Impact model for simulation of base isolated buildings impacting flexible moat walls

Base isolated buildings subjected to extreme earthquakes can exceed their design displacements and impact against the surrounding moat wall. To better understand the consequences of impact on the superstructure, an impact element considering moat wall flexibility is proposed based on impact theory and observations during experimental simulations. It is demonstrated that numerical simulations using the proposed impact element can capture the dominant characteristics of the contact force observed in experiments of base isolated buildings impacting various moat wall configurations including concrete walls with soil backfill and rigid steel walls. The contact force is dependent on impact velocity, geometry, and material properties at the contact surface, and the global dynamic characteristic of the moat wall. Properties of the moat wall impact element are derived based on mechanics‐based models considering material properties and geometric measurements of the experimental setup. For this purpose, the moat wall is modeled as a flexural column with a concentrated nonlinear hinge at its base and soil backfill considered through a damped elastic foundation then generalized into a single degree of freedom system. The resulting impact element is shown to accurately capture both local deformation and the vibration aspects of impact observed in experiments and the effects of impact on superstructure response. Copyright © 2012 John Wiley & Sons, Ltd.     

Full‐scale shaking table test of a base‐isolated medical facility subjected to vertical motions

Base isolation is a well known technology that has been proven to reduce structural response to horizontal ground accelerations. However, vertical response still remains a topic of concern for base‐isolated buildings, perhaps more so than in fixed‐base buildings as isolation is often used when high performance is required. To investigate the effects of vertical response on building contents and nonstructural components, a series of full‐scale shaking table tests were conducted at the E‐Defense facility in Japan. A four‐story base‐isolated reinforced concrete building was outfitted as a medical facility with a wide variety of contents, and the behavior of the contents was observed. The rubber base isolation system was found to significantly amplify vertical accelerations in some cases. However, the damage caused by the vertical ground motions was not detrimental when peak vertical floor accelerations remained below 2 g with three exceptions: (1) small items placed on shelves slid or toppled; (2) objects jumped when placed on nonrigid furniture, which tended to increase the response; and (3) equipment with vertical eccentricities rocked and jumped. In these tests, all equipment and nonstructural components remained functional after shaking. Copyright © 2013 John Wiley & Sons, Ltd.     

Development and utilization of a national web-based chronology of hydrological events/Développement et utilisation sur internet d’une chronologie nationale d’événements hydrologiques

Abstract

Abstract The Chronology of British Hydrological Events (CBHE) has been created as an on-line information resource (http://www.dundee.ac.uk/geography/cbhe/) in order to enhance access to and use of historical facts pertaining to British hydrological phenomena. Its scope covers floods, droughts and all other notable historical phenomena of hydrological interest. This paper sets out the technical means by which the CBHE has been created, explains the benefits to hydrologists in creating such a facility, and illustrates its utility with a number of examples. Benefits include hydrological risk assessments, historical studies of individual events and objectives in environmental education. The scope for establishing comparable national chronologies for other countries is identified, along with prospects for enhancing the utility of such systems with additional functionality such as links to on-line gazetteers and maps.     

CORS站在POS辅助航空摄影中的应用

以某摄区为例,介绍了CORS站在POS辅助航空摄影测量中的应用,并对检校场空三精度、IMU和GPS数据联合解算精度进行分析,指出了目前存在的问题。结果表明,CORS站可以应用在航摄中,精度满足相关的技术要求。     

测量学实践教学的改革与实践

测量学是一门技术性和实践性很强的专业基础课,实践教学是整个教学过程中的重要环节。近几年来,测绘工程系以土木工程等6个本科专业为试点,从更新实践教学内容和教学方法、加强实践教学基础条件建设、创新实践教学考核评价方法等方面进行了系统的研究和大胆的改革,建立与完善了一套完整的测量学实践教学体系,在培养学生的合作精神和动手能力方面收到了良好效果。     

Research Note: Neighborhoods as Territorial Units: The Case of Tel Aviv-Jaffa

This paper suggests a GIS-based methodology for the investigation of the extent to which the inhabitants of a representative sample of city residents perceives itself as living in socially constituted neighborhood territories. We ask residents about the relevancy of the neighborhood as a social unit and to delineate their neighborhood boundaries. We then define these delineations as polygons in GIS, measuring the tendency of neighbors to define merging territorial bases for their neighborhoods. Three possible patterns are identified: (1) lack of perceived boundaries resulting from the irrelevancy of the neighborhood, (2) personal senses of localities that do not merge into communal territories by immediate neighbors—in this case we conclude that residents experience some sense of locality but they do not share any common sense of neighborhood—and (3) the tendency of residents' delineations to merge with those of their neighbors demonstrating, by thus, the social constitution of communal sense of neighborhood. We conclude that in most of the city the neighborhood is marginally relevant with only several areas, located in the outer ring of the city, presenting a coherent territorial sense of neighborhood.     

浅谈利用遥感卫星ALOS1B1级数据制作外业调绘用图的方法——以芜湖县第二次土地调查为例

全国第二次土地调查于2007年下半年启动,2009年完成,安徽省于2008年4月率先启动了芜湖县的试点工作,并自行购买了ALOS1B1级数据制作DOM,套合上矢量的原始土地利用现状图,以便于外业调绘的全面开展.下面,是笔者对利用ALOS1B1级数据制作正射影像图以及外业调绘用图的方法进行了探讨,研究发现,此方法易于掌握,调绘底图的生产快速,质量可靠,效果显著.     

哥伦比亚OMBU区古近系Em组层序地层研究

综合利用地震、测井等地质资料,运用层序地层学方法和技术,建立了层序地层格架和对比模式,对研究区古近系Em组地层的发育展布特征以及沉积环境进行了研究。Em组顶底均为区域上的不整合面,内部划分为两期基准面升降体系域。构造运动和沉积物供应控制下的基准面升级使得沉积初期研究区发育辩状河-曲流河沉积体系,至晚期演变为曲流河沉积体系。     

济阳坳陷惠民凹陷临盘地区始新统孔店组一段—沙河街组四段红层划分和对比

受气候控制的洪水事件沉积因其短暂性、广布性和周期性等特征,具有相对的等时效应,可以作为地层划分和对比的标志层。通过分析不同规模周期下的事件沉积和正常沉积特征,并结合基准面旋回理论,识别出济阳坳陷惠民凹陷临盘地区始新统孔店组一段—沙河街组四段下亚段红层短期、中期和长期三个级次的基准面旋回特征,短期旋回以洪水期和间洪水期内发育的不同类型沉积微相组合为特征,中期旋回以发育一套完整的洪水期—间洪水期沉积为标志,长期旋回则以多个中期旋回组成的地层叠加为特征;以此为依据将惠民凹陷临盘地区孔店组一段—沙河街组四段下亚段划分为5个长期旋回、16个中期旋回及若干个短期旋回层序,并对第一个长期旋回进行了精细层序地层对比,在此基础上建立了干旱气候控制下的红层层序的划分和对比模式。     

Terrestrial laser scanning to estimate plot-level forest canopy fuel properties

This paper evaluates the potential of a terrestrial laser scanner (TLS) to characterize forest canopy fuel characteristics at plot level. Several canopy properties, namely canopy height, canopy cover, canopy base height and fuel strata gap were estimated. Different approaches were tested to avoid the effect of canopy shadowing on canopy height estimation caused by deployment of the TLS below the canopy. Estimation of canopy height using a grid approach provided a coefficient of determination of R² = 0.81 and an RMSE of 2.47 m. A similar RMSE was obtained using the 99th percentile of the height distribution of the highest points, representing the 1% of the data, although the coefficient of determination was lower (R² = 0.70). Canopy cover (CC) was estimated as a function of the occupied cells of a grid superimposed upon the TLS point clouds. It was found that CC estimates were dependent on the cell size selected, with 3 cm being the optimum resolution for this study. The effect of the zenith view angle on CC estimates was also analyzed. A simple method was developed to estimate canopy base height from the vegetation vertical profiles derived from an occupied/non-occupied voxels approach. Canopy base height was estimated with an RMSE of 3.09 m and an R² = 0.86. Terrestrial laser scanning also provides a unique opportunity to estimate the fuel strata gap (FSG), which has not been previously derived from remotely sensed data. The FSG was also derived from the vegetation vertical profile with an RMSE of 1.53 m and an R² = 0.87.