【作者】 张启灵；

【导师】 伍鹤皋；

【作者基本信息】 武汉大学 ， 水利水电工程， 2010， 博士

【摘要】 垫层蜗壳由于其混凝土结构承担内水压力小,且施工方便、工期较短和造价低,应用前景广泛。我国已建的三峡、拉西瓦和在建的向家坝等单机容量超过700MW的水电站部分机组采用了垫层蜗壳结构型式,这也提出了一系列新的课题,如垫层蜗壳配筋计算问题、配筋原则问题、座环结构受力特性问题、垫层平面铺设范围问题等。另外随着近年来地震活动的日益频繁,位于我国西南地震高发地区的水电站厂房抗震问题受到各方高度关注。本文针对以上问题,以有限元方法为主要分析手段,采用ABAQUS软件,结合多个工程实例,从以下几个方面展开研究：(1)为研究“Γ”形框架简化、平面简化和接触摩擦对垫层蜗壳配筋计算的影响,分别采用结构力学法和有限元法对某垫层蜗壳进行计算。计算结果表明,采用平面“Γ”形框架法可能造成计算配筋面积偏小；在考虑接触摩擦的前提下,将蜗壳结构简化为轴对称结构进行初步配筋计算是可行的；对垫层蜗壳结构进行有限元分析时有必要考虑接触摩擦,摩擦系数f应慎重取值。(2)现行规范把蜗壳结构归为非杆件体系钢筋混凝土结构并按主拉应力图形面积确定配筋数量存在原则性缺陷,计算出的配筋量往往偏多。本文列出了现行计算方法存在的问题,并具体分析了产生问题的原因,提出了改进配筋计算的原则,引入有限元方法,明确了蜗壳结构应按限裂要求配筋。应用实例表明,局部配筋量减少后混凝土损伤区没有显著变化,钢筋应力增幅很小,改进后的配筋计算原则对优化局部配筋量是合理有效且操作性强的。(3)为研究蜗壳和外围混凝土联合受力情况下座环的结构特性,本文结合一实际工程垫层蜗壳结构,采用三维有限元方法,从座环应力、位移和变形以及抗剪性能几个方面分析座环结构。研究结果表明,相比于座环结构强度,位移和变形更应值得重视,垫层变形模量和摩擦系数的大小应该成为座环结构分析的重要考虑因素。座环承受较大的剪力,垫层蜗壳结构设计中不能忽视此问题。(4)目前学术界和工程界对如何合理确定蜗壳垫层平面铺设范围尚无统一认识,针对此问题,本文从座环位移变形、座环抗剪性能、机墩结构位移变形和流道结构承受的扭转力比例四个方面讨论了垫层平面铺设范围的确定原则。研究结果表明,若蜗壳结构问题的主要矛盾是座环和机墩位移变形过大,则平面上垫层末端宜设置在蜗壳135°～180°断面之间；若意图改善座环抗剪性能和流道结构受力条件,垫层末端宜设置在蜗壳0°～90°断面之间或270°断面之后。(5)为研究行波效应对平面尺寸较大的水电站厂房结构地震响应的影响,探讨对厂房结构抗震合理适用的抗震措施,选取某实际厂房结构,采用时程分析法进行结构动力计算。结果表明当波速不大时(小于1000m／s),考虑行波效应可使厂房结构设计更趋科学合理。在水电站地面厂房中设置粘滞阻尼器是有效的抗震措施,可以增强上游排架和上游墙以及下游排架的抗震能力,但应重点考虑阻尼器支撑高度。更多还原

【Abstract】 The spiral case with a membrane can resist most of internal water pressure with only a small load being transmitted into the surrounding concrete. This embedding type of spiral case brings convenience of construction, short project duration and low project cost, so it is being applied more and more. For example, some generating units with a unit capacity greater than 700MW adopt this kind of embedding type, including the Three Gorges, Laxiwa and Xiangjiaba hydroelectric power plant in China. Due to these applications, some new problems arise, such as reinforcement calculation of spiral case with a membrane, calculation principle for reinforcement, structural characteristics of stay ring, plane covering range of membrane, etc. Furthermore, with a higher seismicity in recent years, high attention has been given to the earthquake-resistance of hydropower houses located in southwest China with a frequent seismic activity. On account of the aforementioned problems, by means of the finite element method (FEM) using ABAQUS, this dissertation is restricted to the discussion of the following aspects based on some case studies.(1) Both structural mechanics and FEM were used to analyze a spiral case with a membrane, in order to study the influencing factors of reinforcement calculation for it. The influencing factors includeΓ-frame simplification, plane simplification and contact friction between spiral case and concrete. It is concluded that theΓ-frame simplification may cause the calculated reinforcement area to be smaller than needed. It is feasible to simplify a spiral case structure as a plane axisymmetric model in the preliminary reinforcement calculation on condition that the contact friction is considered. It is necessary to take the contact friction into consideration in FEM calculation for spiral case with a membrane, and the friction factor should be defined cautiously.(2) Spiral case structure is classified as non-member bar reinforced concrete structure in the applicable code. It is improper in principle to calculate reinforcement area according to the area of tensile stress figure, which often causes the calculated reinforcement area to be more than needed. The problem of applicable calculation method was illuminated, and the reason for the problem was analyzed specifically. The principle of improving reinforcement calculation was put forward by using FEM. It is confirmed that crack width restriction should be the requirement for the reinforcement of spiral case structure. The case study shows that the damaged range of concrete does not vary remarkably and the increasing ratio of reinforcing bar stress is small, when the partial reinforcement area is reduced. It is proved that the improved calculation principle of reinforcement is effective and operative for reducing partial reinforcement area.(3) In order to analyze the structural characteristics of stay ring on condition that the spiral case and the surrounding concrete jointly resist the internal water pressure, several aspects including stay ring’s stress, displacement, deformation and shear capability were studied using three-dimensional FEM, based on a case study of spiral case structure with a membrane. The result shows that great importance should be attached to the stay ring’s displacement and deformation other than its structural strength. The membrane’s deformation modulus and the friction factor both produce a great effect on the structural characteristics of stay ring. The stay ring resists a great shear, which cannot be ignored in the design of spiral case structure with a membrane.(4) The academia and engineering have not reached a consensus on how to determine a proper plane covering range of membrane for spiral case up to now. Four factors including stay ring’s displacement and deformation, stay ring’s shear capability, generator pedestal’s displacement and deformation, flow channel’s torsional strength were considered to solve this problem. The result suggests that if the primary design objective of spiral case structure is to control stay ring and generator pedestal’s displacement and deformation, the plane covering end of membrane is suitable to be located between 135°cross section and 180°cross section of spiral case. If the primary design objective of spiral case structure is to enhance stay ring’s shear capability and improve flow channel’s loading condition, the plane covering end of membrane is suitable to be located between 0°cross section and 90°cross section, or after 270°cross section of spiral case.(5) In order to study the traveling wave effect on seismic response of hydropower house structure with a large plane scale and discuss the effective aseismic measure, a dynamic structural analysis of an actual powerhouse structure was carried out using time-historic analytical method. The result shows that if the earthquake wave speed at the project site is small (smaller than 1000m/s), the traveling wave effect can be taken into consideration properly to make the structural design of powerhouse more reasonable. It is effective to install some viscous dashpots in the surface hydropower house for its earthquake-resistance. The aseismic measure can help enhance the earthquake-resistance capacity of framed bent and powerhouse wall. The supporting height is of great importance to the earthquake-resistance effect of dashpots.更多还原