【作者】 李昕；

【导师】 刘幸；

【作者基本信息】 武汉大学 ， 结构工程， 2005， 硕士

【摘要】 水工非杆系结构是工程上广泛采用的结构形式。由于此类结构形式的复杂性,目前尚无成熟的工程设计方法。钢衬钢筋混凝土坝内埋管结构是非杆系构件中的重要一类,随着坝工技术的发展,大坝高度的不断增加,其重要地位也越来越突出。在实际情况中,坝内埋管的荷载水平不可能超过设计荷载。大量的调查和研究表明,结构在设计荷载作用下,受拉区混凝土远没有完全开裂,钢衬、钢筋也未受拉屈服,受压区混凝土没有压坏,钢衬、钢筋也未受压屈服。因此,对于水工非杆系结构,不能简单地像杆系结构那样将混凝土或钢筋达到材料强度时的应力状态作为设计依据。由此可见,现有的设计理论和方法已难以满足工程要求,这就需要研究埋管结构的破坏机理,建立新的极限状态评价方法,并以此提出相应的结构设计方法。 本文密切结合工程实际,收集了大量坝内埋管结构资料,对其进行了归纳和分析,结合现有理论,选取了具有代表性的计算模型。基于弹塑性理论,采用考虑混凝土应变硬化的有限元程序ANSYS对钢衬钢筋混凝土管道进行了全过程分析,确定了坝—管间相互作用的拉应变状态。计算结果表明,在设计内水压力荷载的作用下,管周混凝土未出现裂缝或局部出现细小裂缝,结构部分处于塑性阶段。因此,本文提出以管周混凝土拉应变值来定义坝内埋管极限状态的建议,认为当拉应变达到某一特定值时的状态为埋管结构的极限状态,超过极限值我们就通过改变埋管特征和材料用量来降低应变值。 本文研究了不同极限拉应变的混凝土材料、不同管顶混凝土厚度和管径的比值、不同钢材用量和温度荷载,对管周混凝土拉应变的影响。在分析现有极限状态现状的基础上,结合实际数据和仿真计算的结果,归纳出了既简便又省时的管周混凝土拉应变图表方法。并用实际工程算例进行了说明。 本文的分析建立在对实际工程中的坝内埋管结构进行归纳总结的基础上,所得到的规律和结论可为今后的实际工程设计和理论研究提供参考。更多还原

【Abstract】 Massive hydraulic structures have been widely used in practice. Because of the complexity of structural types and the multiplicity of loads, there are not acceptable methods of design up to now. The steel-lined reinforced concrete penstock embedded in concrete dam is very important to the dam. With the progress of hydraulic technology and the increase of the dam’s height, the structure becomes more important. The load of the penstocks is impossible to exceed the design level in fact. A large amount of investigation and research indicate that, under the design load, concrete is far away from cracking entirely while steel-line and reinforced steel are not yielded in the stretch area, nor is concrete crushed while steel-line and reinforced steel yielded in the press area. Therefore, the ultimate state of massive hydraulic structures can’t be defined as material intensity that concrete or steel attains. The design method for bar-structures has been on this ultimate state and therefore the design method for massive hydraulic structures is behind the times. So we should research the destroy mechanism of the penstocks, and establish a new ultimate state, on basis of which to put forward a design method.With close reference to actual projects, the paper collects and analyzes a large amount of information about penstocks embedded in concrete dams, then creates the typical finite element models on the basis of the theory and the collected information. By applying ANSYS procedure with consideration of strain hardening model and on the basis of elastic-plastic theory to thewhole process analysis of steel-lined reinforced concrete penstocks, the paper defines the tensile strain state of the combined function of dam-penstock. The ANSYS results show that there is micro-crack in the part of concrete around the penstock under the design load of internal water pressure. The structure is partly in the state of plasticity. So the paper puts forward a newly reasonable definition of the ultimate tensile strain of concrete on ultimate state for the penstocks embedded in concrete dams.The paper studies the effects of different ultimate tensile strain of concrete, ratio of thickness of concrete to diameter of penstock, the reinforcement in concrete and temperature load on the tensile strain of the concrete around the penstock. On the basis of common theory about the ultimate state, a chart method is introduced to design penstock embedded in concrete dams easily and quickly, combined with the actual data and the result of analysis. By an actual instance, this paper clarifies the corresponding calculation method of reinforcement.The analysis in this paper is based on practical penstocks embedded in concrete dams. The law and conclusion can provide reference for practical engineering and theoretical research in the days to come.更多还原