| 开放系统悬臂类结构的动力特性计算方法 |
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| 引用本文： | 付相球,潘旦光. 开放系统悬臂类结构的动力特性计算方法[J]. 工程力学, 2023, 40(1): 40-50. DOI: 10.6052/j.issn.1000-4750.2021.07.0568 |
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| 作者姓名： | 付相球 潘旦光 |
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| 作者单位： | 北京科技大学土木工程系,北京100083;北京科技大学土木工程系,北京100083;城市地下空间工程北京市重点实验室,北京科技大学,北京100083 |
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| 基金项目： | 土木工程防灾国家重点实验室开放基金项目(SLDRCE15-01) |
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| 摘 要： | 结构总是修建在一定的场地而形成土-结构相互作用的开放系统。为解决开放体系下悬臂类结构的自振频率、振型和考虑辐射阻尼下模态阻尼比的计算问题,提出了脉冲荷载响应模态分析法。该方法采用直接有限元法建立土-结构相互作用有限元模型,对结构施加脉冲荷载得到结构动力反应后,由模态识别方法计算结构的动力特性。随后,以一个悬臂类五层框架结构为例研究了计算动力特性随土体计算范围变化的规律和脉冲荷载激励点位置对计算结果的影响。在此基础上,讨论了土体材料阻尼对模态阻尼比的影响,并与集总参数模型和直接模态分析法进行对比,说明不同方法的计算精度。计算结果表明,随着土域计算范围的增加,脉冲荷载响应模态分析法所得的动力特性将逐渐收敛到精确解;当土体计算范围大于结构基频所对应的波长的2倍时,结构自振频率的误差小于1%,模态阻尼比的误差小于5%;以非模态节点作为激励点都可以得到比较精确的结果;三参数集总参数模型所得模态阻尼比存在显著误差,直接模态分析法所得模型的基频随土域范围增大而趋向于零;相比于辐射阻尼,土体材料阻尼对结构的各阶模态阻尼比的影响较小。
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| 关 键 词： | 结构工程 动力特性 开放系统 土-结构相互作用 脉冲荷载响应模态分析法 |
| 收稿时间： | 2021-07-23 |
A CALCULATION METHOD FOR DYNAMIC CHARACTERISTICS OF THE CANTILEVER-TYPE STRUCTURE IN OPEN SYSTEMS |
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| Affiliation: | 1.Department of Civil Engineering, University of Science and Technology Beijing, Beijing 100083, China2.Beijing Key Laboratory of Urban Underground Space Engineering, University of Science and Technology Beijing, Beijing 100083, China |
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| Abstract: | Structures are always built on sites to form open systems of soil-structure interaction. To calculate natural frequencies, mode shapes and modal damping ratios including the influence of radiation damping for the cantilever-type structure in open systems, an impulse-load-based modal analysis method is proposed. In the method, the finite element model of soil-structure interaction is excited by an impulse load to obtain the dynamic response, and then the dynamic characteristics can be obtained by modal identification method.Then, a cantilever-type five-story frame structure is taken as an example to investigate the effect of soil region and excitation location on the dynamic characteristics. On this basis, the influence of soil material damping on the modal damping ratio is discussed, and the results are compared with those of lumped-parameter models and the direct modal analysis method. The numerical results show that, the dynamic characteristics of the structure would converge to exact values with the increase of soil region. When the size of soil region is two times wider than the wavelength corresponding to the fundamental frequency of the structure, the relative errors of structural natural frequencies are less than 1%, and the relative errors of modal damping ratios are less than 5%. Any location, as long as it is not the modal node, can be used as excitation location to get accurate dynamic characteristics. However, there are obvious errors on the modal damping ratios by the three lumped-parameters model, and the fundamental frequency would approach zero with the increase of the size of soil region using the direct modal analysis method. Compared with the radiation damping, soil material damping has slight contribution to structure modal damping ratio. |
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