【作者】 林寅；

【导师】 赵阳；

【作者基本信息】 浙江大学 ， 结构工程， 2014， 博士

【摘要】 储罐结构是一类典型的薄壳结构,广泛应用于工农业生产中,如石油、液化天然气、粮食、水泥等各类液体和固体的储存,其中,石油化工业中的钢制储油罐最为常见。近年来,随着国民经济的发展和国家能源战略的实施,以大型储油罐为代表的大型钢储罐结构的建造方兴未艾。大型钢储罐结构的特点是径厚比大、高径比低,属风敏感结构,在强风甚至是长时间和风作用下容易失稳破坏,特别是在空罐或储液、储料不多的情况下。在过去几十年中,世界各国和地区已先后发生过多起钢储罐的风毁事故。由于钢储罐的风毁造成巨大的经济损失和严重的环境污染,其风力稳定问题长期以来受到众多学者的广泛关注和重视,然而已有的文献主要关注中小型储罐及筒仓结构,对大型变壁厚钢储罐结构鲜有涉及。因此,开展大型钢储罐风荷载和风力稳定的研究有着迫切的现实意义与广泛的应用前景。本文主要通过风洞试验和有限元分析对以十万方立式圆柱形钢油罐为代表的大型钢储罐结构的风荷载和风致屈曲进行系统的研究,力求揭示这类结构的风致屈曲机理及行为,为大型钢储罐结构的合理抗风设计提供参考和建议。全文主要内容如下：第1章介绍本文研究的背景,回顾钢储罐及金属圆柱壳结构风荷载和风致屈曲的研究历史,总结现行规范的设计规定,指出本文工作的出发点和思路。第2章简要介绍流体动力学原理及其数值解法——计算流体动力学(CFD)的基本理论,采用CFD商用软件Fluent对十万立方大型钢储罐进行数值风洞分析,初步了解这类结构的风场绕流特点和风荷载分布特征,并为后文大型钢储罐的风洞试验设计提供参考。第3章针对十万立方大型钢储罐单体条件下的风荷载进行风洞试验,考察三种不同的储罐形式：敞口储罐、平顶储罐和穹顶储罐；获得上述三种储罐的基本风荷载数据,包括平均风压和脉动风压、偏度和峰度,对风压脉动的概率分布进行分析并与高斯分布比较；讨论顶盖形式对钢储罐罐壁部分风荷载的影响、平均风压和脉动风压的相关性,将获得的风荷载数据和以往相关研究成果和规范进行对比,拟合圆柱壳罐壁平均风荷载体型系数的傅里叶公式,以供设计应用参考。第4章以敞口储罐为例,通过519种工况试验,考察群体效应对储罐表面风荷载的影响。试验包括三种典型的排列：两相邻储罐包括串列、并列和错列、三角形三罐排列和正方形四罐排列；重点研究来流风向角和罐群间距对钢储罐风荷载分布的影响。第5章简述薄壳结构的力学特点、稳定问题的基本概念和薄壳结构非线性稳定理论的发展历程；简单介绍圆柱薄壳结构稳定问题的有限元求解方法；概括圆柱薄壳结构稳定问题的分类并提出侧压稳定的概念；以实际工程中常用的五种圆柱钢储罐(容量为2000-50000m3)为例,建立有限元模型,对其风致屈曲的一般行为进行分析,讨论焊缝缺陷和特征值模态缺陷对风致屈曲性能的影响。第6章以十万方钢油罐为研究对象,建立有限元模型,进行大型钢储罐结构在平均风荷载下的稳定分析,包括线性特征值屈曲分析和几何非线性分析,研究初始几何缺陷对钢储罐稳定性能的影响；讨论壁厚腐蚀和储液高度等基本参数对钢储罐风致屈曲性能的影响；研究群体条件下钢储罐风致屈曲承载力的变化特点。第7章简述结构动力稳定性原理和结构动力稳定性的实用判定准则；采用非线性动力时程分析方法对大型钢储罐结构的风振屈曲行为进行研究,考察初始缺陷对大型钢储罐结构风振屈曲性能的影响。第8章结合现行规范和工程设计方法,从包边角钢、抗风圈和加强圈三方面对大型钢储罐抗风结构的加强机理和破坏特点进行剖析,讨论不同国家规范所采用设计方法的差异,研究采取抗风设计后钢储罐的风致屈曲性能和破坏特点,提出大型钢储罐结构的抗风设计建议。第9章总结全文,概括全文主要结论,并提出进一步研究工作的建议。更多还原

【Abstract】 Vertical cylindrical welded steel tanks are typical thin-walled structures which are widely used for fluid and bulk storage, such as oil, natural gas, grain and cement in industrial and agricultural plants. The welded steel oil tanks are representative of these structures. With the development of economy and oil industry and the implementation of the national energy strategy, more and more oil storage tanks are put into service in recent decades, especially large steel tanks. Because of high diameter-thickness ratios and low aspect ratios, tanks are wind-sensitive and therefore very susceptible to buckling under wind loads especially when they are empty or partially filled. Buckling of tanks sometimes even occurs under moderate wind load during their construction. Over the past few decades, buckling failures of cylindrical steel tanks and silos during windstorm have occurred in many countries and regions. Because of serious economic losses and environmental problems due to the destruction of storage tanks, studies about buckling of tanks under wind load have been conducted extensively over the past few decades. However, it is found that most of the literatures focus on small and medium tanks and silos while few studies have been conducted on the buckling behavior of large practical steel tanks with stepped wall. It is thus very important to conduct research on the wind loads and wind-induced buckling behaviour of large steel tanks which will also be put into a wider application.This dissertation reports the work done to evaluate the wind loads and the wind-induced buckling strength of large steel tanks, with aim to.r.eveal the wind-induced buckling mechanism and behavior of large steel tanks and provide advices for reasonable wind-resistant design of large steel storage tank. The strategy in the research is experimental and computational, in which wind tunnel experiments are carried out on rigid models to obtain wind loads on large cylindrical tanks, and the pressures are next used in a finite element model to evaluate the buckling behaviour of large steel tanks. The layout is organized as follows:Chapter1introduces the background of this dissertation. Literature of topic on the wind loads and wind-induced buckling of cylindrical tanks as well as silos is reviewed and the suggestions of several national design codes are summarized. The argument and idea of this thesis are also given.Chapter2presents the numerical simulation of wind loads on large vertical cylindrical tanks. The basic principles of fluid dynamic and its numerical solution method, computational fluid dynamics (CFD), are fist introduced. The commercial software package for general purpose Fluent is then used to carry out the simulation of wind loads on tank models. Results of wind field around a tank and wind loads on tanks are discussed, providing a reference for the design of wind tunnel test of large storage tanks.Chapter3reports the wind tunnel test of the wind loads on an isolated tank. The test covers three types of tanks:open-top tank, flat-roof tank and the dome-roof tank. The first four moments of the measured wind pressure, including the mean and normalized deviation pressure, kurtosis and skewness of the pressure signal, are obtained to study the feature of the wind loads. The probability distribution of fluctuating wind pressure is examined and compared with the Gaussian distribution. The effect of roof on the wind loads of cylindrical wall and the correlation of the mean wind pressure and fluctuating wind pressure are discussed. Comparison of wind loads between present study and related literatures is carried out. Based on the data of wind loads obtained from wind tunnel test, a Fourier formula is fitted for the wind load distribution of the cylindrical shell for design.Chapter4contains the wind tunnel test conducted to investigate the wind loads on grouped tanks. Three types of tank groups are covered in this study:two adjacent tanks including tandem, parallel and staggered configurations, three adjacent tanks in triangular array and four adjacent tanks in square array. All together, there are519cases in the test. The effects of spacing between tanks and wind attack angle on wind pressure distributions of both external and internal wall are investigated, and the difference of wind loads on tanks in a group compared with those on an isolated tank is discussed.Chapter5describes the general behavior of wind buckling of cylindrical tanks. The basic mechanics characteristics, the basic concept of stability theory and the development history of nonlinear stability theory of thin-walled structures are fist introduced. The finite element method for buckling analysis is described. The classification of buckling of thin cylindrical shells and the concept of lateral pressure stability are put forward. Several common practical tanks with volume of2000m3～50000m3are then chosen to investigate the buckling behavior of this type of structures. Both the linear elastic bifurcation analysis and the geometrically nonlinear analysis are carried out. The sensitivities of the welded-induced and eigenvalue mode imperfections are also discussed.Chapter6examines the buckling behaviour of large steel tanks under wind loads. The wind loads applied on finite element models are obtained from the wind tunnel test and the investigation is carried out by using bifurcation analysis and non-linear analysis. The effect of initial geometric imperfections on buckling behavior is analyzed through geometrically non-linear analysis. The effects of thickness reduction of cylindrical shell and the liquid stored in tank are also included. The buckling capacity of grouped tanks is also considered and compared with that of an isolated tank.Chapter7considers the nonlinear dynamic buckling behaviour of large steel tanks under wind loads. The dynamic stability theory and the criterion for evaluate the dynamic stability of a structure are first introduced and then the dynamic buckling behaviour of large steel tanks is investigated by using dynamic time history analysis. The effect of initial geometric imperfections on dynamic buckling behavior is also included.Chapter8discusses the design method of wind girders for large steel tanks. In light of current design code and engineering method, the strengthening mechanism and damage feature of the components for wind buckling resistance, including the top angle iron, the upper wind girder and the middle wind girder of tanks, are investigated. The difference of formula for wind girder design between several standards is discussed. The buckling performance of tanks with wind girders is examined and some suggestions for design of the components for wind buckling resistance of tanks are also given.Chapter9summarizes some important conclusions and indicates some further work which may contribute to the research on this topic.更多还原