时间拓扑关系在单个要素历史管理中的应用

当前的GIS大多基于图层的技术实现历史变化信息的管理,不具有存储单个要素时空属性的机制。对此,改进了ISO的时间模型,并提出了一种时间拓扑关系模型,目的是便于对单个要素的历史信息进行有效的管理。实验表明,该模型可以实现单个要素的历史信息查询。     

Prediction and validation of sidesway collapse of two scale models of a 4‐story steel moment frame

A research program is summarized in which collapse of a steel frame structure is predicted numerically and the accuracy of prediction is validated experimentally through earthquake simulator tests of two 1:8 scale models of a 4‐story code‐compliant prototype moment‐resisting frame. We demonstrate that (1) sidesway collapse can occur for realistic combinations of structural framing and earthquake ground motion; (2) P?Δeffects and component deterioration dominate behavior of the frame near collapse; (3) prediction of collapse is feasible using relatively simple analytical models provided that component deterioration is adequately represented in the analytical model; and (4) response of the framing system near collapse is sensitive to the history that every important component of the frames experiences, implying that symmetric cyclic loading histories that are routinely used to test components provide insufficient information for modeling deterioration near collapse. Copyright © 2010 John Wiley & Sons, Ltd.     

The development of shaking tables–A historical note

The earliest known shaking table, driven by hand‐power, was constructed in Japan at the end of the 19th century. At the beginning of the 20th century developments had moved to the Stanford University in the U.S. with the introduction of an electric motor to produce a more refined oscillatory motion in one direction, the response of the testpiece being recorded mechanically by pens on a rotating drum. Major earthquakes in the 1920s prompted renewed interest at Stanford resulting in a uni‐directional table moving on rails, activated either by a pendulum striking at one end—the other being resisted by springs—or by a wheel with an eccentric‐mass attached to the table. A valuable feature here was that the size of the eccentric mass could be varied as the harmonic motion continued, thereby providing a method of control. In the 1950s, a similar pendulum input was used on a table constructed at the University of California, but instead of rails, it was supported by a group of vertical bars flexible in one direction only, and the 1939–1945 war had resulted in the availability of electrical devices for measuring response. Also, in Italy at this time the use of pendulums was augmented by contra‐rotating mass input devices giving better frequency control; arrays of several electrodynamic exciters were also used. In Japan, motion was induced by the release of compressed springs. The idea of producing input by an oil‐filled piston was introduced at MIT after the 1933 Long Beach earthquake to a table suspended from above by wires. Two other innovations here were of the greatest significance. First was an analogue device for using an actual earthquake record as input, and the second was control of the motion by an error‐driven electrically controlled feedback loop. The development of these ideas into the shaking tables, which we use today, had to wait upon the general development of control engineering during the 1939–1945 war, followed by progressively greater speeds in digital computation. This history ends (c.1985) after the continuation of these advances made possible full 6‐DOF control using many oil‐filled actuators, but before they became able to give us real‐time control with the attendant abilities of multi‐support input and the experimental study of inelastic behaviour. Copyright © 2010 John Wiley & Sons, Ltd.     

抗震分析反应谱法和时程分析法数值仿真比较

基于ANSYS有限元软件比较抗震分析反应谱法和时程分析法的地震数值仿真结果,研究二者的共同性和仿真结果的可比较性。结果表明,反应谱法和时程分析法在抗震反应计算中都体现了地震动特性和结构动态特性对结构地震响应的影响,二者在响应最值和响应频率上的仿真结果具有一致性。     

钢框架结构直接基于位移的抗震设计方法研究

将钢框架结构按其性能划分为使用良好、人身安全、防止倒塌三个水平,并用层间侧移角予以量化采用钢框架的最大层侧移模式来确定其目标侧移曲线在等效线性化的前提下,由等效位移用弹性位移反应谱求出等效周期,然后对构件进行刚度设计和承载力设计用静力弹塑性分析方法对结构进行分析,校核其实际侧移曲线与满足性能目标的侧移曲线是否一致.采用...     

双塔连体结构弹塑性时程分析

双塔连体结构是我国实际工程中应用越来越多的一种结构形式.该结构形式是在两塔楼顶部设置连体部分的新型建筑结构形式.本文针对某一连体结构,采用NosaCAD有限元软件建立整体结构分析模型.通过建立模型,分析结构在7度多遇和罕遇地震下的弹塑性时程反应,得到结构在地震作用下的变形、内力和破坏情况的变化过程.结果表明,小震情况下...     

温度和食物密度对两种形态型裂足臂尾轮虫(Brachionus diversicornis)生活史特征和后代形态型的影响

运用单个体培养方法研究了温度(15℃、20℃、25℃和30℃)和斜生栅藻(Scenedesmus obliquus)密度(0.75×106、1.5×106、3.0×106和6.0 x 106 cells/ml)对等棘刺型和不等棘刺型裂足臂尾轮虫(Brachionus diversicornis)的净生殖率、种群内禀增长...     

Study on the effect of the infill walls on the seismic performance of a reinforced concrete frame

Motivated by the seismic damage observed to reinforced concrete (RC) frame structures during the Wenchuan earthquake, the effect of infill walls on the seismic performance of a RC frame is studied in this paper. Infill walls, especially those made of masonry, offer some amount of stiffness and strength. Therefore, the effect of infill walls should be considered during the design of RC frames. In this study, an analysis of the recorded ground motion in the Wenchuan earthquake is performed. Then, a numerical model is developed to simulate the infill walls. Finally, nonlinear dynamic analysis is carried out on a RC frame with and without infill walls, respectively, by using CANNY software. Through a comparative analysis, the following conclusions can be drawn. The failure mode of the frame with infill walls is in accordance with the seismic damage failure pattern, which is strong beam and weak column mode. This indicates that the infill walls change the failure pattern of the frame, and it is necessary to consider them in the seismic design of the RC frame. The numerical model presented in this paper can effectively simulate the effect of infill walls on the RC frame.     

The geological history of the Isle of Wight: an overview of the ‘diamond in Britain's geological crown’

The geology of the Isle of Wight has attracted both the amateur and professional geologist alike for well over two centuries. It presents a cornucopia of things geological and offers a window into the fascinating story of the geological history and landscape development of southern England, as well as an important teaching resource for all levels of study from primary education through to academic research.This paper provides a geological framework and a summary of the history of research as context for the papers in this issue can be placed. Inevitably, it can only offer a précis of the huge amount of information available, but it is hoped will also give added impetus to further investigation of the literature or, indeed, new research.The island offers a field workshop for topics such as lithostratigraphy, sequence stratigraphy, tectonics and climate change; studies that are becoming ever more international in their influence. There are 15 Sites of Special Scientific Interest designated because of their geological importance and a number of these are internationally significant.After a brief discussion on the concealed geology, this paper concentrates on an outline of the near-surface geology on the coast and inland, and introduces a different view on the structure of the Cretaceous and Palaeogene strata. The enigmatic Quaternary deposits are discussed particularly with reference to the development of the Solent River, human occupation and climate change.     

Geotechnical reconnaissance and liquefaction analyses of a liquefaction site with silty fine sand in Southern Taiwan

Geotechnical reconnaissance of a recurrent liquefaction site at a Quaternary alluvial deposit in southern Taiwan was conducted to establish a comprehensive case history for liquefaction on silty fine sand with high fines content. The liquefaction occurred at a silty fine sand layer with D₅₀ = 0.09 mm and fines content greater than 35% and was triggered by a M_w = 6.4 earthquake on March 4, 2010, which induced maximum horizontal acceleration up to 0.189 g at the site. In situ subsurface characterizations, including standard penetration test, cone penetration test, and shear wave velocity measurement, were performed as well as cyclic simple shear tests on undisturbed specimens retrieved by a modified hydraulic piston sampler. Comparisons of cyclic resistance ratios (CRRs) indicate that CPT sounding with standard penetration rate could overestimate the resistance ratio and drainage conditions during penetration should be considered for high fines content soil in the liquefaction analysis. Additionally, variations of CRRs from different in situ tests indicate that correlations among in situ tests and CRR could be soil specific and precautions should be taken when using these curves on silty fine sands.