【作者】 葛颂；

【导师】 蒋家羚；

【作者基本信息】 浙江大学 ， 化工过程机械， 2006， 硕士

【摘要】 本文针对大型非锚固式储罐,采用有限元数值模拟方法研究了以下三个方面问题:静载荷下罐-土接触问题,准静态载荷工况下象足现象,及罐-液耦合模型的地震响应。本文研究的主要目的是探寻该复杂非线性系统的科学数值建模方法,以下是本文的三个主要创新点: 1.基于有限元接触分析,提出了一个新的地基-结构耦合建模方法,以求更合理的描述下节点区域(罐壁底部和底板焊接区域附近)的应力情况和地基之间的关系。该法能通过监测地基沉降量,方便地得知罐壁及底板的应力应变水平和分布情况。 2.总结并改进了多种象足屈曲现象模拟分析的准静态方法,并创新性地提出了局部罐壁底部预提离工况下,非锚固罐象足屈曲的动力学建模方法。 3.通过在地基上作用水平脉冲激励,来研究罐-液耦合系统的自由振动特性。在这些方法创新基础上的数值模拟研究,获得了一些重要结果: 1.罐底地基沉降量和罐壁罐底板之间应力水平存在对应关系,具有工程应用的价值。 2.利用非线性有限元研究象足屈曲产生的机理,证实了:罐壁竖直轴向压应力和由内压(静水和动水压力叠加)所产生的罐壁环向拉应力共同导致罐壁失稳,发生弹塑性屈曲变形。并且与目前国内外众多储罐抗震规范一致的是,罐壁的竖直轴向压应力是发生屈曲失稳的主导因素。 3.考虑罐-液耦合系统的固有频率求解是非线性问题,本文运用脉冲响应试验方法建立有限元模型,通过Fourier变换,从时域相应结果获得系统的频谱。 4.另外,对地面加载单项正弦共振波和三向El Centro地震波,成功地模拟出了非锚固罐的翘离现象,在此基础上深入地研究了翘离形成机理,定性的给出了翘离的地面区域形状,翘离高度及翘离发生时的关键应力水平。验证了即使15万方大型立式储罐也会发生翘离现象。更多还原

【Abstract】 The present study investigates three main points of the unanchored large storage tanks by finite element analysis, including structure-foundation contact under static load, elephant foot bulking, and seismic response using FSI(fluid-structure interaction) model. The main objective of this research is to explore scientific numerical simulation modeling solutions of this nonlinear complex system. The three primary innovation points are concluded as follows:1. Based on finite element contact analysis, a novel modeling method called foundation-structure coupling method is presented in order to describe the relation between the stress of the shell-to-bottom joint and the foundation. The stress in tank shell and bottom plate can be easily achieved according to investigating foundation settlement.2. A variety of quasi-static simulation approaches of elephant foot buckling are concluded and further developed. The dynamic model of elephant-foot buckling of unanchored tank is also built on condition that bottom plate is partial pre-uplifted.3. By applying lateral impulsive load on the foundation, there is a new approach of the free vibration response analysis of a structure-fluid interaction system.According to numerical simulation research of the method innovations above, it shows some important results:1. There is a certain relation between the foundation settlement and stress distribution in both tank shell and plate. This relation is applicable in engineering field.2. The mechanism of elephant-foot buckling near the tank base is proved by nonlinear finite element study, which is in accordance with typical codes. It occurs predominantly due to the axial compressive stress in the tank shell, though it is significantly affected by the circumferential membrane stress caused by internal pressure (both hydrostatic and hydrodynamic).3. To solve the natural frequency of the nonlinear FSI system, impulsive excitation method is applied to the finite element modeling. And the frequency spectrum of the FSI system is achieve through Fourier Transform from time domain.4. Additionally, as the ground acceleration, one dimensional sinusoidal resonant wave and three dimensional 1940 El Centro earthquake wave are applied on the foundation. Based on successful simulation of uplifting phenomenon, the mechanism of uplifting is further studied. Qualitative analysis shows the shape of uplifting area, uplifting height and stress level when uplifting happens. And it is proved that uplifting can still happen for 150,000 m~3 liquid storage tank.更多还原