【作者】 孙香红；

【导师】 王社良；

【作者基本信息】 西安建筑科技大学 ， 结构工程， 2010， 博士

【摘要】 在强风、地震以及海浪等自然灾害的作用下,结构的安全性已成为人们越来越关注的问题。增加结构刚度、承载力或材料强度等传统方法已经很难满足人们越来越高的要求。因此,结构抗灾控制理论与工程应用方法作为一种新的提高结构安全性、适用性和舒适性的途径,其研究与应用已日趋广泛。众所周知,在结构的适当部位合理安装一定数量的耗能减震装置或被动阻尼控制系统将会减小结构系统的地震响应。但结构系统的抗震控制效果对耗能减震装置或者被动阻尼控制系统的物理参数、设置数量以及空间分布等非常敏感,在没有较好的分析理论和设计方法时,最简便的办法就是在结构的所有层均匀布置耗能减震装置或被动阻尼控制系统。但这种布置并不能取得最佳减震效果,而且工程量大,造价高,影响了工程应用。目前对此方面的研究都是基于确定性目标进行优化,虽然在一定程度上找到了较优布置,取得了较好效果,但并非最优。另一方面,由于结构系统的复杂性、优化方法的局限性以及地震动的随机性等,使得结构抗震优化控制研究成为一个多学科交叉的课题。因此,深入研究被动阻尼控制系统在结构中的拓扑优化设计具有重要的理论意义和工程应用价值。本文首先分析了结构控制的各种理论与优化算法,接着对框架结构采用粘滞阻尼系统的拓扑优化设计进行了研究,解决了基于结构体系可靠度的粘滞阻尼系统的拓扑优化问题。主要研究内容和成果如下：(1)对遗传算法的编码规则、种群设定、适应度函数的选择以及遗传算子的设计和收敛准则等进行了探讨,特别是对交叉算子和变异算子进行了改进设计,自主编制形成了适合于设置粘滞阻尼系统框架结构的MATLAB工具箱函数。分析表明,文中所提改进后的遗传算法,能较快地寻找到最优个体,并不会导致早熟现象的发生。(2)采用文中建议改进的遗传算法,以确定性指标,如层间位移等作为结构优化控制的目标函数,确定了优化算法的关键参数,利用MATLAB编程软件,编制了地震作用下粘滞阻尼系统的拓扑优化程序(FSVDO);分别在Ⅱ类场地和Ⅲ类场地条件下,选用实际记录地震波和人工地震波,采用自编的FSVDO程序,进行了受控结构的最优拓扑分析,并将其结果与穷举法的优化结果进行了比较,两者吻合较好,证实文中所发展的算法是可靠有效的,可用于复杂结构的优化分析和设计。(3)地震动的随机性将导致即使在同样场地条件下,输入的地震波不同,受控结构的粘滞阻尼系统的最优拓扑形式也可能有所不同,这就是所谓的“样本冲突”。文中最优拓扑分析结果验证了该现象,这说明基于某个确定性指标进行粘滞阻尼系统位置的拓扑优化存在一定缺陷,因此在进行结构的拓扑优化分析时,需要考虑地震动随机性的影响。(4)采用概率密度演化方法和文中发展的优化算法,提出了以结构体系可靠度为目标函数时,粘滞阻尼系统空间拓扑优化的计算原理,编制了基于结构体系可靠度的粘滞阻尼系统拓扑优化分析程序(SRBTOVD),实现了基于结构体系可靠度的粘滞阻尼受控结构系统的最优拓扑优化,解决了上述的“样本冲突”问题。为了比较,分别计算了无控结构、均布粘滞阻尼系统结构以及最优布置粘滞阻尼系统结构的体系可靠度。结果表明,利用文中发展的优化算法进行粘滞阻尼系统的优化布置,不仅可明显提高结构体系的抗震可靠度,而且其值与传统的各层均布粘滞阻尼系统的体系抗震可靠度非常接近,然而设置的粘滞阻尼系统数量仅为传统方法的50%左右,反映出较好的经济性和实用性。(5)在实现结构体系抗震可靠度的迭代优化计算中,考虑到MATLAB计算效率不高,文中的计算核心程序采用C++语言编程,在MATLAB环境中调用C++程序计算结构的体系抗震可靠度,实现了文中的拓扑优化程序。结果表明,文中所提出的方法操作简单,计算效率高,具有较好的应用前景。(6)应用概率密度演化方法,在非平稳随机地震动激励下,分别获得了无控结构、均布粘滞阻尼系统的受控结构以及基于结构体系抗震可靠度的优化布置粘滞阻尼系统的受控结构的概率密度曲线随时间演化的全过程,进行了相应的概率密度演化分析,计算了各层的动力可靠度。分析结果表明,采用文中基于结构体系可靠度的粘滞阻尼系统受控结构具有可靠度高、成本低的优势。更多还原

【Abstract】 Structural safety has gained more and more importance under disastrous loads such as strong winds, earthquakes and ocean waves, etc. It is hard for traditional methods, e.g. to increase the stiffness, bearing capacity and material strength, to meet the current requirement. Therefore, the theory and engineering applications of structural control, which can promote the safety, serviceability and/or comfortability of structures, have being increasingly paid attention to by researches and engineers.As we know, the responses of structures can be reduced effectively by energy dissipation devices or dampers. However, the effect of seismic control is very sensitive to the number, space distribution and the physical parameters of the energy dissipation devices or dampers. The easiest strategy is to install energy dissipation devices or dampers in each story. However, such a strategy cannot always obtain the best effect of seismic control, not to mention its high cost. Thus, it has not been widely applied as yet in the field of engineering. Actually, up to now, most researches on the system optimization of passive control devices are still limited to the deterministic objective function. Such methods may find optimal arrangement of the control devices in some sense, but it might not be the best arrangement if more realistic factors are involved. On the other hand, due to the complexity of structures, the limitation of optimization methods and the randomness of earthquakes, optimization of structural control under earthquake becomes a multidisciplinary topic. Therefore, the study on topological optimization of the structures with dampers is of very significance and application value for civil engineering.Firstly, the most widely used theories for structural control and optimization algorithm are discussed in this paper. Then the topological optimization method for arrangement of the viscous dampers installed on frame structures is specially studied. Based on the system reliability of structures, the topological optimization of the viscous dampers is solved. The main research contents and results are shown as follows:(1) The encoding rules, population settings, selection of the fitness function, design of genetic operator and the convergence criterion of the genetic algorithm are further studied in this paper. Especially, some MATLAB toolbox functions are developed for the frame structures installed with viscous dampers. The analysis indicates that the improved genetic algorithm can quickly find the optimal individual without precocity phenomena.(2) Setting the deterministic indices, e.g. the inter-floor drift, as the objective function of the structural control, and using the improved genetic algorithm, the parameters of the optimization algorithm are defined. Then, the program for topological optimization of the viscous dampers installed in the frame structure is developed in MATLAB, in short as FSVDO. To the situations of classification II and III of the site soil, using the FSVDO program, the topological optimization analyses of the structures are carried out under realistic earthquakes and artificial earthquake. The result is consistent to that obtained by the method of exhaustion, which means that the Improved Genetic Algorithm (IGA) is very effective and reliable, and can be used in the optimization analysis and design of similar structures.(3) Even in the same classification of site soil, due to the randomness of earthquake, the optimal topology of the viscous dampers in the fame stru ctures can be different to different earthquake inputs, and such phenomenon can be referred to as "samples conflict". The analysis in this thesis also shows this phenomenon, which means the randomness of earthquakes has obvious effect on the topology of dampers. In other words, topological optimization of dampers with deterministic indices exhibits some defects, whereas the randomness of earthquakes can not be ignored.(4) With the probability density evolution method and the improved genetic algorithm, setting the reliability of structure as the objective function, a novel method which can solve the problem of "samples conflict" for topological optimization of dampers is proposed. The program is developed in MATALB, named as SRBTOVD. For comparison, the reliabilities of the un-controlled structure, the structure installed dampers in every floor and the structure installed topologically optimized dampers are calculated, respectively. The result indicates that, with the proposed IGA, not only the reliability of the structure system can be improved obviously, but the reliability is also very close to the structure installed dampers in every floor, whereas the number of dampers can be reduced to 50% of the traditional arrangement, which shows the advantage on economy and applications.(5) Due to the low efficiency of MATLAB, for the iteration calculation of topological optimization, C++ was employed as the programming language in the computing kernel program. With the C++ program, the system reliability of the structures with dampers can be obtained, and then the topological optimization analysis can be performed in the environment of MATLAB. The results of analysis indicate that, due to its high efficiency and practicability, the proposed method can be widely used in the civil engineering.(6) Using the probability density evolution method, under non-stationary random earthquake excitations, the evolution processes of the probability density of the uncontrolled structure, the controlled structure installed with dampers in each floor and the controlled structure installed with the topological optimized dampers are obtained, respectively. With the analysis on the processes of the probability density, dynamic reliabilities are evaluated and compared, which shows that, in the three cases, the controlled structure installed with dampers via topological optimization has the highest reliability and lowest cost.更多还原