【作者】 刘学武；

【导师】 郭彦林；

【作者基本信息】 清华大学 ， 土木工程， 2008， 博士

【摘要】 近年来,一大批大型复杂钢结构工程在我国落成或在建,其在施工过程中表现出了诸多新的力学问题。本文对若干亟须解决的钢结构施工力学问题进行了深入的理论研究,提出了相应的解决思路和方法,对实际工程的建设起到了指导作用。主要完成了如下工作:(1)从数学和物理上揭示了单元生死技术模拟施工过程的单元“杀死”、“漂移”和“激活”的机理,研究了单元“生死”系数的取值。探讨了结构施工过程模拟的分步建模技术。采用单元生死技术对CCTV新台址主楼的施工过程进行了分析,揭示了其在施工过程中的受力机理。(2)提出了钢结构施工变形预调值计算的正装迭代法、倒拆迭代法和分阶段综合迭代法。采用分阶段综合迭代法对CCTV新台址主楼的变形预调值进行了分析,给出了构件的加工和安装预调值,且评估了地基不均匀沉降对变形预调值的影响。(3)建立了大跨度钢结构拆撑过程数值模拟的千斤顶单元法。基于非线性有限元法,提出了拆撑过程数值模拟的千斤顶-间隙单元法和千斤顶-接触单元法。采用千斤顶单元法对国家体育场钢屋盖的拆撑过程进行了模拟分析。(4)研究了索-滑轮结构体系力学状态求解的滑移索单元,采用延拓牛顿法改进了单元的收敛性,编制了索-滑轮结构体系分析的有限元程序,可用于结构的施工过程分析。(5)提出了钢结构吊装平衡状态确定的椭圆简化算法。建立了一种模拟钢结构吊装可动体系的力学模型,在此基础上提出了其平衡状态确定的一种优化迭代算法,可精确模拟吊装可动体系空间姿态和力学状态的演变历程。(6)建立了索结构初状态及零状态确定的二次求解技术,所求得的初状态能够考虑弹性变形和自重等作用的影响,同时可确定梁的加工位形以及索和杆的下料长度。更多还原

【Abstract】 Lots of new mechanical problems have emerged in the construction of large complex steel structures. In this paper, several key mechanical problems in the construction of steel structures are intensively studied, and the numerical results obtained are used directly to the construction of several actual projects. The main research work covered in this paper includes:(1) The principles of element’s“death”,“floating”and“birth”for the element birth and death technology are studied theoretically. Another construction simulation method, the step-by-step modeling technology, is also discussed. The construction of the new CCTV headquarters is simulated by using the element birth and death technology and its internal force and deformation in the construction is given.(2) Several computational procedures, forward iteration method, backward iteration method and stepped comprehensive iteration method, for determining the pre-set deformation value of steel structures are proposed. The stepped comprehensive iteration method is applied directly to determine the manufacture and erection pre-set deformation values of the new CCTV headquarters where the influence of the settlements of the foundation is involved in the analysis.(3) A jack element model, a jack-gap element model and a jack-contact element model for simulating removing temporary supports of large steel structures are proposed respectively, where the jack element model is used to simulate removing temporary supports of the National Stadium.(4) Gliding cable element for simulating accurately the cable-sheave structures is discussed systematically, and its convergence is improved by the continuation Newton method. Analytical procedures for simulating the construction of the cable-sheave structures are discussed.(5) Two methods, elliptic simplified method and optimization iteration method, for determining the equilibrium state of the steel structures during their hoisting process are proposed. And the latter can accurately simulate the variation of the mechanic and geometric state of the structure during the hoisting process.(6) A secondary solution technology for determining the pre-stressed state and unstrained state of the cable structures is proposed, and the effect of the elastic deformation and self-weight of the structure can be involved in the analysis automatically. At the same time the manufacture configuration of the members can be obtained.更多还原