹效应和梁端弯矩共同抵抗;支座瞬时失效对相邻支座损伤指数影响最大;在多向动力耦合激励下失效区域的动力响应比仅考虑竖向不平衡荷载下更显著,隔震层损伤指数分布相比地震单独作用下更加离散.     

三跨连续隔震梁桥在地震作用下的碰撞分析

近场地震动具有高峰值地面加速度以及高峰值地面速度的特性,可显著的改变结构响应,使结构产生较大的内力和位移。对于隔震连续梁桥,在近场地震作用下由于伸缩缝相邻两跨梁之间或是梁与桥台之间运动的不协调导致发生碰撞,这种碰撞现象可能会造成梁体的严重破坏.而由于隔震支座的影响,会放大桥梁上部结构的位移,加重桥梁碰撞。本文即对碰撞现象对隔震连续梁桥结构产生的不利影响进行了研究。     

支座的仅受压特性对大跨双层斜拉桥地震响应影响研究

由于边跨与中跨跨重比大,通常在计算大跨斜拉桥时域地震响应时,可忽略桥梁支座的仅受压特性;但若跨重比小或竖向地震较为明显时,地震中可能出现梁端上抬的现象.本文首先给出考虑支座仅受压特性的简化模拟方法,其次以一座大跨双层斜拉桥为例,研究考虑支座仅受压特性后,结构地震响应的特点及地震中梁端可能出现的上抬现象.考虑支座仅受压特性后,文中研究表明:(1)边跨与中跨跨重比小或竖向地震较明显时,梁端可能出现上抬现象,应当引起充分重视;(2)如果地震中会出现支座脱开现象,该特性对大跨度双层斜拉桥边跨辅助墩墩间加劲梁挠度和墩顶附近腹杆轴力及部分斜拉索内力等地震响应影响很明显.     

预应力桥梁的竖向振动特性和地震反应分析

基于模态摄动法和振型叠加法,建立了预应力桥梁竖向地震反应分析的计算方法.通过2个典型工程实例分析,讨论了桥梁竖向地震反应分析中的几个问题.算例结果表明:①预加力使桥梁的自振频率升高,影响主要体现在低阶自振频率上,随着振型阶序的增加,预加力的影响变小.对于20 m和32 m跨度的预应力桥梁来说,竖向基频分别升高5.3％和6.3％,而第5阶竖向频率升高只有1％左右.②在地表波作用下预应力梁跨中截面弯矩减小约30％和25％,预加力提高了桥梁的抗震能力.③竖向地震反应中高阶振型的贡献可以忽略.④7度设防烈度下,在预应力桥梁跨中截面弯矩的荷载组合效应中,竖向地震作用效应所占比例分别达24.56％和26.15％,8度设防烈度时所占比例分别为38.93％和41.46％,说明在这类预应力桥梁抗震设计中应考虑竖向地震反应的影响.     

冲击荷载下钢筋混凝土梁局部响应特征研究

从分析已有冲击试验结果入手,将钢筋混凝土梁的动态响应区分为局部响应阶段和整体响应阶段.由于钢筋混凝土梁在局部响应阶段更易发生脆性剪切破坏,本文主要研究此阶段梁的瞬态响应.讨论了惯性力和负向支座反力对梁内力分布的影响;根据荷载平衡基本原理和参数分析结果建立了梁内力分布的计算方法.结果表明:惯性力和负向支座反力均会影响梁体局部响应阶段的内力分布;负向支座反力近似与梁的跨高比和碰撞力呈线性关系;将惯性力的分布简化为线性分布能够较好地反映梁的实际受力状态.     

近断层地震作用下大跨度拱桥响应研究

目的对比研究近场地震作用下大跨度拱桥采用7组时程波的计算结果平均值与采用3组时程波的计算结果最大值的差异,为近断层地区大跨度拱桥的抗震设计提供参考.方法针对某大跨度拱桥建立有限元分析模型,在PEER数据库选取近场地震作用并施加于拱桥,得到时程响应的峰值.针对现行规范7组波作用时响应峰值的平均值与采用3组波组合时计算结果的最大值以及7组近场和远场地震作用的响应峰值的平均值进行对比研究.结果采用3组近场地震波组合计算所得的拱顶竖向位移、拱顶轴力、拱脚弯矩和跨中吊杆内力响应最小值分别是7组近场地震波计算结果平均值的0.42倍、0.48倍、0.79倍、0.75倍;采用3组近场地震波组合计算所得的四项响应最大值分别是7组近场地震波计算结果平均值的2.7倍、2.8倍、1.9倍、1.5倍.7组近场地震波作用所得的四项响应峰值的平均值分别是远场地震作用相应值的0.82倍、0.85倍、0.61倍和0.61倍.结论对于Ⅲ类场地的大跨度拱桥,按照规范规定采用3组近场地震波进行响应计算时,3组地震响应结果的最大值与按7组地震波计算结果的平均值之间存在很大差异、离散性很大;采用7组地震波进行时程响应计算时,近场地震响应峰值的平均值小于远场的平均值.     

近场地震作用下隔震支座的破坏形式及防护

建立了考虑支座竖向变形以及上部结构转动时隔震结构的运动方程,研究了近场地震作用下结构高宽比和隔震结构周期对支座破坏形式的影响;提出了利用支座软碰撞和软提离防护支座在强烈近场地震作用下发生破坏的措施;对不同类型的橡胶缓冲挡块的力学性能进行了试验研究,并利用有限元软件对其进行了理论计算,给出了橡胶缓冲挡块的荷载一位移关系表达式;对具有软提离功能的支座,根据所需提离量的大小,设计了支座的具体构造．以某高层隔震结构的8度地震响应分析为例,验证了当支座具有软碰撞和软提离功能时,虽然支座的竖向位移有很多的增加,但支座所受的竖向拉压应力以及底层柱的剪力均有很大的减小．     

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…     

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。     

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     

《Chinese Science Bulletin》SUBJECT INDEX TO VOLUME 59(2014)

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An on-line scaling method for improving scalability of a database cluster

The explosive growth of the Internet and database applications has driven database to be more scalable and available, and able to support on-line scaling without interrupting service. To support more client's queries without downtime and degrading the response time, more nodes have to be scaled up while the database is running. This paper presents the overview of scalable and available database that satisfies the above characteristics. And we propose a novel on-line scaling method. Our method improves the existing on-line scaling method for fast response time and higher throughputs. Our proposed method reduces unnecessary network use, i.e. , we decrease the number of data copy by reusing the backup data. Also, our on-line scaling operation can be processed parallel by selecting adequate nodes as new node. Our performance study shows that our method results in significant reduction in data copy time.     

An improved R-tree based on childnode''s probability

R-Tree is a good structure for spatial searching. But in this indexing structure,either the sequence of nodes in the same level or sequence of traveling these nodes when queries are made is random. Since the possibility that the object appears in different MBR which have the same parents node is different, if we make the subnode who has the most possibility be traveled first, the time cost will be decreased in most of the cases. In some case, the possibility of a point belong to a rectangle will shows direct proportion with the size of the rectangle. But this conclusion is based on an assumption that the objects are symmetrically distributing in the area and this assumption is not always coming into existence. Now we found a more direct parameter to scale the possibility and made a little change on the structure of R-tree, to increase the possibility of founding the satisfying answer in the front sub trees. We names this structure probability based arranged R-tree (PBAR-tree).     

Integrating GIS Web services based on mediating architecture

The geographic information service is enabled by the advancements in general Web service technology and the focused efforts of the OGC in defining XML-based Web GIS service. Based on these models, this paper addresses the issue of services chaining,the process of combining or pipelining results from several interoperable GIS Web Services to create a customized solution. This paper presents a mediated chaining architecture in which a specific service takes responsibility for performing the process that describes a service chain. We designed the Spatial Information Process Language (SIPL) for dynamic modeling and describing the service chain, also a prototype of the Spatial Information Process Execution Engine (SIPEE) is implemented for executing processes written in SIPL. Discussion of measures to improve the functionality and performance of such system will be included.     

Tracking data management using topology of moving object database system for moving object constrained trajectory in LBS application

Advances in wireless technologies and positioning technologies and spread of wireless devices, an interest in LBS (Location Based Service) is arising. To provide location based service, tracking data should have been stored in moving object database management system (called MODBMS) with proper policies and managed efficiently. So the methods which acquire the location information at regular time intervals then, store and manage have been studied. In this paper, we suggest tracking data management techniques using topology that is corresponding to the moving path of moving object. In our techniques, we update the MODBMS when moving object arrived at a street intersection or a curved road which is represented as the node in topology and predict the location at past and future with attribute of topology and linear function. In this technique, location data that are corresponding to the node in topology are stored, thus reduce the number of update and amount of data. Also in case predicting the location,because topology are used as well as existing location information, accuracy for prediction is increased than applying linear function or spline function.