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This paper is the first in a two-part series that discusses the principal axes of M-DOF structures subjected to static and dynamic loads. The primary purpose of this series is to understand the magnitude of the dynamic response of structures to enable better design of structures and control modification devices/systems. Under idealized design conditions, the structural responses are obtained by using single direction input ground motions in the direction of the intended control devices/systems,and by assuming that the responses of the structure is decoupleable in three mutually perpendicular directions. This standard practice has been applied to both new and retrofitted structures using various seismic protective systems. Very limited information is available on the effects of neglecting the impact of directional couplings (cross effects - of which torsion is a component) of the dynamic response of structures. In order to quantify such effects, it is necessary to examine the principal axes of structures under both static and dynamic loading.This first paper deals with quantitative definitions of principal axes and "cross effects" of three-dimensional structures under static load by using linear algebra. It shows theoretically that, for three-dimensional structures, such principal axes rarely exist. Under static loading conditions, the cross effect is typically small and negligible from the viewpoint of engineering applications. However, it provides the theoretical base for subsequent quantification of the response couplings under dynamic loads, which is reported in part Ⅱ of this series. 相似文献
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DING Yongjian YANG Jianping LIU Shiyin CHEN Rensheng WANG Genxu SHEN Yongping WANG Jian XIE Changwei ZHANG Shiqing 《地理学报》2003,13(2):172-180
Based on geographical and hydrological extents delimited, four principles are identified, as the bases for delineating the ranges of the source regions of the Yangtze and Yellow rivers in the paper. According to the comprehensive analysis of topographical characteristics, climate conditions, vegetation distribution and hydrological features, the source region ranges for eco-environmental study are defined. The eastern boundary point is Dari hydrological station in the upper reach of the Yellow River. The watershed above Dari hydrological station is the source region of the Yellow River which drains an area of 4.49×104 km2. Natural environment is characterized by the major topographical types of plateau lakes and marshland, gentle landforms, alpine cold semi-arid climate, and steppe and meadow vegetation in the source region of the Yellow River. The eastern boundary point is the convergent site of the Nieqiaqu and the Tongtian River in the upstream of the Yangtze River. The watershed above the convergent site is the source region of the Yangtze River, with a watershed area of 12.24×104 km2. Hills and alpine plain topography, gentle terrain, alpine cold arid and semi-arid climate, and alpine cold grassland and meadow are natural conditions in the source region of the Yangtze River. 相似文献
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西藏得几蛇绿岩体中玻安岩的地球化学特征及其地质意义 总被引:15,自引:0,他引:15
西藏日喀则蛇绿岩是我国发育最好的蛇绿岩之一,目前有关日喀则蛇绿岩形成的构造背景存在多种不同的认识。作者在研究得几蛇绿岩剖面时发现存在玻安岩,从而为日喀则蛇绿岩具有弧前背景提供了直接证据。得几蛇绿岩中玻安岩类样品具有高硅、高镁、低铁的特征,岩石中Zr、Yb和Y的含量也较低,具有明显的玻安岩特征。根据这些岩石的地球化学性质,认为岩石是由早期经历过较高程度的部分熔融的残余在含水条件下再发生部分熔融形成的。得几蛇绿杂岩体部分形成于弧前环境。 相似文献
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DENG Jun YANG Liqiang SUN Zhongshi WANG Jianping WANG QingfeiXIN Hongbo LI Xinjun Key Laboratory of Lithospheric Tectonics Exploration. China University of Geosciences Ministry of Education Beijing Institute of Geology Geophysics Chinese Academy of Sciences Beijing Faculty of Earth Sciences Jilin University Changchun Jilin 《《地质学报》英文版》2003,77(4):537-546
An analysis of trace elements and isotopic geochemistry suggest that the ore-forming materials of gold deposits in the Jiaodong granite-greenstone belt have multiple sources, especially the mantle source. Seismic wave, magnetic and gravity fields show that the crust-mantle structure and its coupling mechanism are the fundamental dynamic causes for the exchange and accumulation of materials and energy in the metallogenic system. Considering the evolution history of the structural setting, the tectono-metallogenic dynamics model of the area can be summarized as follows: (1) occurrence of the greenstone belt during the Archean-Proterozoic-the embryonic form of Au-source system; (2) stable tectonic setting in the Paleozoic-an intermittence in gold mineralization; (3) intensive activation and reformation of the greenstone belt in the Mesozoic-tectono-mineralization and tectono-diagensis; (4) posthumous structural activity in the Cenozoic-destruction of orebodies in the later stage. In the middle and late Ind 相似文献
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金沙江上游某巨型复合型滑坡的基本特征及稳定性分析 总被引:6,自引:0,他引:6
在对西南某水电站库区一特大型、多期复合型滑坡所处的工程环境条件、自身结构及各期次滑坡体物质组成特征认真调查和研究的基础上.结合ESR测龄试验研究,对该滑坡的变形破坏机制及形成年代进行了综合分析,并对其稳定性进行了定性评价。 相似文献
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滨里海盆地内充填了巨厚的古生代、中生代和新生代沉积物。在剖面上可分为三套地层组合,即盐下层系、含盐层系和盐上层系。盐下层系为下古生界-下二叠统,包括巨厚的碎屑岩和碳酸盐岩沉积,在泥盆纪-早二叠世,滨里海盆地周缘广大地区普遍发育碳酸盐岩,在许多古隆起上还发育生物礁体,说明这一时期盆地的滨、浅海地带具有浅、清、暖的沉积环境,盆外陆源碎屑供应较少。含盐层系为下二叠统上部孔谷阶。早二叠世中-后期由于持续构造抬升,盆地气候变得干旱,海水变浅,潮上带蒸发环境发育,以致这一时期广泛发育盐类沉积,形成含盐层系,主要由盐岩和硬石膏层构成,并形成许多大小不等的盐丘构造。盐上层系为上二叠统-第四系。晚二叠世-三叠纪盆地又经历了一次大的海侵,为浅海陆棚环境,局部为海陆过渡三角洲相。侏罗纪-白垩纪在总的浅海陆棚环境下,盆地不同地区也形成了湖泊和瀉湖环境。晚二叠世以后形成的盐上层系沉积,主要为碎屑岩,在局部地区有碳酸盐岩。 相似文献