北京市建筑抗震能力分类及地震灾害风险分析

北京市作为国家重点设防超大型城市,其地震灾害的敏感性和脆弱性极高。本文研究得到了以公里网格为单元的北京市建筑物抗震能力分类评价及其地震灾害风险分析结果。主要研究工作有:(1)针对北京市房屋抗震能力差异较大的现状,开展了建筑结构现场调查;(2)分析社会多元因素对北京市建筑物抗震能力的影响程度,建立了北京市建筑抗震能力分区分类方法;(3)建立了北京市各类建筑物地震易损性矩阵;(4)基于易损性分析结果,得到了北京市在不同概率地震作用下的建筑物直接损失和人员死亡评估模型。本文相关工作可为北京市政府和民众了解地震可能造成的威胁,做好震前准备和规划提供理论依据。     

地震力作用下刚性旋转壳贮液罐液体的动力反应

本文利用有限元法分析了在水平地震作用下刚性(?)转壳贮液罐液体的动力反应。理论分析与形成有限元公式所作的基本假设是罐内液体为理想流体以及它的流动是无旋的。 上述问题只有在圆柱形罐时才有解析解。根据理论分析与本文所建立的有限元公式设计了计算机程序,用它算出的贮液罐内液体晃动的固有频率与地震动力反应值与解析解相比具有很好的精确度。我们利用这一程序计算还得出结论:尽管Housner法是一种近似法,它只能求出液体晃动的基频,但该法仍具有相当的精确度。     

地震作用下储液罐的动力和稳定分析

本文分两部分:1.联合应用有限元和边界积分法对带顶盖的圆柱形储液罐进行自振分析,并用反应谱方法求地震反应。研究了顶盖、静水压力等因素对各阶环向振型频率的影响和罐体自身质量、液面以上罐体刚度对包含有cosθ的振型的频率和地震内力的影响,建议了一个计算拱顶罐动力反应的简化模型。2.在此基础上,用有限元-级数展开法对水平地震作用下的储液罐的稳定性作了探讨,讨论了环向内力和平错内力对储液罐稳定性的影响以及液面附近罐壁失稳的现象,对目前规范中有关储液罐稳定验算方法作了评价。两部分的计算结果与试验结果作了比较。     

广西南部农村群体建筑抗震能力评价

广西近年来陆续发生3次5级以上中强地震,给当地农村建筑造成不同程度的破坏。为掌握广西南部地区农村民居抗震能力现状,对广西3个市中的6个县(区) 12个村122栋农村房屋开展了抗震能力详细抽样调查。本文分析了调查区不同结构类型建筑比例和现状,指出农村房屋在抗震设计、构造和施工中存在的不足,利用改进的区域房屋抗震能力快速评价方法,对各个村的总体建筑抗震能力进行评价,提出增强房屋抗震性能的意见和建议。结果显示：2个村的总体房屋抗震能力为“较强”;10个村为“一般”。     

滇西北地区房屋建筑特征和抗震能力评价

选取滇西北地区16个具有代表性的县(区)为研究对象,根据实地调查总结滇西北房屋总体建筑特征,并结合区域内历史地震房屋震害矩阵分析不同烈度区下各结构类型房屋的震害特征,在此基础上建立区域房屋抗震能力综合指数评价滇西北房屋抗震性能,给出滇西北房屋抗震能力等级分布图和分布规律。     

地下储液罐抗爆炸地冲击作用的流固耦合有限元分析

储液罐的抗震性能虽然得到了较为深入的研究,但对其抗爆炸产生的地冲击作用的研究还十分罕见。本文通过建立流固耦合的数值分析模型,研究爆炸地冲击作用下地下立式储液罐的动力特性,包括储液晃动波高、罐壁的应力和应变、底板的提离和浮放储液罐的“象足”变形产生原因及破坏机理等。研究结果表明,储液罐在爆炸地冲击荷载和地震荷载作用下的动力响应有明显区别,地震荷载作用下的储液罐抗震验算方法不适用于爆炸地冲击荷载。     

大跨预应力混凝土框架结构的静力弹塑性(pushover)分析

基于美国规范ATC-40和N2方法,建立了大跨预应力混凝土框架结构竖向地震反应的静力弹塑性(pushover)分析方法。编制了预应力混凝土构件截面弯矩-曲率的计算程序。这些为评价大跨预应力混凝土框架结构的竖向抗震能力提供了有益的参考。结合具体工程实例进一步说明了该方法的实施步骤。     

城市房屋抗震能力综合评定

房屋震害指数是对房屋地震破坏程度的一种定量描述。根据城市房屋震害预测结果,应用房屋综合震害指数对城市房屋抗震能力评定方法进行了探讨,并以胜利油田基地地区为例(东营市西城区)进行了房屋抗震能力综合评定。     

地震作用下立式储液罐罐壁“象足”变形仿真分析

基于ANSYS软件建立了考虑液体晃动和罐底提离立式储液罐有限元模型,分别进行了水平地震和竖向地震作用下罐壁“象足”变形分析。分析表明:立式储液罐罐壁“象足”变形主要是由罐壁纵向压应力超过临界应力而产生的局部屈曲破坏,并非强度破坏。因罐底提离导致的罐底与基础反复撞击加大了作用在罐壁上的应力,使罐壁底部“象足”变形不断发展,最终导致罐壁撕裂。在完全相同地震加速度作用下,水平地震作用比竖向地震作用罐壁更早更容易进入屈曲状态,产生“象足”变形。     

地震作用下立式储液罐罐壁"象足"变形仿真分析

基于ANSYS软件建立了考虑液体晃动和罐底提离立式储液罐有限元模型,分别进行了水平地震和竖向地震作用下罐壁"象足"变形分析.分析表明:立式储液罐罐壁"象足"变形主要是由罐壁纵向压应力超过临界应力而产生的局部屈曲破坏,并非强度破坏.因罐底提离导致的罐底与基础反复撞击加大了作用在罐壁上的应力,使罐壁底部"象足"变形不断发展,最终导致罐壁撕裂.在完全相同地震加速度作用下,水平地震作用比竖向地震作用罐壁更早更容易进入屈曲状态,产生"象足"变形.     

A Monte Carlo study of rainfall forecasting with a stochastic model

A procedure for short-term rainfall forecasting in real-time is developed and a study of the role of sampling on forecast ability is conducted. Ground level rainfall fields are forecasted using a stochastic space-time rainfall model in state-space form. Updating of the rainfall field in real-time is accomplished using a distributed parameter Kalman filter to optimally combine measurement information and forecast model estimates. The influence of sampling density on forecast accuracy is evaluated using a series of a simulated rainfall events generated with the same stochastic rainfall model. Sampling was conducted at five different network spatial densities. The results quantify the influence of sampling network density on real-time rainfall field forecasting. Statistical analyses of the rainfall field residuals illustrate improvement in one hour lead time forecasts at higher measurement densities.     

Earthquake Engineering and Engineering Vibration Aims And Scope

正This journal is established by the Institute of Engineering Mechanics(IEM),China Earthquake Administration,to promote scientific exchange between Chinese and foreign scientists and engineers so as to improve the theory and practice of earthquake hazards mitigation,preparedness,and recovery.To accomplish this purpose,the journal aims to attract a balanced number of papers between Chinese and     

Foreword

Destructive earthquakes have caused great damage in China and the United States and collapsing buildings havecaused many deaths and injuries. The field of earthquake engineering studies earthquake hazards, the occurrence ofearthquakes of various magnitudes, the nature of the ground shaking during an earthquake, the vibration of structuresduring earthquakes, the strengthening of existing structures and the design of new structures to be earthquake resistant,and finally, how to cope with earthquake damage and restore a city to normal functioning. Such efforts are in progressin both countries, but unfortunately, the language barrier interferes with the free flow of information between China andthe Untied States. It would be mutually beneficial if some means could be developed to promote the exchangeof information across the Pacific Ocean. This new journal has been established for this purpose and its success willbe an important step in promoting earthquake engineering in China and the United States.     

WORLD ASSOCIATION FOR SEDIMENTATION AND EROSION RESEARCH(WASER)

正President:Giampaolo Di Silvio,Italy Vice Presidents:Ulrich C.E.Zanke,Germany Zhao-yin Wang,China The World Association for Sedimentation and Erosion Research(WASER),inaugurated on Oct.19,2004,is an independent non-governmental,non-profit organization.The mission of WASER is to promote international co-operation on the study     

Enhancing remote sensing research on global change to improve our understanding on Earth system processes

正Global Change includes climate change and other environmental changes caused by the joint interaction among various layers of Earth. From the positive side, global change provides new opportunities to human and other living forms on Earth. In the meantime, it creates tremendous challenges and negative impact. At present, the negative impacts have reached all primary processes of the global ecosystem and every aspect of human society, especially causing degradation of the ecosystem. For instance, intensive deforestation causes decline of biodiversity; global warming causes sea level rise and increases     

Dissolved Carbohydrate Concentration,Composition, and Bioavailability to Microbial Heterotrophs in Stream Water

Dissolved total carbohydrates (DTCH), dissolved free monosaccharides (DFMS), dissolved organic carbon (DOC), biodegradable DOC (BDOC), and humic substances (HS) were measured in White Clay Creek (WCC), a stream in southeastern Pennsylvania Piedmont, USA. Samples were collected over different seasons and under baseflow and stormflow conditions. DOC concentrations ranged from 1.0 to 12.8 mg/L C with the highest concentrations associated with stormflows. Carbohydrates ranged from 0.42 to 12.4 μM and accounted for 2.9 to 12.7% of the DOC. Humic substances represented the major DOC fraction, accounting for 55 to 72% of the DOC pool under all flow conditions. The humic fraction had a lower carbohydrate content (4.4%) than the non-humic fraction of DOC (7.2%). Stormflow DOC was enriched in carbohydrates relative to baseflow DOC, but the percentage of humic-C changed little. Carbohydrates were primarily present as dissolved polysaccharides (55%), but a significant fraction was bound to humic substances (40%), while a small proportion was present as monosaccharides (5%). The major monosaccharides in stream water, listed in order of decreasing concentration, included glucose, galactose, rhamnose, xylose, arabinose, mannose, and fucose. On average (30.6 ± 7.4)% (n = 44) of the stream water DOC was biodegradable, and carbohydrates accounted for 9.9 to 17.7% of the BDOC.