【作者】 查小鹏；

【导师】 瞿伟廉；

【作者基本信息】 武汉理工大学 ， 结构工程， 2008， 博士

【摘要】 桅杆、输电塔等高耸钢塔架结构受气候影响十分显著,风荷载是其主要荷载。由于结构的高柔性和风荷载的随机性,高耸结构对风的作用特别敏感,较易因风力引起的结构构件的疲劳破坏而造成整个结构的倒塌。考虑到结构构件的风致疲劳破坏是一种累积效应,若能建立起在结构构件达到80%或90%的疲劳极限寿命时就可告知用户的结构风致疲劳的安全预警系统,那就可据此更换构件,防止结构发生因风致疲劳造成的倒塌。由此可知,研究高耸结构风致疲劳安全预警的基本理论与方法有着重要的工程意义,能提高结构在使用中的安全保障能力。本文主要以桅杆结构为例,详细地研究了结构风致疲劳安全预警系统的各组成部分,探讨了结构有限元分析模型的建立、风振响应计算、结构动态荷载识别、模型修正、风致疲劳分析、结构安全预警的系统组成等内容。本文研究了桅杆结构非线性有限元模型的建立方法。推导了用多项式表达的纤绳等效非线性弹簧模型,同时研究了纤绳的多节点曲线索元模型。阐述了用梁单元和杆单元来描述的桅杆杆身有限元模型。研究了多维动力风荷载的模拟和时域内桅杆结构非线性静力、动力计算方法。本文的桅杆结构建模与动力分析方法也适用于输电线塔结构。动态荷载的确定是一个较难的问题,自由度多且具有非线性的桅杆、输电线塔结构的动态荷载识别更少有人涉足。本文提出了高耸结构等效二维动力风荷载的概念,建立了桅杆结构和输电塔结构考虑非线性的等效二维动力风荷载识别模型,针对桅杆等非线性结构动态荷载识别的特点,采用基于简化模型的直接识别法、基于精细时程积分的荷载识别法和基于模态分析的动态荷载识别方法较好地解决了桅杆结构动态荷载的识别问题。在结构安全预警系统中,有限元理论模型与实际结构模型的差异可能会导致预警失实而无效,因此需要进行模型修正。本文分析总结了常用结构有限元模型修正方法的优缺点和适用范围。根据高耸塔架结构的特点,以桅杆结构为例,基于规划优化的原理,提出了高耸结构模型修正的方法,建立了端部刚度可调的杆件单元模型,在此基础上以组合单元杆件形式的有限元模型为对象,对桅杆结构进行了模型修正。本文建立了高耸塔架结构中广泛使用的螺栓节点板联结节点的精细有限元模型,提出了一种优化等效的方法,以刚度矩阵的误差最小为等效原则,在把节点处杆件的半刚性联接等效为杆端截面抗弯刚度下降的基础上,得到了螺栓节点联结杆件的精细有限元模型与简化有限元模型的等效关系。本文研究了结构风致疲劳安全预警中的构件疲劳累积损伤和剩余寿命估计问题。阐述了适用于高耸钢结构疲劳分析的S-N曲线法和断裂力学方法,给出了桅杆等高耸结构风致疲劳累积损伤和剩余寿命的计算方法和步骤,论述了改进的简化雨流法的基本原理与程序实现,并分析了桅杆结构改善构件的疲劳性能和进行风振疲劳控制设计的方法,对一现役桅杆结构进行了基于S-N曲线法和断裂力学方法的疲劳损伤和剩余寿命仿真计算。基于结构动力风荷载识别、有限元模型修正和风致疲劳分析,本文对桅杆结构风致疲劳安全预警的系统组成和工作原理进行了研究。阐述了安全预警系统的工作原理和各子系统的功能,并研究了使用疲劳寿命计进行结构健康监测与安全预警的方法。更多还原

【Abstract】 High-rise structures like guyed mast and power transmission tower are influenced by climate obviously,whose main load is wind load.Due to structural highness and slenderness and the randomicity of wind load,high-rise structures are especially sensitive to the action of wind and tend to produce wind-induced fatigue rupture of structural members that may cause the collapse of the whole structure. Since the wind-induced fatigue is a cumulative effect,if we can establish a safety prewarning system for wind-induced fatigue which will inform customers when a structural member come up to 80%or 90%of limit fatigue lifetime,then we can replace this member accordingly to avoid the collapse of the whole structure caused by wind-induced fatigue.Hence,it is completely necessary to carry out the research on safety prewarning theory,method and system integration method for wind-induced fatigue of high-rise structures,which can improve the security capacity of structures in use.Taking guyed mast for instance mainly,this dissertation studied every integral part of structural safety prewarning system for wind-induced fatigue in detail including the finite element analysis model,analysis method of nonlinear system’s wind-induced response,dynamic load identification,model updating,safety prewarning system integration and so on.In this dissertation,nonlinear finite element model establishment method of the guyed mast is studied.The equivalent nonlinear spring model of the guyed cable by polynomial expression is deduced and the multi-node isoparametric curved element is also proposed to represent a cable.The beam element and truss element are discussed to build the mast model respectively.The simulation method of multidimensional cross-correlation fluctuating wind loads and the nonlinear static and dynamic response analysis method in time domain for guyed mast are studied. The methods of model building and dynamic analysis for guyed mast in this dissertation are also suitable for the power transmission tower.Since the determination of dynamic load is difficult especially for structures with a great many degrees of freedom and nonlinearity such as guyed mast and power transmission tower,few researches have focused on this problem.In this dissertation,the concept of equivalent two-dimensional dynamic wind load of high-rise structure is presented and the load identification models of the guyed mast and transmission tower considering nonlinearity are built.The direct load identification based on simplified model,the method of dynamic load identification based on precise time integration and the dynamic load identification method based on modal analysis are proposed to identify high-rise structural equivalent two-dimensional dynamic wind load.Simulation results demonstrate that the methods in this dissertation are effective.In a structural safety prewarning system,difference between the structural theoretical model and the actual structure may lead to inaccuracies and failure of the whole safety system.Therefor,structural finite element model updating is necessary. This dissertation analyzes and summarizes the applicablility,advantages and disadvantages of commonly used FEM updating methods.Taking guyed mast for instance,high-rise structural FEM updating method based on the principle of optimization is proposed according to the characteristics of structure.The element model with adjustable end stiffness is established.Then,combinatorial elements FEM is built to carry on the guyed mast model updating.This dissertation established a fine FEM of bolt connecting joint widely used in high-rise structures.Based on equaling the semi-rigid connecting as the reduction of member end section bending stiffness,an optimization equivalent method is put forward on the principal of minimizing the error term between stiffness matrix of fined model and one of equivalent simple model.In this dissertation,structural fatigue cumulative damage and residual life assessment of wind-induced fatigue safety prewarning system is studied.S-N curve method and fracture mechanics method for fatigue analysis are discussed. Calculation method and procedure of wind-induced fatigue cumulative damage and residual life for high-rise structure like guyed mast is presented.The basic principles and programming procedures of modified simplified rain-flow method are proposed. Methods of improve structural members’ fatigue performance and structural wind-induced vibration control are studied.Numerical sumulation of a guyed mast in use by both S-N curve method and fracture mechanics method is made.Based on "structural dynamic wind load identification—FEM updating—assessment of wind-induced accumulative fatigue of structural members", the system composition and working principle of guyed mast’s wind-induced fatigue safety prewarning system is studied in this dissertation.The system principle and sub-system function is then discussed.Finally,the use of fatigue life gage to structural health monitoring and wind-induced fatigue safety prewarning is put forward.更多还原