动力荷载作用下多自由度结构非线性恢复力识别研究

发布时间：2018-05-21 06:30

本文选题：损伤识别 + 动力荷载作用　；参考：《湖南大学》2013年硕士论文

【摘要】：工程结构在地震等强动力荷载作用下的损伤识别和性能评估是灾后救援、安全评估和恢复重建中所需解决的关键问题。在强动力荷载作用下，工程结构的损伤发生发展过程是一个典型的非线性过程，以往基于结构测量和特征值提取的以结构刚度降低来描述结构损伤的反分析方法严格来讲仅适用于线性动力系统，且结构的非线性特征具有明显的差异性，因此，研究具有一般意义的结构非线性行为识别方法对工程结构在动力荷载作用下损伤的定性和定量评估具有重要意义。基于上述背景，本文将结构的非线性恢复力作为描述结构非线性行为的直接指标进行识别，提出和发展了具有一般意义的多自由度非线性结构的损伤识别方法，为结构在动力荷载作用下损伤的发生发展过程进行监测以及对结构耗能进行定量评估提供了新方法。主要研究内容如下： 1、在理论方法中，提出了一种基于二重切比雪夫多项式的多自由度结构非线性恢复力的识别方法，该方法能够在结构质量和结构非线性特性均未知的条件下，，对体系的非线性恢复力、结构的质量分布及其非线性特性进行有效地识别。基于结构激励及其相应的响应时程，利用最小二乘优化算法和牛顿第三定律，从结构动力平衡方程出发，分别讨论了该识别方法在结构激励完整和非完整两种情况下的具体实现过程。 2、在数值模拟中，利用达芬系统、基于形状记忆合金(shape memory alloy，SMA)材料的阻尼器(简称SMA阻尼器)理想双旗形系统、和基于磁流变阻尼器(Magneto-Rheological damper，简称MR阻尼器)的滞回系统三类非线性模型来模拟结构的非线性行为，分别考虑无噪声影响和6%环境噪声水平影响，并与既有的基于幂级数多项式模型的识别方法进行了对比，且在多自由度数值算例模型中引入多个非线性模型来模拟工程结构可能发生的多处损伤，考虑不同的激励位置，验证了该识别方法的有效性。 3、在一个四层框架模型中分别安装MR阻尼器和SMA阻尼器来模拟结构的非线性行为，利用力锤施加冲击荷载，对该多自由度非线性结构开展了不同激励方式下的动力实验。仅基于结构激励及其响应的时域信号，通过与实测结果的对比分析，进一步验证了本文提出的基于二重切比雪夫多项式的非线性恢复力识别法对结构非线性恢复力、MR阻尼力和SMA阻尼器恢复力的识别效果。
[Abstract]:Damage identification and performance evaluation of engineering structures under earthquake and other strong dynamic loads are the key problems to be solved in post-disaster rescue, safety assessment and reconstruction. Under the action of strong dynamic load, the damage and development process of engineering structure is a typical nonlinear process. In the past, the inverse analysis method based on structural measurement and eigenvalue extraction used to describe structural damage by structural stiffness reduction is strictly applicable to linear dynamic systems, and the nonlinear characteristics of structures are obviously different. It is of great significance to study the identification method of nonlinear behavior of structures with general significance for the qualitative and quantitative evaluation of the damage of engineering structures under dynamic loads. Based on the above background, the nonlinear restoring force of the structure is regarded as the direct index to describe the nonlinear behavior of the structure, and the damage identification method of the multi-degree-of-freedom nonlinear structure with general significance is proposed and developed. It provides a new method for monitoring the occurrence and development of structural damage under dynamic loads and for quantitatively evaluating the energy dissipation of structures. The main contents of the study are as follows: 1. In the theoretical method, a method based on double Chebyshev polynomials is proposed to identify the nonlinear restoring force of multi-degree-of-freedom structures. The method can be used to identify the nonlinear restoring forces of multi-degree-of-freedom structures under the condition that both the mass and the nonlinear characteristics of the structures are unknown. The nonlinear restoring force, mass distribution and nonlinear characteristics of the system are recognized effectively. Based on the structural excitation and its corresponding response time history, using the least square optimization algorithm and Newton's third law, starting from the structural dynamic equilibrium equation, The realization process of the method is discussed in the case of structural excitation integrity and nonholonomic respectively. 2. In the numerical simulation, the ideal double-flag damper (SMA damper) based on shape memory alloy (SMA) material is used in the numerical simulation. And three kinds of nonlinear models based on Magneto-Rheological dampers (Mr dampers) are used to simulate the nonlinear behavior of the structures, taking into account the influence of no noise and 6% ambient noise level, respectively. Compared with the existing identification methods based on the power series polynomial model, several nonlinear models are introduced into the multi-degree of freedom numerical example model to simulate the possible multiple damage of engineering structures, and different excitation positions are considered. The validity of the method is verified. 3. Mr dampers and SMA dampers are installed in a four-story frame model to simulate the nonlinear behavior of the structure. The dynamic experiments of the multi-degree-of-freedom nonlinear structure under different excitation modes are carried out by using the force hammer to exert the impact load. Based only on the structural excitation and its response, the time-domain signal is compared with the measured results. The recognition effect of nonlinear restoring force based on double Chebyshev polynomials on nonlinear restoring force and Mr damping force of structure and SMA damper is further verified.
【学位授予单位】：湖南大学
【学位级别】：硕士
【学位授予年份】：2013
【分类号】：TU317;TU311.3

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