结构鲁棒性的量化研究

发布时间：2018-03-05 01:07

本文选题：鲁棒性　切入点：易损性　出处：《湖南大学》2015年硕士论文　论文类型：学位论文

【摘要】：鲁棒性在工程结构抗连续倒塌领域中一个重要的概念,各国规范中要求结构被设计成鲁棒的以抵抗意外事件导致的连续性倒塌,但都只停留在定性要求层面。尽管目前存在很多结构鲁棒性量化指标,但并没有一个普遍接受的指标对结构鲁棒性进行衡量,这主要是鲁棒性的意义在不同学者中被不同的使用所致。本文对与结构鲁棒性相关的概念进行辨析,建立了半确定性鲁棒性评估框架体系。在特定事件作用下结构本身的不确定性(即材料属性和几何尺寸的变异性)被忽略,而通过发生概率密度函数来考虑不同事件的不确定性。本文中结构鲁棒性是从其反面,即结构易损性来进行研究的。将结构视为离散构件的集合体,则相应的,结构易损性可由构件易损性通过集合理论得到。依据对结构易损性贡献程度的不同,引入基于承载力的构件重要系数作为构件易损系数的权重系数,并进一步得到鲁棒性指标。本文针对桁架结构和钢筋混凝土结构,分别提出适用的构件重要系数和构件易损系数。对于桁架结构,构件重要系数可以通过增量荷载法计算,计算过程中可以得到不同构件失效所导致的失效场景和构件间的拓扑关系。由于仅存在轴力,桁架的构件易损系数可以在应变层次定义;对于钢筋混凝土结构,构件重要系数通过Pushover方法来计算,仅考察结构极限承载力的变化而忽视其复杂的失效场景。由于钢筋混凝土构件内力分布的复杂性,构件易损系数需要从内力层次考虑拉(压)弯剪复合受力的破坏准则来定义。为阐述本文鲁棒性指标的用法,设计了4个桁架结构和5个钢筋混凝土框架结构,分析比较了各结构中构件重要系数和构件易损系数的分布,并对各结构的鲁棒性进行了评估。分析结果表明:本文所提鲁棒性指标能在很好的评估不同事件作用下结构的鲁棒性,增强重要构件的局部抗力和增强结构的冗余度是提高结构鲁棒性的两个行之有效的方法。
[Abstract]:Robustness is an important concept in the field of engineering structures against continuous collapse. Although there are many quantitative structural robustness indicators, there is no universally accepted index to measure the structural robustness. This is mainly due to the fact that the meaning of robustness is used by different scholars. A semi-deterministic framework for robust evaluation is established. The uncertainty of the structure itself (i.e. variability of material properties and geometric dimensions) is ignored under the action of specific events. The uncertainty of different events is considered by the probability density function. In this paper, the structural robustness is studied from its opposite, that is, structural vulnerability. The structural vulnerability can be obtained by means of the set theory. According to the different contribution degree to the structural vulnerability, the important coefficient based on the bearing capacity is introduced as the weight coefficient of the component vulnerability coefficient. Furthermore, the robustness index is obtained. For truss structures and reinforced concrete structures, the suitable important coefficients of members and the vulnerability coefficients of members are put forward, respectively. For truss structures, the important coefficients of members can be calculated by incremental load method. In the process of calculation, the failure scenarios caused by failure of different members and the topological relationship among members can be obtained. Because there is only axial force, the vulnerability coefficient of truss members can be defined at the strain level. The Pushover method is used to calculate the important coefficients of the members. The variation of the ultimate bearing capacity of the structure is investigated, but the complex failure scenario is ignored. Because of the complexity of the internal force distribution of the reinforced concrete members, In order to explain the use of the robustness index, four truss structures and five reinforced concrete frame structures are designed. The distribution of the important coefficient and the vulnerability coefficient of each structure is analyzed and compared. The robustness of each structure is evaluated. The results show that the robustness index proposed in this paper can well evaluate the robustness of the structure under the action of different events. Enhancing the local resistance of important components and enhancing the redundancy of structures are two effective methods to improve the robustness of structures.
【学位授予单位】：湖南大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TU375.4;TU312.3

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