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1.
Chunxiang Li 《地震工程与结构动力学》2002,31(4):897-919
Multiple tuned mass dampers (MTMD) consisting of many tuned mass dampers (TMDs) with a uniform distribution of natural frequencies are taken into consideration for attenuating undesirable vibration of a structure under the ground acceleration. A study is conducted to search for the preferable MTMD which performs better and is easily manufactured from the five available models (i.e. MTMD‐1 – MTMD‐5), which comprise various combinations of the stiffness, mass, damping coefficient and damping ratio in the MTMD. The major objective of the present study then is to evaluate and compare the control performance of these five models. The structure is represented by its mode‐generalized system in the specific vibration mode being controlled by adopting the mode reduced‐order approach. The optimum parameters of the MTMD‐1 – MTMD‐5 are investigated to reveal the influence of the important parameters on their effectiveness and robustness using a numerical searching technique. The parameters include the frequency spacing, average damping ratio, tuning frequency ratio, mass ratio and total number. The criteria selected for the optimum searching are the minimization of the maximum value of the displacement dynamic magnification factor (DDMF) and that of the acceleration dynamic magnification factor (ADMF) of the structure with the MTMD‐1 – MTMD‐5 (i.e. Min.Max.DDMF and Min.Max.ADMF). It is demonstrated that the optimum MTMD‐1 and MTMD‐4 yield approximately the same control performance, and offer higher effectiveness and robustness than the optimum MTMD‐2, MTMD‐3, and MTMD‐5 in reducing the displacement and acceleration responses of structures. It is further demonstrated that for both the best effectiveness and robustness and the simplest manufacturing, it is preferable to select the optimum MTMD‐1. Copyright © 2002 John Wiley & Sons, Ltd. 相似文献
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The five MTMD models, with natural frequencies being uniformly distributed around their mean frequency, have been recently presented by the first author. They are shown to have the near‐zero optimum average damping ratio (more precisely, for a given mass ratio there is an upper limit on the total number, beyond which the near‐zero optimum average damping ratio occurs). In this paper, the eight new MTMD models (i.e. the UM‐MTMD1～UM‐MTMD3, US‐MTMD1～US‐MTMD3, UD‐MTMD1 and UD‐MTMD2), with the system parameters (mass, stiffness and damping coefficient) being, respectively, uniformly distributed around their average values, have been, for the first time here, proposed to seek for the MTMD models without the near‐zero optimum average damping ratio. The structure is represented by the mode‐generalized system corresponding to the specific vibration mode that needs to be controlled. Through minimization of the minimum values of the maximum dynamic magnification factors (DMF) of the structure with the eight MTMD models (i.e. through the implementation of Min.Min.Max.DMF), the optimum parameters and values of Min.Min.Max.DMF for these eight MTMD models are investigated to evaluate and compare their control performance. The optimum parameters include the optimum mass spacing, stiffness spacing, damping coefficient spacing, frequency spacing, average damping ratio and tuning frequency ratio. The six MTMD models without the near‐zero optimum average damping ratio (i.e. the UM‐MTMD1～UM‐MTMD3, US‐MTMD1, US‐MTMD2 and UD‐MTMD2) are found through extensive numerical analyses. Likewise, the optimum UM‐MTMD3 offers the higher effectiveness and robustness and requires the smaller damping with respect to the rest of the MTMD models in reducing the responses of structures subjected to earthquakes. Additionally, it is interesting to note, by comparing the optimum UM‐MTMD3 with the optimum MTMD‐1 recently investigated by the first author, that the effectiveness and robustness for the optimum UM‐MTMD3 is almost identical to that for the optimum MTMD‐1 (without inclusion of the optimum MTMD‐1 with the near‐zero optimum average damping ratio). Recognizing these performance benefits, it is preferable to employ the optimum UM‐MTMD3 or the optimum MTMD‐1 without the near‐zero optimum average damping ratio, when installing the MTMD for the suppression of undesirable oscillations of structures under earthquakes. Copyright © 2003 John Wiley & Sons, Ltd. 相似文献
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针对"数字沈阳"三维地理信息系统中建模质量与建模效率相矛盾的问题,阐述了3DS Max与MultiGen Creator两种建模软件各自的特点,分析和总结了建模过程中需要注意的问题。结合沈阳三维地理信息系统,探讨了3DSMax与Multigen Creator两者相结合的综合建模技术,建立了沈阳市城市三维模型。 相似文献
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随着网络教学的兴起,虚拟现实技术用于实验教学,成为强化实验室建设、改革实验教学手段的一个重要发展方向。介绍虚拟建模和开发软件,并以我院仿真模拟摄影测量与遥感实验室为原型,采用VRML软件为主,三维建模软件SkecthUP和3Ds Max为辅,阐述系统设计与实现的具体过程,构建虚拟航空摄影测量实验系统。该系统主要包括虚拟地形地貌沙盘(虚拟校园模型和虚拟栅格地形)、虚拟全数字摄影测量工作站模型、虚拟无人机和控制轨道动态模型,以及虚拟实验室场景。具有数字摄影测量工作站动态操作演示、无人飞机航空摄影测量操作演示,以及实验室参观展示等功能。研究成果无实体实验室的时空限制,有利于学生开展自主学习,有效地提高摄影测量实验教学质量,其对于虚拟实验系统的研发具有一定的借鉴意义。 相似文献
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研究了3DS Max和MultiGen Creator结合建模的新方法,通过项目实践,证明了此方法建立的三维模型在动态漫游中取得了很好的效果,既保证了模型的精度,又符合实时渲染的数据要求。 相似文献
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3维造型软件3ds Max以其强大的功能,越来越受到广大设计者的青睐,已经成为当前模型、效果图制作的主流软件。文章介绍了用3ds Max建立城市房屋3维模型的基本方法,对建立城市房屋3维模型有一定的参考和应用价值。 相似文献
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1INTRODUCTIONDuringthefloodseasonof1998,anothercatastrophicfloodoccurredinthemiddleandlowerYangtzeRiverfollowingthecatastrophicfloodin1954.Ascomparedwiththe54flood,the1998floodwascharacterizedbythefactsthatthedurationofthehighwaterstagewasmuchlonger,thefloodcontrolwasmuchmoredifficult,andthetotalmanpowerandmaterialresourcesexpelldedintilefloodfightingweremuchmoreenormous.TOsummarizetheexperienceandlessonsfromthefloodissignificanttotilehydraulicengineeringandfloodcontroloftheYangtzeRiver.… 相似文献
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Chunxiang Li 《地震工程与结构动力学》2000,29(9):1405-1421
Multiple tuned mass dampers (MTMDs) consisting of many tuned mass dampers (TMDs) with a uniform distribution of natural frequencies are considered for attenuating undesirable vibration of a structure. The MTMD is manufactured by keeping the stiffness and damping constant and varying the mass. The structure is represented by its mode‐generalized system in the specific vibration mode being controlled using the mode reduced‐order method. The optimum parameters of the MTMD are investigated to delineate the influence of the important parameters on the effectiveness and robustness of the MTMD by conducting a numerical searching technique in two directions. The parameters include: the frequency spacing, average damping ratio, mass ratio and total number. The criterion selected for the optimization is the minimization of the maximum value of the dynamic magnification factor (DMF) of the structure with MTMD (i.e. Min.Max.DMF). In this paper, for the sake of comparison, the MTMD(II), which is made by keeping the mass constant and varying the stiffness and damping coefficient, and a single TMD are also taken into account. It is demonstrated that the optimum frequency spacing of the MTMD is the same as that of the MTMD(II) and the optimum average damping ratio of the MTMD is a little larger than that of the MTMD(II). It is also found that the optimum MTMD is more effective than the optimum MTMD(II) and the optimum single TMD with equal mass. Copyright © 2000 John Wiley & Sons, Ltd. 相似文献
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近年来,数字校园继数字地球、数字城市之后成为各高校研究的热点,三维数字校园虚拟系统构建平台多样、方法多元,却鲜有基于国内自主产权的MapGIS K9数字校园系统。因此,本文以某农业大学(南校区)为研究对象,对三维数字校园虚拟系统进行设计与实现。利用南方CASS、3DS Max、MapGIS K9及其他相关软件,通过资料收集整理、地理信息测量采集、建立1:500校园数字地形图、建立属性数据库、三维建模、多平台融合、交互式设计等一系列步骤,实现了某农业大学(南校区)三维数字校园虚拟系统的三维可视化和信息查询、测距、校园导航、自由路径游览、漫游视频录制的交互式功能,可以有效进行校园建筑属性信息查询与部分管理。 相似文献
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