【作者】 周荣刚；

【导师】 刘国华；

【作者基本信息】 浙江大学 ， 水工结构工程， 2008， 硕士

【摘要】 有限单元法进行拱坝分析具有诸多方面的优点,但存在较大的应力集中,而经等效应力法处理可在一定程度上削除这种应力集中的影响。目前,有限元等效应力法应用于高拱坝分析设计可行性还不确定。有限元等效应力法应用于拱坝分析还处于起步阶段,其可行性有待进一步的深入研究,特别是在高拱坝分析设计中的应用更应慎重考虑。随着我国高拱坝工程的不断发展,有必要对有限元等效应力法在高拱坝分析中的适用性作进一步的研究。本文首先介绍了拱坝等效应力和非线性开裂分析方法,并提出利用非线性分析结果作为参照对等效应力法及其应力控制标准进行检验研究究。坝体分析采用ANSYS有限元软件。运用ANSYS自带APDL语言和结果文件数据,可比较方便地计算拱坝上下游面的等效应力;运用ANSYS中的Concrete65单元和混凝土材料开裂模型可模拟拱坝受荷后的非线性开裂。通过非线性开裂解和有限元等效应力解的对比研究有限元等效应力法进行高拱坝应力分析及规范提出的1.5MPa应力控制标准应用于高拱坝分析时的适用性。从分析结果可以看出,有限元等效应力法计算结果相对于单纯利用有限元法所计算的应力值大大降低,因此等效应力法可以有效削除应力集中的影响。而与非线性开裂分析结果比较后可知,等效应力值与非线性开裂应力值大体接近,并且两者总体的应力分布规律比较相似,因此可以说明等效应力法可以应用于高拱坝的坝体应力分析。其次,由非线性开裂分析结果可知,坝体只在坝基面上游侧产生最大不超过0.3坝厚范围的局部裂缝,裂缝仍处于稳定状态,对大坝正常运行影响不大。而温降和温升工况最大等效主拉应力值均在1.5MPa以内,因此《规范》关于等效应力法最大拉应力控制值1.5MPa的规定在高拱坝的应用中仍能适用。更多还原

【Abstract】 The finite element method has a lot of advantages, but the stress results by this method are always involved with great stress convergence. Fortunately in some degree this kind of stress convergence can be eliminated or reduced to a lower level processed with the finite element equivalent stress method. At present it is doubtable to analyze high arch dam stress with the FEM equivalent stress method. Now the FEM equivalent stress method is being used for arch dam analysis at its initial stage, and its feasibility should be studied about more deeply, especially for high arch dams. So it’s necessary to study the validity of the FEM equivalent stress method further for the analysis of high arch dam stress. Firstly this paper introduces the FEM equivalent stress method and the nonlinear cracking FEM, and intends to study the applicability of the FEM equivalent stress method as well as its tensile stress criterion contained in the design specification by comparison with the results gained by both of the above methods. The arch dam stress is analyzed with the ANSYS FEM software. Meanwhile it is easy to calculate the equivalent stress of arch dam by running an APDL program on the basis of the ANSYS result data; and it is feasible to analyze nonlinear cracking stress of arch dam using the concrete65 element and concrete cracking principle. Through comparison with two kinds of stress results and crack development the validity of the FEM equivalent stress method and the 1.5MPa of the equivalent tensile stress limit will be researched for the stress analysis of high arch dam.After comparing two sets of results referred above, it is clear that the FEM equivalent stress method can cut down the stress result calculated straight by FEM and eliminate the stress convergence. The stress values gained by both methods are basically close as well as the stress distribution about the dam height. So the equivalent FEM can be used to analyze the stress of high arch dam. On the other hand, from the nonlinear cracking analysis results, cracks only happen at some local positions, and they are all in a steady-going state. It’s clear that these cracks have not any important impact on the arch dam’s working order. Meanwhile the greatest equivalent principle tensile stress is less than 1.5MPa.So the 1.5MPa of equivalent tensile stress limits by the current design specification is also feasible.更多还原